Hieronder krijgt u uitleg over de risico’s van diverse vormen van oogcorrectie – ook niet-chirurgische, zodat u een overwogen beslissing kunt maken. Het is bekend dat elke chirurgische ingreep een bepaalde kans op complicaties heeft. Dat geldt ook voor chirurgische oogcorrectie. Wat minder bekend is, is dat ook contactlenzen niet risico vrij zijn. Hieronder zetten we alles voor u op een rij.
Omdat complicaties en risico’s erg individueel zijn bepaald is het van groot belang dat u met uw eigen oogarts de informatie bespreekt zodat dit in het kader van uw persoonlijke situatie geplaatst kan worden.
Sommige complicaties kunnen aanleiding geven tot blijvende verslechtering of kwalitatieve vermindering van de gezichtsscherpte. Ter voorkoming van complicaties bij een behandeling zijn zorgvuldig vooronderzoek, kritische selectie door de oogarts, hoogwaardige omstandigheden gedurende de behandeling, ervaring van de oogarts en adequate nazorg zijn van groot belang om de risico’s te minimaliseren. Indien zich toch onverhoopt een complicatie voordoet is adequaat ingrijpen noodzakelijk voor een optimaal herstel.
Potentiële complicaties van behandelingen kunnen onderverdeeld worden in 3 groepen; tijdens de operatie (intra-operatief), na de operatie (postoperatief) en neveneffecten (verandering van de kwaliteit van de gezichtsscherpte).
Risico’s van het dragen van contactlenzen:
* Infectie (risico 0,29% – 0,98% per jaar, ernstiger bij extended wear contactlenzen)
* Op lange termijn verdunning en vertroebeling van het hoornvlies steunweefsel
* Beschadiging van het hoornvlies
* Allergie
* Kwetsbaarheid en functievermindering bij verlies
Neveneffecten:
* Afname van contrast en beeldscherpte afhankelijk van kwaliteit en reinheid van de lens en traanvocht
* Halo’s en glare bij nachtzicht ten gevolge van verplaatsen van de contactlens en vergroting van de pupil
Referenties:
Recente literatuur:
Laser in situ keratomileusis versus long-term
contact lens wear: Decision analysis
Hall T. McGee, MD, MS, William D. Mathers, MD
PURPOSE: To compare the risk for vision loss from laser in situ keratomileusis (LASIK) versus
long-term contact lens wear using decision analysis.
SETTING: Oregon Health & Science University, Portland, Oregon, USA.
METHODS: Based on previously published data, a decision tree was constructed using Markov
modeling to calculate the probability of vision loss from LASIK versus contact lenses over time.
An outcome variable, visual acuity–adjusted life-year (VALY), was defined to account for timing
and severity of vision loss. The VALYs were tallied over a 30-year simulation to determine whether
the risk for vision loss with contacts exceeded that with LASIK. Sensitivity analyses were performed
to test the effect of changes in key variables including probability of contact lens–related keratitis,
probability of ectasia after LASIK, and probability of early post-LASIK vision loss.
RESULTS: The model’s conclusions were highly sensitive to changes in several variables tested,
especially risk for post-LASIK ectasia, risk for early vision loss after LASIK, and risk for contact
lens–related keratitis (which correlated with type of lenses worn). Rigid gas-permeable lenses
were safer than LASIK in every analysis. The safety of LASIK exceeded that for daily-wear soft lenses
only when assumptions were most favorable to LASIK, whereas the safety of LASIK always
exceeded that for extended-wear lenses except when assumptions were least favorable to LASIK.
CONCLUSION: This decision analysis found that the risk for vision loss associated with LASIK and
with long-term contact lens wear might be closer than generally assumed.
J Cataract Refract Surg 2009; 35:1860–1867 Q 2009 ASCRS and ESCRS
=================================================================
Presented at: American Academy of Ophthalmology Meeting Paper, October 2014, Chicago, Ilinois (interim results).Marianne O. Price, PhD,David A. Price, BS,Frank A. Bucci Jr., MD,Daniel S. Durrie, MD,William I. Bond, MD, Francis W. Price Jr., MDManuscript no. 2016-436.
To assess patient satisfaction and perceived outcomes with different methods of refractive error correction through annual surveys administered over a 3-year period.
Prospective, longitudinal, parallel-group, multicenter survey.
A total of 1800 subjects, aged 18 to 60 years, who had LASIK or continued using contact lenses.
Twenty sites across the United States enrolled subjects who completed a study-specific baseline survey during a contact lens examination or while being evaluated as a candidate for LASIK. Links to follow-up surveys were emailed annually for 3 years. Between-group differences were assessed by analysis of variance, and associations were assessed by logistic multivariate regression.
Visual satisfaction.
Of 1800 subjects, 694 (39%) comprised the control group who continued contact lens wear, 819 (45%) wore contacts at baseline and had LASIK, and 287 (16%) wore glasses at baseline and had LASIK. Most contact lens users had worn them successfully ≥5 years. The proportion expressing strong satisfaction with their current vision correction method decreased from 63% at baseline to 54% at year 3 in the contact lens control group, whereas 88% of former contact lens wearers and 77% of former glasses wearers were strongly satisfied with LASIK at year 3. Patients 40 years of age or younger when they had LASIK were somewhat more likely to be strongly satisfied than older patients. LASIK significantly reduced difficulties with night driving and nighttime visual disturbances among former contact lens users and former glasses users. The proportion with dry eye symptoms at 1, 2, or 3 years after LASIK was not significantly increased relative to baseline contact lens wear but was significantly increased relative to baseline glasses use, consistent with many glasses users having tried and abandoned contact lenses because of latent dry eye problems. Compared with continued contact lens wear, LASIK significantly reduced the self-reported rates of eye infections, ulcers, and abrasions each year.
Compared with contact lens wear, current LASIK technology improved ease of night driving, did not significantly increase dry eye symptoms, and resulted in higher levels of satisfaction at 1, 2, and 3 years follow-up.
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Other References:
1. Barr JT. Contact lenses 2005. Contact Lens Spectrum 2006;
21(1): 26, 28, 30, 21–34. Available at http://www.clspectrum.
com/article.aspx?articleZ12913. Accessed July 21, 2009
2. Andrews M. A lighter, defter touch; years of refinement have
made laser eye surgery better than ever. U.S. News and World
Report, March 5, 2007; 59–61; posted online February 25,
2007. Available at: http://health.usnews.com/usnews/health/
articles/070225/5laser.htm. Accessed July 15, 2009
3. Hammond MD, MadiganWPJr, Bower KS. Refractive surgery in
the United States Army, 2000–2003. Ophthalmology 2005;
112:184–190
4. Cheng KH, Leung SL, Hoekman HW, Beekhuis WH,
Mulder PGH, Geerards AJM, Kijlstra A. Incidence of contactlens-
associated microbial keratitis and its related morbidity.
Lancet 1999; 354:181–185
1. Holden B et al. Microbial keratitis in prospective studies of extended wear with disposable hydrogel contact lenses. Cornea 2005;24(2):156-161
2. Morgan PB et al. Incidence of keratitis of varying severity among contact lens wearers. British. Journal of Ophthalmology 2005;89(4):430-436
3. Jalbert I et al. The corneal stroma during contact lens wear. Contractlens and anterior eye 2005; 28(1):3-12
Intraoperatief
* Decentratie Gedecentreerde behandelingen en ”central islands” kwamen in het verleden met de oudere laserapparatuur wel eens voor. Studies van voor 1989 meldden percentages variërend van 1,2% voor bijziendheid tot 6,8% voor verziend-astigmatisme correcties.
* Laserfailure: uitvallen van de apparatuur dient te worden voorkomen door noodvoorzieningen die continuïteit van de energietoevoer moet waarborgen. Vastlopen of anderszins defect raken van de scanners van de laserapparatuur is bij moderne apparatuur, adequaat onderhoud en goed doorlopen van de testprocedures zeer ongebruikelijk.
Omdat de ecximer laser technologie en de chirurgische technieken de laatste decennia enorm is verbeterd en doorontwikkeld, worden deze complicaties hedendaags weinig meer gezien.
De recente verbeteringen in de laser technologie, de zogenaamde wavefront en cornea topografie gestuurde customized ablations, beloven veel goeds voor het behandelen van deze problemen en verlichten van de visuele probleem deze complicaties met zich mee kunnen brengen.
Postoperatief
* Infectie.
Steriel werken, antibiotica, geregelde controle en hygiëne zijn belangrijk ter preventie.
* Vertraagde epitheelgenezing.
Zeldzaam. Vooral roken en slechte traankwaliteit beinvloeden het epitheelherstel negatief.
* Haze
Haze is littekenvorming op de plaats waar de laserbehandeling heeft plaatsgevonden: het grensvlak tussen epitheel/steunweefsel. Komt vooral voor bij hogere correcties. Kan spontaan optreden en onder invloed van UV licht. Jongere patienten zijn gevoeliger voor dit effect van UV licht en tonen dus soms meer haze of een toename van de haze indien vroegtijdig helemaal gestopt wordt met locale steoiden. Overigens verdwijnt haze ook vanzelf, maar soms pas na jaren. Sommige patienten hebben wel haze, maar hebben daar zelf helemaal geen klachten van. Deze vormen van haze worden dan ook niet behandeld.
Neveneffecten
Voorspelbaarheid van het resultaat
Kleine over- of onder correctie van de refractie afwijking is niet ongebruikelijk. Elk mens heeft zijn eigen herstelpatroon en dat kan van individu tot individu verschillen. Vandaar dat de computer voorspelde uitkomst niet altijd het verwachte resultaat geeft en soms overcorrigeert, soms ondercorrigeert. In dergelijke gevallen is aanvullende behandeling nodig en dit komt voor in 5-15% van de behandelingen.
Kwaliteit van zicht
Kwaliteit van zicht wordt voor een groot deel bepaald door het vermogen om beelden te kunnen onderscheiden van de achtergrond. Dit noemen we contrastgevoeligheid en dit is een maat voor hoe vaag beelden kunnen zijn voordat ze niet meer te onderscheiden zijn van de achtergrond. Beeldt u zich in om in de mist te rijden- hoe dikker de mist, hoe grijzer de objecten worden en hoe moeilijker het wordt om hun vormen te onderscheiden.
Er zijn de laatste jaren verschillende studies gedaan om het effect van excimer laserbehandeling op contrastgevoeligheid te bepalen. Alle studies hebben een vermindering in contrastgevoeligheid beschreven van 1 tot 6 maanden na de behandeling. Na 3-6 maanden wordt in het algemeen terugkeer van de preoperatieve metingen bereikt.
Bij een normaal verlopen behandeling is subjectieve rapportage van glare, vermindering van contrastgevoeligheid, en verminderd zicht in het donker gebruikelijk maar tijdelijk. Recente studies (“Straylight values one month after PRK and LASIK”, Beerthuizen, Landesz, Van den Berg, nog niet gepubliceerde data)) tonen aan dat strooilichtwaardes kort na behandeling (Lasik, LasekPRK) genormaliseerd zijn. Omdat complicaties het herstel hiervan negatief kan beinvloeden, raden wij u aan om dit met uw oogarts te bespreken.
Moderne technologie
Het ablatieprofiel verschilt per laserfabrikant. Bespreek met uw oogarts of dit een belangrijk punt is in uw geval. Enkele moderne lasersystemen zijn in staat om de zogenaamde asfericiteit van de cornea (kromming profiel van het hoornvlies) te behouden of zelfs te verbeteren. Deze asfericiteit is van groot belang. Patiënten wier pupillen groter zijn in het donker dan het gebied dat met de laser behandeld wordt, moeten zich realiseren dat dit een potentieel risico vormt voor problemen met het zien in het donker.
Maar niet iedereen met grote pupillen zal een slechtere gezichtsscherpte hebben in het donker. En ook mensen met kleine pupillen en een kleine afwijking kunnen problemen van halo’s en verminderd zicht in het donker ervaren. Op dit moment is het onmogelijk om van te voren te bepalen wie er wel of geen last van deze bijwerking zal krijgen.
Omdat er steeds meer onderzoek gedaan wordt op dit gebied, verwachten wij dat deze problemen steeds minder voor zullen komen en steeds beter te verhelpen zullen zijn.
Referenties:
1. Claringbold TV 2nd. Laser-assisted subepithelial keratectomy for the correction of myopia. J Cataract Refract Surg 2002 Jan;28(1):18-22
2. Azar DT, Ang RT, Lee JB, Kato T, Chen CC, Jain S, Gabison E, Abad JC. Laser subepithelial keratomileusis: electron microscopy and visual outcomes of flap photorefractive keratectomy. Curr Opin Ophthalmol 2001 Aug;12(4):323-8
3. Kornilovsky IM. Clinical results after subepithelial photorefractive keratectomy (LASEK). J Refract Surg 2001 Mar-Apr;17(2 Suppl):S222-3
4. Scerrati E. Laser in situ keratomileusis vs. laser epithelial keratomileusis (LASIK vs. LASEK). J Refract Surg 2001 Mar-Apr;17(2 Suppl):S219-21
5. Lee JB, Seong GJ, Lee JH, Seo KY, Lee YG, Kim EK. Comparison of laser epithelial keratomileusis and photorefractive keratectomy for low to moderate myopia. J Cataract Refract Surg 2001 Apr;27(4):565-70
Wanneer U voorafgaande aan uw behandeling een Informed Consent ondertekend hebt voor akkoord dan voldoet de kliniek aan de Wet op de Geneeskundige Behandelovereenkomst (WGBO). Een toestemmingsverklaring als deze ontslaat de behandelende kliniek echter geenszins van de medische verantwoordelijkheid zoals die gesteld is in de Nederlandse wetgeving.
De Kliniek doet al het mogelijke om u te informeren over de voordelen en risico’s, alsmede de alternatieven voor de behandeling, zoals het dragen van een bril of contactlenzen. De beslissing om te behandelen ligt uiteindelijk geheel bij u. De behandeling is niet beslist noodzakelijk, u bent, bij gebleken geschiktheid, vrij om er al dan niet voor te kiezen.
Velen zijn u al voorgegaan in het ondergaan van deze behandeling en hiermee geholpen. Vaak ziet met net zo goed als voorheen met een bril of contactlenzen, een enkele keer gaat men er zelfs beter door zien. Het blijft echter een medische ingreep, met daaraan verbonden risico’s, hoe nauwgezet en zorgvuldig de behandeling ook wordt verricht. Het is onmogelijk om in deze toestemmingsverklaring alle mogelijke complicaties van de behandeling te bespreken. Complicaties die slechts heel zelden voorkomen (minder dan 1 op de 10000) worden misschien niet genoemd.
Er is mij verteld dat:
– de oogarts van plan is om met behulp van een laserapparaat (femtosecond laser) een flapje te maken in het voorste gedeelte van mijn hoornvlies. Na omleggen van het flapje zal met behulp van een andere laser (excimer laser) van het blootliggende hoornvlies heel oppervlakkig een laagje worden verdampt voor de correctie van de oogsterkte, waarna het voorste deel, het flapje weer in de oorspronkelijke positie wordt teruggeplaatst. Dit flapje ligt niet op maar in het hoornvlies en zuigt zich onmiddellijk vast.
– het doel van de behandeling is het corrigeren van de bijziendheid of verziendheid en/of astigmatisme. De mate waarin dit behaald kan worden is afhankelijk van de meetwaarden van de ogen, het type behandeling en het genezingsproces en is vooraf met mij besproken.
– de Lasik behandeling geen oplossing is voor alle oogziekten of oogproblemen van nu en in de toekomst, maar het corrigeert alleen de oog-sterkte. Ik begrijp dat na de behandeling ik niet per definitie gevrijwaard blijf van het dragen van een bril of ander optisch hulpmiddel. De behandeling kan niet voorkomen dat er op latere leeftijd door ouderdom een leesbril nodig is.
Ik ben mij ervan bewust dat de volgende risico’s en complicaties bij LASIK kunnen optreden. Complicaties zijn meestal te behandelen op voorwaarde dat ze op tijd worden opgemerkt, door het nakomen van alle controle afspraken, die worden afgesproken. De kliniek heeft zich verplicht deze controles uit te voeren tot ten minste een jaar na de ingreep. De eerste weken na de behandeling zijn de ogen kwetsbaar en u dient dus niet in uw ogen te wrijven.
Welke complicaties kunnen er optreden?
Deze worden verdeeld in a. tijdelijke complicaties en bijverschijnselen en b. in blijvende complicaties.
a. Tijdelijk:
– Na de behandeling kunnen de ogen tijdelijk droger worden. Dit kan een periode van enkele weken tot maanden aanhouden. Gedurende die periode moet er vervolgens met kunsttranen gedruppeld worden om het ongemak op te lossen. Hiermee wordt ook oppervlakkige uitdrogingsschade aan het oog voorkomen. De meeste klinieken hanteren een preventief protocol met kunsttranen druppelen na de ingreep. Had u voor de ingreep al droge ogen, waardoor bijvoorbeeld contactlenzen niet meer gedragen konden worden, dan zult u na de ingreep wat dit betreft intensief moeten worden begeleid.
– Over of onder-correctie, wat inhoudt dat er een kleine sterkte (in de regel tot + of – 1) als reststerkte overblijft. Bij een hoge sterkte voor de behandeling ( S -6.00 of hoger en eigenlijk bij alle behandelingen voor verziendheid) is de kans op zo’n reststerkte groter dan bij een lagere sterkte voor de behandeling (kleiner dan S -6.00). Een reststerkte is in de meeste gevallen prima na te behandelen. In de regel kan dit na 6 maanden, als het zicht en de sterkte volledig stabiel zijn.
– Vlak na de behandeling is er kans op toename van de lichtgevoeligheid, schitteringen en wisselingen in de gezichtsscherpte. De verschijnselen kunnen in de herstelperiode van 1 tot 3 maanden aanhouden en kunnen, slechts zelden, langer aanhouden.
– Direct na de behandeling zijn vaak kleine bloedinkjes onder het slijmvlies van het oog (op het oogwit) zichtbaar. Deze verdwijnen vanzelf. Op de dag van de behandeling is het zicht eerst nog mistig (door vocht in het flapje) hetgeen gemiddeld na 12 uur verdwijnt. Heel zelden duurt deze mistigheid langer. De meeste klinieken hanteren een standaard druppelprotocol voor na de behandeling (met een combinatiedruppel met antibiotica en ontstekingsremmers) om dit te voorkomen en/of te behandelen.
b. Blijvende en/of ernstige complicaties:
– Optische bijverschijnselen, zoals het ’s nachts zien van stervorming of halo’s rondom lichtbronnen. Dit is bijvoorbeeld op de eerste dag altijd te zien, verdwijnen overdag, maar houden soms, in het donker of schemering aan gedurende de herstelperiode van 1 tot 3 maanden. Ze kunnen, heel zelden, permanent zijn. Dit is vooral bij uitzonderlijk grote pupillen het geval ( > 6 mm). De behandeling kan bestaan uit het vergroten van de optische zone met een laser her-behandeling.
– Blijvend droge ogen na de behandeling. Zelden kan het voorkomen dat het herstel van gevoel aan het oppervlak van het hoornvlies langer dan het gemiddelde (6 maanden) duurt en dat er na 12 maanden nog sprake is van droogheidsklachten met of ondanks eenvoudige behandeling met kunsttranen. Er moet ook rekening gehouden worden met het spontaan kunnen optreden van droge ogen, zijnde een van de meest voorkomende oogkwalen. De complicatie is goed te behandelen met speciale oogdruppels, afsluiting van de traanafvoer, bandage-lenzen en behandeling van de ooglidrandjes, waar vaak de oorzaak van het probleem zit. De frequentie van echt blijvend droge ogen na een Lasik behandeling bij kandidaten, die vooraf met een goede traanfilmkwaliteit waren getest, wordt geschat op minder dan 1 op 10000.
– Infecties. Uitwendige bindvlies- of hoornvliesinfectie, die niet met de standaard antibiotica worden voorkomen of genezen. Door tijdig te reageren op deze complicatie bij de eerste controles na 1 dag en 1 week, of wanneer u zich tussendoor meldt met klachten, is dit in de meeste gevallen goed behandelbaar met andere medicatie met tijdelijke beperkte schade.
– Postoperatieve flap verschuivingen en/of plooien of debris, vuil (vaak ooglidrandtalg) of epitheelingroei onder de flap. Hoewel de kans hierop bij Femtosecond Lasik veel kleiner is dan bij gewone Lasik met een mechanisch werkend keratoom kan het door uitwendig trauma, zelfs door flink oogwrijven toch onstaan, vooral op de eerste dag. Met uitzondering van debris en epitheelingroei onder de flap wordt het direct door u ontdekt door pijn en slecht zicht. Het is goed te behandelen indien u zich ook zo snel mogelijk hiermee meldt in de behandelende kliniek. Hier heeft men ervaring met het opnieuw spoelen en vlak leggen van het flapje met genezing onder een bandagelens, wat ook geldt voor het debris of epitheelingroei onder de flap. Dit geneest doorgaans zonder restverschijnselen.
– Steriele ontsteking onder het flapje in de interface (diffuse laminaire keratitis) met klachten van toenemende lichtgevoeligheid, kan in de eerste dagen of weken na de behandeling optreden. Wordt behandeld met ontstekingsremmende druppels, wordt de laatste jaren steeds minder gezien, vermoedelijk omdat de standaard behandeling na de ingreep dit voorkomt. Ook dit geneest doorgaans na behandeling zonder restverschijnselen. Recent wordt bij Femtosecond Lasik dit risico ook geschat op minder dan 1 op 10000.
– Het kan voorkomen dat de Femtosecond laser of de Excimer Laser niet naar behoren functioneert, waardoor de operatie gestaakt moet worden. De operatie kan dan later gewoon opnieuw worden gedaan of worden afgemaakt.
– Vaatafsluitingen of bloedingen in het oog. Tot op heden in Nederland nog niet gemeld.
– Netvliesloslating bij kandidaten met een hoge bijziendheid. De Lasik behandeling veranderd niets aan de lengte van het oog en kandidaten met een hoge bijziendheid door een hoge aslengte lopen ook een risico op spontane netvliesloslating of een loslating bij een gering trauma voor of na de Lasik behandeling. Een relatie met de Lasik behandeling is in de internationale literatuur niet bewezen of aannemelijk gemaakt noch in Nederland gerapporteerd.
– Hoornvlies ectasie. Dit is een progressieve vervorming van het hoornvlies juist langer na de behandeling. Er is ervaring met deze complicatie zoals deze vroeger wel eens optrad na Lasik met mechanisch keratoom en dus dikkere flappen en bij behandelingen bij kandidaten met eigenlijk, volgens de huidige normen een te dun hoornvlies. De complicaties trad dan na één of enkele jaren na de behandeling op. Essentieel is dat door moderne beeldvorming van de anatomie van het hoornvlies geen kandidaten worden behandeld die al in aanleg risico lopen op spontane vervorming van het hoornvlies (keratoconus) of risico lopen op de hoornvlies ectasie als gevolg van de Lasik behandeling. Net zo belangrijk is dat ook gezonde hoornvliezen niet worden behandeld buiten de consensus in de zin van te hoge sterktes behandelen of sterktes behandelen die gezien de individuele dikte van uw hoornvlies niet kunnen. Ondanks allerlei voorzorgsmaatregelen zou het risico 1 op de 10.000 kunnen bedragen hoewel onze landelijke inventarisatie van dit risico veel lager uitkomt voor Femtosecond Lasik. Het betreft eigenlijk een complicatie die door uitsluiting van te jonge kandidaten (<18 jaar), goed vooronderzoek en een kwalitatief goede behandeling van uw kliniek in hoge mate kan worden voorkomen.
– Neuropatische Pijn aan 1 of twee ogen. Uiterst zeldzaam, maar ernstige complicatie na Femtosecond Lasik, waarbij er pijn achter/rondom het oog wordt ervaren, typisch niet direct of in de eerste maanden na de ingreep, maar pas later ontstaan. Er zijn geen oogheelkundige afwijkingen aan de ogen te constateren en de aandoening reageert niet op verdovende oogdruppels of andere oogdruppels. Er zijn in Nederland slechts enkele patiënten met deze complicatie bekend, niet alleen door Femtosecond Lasik, maar ook door gewone Lasik en Lasek. Het voorkomen in Nederland wordt geschat op zeker minder dan 1 op 10.000. In Spanje zijn grotere aantallen patiënten met Femtosecond Lasik behandeld dan in Nederland en daar komt men op een risico inschatting van 1 op 55.000.
Wanneer u een toestemmingsverklaring ondertekent verklaart u
– toestemming te geven één of beide ogen te laten behandelen middels Femtosecond Lasik.
– zo volledig mogelijk geïnformeerd te zijn over de behandeling en over de mogelijkheden en onmogelijkheden. Voor en nadelen, alsmede alternatieve behandelmogelijkheden zijn besproken. U heeft de noodzaak van deze behandeling goed overwogen. U bent volledig op de hoogte gebracht van de risico’s die aan deze ingreep zijn verbonden.
– aanvullende informatie te hebben gehad uit deze schriftelijke toestemmingsverklaring, andere schriftelijke en mondelinge informatie van de kliniek, één van de oogartsen of optometristen van de kliniek alsmede andere informatiebronnen zoals op deze site. U heeft gelegenheid gehad tot het stellen van vragen en voldoende antwoord gekregen op alle vragen naar aanleiding hiervan.
– te erkennen dat niemand u enige garantie heeft gegeven over de te behalen resultaten
– dat u begrijpt dat er een kans bestaat op één of meerdere complicaties
– te hebben begrepen dat na de behandeling periodieke controles worden verricht
– dat u toestemming heeft gegeven dat alle verslaglegging (op schrift, video, beeldmateriaal) met in acht neming van zorgvuldigheid en anonimiteit, gebruikt kan worden voor onderwijs, onderzoek of training van anderen (oogartsen en paramedisch personeel) of lezingen/ presentaties wereldwijd. Ook kan de behandelend oogarts anonieme gegevens over de operatie, nabehandeling en resultaten gebruiken voor evaluatie, bv voor verbetering van de kwaliteit van de behandelingen.
– op de hoogte te zijn van de algemene voorwaarden van de kliniek en begrijpt u dat u zelf verantwoordelijk bent voor de kosten van de behandeling.
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Intraoperatief
FemtoSecond laser gerelateerd
De complicaties bij het maken van een flap, waarbij de femtosecond laser eigenlijk alleen de voorbereiding doet, zijn uiterst zeldzaam en zonder gevolgen indien de procedure wordt afgebroken. Groot voordeel van deze procedure t.o.v. het mechanisch snijden met de microtoom met een mes (zie onder) is dat de dokter meekijkt met wat de laser doet, kan zien dat het goed gaat, en dat de laser een grotere precisie heeft tijdens het snijden, omdat er geen mechanische invloed is op het hoornvlies tijdens het maken van de sneevlakken. Bij verlies van vacuum kan ook opnieuw vacuum worden aangelegd en de procedure herhaald worden. Ook bij het later losmaken van het flapje kan theoretisch het flapje beschadigd worden. Ook hier geldt dat dan de procedure afgebroken kan worden, zodat er verder geen schade ontstaat. Indien de procedure wordt afgebroken is eigenlijk een dag later het oog alweer genezen en er niets veranderd aan het gezichtsvermogen.
Microkeratoom gerelateerd
Het voorkomen van dit soort complicaties is in het algemeen zeldzaam. Als er een optreedt, dan zullen de meeste chirurgen niet doorgaan met de laserbehandeling op dat moment. Onregelmatig snijden van de flap leidt zelden tot permanente schade van de gezichtsscherpte, en meestal zal de oogarts de procedure beëindigen en de uiteindelijke behandeling uitstellen tot een paar maanden erna. Het voorkomen van alle microkeratoom gerelateerde complicaties beschreven in de literatuur varieert van 0,7 tot 11,8%, maar studies met de grootse onderzoeksgroep laten een complicatie percentage van 2,2% of minder zien. Het is erg afhankelijk van de ervaring van de oogarts.
Excimer LASER Abalatie gerelateerd
Zie PRK/Lasek/Epilasik.
Postoperatief
Complicaties na Lasik:
* Striae zijn oneffenheden en plooien in de lamellaire cornea flap.
* Epitheelingroei is ingroei in het snijvlak van oppervlaktecellen van het hoornvlies
* Diffuse lamellaire keratitis is een steriele ontsteking van het snijvlak
* Infectie. Steriel werken, antibiotica, geregelde controle en hygiëne zijn belangrijk ter preventie.
* De hechting van de dunne femtosecond lamellaire hoornvliesflap is de eerste dag op basis van constructie en dikte behoorlijk stevig, de tweede dag extra geseald door herstel van het oppervlakkige cel-laagje, Geleidelijk zal daarna de stevigheid door vergroeiing aan de onderlaag nog verder toenemen. Door de constructie van de flap (geen contactlens, maar meer een putdeksel) is traumatische verschuiving minder waarschijnlijk dan bij een mechanische keratoomflap.
* Neuralgische pijn: dit is een zeer zeldzame complicatie (in NL voor zover bekend 1 of 2 gevallen sinds dat Lasik behandelingen in Nederland gedaan worden (1998), jaarlijkse schatting Lasik procedures 10000/per jaar (2015))
* Cornea ectasie (met speciale meetapparatuur toenemende vervorming van het hoornvlies): dit werd wel gezien bij microkeratoomflappen in het verleden, maar het is niet zeker of dit nog kan voorkomen met de huidige behandelmethodes en screeningsprotocollen en nieuwe normen voor veiligheidsmarges.
Neveneffecten
Zie PRK/Lasek/Epilasik : Neveneffecten
Droge ogen
Patiënten zullen in meer of mindere mate symptomen van droge ogen ervaren in de postoperatieve fase, hetgeen tot 6 maanden kan aanhouden en waarop geanticipeerd wordt doordat iedereen naar behoefte kunstranen dient te gebruiken. Maar mocht u al bekend zijn met droge ogen, dan zal er met name bij Lasik een verhoogde kans bestaan op het langdurig of soms zelfs blijvende droge ogen en behoefte aan kunstranen. Om die reden is slechte traanfilmkwaliteit een reden tot terughoudendheid met Lasik. In uitzonderlijke gevallen kunnen droge ogen ook blijven bestaan indien vooraf de traanfilmkwaliteit geheel normaal was. Dit is echter uiterst zeldzaam.
Referenties:
Recente literatuur betreffende FS Lasik:
William J. Dupps Jr., MD, PhD
Journal Of Cataract and Refractive Surgery Aug 2016 Volume 42, Issue 8, Pages 1109–1110
More than 16 million laser in situ keratomileusis (LASIK) surgeries have been performed globally in the procedure’s 25-year history.1 By all measures, LASIK is not only one of the most common surgical procedures performed, it is also one of the most successful.
In this month’s issue of the JCRS, Sandoval et al. present a major review of the recent published literature on LASIK outcomes (pages 1224–1234). As perhaps the largest aggregation of data of its kind, it is one of the most important assessments of LASIK safety and effectiveness in the literature. It is also the most up-to-date, and for those readers who perform LASIK, I recommend putting it at the top of your summer reading list. This review presents an excellent opportunity for surgeons to assess their own outcomes in the context of the worldwide experience of LASIK. For those of us who do not already have a system in place for tracking LASIK outcomes, it provides an impetus to start. Through the strength of large numbers and a systematic approach to reviewing the literature, the authors leverage the variety of treatment platforms, ablation strategies, refractive errors, and some interesting nonclinical study characteristics to make useful observations, pointing not only to what makes LASIK successful but also to how it can be improved.
The review encompassed a global sampling of published outcomes for primary LASIK procedures published from January 2008 to August 2015. Search terms in PubMed produced candidate articles that were down-selected to 97 relevant articles based on a focus on primary LASIK in previously unoperated eyes. These references were then graded according to 2 systems for evaluating the level of clinical evidence. Clinical results were then abstracted and analyzed, and the results were compared with reference data from publicly available U.S. Food and Drug Administration (FDA) studies, including the FDA-initiated Patient-Reported Outcomes with LASIK (PROWL) studies that included a total of 534 patients. The 97 references produced a total of 67 893 eyes for analysis. Eyes that were treated for myopic astigmatism (97.3%) dominated the sample; however, all qualifying references on hyperopic and mixed astigmatism results were also analyzed.
The results suggest a high level of safety and effectiveness, with outcomes that appear to be better than those reported for earlier laser refractive surgery systems. The overall rate of loss of 2 or more lines of corrected distance visual acuity (CDVA) was 0.61%, less than one half the number of eyes that had an increase in CDVA of 2 lines or more (1.45%). The percentage of eyes achieving an uncorrected distance visual acuity (UDVA) of 20/20 or better was 90.8%, and 99.5% achieved 20/40 or better. The spherical equivalent refraction was within ±0.50 diopter (D) of the target in 90.9% of eyes and within ±1.00 D of the target in 98.6% of eyes. In the much smaller subset of studies reporting patient satisfaction, 1.2% of patients (129/9726) were dissatisfied with LASIK. Newer wavefront-guided, wavefront-optimized, and topography-guided ablation modes were associated with a UDVA nearly a full line better than in eyes treated with conventional ablation, and no significant differences were observed between the wavefront-guided, wavefront-optimized, and topography-guided modalities.
Some nonclinical data analyzed by the authors lead to interesting observations about the nature of published clinical research related to LASIK. In 34% of the articles, 1 or more authors reported a financial interest related to the laser or the procedure. However, there was no relationship between presence of a conflict of interest and the “impression” projected by the article’s authors about LASIK. This subjectively graded impression, defined as positive, negative, or neutral, was positive in 73% of studies and no studies projected a negative impression of LASIK. Similarly, there were no significant differences in impression (positive versus neutral) as a function of the study quality score. Although these results suggest that financial conflicts of interest were not linked to the tone of statements made about LASIK, the absence of negative statements limits the resolution of this comparison. The lack of negative impressions could be explained by a tendency in writing to emphasize positive study outcomes; however, they might also reflect the legitimately excellent outcomes observed in most studies.
Where is improvement needed, and how can we do better? More thorough documentation of safety and effectiveness metrics in clinical research is critical. Surprisingly, only 64% of the included studies provided data on gain or loss of CDVA, a core safety metric for refractive surgery. The adoption of consensus-based standardized graphs for reporting refractive surgery results by several major journals should address this shortcoming in the literature and support comparability of outcomes.2, 3, 4, 5 Hyperopic corrections, although representing less than 3% of the eyes in this review (1738 of 67 893 eyes), showed a higher percentage of eyes with a loss of 2 or more lines of CDVA compared with myopic treatments (2.13% versus 0.95%). Furthermore, the only groups losing 2 or more lines of CDVA at rates higher than the FDA’s nominal safety threshold of 5% were hyperopic corrections over 5.00 D and astigmatic corrections between 1.00 D and 4.00 D. The greater sensitivity of visual optics to centration of hyperopic ablation profiles and to torsional alignment of astigmatic treatments increases the risk for induced aberrations and probably accounts for the majority of lost CDVA in such cases. Advances in technologies for eye tracking, visualization of torsional alignment, biomechanical measurement, treatment planning with nomograms or simulations, and continued research on optimum centration of laser refractive treatments all have the potential to improve outcomes in these and other challenging cases. Another confounder of outcomes in hyperopia and higher astigmatism is refractive regression, and the use of corneal crosslinking as an adjunct to laser treatment6 offers an exciting emerging option for controlling refractive outcomes.
Laser in situ keratomileusis is a major success story. Throughout its 25-year history, LASIK has provided a remarkably safe and effective mechanism for refractive surgeons to positively affect millions of lives. Through thoughtful collaboration between clinicians, patients, scientists, industry, and regulators, the safety and predictability of LASIK and other forms of refractive correction will reach new heights.
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Journal Of Cataract and Refractive Surgery Dec 2016 Vol 42(12) pp 1797-1803
Short-term Complications of Femtosecond-Laser-Assisted Laser in situ Keratomileusis Cuts: Review of 1210 consecutive Cases.
Thomas Kohnen, MD, PhD, FEBO , Luisa Schwarz, MD ,Matthias Remy, MD, Mehdi Shajari, MDFrom the Department of Ophthalmology, Goethe-University, Frankfurt, Germany
To evaluate short-term complications after femtosecond laser cuts for laser in situ keratomileusis (LASIK).
Department of Ophthalmology, Goethe University, Frankfurt, Germany.
Retrospective consecutive case series.
Consecutive femtosecond laser cuts (1210 cuts in 624 patients) from LASIK performed with the Intralase FS60 between 2006 and 2014 were analyzed. The analysis looked at intraoperative and postoperative complications at 1 day, 1 week, and 1 month and factors with potential impact on the complication rate, such as ablation depth.
No irregular, incomplete, or thin flaps, buttonholes, gas breakthrough, or free caps were observed. Intraoperatively, incomplete side cuts were observed in 4 cases (0.3%). Three of the 4 occurred during the first year of femtosecond laser usage and were explained by a software problem. Epithelial defects, limbal bleeding, and decentered flaps without negative impact on outcome were observed in 45 (3.7%), 12 (1.0%), and 5 (0.4%) eyes, respectively, on the treatment date. Diffuse lamellar keratitis (DLK) stage 1 was observed in 69 (5.7%), 36 (3.0%), and 3 (0.2%) eyes at 1 day, 1 week, and 1 month, respectively, and DLK stage 2 in 20 (1.7%), 6 (0.5%), and 2 (0.2%) eyes, respectively. An increase in total ablation depth resulted in a higher incidence of microstriae (P < .01 at 1 day, 1 week, and 1 month). An increase in the optical zone resulted in a significantly higher incidence of epithelial ingrowth at 1 day and 1 week (P < .01).
No major cut-related complications were observed. The femtosecond laser is a safe option to create a flap in LASIK.
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Presented in part at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Diego, California, USA, April 2015.Helga P. Sandoval, MD, MSCR, Eric D. Donnenfeld, MD, Thomas Kohnen, MD, PhD, FEBO, Richard L. Lindstrom, MD, Richard Potvin, OD, David M. Tremblay, MD, Kerry D. Solomon, MDFrom Carolina Eyecare Physicians, LLC (Sandoval, Solomon, Tremblay), Mount Pleasant, South Carolina, Ophthalmic Consultants of Long Island (Donnenfeld), Long Island, New York, Minnesota Eye Consultants, P.A. (Lindstrom), Minneapolis, Minnesota, and Science in Vision (Potvin), Akron, New York, USA; the Department of Ophthalmology (Kohnen), Goethe University, Frankfurt, GermanyLaser in situ keratomileusis (LASIK) articles published between 2008 and 2015 that contain clinical outcomes data were reviewed and graded for quality, impression, and potential bias. All 97 relevant articles (representing 67 893 eyes) provided a positive or neutral impression of LASIK. Industry bias was not evident. The aggregate loss of 2 or more lines of corrected distance visual acuity was 0.61% (359/58 653). The overall percentage of eyes with uncorrected distance visual acuity better than 20/40 was 99.5% (59 503/59 825). The spherical equivalent refraction was within ±1.0 diopter (D) of the target refraction in 98.6% (59 476/60 329) of eyes, with 90.9% (59 954/65 974) within ±0.5 D. In studies reporting patient satisfaction, 1.2% (129/9726) of patients were dissatisfied with LASIK. Aggregate outcomes appear better than those reported in summaries of the safety and effectiveness of earlier laser refractive surgery systems approved by the U.S. Food and Drug Administration. Modern results support the safety, efficacy, and patient satisfaction of the procedure.
Laser in situ keratomileusis (LASIK) is one of the most commonly performed elective procedures in the United States. To date, more than 16 million LASIK procedures have been performed globally.1 Laser in situ keratomileusis was introduced by Pallikaris et al.2 in 1990. The excimer laser was approved by the U.S. Food and Drug Administration (FDA) in 1995, and LASIK was approved by the FDA in 1999.
Patient selection, an important factor in LASIK success, has improved greatly over the past 2 decades. Candidacy criteria include sufficient corneal bed thickness following flap formation and corneal ablation, a healthy tear film, and the presence of a regular corneal topography.3 Results in numerous studies have shown good efficacy, safety, stability, and predictability in treating both myopia and hyperopia with or without astigmatism.4, 5, 6, 7
An analysis of early outcomes data from 1994 to 20048 documented the complications associated with LASIK. Most were related to the use of early microkeratomes, excimer laser ablation profiles, and surgeon experience. An FDA panel meeting was held in 2008 in response to 140 dissatisfied LASIK patients to reevaluate the procedure. As a result of the panel, a comprehensive literature review of patient satisfaction was conducted in 2008. Results showed high patient satisfaction; approximately 95% of patients were satisfied with their visual outcome after myopic and hyperopic LASIK.1
In October 2009, the FDA instituted the LASIK Quality of Life Collaboration Project. Two major components of this project were the first FDA-initiated clinical studies of LASIK, the Patient Reported Outcomes with LASIK (PROWL) studies.A PROWL-1 and PROWL-2 were primarily concerned with the development and testing of a validated questionnaire to capture patient’s perceptions of LASIK and the percentage of patients having difficulty after surgery. However, by necessity, the studies also included clinical outcomes data. The PROWL-1 trial was conducted by a single Naval refractive surgeon, and the PROWL-2 trial was conducted by 5 refractive surgeons in clinical practice. Industry and organized ophthalmology were not involved in the study design or the evaluation of data.
The results of the PROWL-1 and PROWL-2 trials are considered the most definitive evaluation of the efficacy of LASIK and will be highlighted and compared with studies in the peer-reviewed literature. The results of the LASIK Quality of Life Collaboration Project were presented at the American Academy of Ophthalmology in 2014 by Malvina Eydelman, MD, Director, Division of Ophthalmic and Ear, Nose and Throat Devices of the FDA.B Questionnaire components included vision quality, symptoms of aberration (glare, halos, starbursts, ghosting), work productivity, dry-eye symptoms, depressive/anxiety symptoms, optimism, coping, expectations prior to surgery, satisfaction after surgery, and social desirability. A total of 534 patients had LASIK surgery and were followed for 6 months postoperatively.
The purpose of this review was to summarize the objective clinical outcomes of LASIK reported in the peer-reviewed literature between 2008 and 2015 and to compare these data with historical summaries of the safety and effectiveness associated with laser systems approved for use by the FDA, as well as with the results of the PROWL studies in which comparative data were available.
Material and Methods.
A search for relevant articles related to the clinical outcomes of standard LASIK was conducted using the online search engine PubMed Central, a free full-text archive of biomedical and life-science journal literature at the U.S. National Institutes of Health’s National Library of Medicine.C The search was limited to articles published from January 2008 to August 2015. Three keywords were used to search for articles: “LASIK,” “laser in situ keratomileusis,” and “laser vision correction.” Of interest were articles that included human clinical studies, reported primary procedures, and included visual and refractive outcomes. Articles related to retreatment, presbyopia treatment, or treatment in eyes that had previous corneal surgery (eg, radial keratometry) or any intraocular surgery (eg, cataract surgery) were not included.
Abstracts from the identified articles were reviewed to determine whether they met the above criteria. Full copies of all potentially relevant articles were then obtained for more detailed review. Non-English articles were translated with the collaboration of the American Society of Cataract and Refractive Surgery. After article review, relevant articles were specifically identified. The references of the reviewed articles were examined to identify potential articles that might have been missed.
All relevant articles were rated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE)D as well as the University of Michigan Practice Guidelines.E The GRADE scoring considered study size and financial interest disclosures in evaluating the quality of the evidence. The Michigan guidelines included considerations such as whether the study was prospective or retrospective, randomized or nonrandomized. The financial interest categorization does not imply that sponsored studies are lower quality than independent research but is included to acknowledge the potential for bias in clinical outcomes. An article was rated “high” if it fulfilled both the A criteria in the University of Michigan Practice Guidelines and the definition of “high” in the GRADE system. Similarly, B and “moderate,” C and “low,” and D and “very low” from the University of Michigan Practice Guidelines and the GRADE rating systems, respectively, were also used to rate each article. The final grade was the lower rank from the 2 grading systems.
Additional characteristics of relevant articles were recorded. Each was subjectively reviewed for the impression they left with the reader—“positive,” “neutral,” or “negative”—with regard to the clinical outcomes of LASIK. Financial interest was specifically identified.
The clinical outcomes in each article were then summarized. If results from different test groups were included in an article, the groups were analyzed separately. Characteristics such as the nature of the treatment (ie, myopia, astigmatism, hyperopia), the treatment profile (eg, conventional, wavefront guided, wavefront optimized, topography guided), the laser system, and the flap creation method were recorded. Relevant preoperative and postoperative clinical outcomes were recorded when provided. Of most interest were the refractive data, the uncorrected and corrected visual acuities, and the loss or gain of lines of corrected acuity. If reported, complications and satisfaction data were also tabulated.
The aggregate data from these articles were compared with historical data from several available summaries of safety and effectiveness for various laser systems when they were approved for use by the FDA, including the Summit Apex laser system,F the Visx Star S2 laser system,G and the Wavelight Allegretto laser system,H as well as with the results of the PROWL studies.
Each article was catalogued in an Access database (Microsoft Corp.) specifically designed for the purpose. Clinical data associated with each subgroup in an article were recorded in the same database. Because the raw data for all articles were not available, the analyses were limited to comparing means of means (eg, mean postoperative refractive error by group) or critical values (eg, percentage of 20/20 uncorrected visual acuity by group).
Statistical analysis of continuous variables was performed using analysis of variance (ANOVA), and categorical data were analyzed using appropriate nonparametric tests. Statistical significance was set at a P value of 0.05.
Literature Review.
The PubMed search yielded 4474 potential articles, with 2189 related to the term “LASIK,” 2007 related to the term “laser in situ keratomileusis,” and 269 related to the term “laser vision correction.” The subsequent abstract review reduced the number of potentially relevant references to 213. A review of each of these identified 97 that were considered relevant.
Table 1 summarizes the relevant articles by the impression they provided and the quality of the study on which they were based. There were no peer-reviewed articles with a negative impression of LASIK; 73% (71/97) of studies had a positive impression and 27% (26/97), a neutral impression. A comparison of the ratio of high/moderate to low/very low studies by impression showed that there was no statistically significant difference in subjective impression by study quality (P = .38, 2-tailed Fisher exact test).
| Impression | Study Quality | ||||
|---|---|---|---|---|---|
| High | Moderate | Low | Very Low | Total | |
| Positive | 42 | 25 | 4 | — | 71 |
| Neutral | 6 | 17 | 3 | — | 26 |
In 34% (33/97) of the articles, the authors reported a financial interest relative to the laser or procedure being tested; in 55% (53/97), the authors were independent; in 5% (5/97), neither an affiliation nor a financial interest was stated; and in 6% (6/97), there were non-company sources of funding. Comparing the ratio of positive studies to neutral studies by financial interest (affiliated or not affiliated) showed no statistically significant difference in results (P = .49, 1-tailed Fisher exact test).
Clinical data specific to LASIK study arms in each of the articles were tabulated. Comparative study groups using other technology (ie, implanted intraocular lenses, surface ablation) were not included. Of the 97 articles, 58 included only 1 study arm; 5 of these articles included data from several timepoints but only the latest follow-up time was included in the analysis. The remaining articles included 2 (33 studies), 3 (5 studies), and 4 (1 study) study arms. A total of 143 study arms, representing 67 893 eyes, were available for specific analysis of outcomes. Study arms varied significantly in size, from a maximum of 32 569 eyes (48% of the total) to a minimum of 10 eyes. Study arms were categorized by size for comparative purposes; large study arms had 1000 or more eyes (8 study arms); medium study arms, 100 to 999 eyes (48 study arms); and small study arms, fewer than 100 eyes (87 study arms). Table 2 summarizes the articles by the nature of the planned correction and the study arm size. Correction of myopic astigmatism accounted for 90% (128/143) of all articles and 97.3% (66 047/67 893) of all eyes. To simplify, categorization in this analysis is by article and 143 articles were identified based on the above criteria.
| Preoperative Prescription | Study Arm Size | ||||
|---|---|---|---|---|---|
| Total | Large | Medium | Small | Eyes | |
| Myopia (with/without astigmatism) | 128 | 8 | 44 | 76 | 66 047 |
| Hyperopia (with/without astigmatism) | 12 | — | 4 | 8 | 1738 |
| Mixed astigmatism | 1 | — | — | 1 | 48 |
| Unspecified | 2 | — | — | 2 | 60 |
A large number of excimer laser systems and microkeratomes are represented in the data collected. Specific laser system data were not always available, but when the system was unspecified, it was grouped by laser manufacturer or family (eg, Allegretto). Using this categorization, 30 laser systems were identified. A similar methodology was used for the microkeratomes, including femtosecond laser systems. A total of 26 systems were identified. Table 3 contains the 7 most common excimer laser systems and the 6 most common microkeratome and femtosecond laser systems. These specific combinations represented 40% (57/143) of the articles and 85% (58 099/67 893) of the eyes in the data set.
| Laser Group | Total Articles (Eyes) | Moria Evo3 One Use-Plus | Ziemer LDV | Intralase | Moria M2 | Visumax | Ziemer LDV Crystal Line | Multiple | Other |
|---|---|---|---|---|---|---|---|---|---|
| Visx Star S4 | 31 (38 199) | 2 (33 569) | — | 10 (2037) | 4 (1154) | — | — | 3 (399) | 12 (1040) |
| Tecnolas 217z | 27 (1873) | — | — | — | — | — | — | 3 (389) | 24 (1484) |
| Allegretto Eye-Q 400 | 20 (6222) | — | — | 8 (2797) | — | 2 (426) | 1 (887) | 3 (1699) | 6 (405) |
| Schwind Amaris | 14 (13 082) | — | 7 (11 230) | 3 (133) | 1 (31) | — | 1 (1280) | 1 (358) | 1 (50) |
| Schwind Esiris | 8 (525) | — | — | 1 (72) | 1 (72) | — | — | — | 6 (381) |
| Mel 80 | 6 (1557) | — | — | — | — | 5 (1453) | — | — | 1 (104) |
| Nidek CXIII | 5 (731) | — | — | — | 1 (74) | — | — | — | 4 (657) |
| Other (eg, unspecified) | 31 (5712) | — | 1 (0) | — | 8 (0) | 2 (282) | — | 2 (82) | 18 (4642) |
| Total | — | 2 (33 769) | 8 (11 230) | 22 (5059) | 15 (1331) | 9 (2161) | 2 (2653) | 12 (2927) | 72 (8763) |
The laser systems were used to create a variety of profiles in the eye. The profiles were categorized as “conventional” for standard treatment; “advanced treatment profile” for treatments that involved wavefront-guided, wavefront-optimized, or topography-guided treatments; and “other” when the treatment was neither conventional nor advanced or the ablation profile was not specifically identified. Table 4 summarizes the articles by ablation profile.
| Treatment Category | Treatment Type | Number of Articles | Eyes |
|---|---|---|---|
| Conventional | Conventional | 26 | 2492 |
| Advanced | Wavefront guided | 49 | 39 880 |
| Wavefront optimized | 20 | 4512 | |
| Topography guided | 5 | 2959 | |
| Other | Other | 34 | 15 308 |
| Not specified | 9 | 2742 | |
| Total | — | 143 | 67 893 |
The loss or gain of corrected distance visual acuity (CDVA) was reported in 64% of the articles (92/143), comprising 86.4% of all eyes (58 653/67 893). In most eyes, there was no measured change in CDVA. In aggregate, more than twice as many eyes gained 2 or more lines of CDVA (1.45%, 853/58 653) as lost 2 or more lines (0.61%, 359/58 653). In the PROWL-1 study, 1/450 eyes (0.2%) lost 2 lines of visual acuity and had a CDVA of 20/25. In the PROWL-2 study, 0/540 eyes lost 2 lines of CDVA.
From the point of view of safety, the percentage of eyes that lost 2 or more lines of CDVA, a required measure in any submission for FDA approval, was significant. Figure 1 shows the aggregate percentage of eyes that lost 2 or more lines of CDVA by treatment type (conventional, advanced, and other) in the peer-reviewed literature, along with the reported losses from the summaries of safety and effectiveness data of several approved laser systems. In the peer-reviewed literature, there was a statistically significant difference in the reported losses of 2 or more lines of CDVA by treatment type (P < .01, ANOVA). The percentage of eyes with a loss of 2 or more lines was statistically significantly lower in the advanced group than in the conventional group (0.6% versus 0.94%; P < .03, Tukey honest significant difference test). The results appear consistent with the results in the PROWL studies, in which a rate of 0.44% (1/225) was reported in PROWL-1 and a rate of 0% (0/540) was reported in PROWL-2.A
Percentage loss of 2 or more lines of CDVA (FDA = U.S. Food and Drug Administration).
Although several studies accounted for most eyes in the peer-reviewed literature, the loss of 2 or more lines of CDVA was uniformly low in all studies. Figure 2 shows the distribution of the percentages of eyes in each study that lost 2 or more lines of CDVA categorized by treatment type. More than half of all articles and 82% (42/51) of the advanced treatment articles reported no loss of 2 or more lines of CDVA. Also shown is the nominal indicator of safety used by the FDA, a level lower than 5% loss of 2 or more lines of CDVA. Only 2 study groups had a level higher than this. The first included patients treated for 5.0 D or more of hyperopia, and the second included patients treated for 1.0 D to 4.25 D of astigmatism.
Percentage loss of 2 or more lines of CDVA by article (n = 92) and treatment type (CDVA = corrected distance visual acuity; FDA = U.S. Food and Drug Administration).
The percentage of eyes with a loss of 2 or more lines of CDVA was statistically significantly higher in eyes treated for hyperopia than in those treated for myopia (2.13% versus 0.95%; P < .01, chi-square test). There was no statistically significant difference by study size.
The final uncorrected distance visual acuity (UDVA) is a measure of the effectiveness of LASIK surgery. Of most interest are the rates of 20/20 and 20/40 Snellen acuity. In 68% (98/143) of the groups, comprising 90% (61 331/67 893) of eyes, the percentage of eyes with a UDVA of 20/20 or better was reported and in 65% (93/143) of studies, comprising 88% (59 833/67 901) of eyes, the percentage of eyes with a UDVA of 20/40 or better was reported. Figure 3 shows the rates of 20/20 and 20/40 by treatment type along with historical summaries of safety and effectiveness data. In the peer-reviewed literature, there were no statistically significant differences in the percentage of eyes with 20/20 or better and 20/40 or better between treatment types or by refractive error corrected. In aggregate across all articles, the weighted percentage of eyes with a UDVA of 20/20 or better was 90.8% (55 689/61 331) and the percentage with a UDVA 20/40 or better was 99.5% (59 503/59 833). A UDVA of 20/20 or better was reported in 97% of right eyes, 98% of left eyes, and 99% of both eyes in the PROWL-1 study and in 91% of right eyes, 92% of left eyes, and 96% of both eyes in the PROWL-2 study, consistent with the results in this review.A Of note is that no patient in either PROWL study had refractive enhancements and the results were at 3 months, prior to the normal resolution of dry eye following LASIK.
Percentage of eyes with 20/20 and 20/40 UDVA by treatment type (ATP = Advanced Treatment Profile; SSE = summary of safety and effectiveness data, from U.S. Food and Drug Administration data; UDVA = uncorrected distance visual acuity).
Figure 4 shows the distribution of the percentages of eyes with a UDVA of 20/40 or better by treatment type in the 93 articles with data. The nominal effectiveness rate for FDA reporting, 85%, is also shown. The percentage of eyes with a UDVA of 20/40 or better was 99% or higher in 70 of the 93 articles with available data, representing 95.5% of all eyes for which these data were reported. In 68% (63/93) of articles, all eyes had a UDVA of 20/40 or better. No article reported a value lower than the nominal FDA effectiveness value of 85%.
Percentage of eyes with 20/40 or better UDVA by article (n = 93) and treatment type (FDA = U.S. Food and Drug Administration; UDVA = uncorrected distance visual acuity).
The mean UDVA logMAR was tabulated in 67 articles, comprising 30% of eyes (20 273 of 67 893). Applying a weighted mean based on the number of eyes in each of these articles, the mean UDVA was −0.10 logMAR ± 0.10 (SD), with an estimated 77% of eyes (15 619 of 20 273) having a postoperative UDVA of 20/20 or better (0.0 logMAR). The postoperative UDVA was statistically significantly better (P < .01, ANOVA) in the articles reporting advanced treatment results (−0.04 logMAR) than in the articles reporting conventional treatment results (+0.05 logMAR); the difference was almost 1 line of acuity. In the advanced treatment group, there was no difference between wavefront-guided, wavefront-optimized, or topography-guided treatments (P > .15, ANOVA). There was no statistically significant difference by group size (P > .05, ANOVA) or preoperative refractive status (P > .05, ANOVA) between the advanced treatment results and the conventional treatment results.
Another measure of LASIK effectiveness is the residual refractive error after surgery, with the most often reported aggregate data being the percentage of eyes within ±0.5 D of the target refraction. The residual refractive error was reported in 84% (120 of 143) of study groups, comprising 97.2% (65 974 of 67 893) of all eyes. The percentage of eyes within ±1.0 D of the target refraction was also reported in 78% (111 of 143) of study groups, comprising 88% (60 329 of 67 893) of eyes. Summary data for the study groups and the comparative summaries of safety and effectiveness data are shown in Figure 5. All aggregate data from the literature review were better than the corresponding summaries of safety and effectiveness data. Including all articles in which data were reported, the percentage of eyes within ±0.5 D was 90.9% (59 954 of 65 974) and the percentage within ±1.0 D was 98.6% (59 476 of 60 329).
Percentage of eyes within ±0.5 D and ±1.0 D of the target SE refraction (ATP = Advanced Treatment Profile; SEQ = spherical equivalent; SSE = summary of safety and effectiveness data, from the U.S. Food and Drug Administration).
To ensure that the few large studies do not account for the high performance relative to the summaries of safety and effectiveness data, the distribution of the percentage of eyes within ±1.0 D of the target refraction for all studies is shown in Figure 6. The nominal FDA effectiveness standard for this measure is 75%. In all articles, the percentage of eyes within ±1.0 D of the target refraction was greater than 80%; in more than half the articles (59 of 111), comprising 80.7% of eyes with available data (48 684 of 60 329), the percentage was greater than 99%.
Percentage of eyes within ±1.0 D of the target refraction by article (n = 111) and treatment type (FDA = U.S. Food and Drug Administration).
The mean postoperative spherical equivalent (SE) refraction was reported in 114 articles. In 77% (88 of 114) of them, comprising 95% of eyes with data reported (61 861 of 65 278), the mean SE was within ±0.25 D of the intended target. In only 2 articles (including only 113 of 65 278 eyes) was the mean SE greater than ±0.50 D; 1 of these included myopic patients with a preoperative SE between −6.00 D and −10.00 D, and the other included hyperopic patients. The postoperative SE was statistically significantly different between the hyperopic group and the myopic group (P < .01, ANOVA), with a likelihood of slight residual hyperopia in hyperopic eyes and slight residual myopia in myopic eyes. The difference in these mean values was less than 0.25 D. There was no statistically significant difference by treatment type or study size (P > .05 in both cases, ANOVA).
This review includes articles that reported clinical outcomes data. Few of the articles included patient satisfaction or other subjective impression data. In addition, there was no standard reporting methodology, so only qualitative comments can be made based on the available data.
Only 5% of articles (7 of 143) included specific data on patient satisfaction after surgery, but these included 14.3% of all eyes (9726 of 67 893). Just under half the respondents (46.4%) reported being “very satisfied” after surgery; 1.2% of patients reported being dissatisfied. This is consistent with the Summit Apex summaries of safety and effectiveness in which 50.1% of patients reported a satisfaction score of 5 of 5 at 12 months postoperatively. No comparative patient satisfaction data were available from the summaries of safety and effectiveness data for the other approved laser systems included in this review. One other article included in the review included more than 10 108 eyes and reported that 93.4% of patients thought their vision was the same or better after LASIK relative to their preoperative vision using spectacles or contact lenses. This appears consistent with the PROWL-1 and PROWL-2 study data in which 98% and 96% of patients, respectively, reported satisfaction with their vision.
Dry-eye data were reported in only 12 of 143 articles, and reporting was not sufficiently uniform to allow aggregation. The largest study (32 569 eyes, 48% of the total) reported a postoperative dry-eye rate of 0.18%. The highest percentage of dry eye noted, based solely on a question related to the use of artificial tears, was 41% in a set of 207 eyes at 3 months postoperatively. However, no preoperative data were collected in that study and only 12% of the patients reported using artificial tears 2 or more times per day. Other articles reported a mean dry-eye score, but this did not allow determination of frequency in the patient population. No comparative preoperative data were available. In the PROWL-1 trial, dry eye was assessed preoperatively and at 3 months; no corneal staining was 90.9% preoperatively and 87.3% postoperatively. In the PROWL-2 trial, no corneal staining was 78.7% preoperatively and 83.5% postoperatively. Oxford grade 2 or greater staining was 1.4% preoperatively and 2.0% postoperatively in PROWL-1 and 1.8% and 2.6%, respectively, in PROWL-2.
Similarly, night vision, glare, and halos were recorded in very few articles and were often combined. The lowest reported rate was 0.06% in the largest study (32 569 eyes), and the highest rate was 3.5% in the second largest study (10 235 eyes). The weighted mean based on these 2 studies was 0.89%. These results are comparable to the 1.0% or lower rates of visual symptoms reported in the 2 PROWL trials.A In the PROWL trials, ghosting, glare, halos, and starburst symptoms were compared preoperatively (with glasses or contact lenses) with uncorrected symptoms at 3 months. The prevalence of all 4 symptoms was less than preoperatively in both trials. The prevalence of bothersome visual symptoms was evaluated preoperatively with glasses or contact lenses and compared with symptoms postoperatively without correction. Bothersome ghosting, glare, halos, and starburst following LASIK were less in every category in both trials. The reduction in bothersome symptoms was significant in many categories. The number of patients who had difficulty with or inability to perform usual activities because of visual symptoms was evaluated preoperatively and at 3 months. In all 8 groups, the decrease in symptoms was as follows: In PROWL 1, ghosting 0.8% preoperatively, 0% postoperatively; glare 2.8% preoperatively, 0.5% postoperatively; halos 2.8% preoperatively, 0% postoperatively; starburst 2.8% preoperatively, 0% postoperatively. In PROWL-2, ghosting 1.0% preoperatively, 0% postoperatively; glare 0.3% preoperatively, 0% postoperatively; halos 1.7% preoperatively, 0.4% postoperatively; starburst 2.4% preoperatively, 0.4% postoperatively.
Discussion:
Two general findings related to the comprehensive literature review we conducted are important to the overall context of the results. First, there were no peer-reviewed articles with a negative impression of LASIK. Second, there was no apparent industry bias; ie, there was no evidence that financial interests affected the impression of LASIK in the articles reviewed. The most definitive study (PROWL) was performed by the FDA with no industry or physician oversight; although it remains unpublished, the study’s detailed findings are available and were used for comparison purposes.
Over time, technological advancements have generally improved LASIK outcomes. Summaries of the safety and effectiveness FDA data from 1998 to 2004 for 12 FDA-approved laser devices were analyzed.8 The results showed that in a subset of nearsighted patients, the percentage of patients with improved UDVA and decreased residual refractive error improved, probably due to laser technological advancements. A large study of 19 753 myopic and mostly Chinese patients (37 932 eyes) conducted by Yuen et al.9 between February 1998 and December 2007 found a general improvement in surgical outcomes over the years: an increase in the percentage of eyes with a UDVA of 20/40 or better and 20/20 or better, a reduction in the percentage of eyes with a loss of 1 and 2 lines of CDVA, and an increase in the percentage of eyes within ±1.0 D of the target refraction. Our analysis of the peer-reviewed literature appears to corroborate this continuous improvement in LASIK outcomes. With rare exceptions, which appear to be a function of the more extreme patient populations in some articles, the results reported in the recent literature are consistently as good as or better than the data submitted for approval of various laser systems in the U.S. This is even though the summaries of safety and effectiveness data reported for the various laser systems related to the correction of myopic astigmatism only, whereas the analysis in this review included all eyes for which data were available, including hyperopia and/or hyperopic astigmatism, and even though the enrollment criteria are often more relaxed in post-market research studies than in studies designed to submit to the FDA.
In studies in which CDVA was reported, there was generally no change in CDVA; twice as many eyes gained 2 or more lines of vision as lost 2 or more lines. The percentage of eyes that lost 2 or more lines of CDVA was lower in the advanced treatment group than in the conventional treatment group. Both percentages were significantly lower than original data reported 20 years ago for the Summit Apex laser. (The Summit Apex laser, which had the highest reported loss of corrected vision in all summaries of safety and effectiveness data, is no longer available; it was retired in favor of faster, more precise excimer laser systems.)
The benchmark of limiting CDVA loss of 2 or more lines to 5% or less was met in all but 2 studies; both had extreme treatment ranges (high hyperopia in 1 case, high astigmatism in the other). The percentage of eyes with a loss of 2 or more lines was statistically significantly higher (P < .01) in hyperopia than in myopia (2.13% versus 0.95%), but both percentages were well below 5%.
In none of the study groups in which UDVA was reported was the percentage of eyes with 20/40 or better UDVA below the nominal standard of 85%. The weighted mean UDVA was significantly better than outcomes reported by Bailey and Zadnik8 for a range of early laser systems: 62.5% of 6250 eyes achieved a UDVA of 20/20 or better. The aggregate results are also better than the 2007 results reported by Yuen et al.,9 in which 72.8% of 37 932 eyes had a UDVA of 20/20 or better. The mean UDVA of −0.10 logMAR is also better than the mean UDVA of 0.07 reported in 2007 by Yuen et al.9 The percentages of eyes with a UDVA of 20/20 or better and 20/40 or better were higher than the percentages reported in the original FDA summaries of safety and effectiveness data.
Dry eye following LASIK is due to a reduction in corneal innervation. Multiple studies have shown that corneal sensation returns to normal in almost all cases at 6 months postoperatively. Bower et al.10 conducted a long-term prospective follow-up of dry eye following LASIK and photorefractive keratectomy (PRK); they evaluated patients preoperatively and 1 year following surgery. The study reported an incidence of dry eye of 5% following PRK and 0.8% following LASIK. Preoperative dry eye was predictive of postoperative dry eye. For this reason, it is important to evaluate and treat patients preoperatively to improve the ocular surface and reduce postoperative symptoms.
The percentage of eyes within ±1.0 D of the target refraction found in this review was significantly higher than the percentage reported by Yeun et al.9 in a large sample. The percentage of eyes within ±0.5 D of the target refraction in the aggregate data reported is also significantly higher than the 71.6% reported by Bailey and Zadnik.8 Only 2 articles (113 eyes) in the current aggregate data reported a mean SE refraction greater than ±0.50 D of the target refraction. Again, more extreme corrections were a factor: hyperopia in 1 case, high myopia in the other. There was a trend toward mild residual hyperopia in hyperopic eyes and mild residual myopia in myopic eyes.
Although only limited patient satisfaction data were available, results showed very high satisfaction rates, particularly compared with rates of other cosmetic surgery procedures11, 12, 13, 14; 98.7% of all patients were satisfied or very satisfied after their LASIK surgery. This aggregate result is consistent with other recent study data in which patient satisfaction higher than 95% has been reported for patients having myopic or hyperopic LASIK; the high satisfaction was attributed to a low postoperative refraction.1, 15 Results from 2 other articles are worth reporting. The first, by Pasquali et al.,16 involved a survey of physicians who had a refractive surgery procedure. The overall satisfaction rate in this demanding group was 95.3%. A recent study by Kezirian et al.17 included satisfaction data for ophthalmologists who perform refractive surgery and who had the procedure themselves; 97% of respondents (65 of 67) to a survey question indicated they felt they were better off having had the surgery.
The satisfaction rates reported are similar to the 98.7% reported in the PROWL-1 trial and higher than the 96.2% reported in the PROWL-2 trial. In the PROWL trials, patient satisfaction was also evaluated preoperatively with glasses or contact lenses; in PROWL-1, it increased from 25.3% preoperatively to 98.7% postoperatively and in PROWL-2, from 44.3% to 96.2%, respectively. The PROWL studies showed a marked improvement in visual symptoms of ghosting, glare, halo, and starburst after LASIK. These findings suggest that for most patients with visual symptoms, LASIK improves quality of vision. The PROWL trials noted that although many patients with preoperative symptoms showed resolution of these symptoms after surgery, a minority of patients who were asymptomatic preoperatively developed new symptoms after LASIK. Most of the new symptoms were mild and not visually significant. The PROWL trials showed that dissatisfaction is associated with symptoms such as glare, halos, starbursts, and ghosting. The results of the PROWL trials were reported after only 3 months, so it may be that more time was needed for visual symptoms or conditions such as dry eye to resolve.A In addition, in the PROWL trials, postoperative evaluation was performed without correction of residual refractive error with glasses or additional laser treatment. Correction of residual refractive error would reduce visual symptoms and, therefore, might further increase overall satisfaction. In the future, it may be possible to eliminate the majority of postoperative symptoms with improved technology.
Two general comments can be made based on the overall results in this review. First, the clinical results of correcting myopia appear slightly better than those of correcting hyperopia. Despite this difference, patients treated with hyperopic LASIK have reported satisfaction rates as high as 96.3%.1 Second, advanced treatment seems to provide slightly better outcomes than those achieved with conventional treatment. In the review, the UDVA achieved in the advanced treatment group was almost 1 line better than that achieved in the conventional group, although the conventional group mean was within half a line of 20/20.
There are limitations to any review such as the one we report. There is no way to resolve likely differences in test conditions (eg, illumination, chart reflectance), enrollment criteria, or length of follow-up. Even the range of refractive error corrected varies considerably across the reviewed studies. Aggregating data can be confounded by limitations in the clinical outcomes reported; not all studies reported all data of interest. On balance, however, the ability to aggregate results from a broad range of laser systems and generate summary statistics makes this effort worthwhile.
Another important limitation of the current review is the lack of comprehensive subjective data related to visual outcomes such as glare, halos, or night-driving complaints. These are often the subject of separate studies. Although the lack of data in the current data set is regrettable, a more serious concern might be that studies analyzing subjective complaints do not appear to include objective data, as they were not identified in our search. If that is the case, symptoms such as glare and halos or night-vision difficulty may be over-reported as they may be a function of uncorrected refractive error rather than a symptom of the surgery. Without objective and subjective data, this possible correlation cannot be adequately investigated.
In summary, the aggregate data from a large number of recent articles demonstrate that the overall clinical outcomes of modern LASIK surgery are significantly better than when the technology was first introduced. Improved diagnostic and laser technology and patient selection, better refinement of nomograms, more sophisticated ablation patterns, and the introduction of new technology such as the femtosecond laser for flap creation are likely to have played a role. Investigating the specific impacts of these factors was not possible in the current analysis due to the wide variety of lasers and microkeratomes included. It is realistic to expect that with continued technological advancements, LASIK surgical outcomes and safety will continue to improve.
Fiancial Disclosures:
Dr. Donnenfeld is a consultant to Acufocus, Inc., Allergan, Inc., Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Aquesys, Inc., Bausch & Lomb, Beaver-Visitec International, Carl Zeiss Meditec AG, Elenza, Inc., Glaukos Corp., Icon Bioscience, Inc., Kala Eyewear, Katena Products, Inc., Lacriscience, Mati Therapeutics, Inc., Merck Sharp & Dohme Corp., Mimetogen Pharmaceuticals, Novabay Pharmaceuticals, Inc., Novaliq GmbH, Omega Ophthalmics, Pfizer, Inc., Ocuhub, Omeros Corp., Physician Recommended Nutriceuticals, Rapid Pathogen Screening, Inc., Shire, Strathspey Crown LLC, Tearlab Corp., Truvision Systems, Inc., and Versant Ventures. Dr. Kohnen is a consultant to Abbott Medical Optics, Inc., Alcon Laboratories, Inc., Carl Zeiss Meditec AG, Geuder AG, Rayner Intraocular Lenses Ltd., Oculus Optikgeräte GmbH, Schwind eye-tech-solutions GmbH and Co. KG, Tearlab Corp., Thieme Compliance GmbH, and Ziemer Ophthalmic Systems AG; he receives grant support from Abbott Medical Optics, Inc., Alcon Laboratories, Inc., Carl Zeiss Meditec AG, Rayner Intraocular Lenses Ltd., Oculus Optikgeräte GmbH, Schwind eye-tech-solutions GmbH and Co. KG. Dr. Lindstrom is a consultant to Acufocus, Inc., Abbott Medical Optics, Inc., Alcon Laboratories, Inc., Bausch & Lomb, Glaukos Corp., Imprimis Pharmaceuticals, Inc., Ocular Therapeutix, Inc., Tearlab Corp., and Tracey Technologies Inc. Dr. Potvin is a consultant to Alcon Laboratories, Inc., Haag-Streit AG, Imprimis Pharmaceuticals, Inc., Oculus Optikgeräte GmbH, Physiol S.A., and Revision Optics, Inc. Dr. Solomon is a consultant to Alcon Laboratories, Inc., Aquesys, Inc., Clarvista Medical, Glaukos Corp., Icon Bioscience, Inc., Integrity Digital Solutions, Mati Therapeutics, Inc., Octane Visionary VC Fund, Ocuhub, Omeros Corp., Pogotec, Physician Recommended Nutriceuticals, and Versant Ventures. Drs. Sandoval and Tremblay have no financial or proprietary interest in any material or method mentioned.
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Recent literature:
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Older literature:
1. Ambrosio, R, Wilson, SE. Complications of Laser in situ Keratomileusis: Etiology, Prevention, and Treatment. J Refract Surg 17, May/June 2001.
2. Tham VM, Maloney RK. Microkeratome complications of laser in situ keratomileusis. Ophthalmology 2000; 107:920-924.
3. Montes M, Chayet A, Gomez L, Magallanes R, Robledo N. Laser in situ keratomileusis for myopia of -1.50 to -6 diopters. J Refractive Surgery 1999 Mar-Apr;15(2):106-10
4. Lohmann CP, Guell JL. Regression after LASIK for the treatment of myopia: the role of the corneal epithelium. Semin Ophthalmol 1998; 13:79-82.
5. Steinert, RF. Swami, AU. Diffuse Interface Keratitis. Review of Refractive Surgery, January 2000 46-52
6. Yeoh J, Moshegor CN. Delayed diffuse lamellar keratitis after laser in situ keratomileusis. Clin Experiment Ophthalmol 2001 Dec;29(6):435-7
7. Chang-Godinich A, Steinert RS, Wu HK. Late occurrence of diffuse lamellar keratitis after laser in situ keratomileusis. Arch Ophthalmol 2001 Jul;119(7):1074-6
8. Lin RT, Maloney RK. Flap complications associated with lamellar refractive surgery. American Journal of Ophthalmology 1999: 127(2) 129-136.
9. Stulting RD, Carr JD, Thompson KP, Waring GO 3rd, Wiley WM, Walker JG. Complications of laser in situ keratomileusis for the correction of myopia. Ophthalmology 1999; 106:13-20.
10. Wang MY Maloney RK. Epithelial ingrowth after laser in situ keratomileusis. Am J Ophthalmol 2000; 129:746-751.
11. Mutyala S, McDonald MB, Scheinblum KA, Ostrick MD, Brint SF, Thompson H. Contrast sensitivity evaluation after laser in situ keratomileusis. Ophthalmology 2000 Oct;107(10):1864-7
12. Knorz MC, Huger P, Jendritzka B, Liermann A. Twilight visual acuity after correction of myopia with LASIK. Ophthalmologe 1999 Nov;96(11):711-6
13. Montes-Mico R, Charman WN. Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery. J Refract Surg 2001 Nov-Dec;17(6):646-51
14. Cardona Ausina C, Perez Santonja JJ, Ayala Espinsoa MJ, Claramonte Meseguer P, Artola Riog A, Alio JL. Contrast sensitivity after laser in situ keratomileusis for myopia (LASIK-M). Arch Soc Esp Oftalmol 2000 Aug;75(8):541-6
15. Perez-Santonja JJ, Sakla HF, Alio JL. Contrast sensitivity after laser in situ keratomileusis. J Cataract Refract Surg 1998 Feb;24(2):183-9
16. Chen J, Wang Z, Yang B, et al. Laser in situ keratomileusis for correction of myopia. Chung Hua Yen Ko Tsa Chih 1998 Mar;34(2):141-5
17. Holladay JT, Dudeja DR, Chang J. Functional vision and corneal changes after laser in situ keratomileusis determined by contrast sensitivity, glare testing and corneal topography. J Cataract Refract Surg 1999 May;25(5):663-9
18. Miller AE, McCulley JP, Bowman RW, Cavanaugh HD, Wang XH. Patient satisfaction after LASIK for myopia. CLAO J 2001 Apr;27(2):84-8
19. McGhee CN, Craig JP, Sachdev N, Weed KH, Brown AD. Functional, psychological and satisfaction outcomes of laser in situ keratomileusis for high myopia. J Cataract Refract Surg 2000 Apr;26(4):497-509
20. Holladay JT, Dudeja DR, Chang J. Functional vision and corneal changes after laser in situ keratomileusis determined by contrast sensitivity, glare testing and corneal topography.J Cataract Refract Surg 1999; 25:663-669.
21. Wilson SE. Laser in situ keratomileusis-induced (presumed) neurotrophic epitheliopathy. Ophthalmology 2001 Jun;108(6):1082-7
22. Patel S, Perez-Santonja JJ, Alio JL, Murphy PJ. Corneal sensitivity and some properties of the tear film after laser in situ keratomileusis. J Refract Surg 2001 Jan-Feb;17(1):17-24
23. Benitez-del-Castillo JM, del Rio T, Iradier T, Hernandez JL, Castillo A, Garcia-Sanchez J. Decrease in tear secretion and corneal sensitivity after laser in situ keratomileusis. Cornea 2001 Jan;20(1):30-2
24. Yu EY, Leung A, Rao S, Lam DS. Effect of laser in situ keratomileusis on tear stability. Ophthalmology 2000 Dec;107(12):2131-5
25. Lee JB, Ryu CH, Kim J, Kim EK, Kim HB. Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis.J Cataract Refract Surg 2000 Sep;26(9):1326-3
