Ординатура / Офтальмология / Учебные материалы / Color Atlas of Ophthalmology The Quick-Reference Manual for Diagnosis and Treatment

16 Contact Lenses 471

or m ay n ot ben efit th e pat ien t , leading to self-lim itat ion of len s w ear or even discon t in u an ce.

Th e clin ician w ill obser ve a CLARE-t ype red eye w ith ou t in fect ion th at appears to be ch ron ic. Th ere m aybe a m ild to m oderate corn eal stain ing presen t due to len s vau lt . Th e len s m ay appear som ew h at im m obile, suggest ing an in duced t igh t len s syn drom e or sm all petech ial h em orrh ages on th e conju n ct iva ju xtaposed to th e len s edge or on th e paralim bal conjun ct iva. Th ere is n eith er apparen t disch arge n or follicu lar n or papillar y react ion . How ever, in th e long-term sufficien t debris an d len s su rface dr yn ess can in duce a CLPC react ion . Tear film spreading abn or- m alit ies w ill be seen w ith th e u se of various diagn ost ic test ing su ch as Sch irm er st rips, lissam in e green , assessm en t of th e tear break-u p t im e, sodiu m flu orescein stain ing of th e corn ea an d conjun ct iva, assessm en t of th e lacrim al lake–m argin al tear volum e as a variet y of test .

Differential Diagnosis

Con t act len s–in duced edem a, w arpage, over w ear, oth er causes of redn ess an d discom for t associated w ith con tact len s u se. CLIDE is directly related to oth er ocu lar con dit ion s affect ing th e lacrim al– ocular su rface balan ce in cluding eyelid an d glan - du lar dysfu n ct ion or disease, poor blin king m ech an ism su ch as lagoph th alm os, floppy lid, an d/or dysfun ct ion of th e lacrim al an d m eibom ian glan ds. Oth er associat ion s to CLIDE an d dr y eye in clude Sjögren syn drom e, au toim m un e disease, rh eu m atoid disorders, an d m edicat ion s, especially an t ih ist am in es, an t idepressan t s, an d oral con t racept ives.

Management

Th e t reat m en t for dr y eye an d CLIDE is to relieve th e un derlying problem by first iden t ifying th e por t ion of th e tear film th at is dysfun ct ion al. On ce iden t ified, th e t reat m en t sh ou ld be biased to com plem en t th e len s w ith m in im al com plexit y to th e pat ien t . W ith th e u se of ocu lar lubrican ts as a su pplem en t or st im u lan t , th e eye becom es “subject ively com for table,” bu t lit tle is kn ow n in regard to th eir longterm effect on th e various tear film st ruct ures an d corn eal physiology. W ith respect to su pplem en t in teract ion w ith th e m aterial an d th e m aterial’s in teract ion w ith th e eye, th e con t act len s design an d m aterial are th e key long-term com for t an d physiological balan ce in th e poten t ial su ccess of th e con t act len s pat ien t .

To ach ieve th e proper tear-film balan ce, th e CLIDE p at ien t m u st be t reated as a n orm al dr y-eye pat ien t . Follow ing a flow ch ar t of t reat m en t such as proper tear an d n ut rit ion al supplem en tat ion is th e first step . Th e select ion of supplem en ta- t ion an d/or m edicin al t reat m en t is crit ical. I prefer to t r y to defin e m edicin al care by th e determ in at ion of dr y eye as a “w h ite” or “red” dr y eye. If th e pat ien t presen ts sym ptom at ically an d object ively as a dr y eye yet h as a w h ite, n on in flam ed conju n ct iva, th e use of goblet cell–m ucin en h an cers in conju n ct ion w ith lacrim al glan d st im u lus (e.g., cyclosporin e) w ould be con sidered appropriate. If th e pat ien t appears w ith a red, in flam ed dr y eye, th en th e in ter ven t ion w ith steroids w ould be deem ed m ore ap propriate. Th is m ay also be com plem en ted w ith th e use of n u t ri- t ion al su pplem en t at ion of om ega 3 an d 6 essen t ial oils (fish an d seed oil sou rces), w h ich h ave a n at ural n on steroidal an t iin flam m ator y effect . In addit ion , tear an d len s rehydrat ion is w ell accom plish ed by using an t ioxidan t or elect rolyte-balan ced tear su pplem en t s. At th e sam e t im e, a clin ical decision m ust be m ade to refrain from con tact len s u se or lim it it during th e in it ial stages of th erapy. Pun ctal occlusion sh ould be reser ved for long-term len s com for t m ain ten an ce un t il posit ive result s are est ablish ed w ith topical an d oral th erapies.

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Material select ion is crit ical in th e t reat m en t of th e CLIDE pat ien t . Alw ays con - sider RGP len ses first for borderlin e dr y eye pat ien ts. A deficien t or u n st able tear film requires h igh oxygen perm eabilit y an d a len s w ith low surface react ivit y th at m oves adequ ately to m in im ize th e risk of com plicat ion s. Also con sider th e rech allenge of hydrogel-based grou p 2 m aterials of h igh -w ater, n on ion ic ch aracter such as h ioxifilcon an d ph osph at ylch olin e. As n oted, silicon e hydrogel m aterials m ay be appropriate for oxygen en h an cem en t bu t are n ot prom ising w h en t reat ing a defin ed CLIDE pat ien t . Silicon e hydrogels w ou ld be h igh ly desirable on ce th e CLIDE p at ien t h as been t reated an d th e eye h as resu m ed a feasible level of com for t an d p roper tear film balan ce.

Superior Epithelial Arcuate Lesions

Th e separat ion of th e corn eal epith elium , occurring m ore so at th e superior lim bal m argin , is know n as superior epith elial accurate lim bal split (SEALS), or a sim ilar form of epith elial split ting th at follow s th e corn eal-lim bal border aroun d the cornea is know n as int ra-epithelial split ting (ILES). It is ch aracterized by an obser vat ion of an arcuate staining ju xtaposed to the lim bus. Th e pat tern of th e full-th ickness corneal epithelial separation usually occurs in th e lim bal corn ea covered by th e upper eyelid, w ithin 2 to 3 m m of th e superior lim bus in th e 10and 2-o’clock region .

Th e m ain cause for th is en t it y is con sidered to in clude m ech an ical irrit at ion an d dehydrat ion of th e len s su rface. Th e et iology of SEALS an d/or ILES is con sidered to be eith er a m ech an ical pull or st ress on th e epith elial ju n ct ures du e to a t igh t len s or len s dehydrat ion or a m ech an ical ch afing w ith in th e paralim bal corn ea. As for SEALS, sup erior m ech an ical ch afing m ay be th e resu lt of inw ard pressure of th e upper lid at th e su perior in t ralim bus associated w ith len s design , rigidit y, an d surface ch aracterist ics. In com bin at ion th e excessive “frict ion al” p ressure an d abrasive sh ear force on th e epith elial surface in du ce a separat ion of th e epith elial cell jun ct u res. New m aterials, first-gen erat ion silicon e hydrogels, w h ich possess a st iffer elast ic m odu lu s, m ay cau se an in crease in th e sh earing force n ot on ly on th e corn ea, but also m ay in duce a sim ilar force on th e conju n ct iva leading to a pseu doim pression ring called a conju n ct ival flap .

Th e con cern s w ith SEALS or ILES are th e provocat ion of an in flam m ator y an d/ or bacterial in filt rat ive respon se. Addit ion ally, excessive sh earing forces m ay lead to a degradat ion of lim bal stem cells require for corn eal repair m ech an ism s (Fig. 16.7).

Presentation

Presen tat ion is gen erally asym ptom at ic oth er th an m ild, obser vable inject ion to th e eye, par t icu larly upon len s rem oval. Th e pat ien t m ay also com plain of a m ild to m oderate len s aw aren ess, difficu lt len s rem oval, burn ing, or itch ing sen sat ion . Th e pat ien t m ay describe a sligh tly greater len s in toleran ce to stan dard low m odu lu s 2-hydroxyethyl m eth acr ylate-based len ses as com pared w ith h igh er m odu lus silicon e–hydrogel com bin ed polym ers.

Upon biom icroscopic exam , th e gen erally asym ptom at ic p at ien t m ay presen t w ith conjun ct ival inject ion ju xt aposed to th e affected area. In th e case of SEALS, th e conju n ct ival inject ion w ou ld appear m ore st rictly bet w een 10 o’clock an d 2 o’clock versu s a 360-degree-t ype epith elial split t ing, w h ich w ou ld app ear m ore as th e CLARE-t ype eye associated w ith a t igh t len s syn drom e. Su bsequen tly, sign ifican t paralim bal stain ing appears in an arc abou t th e in t ralim bal corn ea.

16 Contact Lenses 473

Fig. 16.7 (A) Classic circumlimbal epithelial split ting with tear-film irregularit y. (B) Classic circumlimbal superior epithelial arcuate limbal split ting (SEALS) due to a tight lens syndrome with tear-film disruption and conjunctival congestion [contact lens acute red eye (CLARE)]. (C) Classic SEALS due to a tight lens syndrome with tear film disruption and conjunctival congestion (CLARE).

A

B

C

Differential Diagnosis

Th is is sim ply related to th e h istor y of len s use or th e lack th ereof. If th ere is n o h istor y of len s u se, th en on e n eeds to evalu ate th e localized conjun ct ival respon se to determ in e th e level of inject ion . A su perior lim bic kerat it is (SLK) m ay be an in dicator of su bsequ en t thyroid disease. If th e conju n ct ival respon se is tem poral or n asal, th en determ in e in flam m ator y con cern s of vascu larized lim bic kerat it is, episcleri-

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t is, phylcten ulit is, pin qu ecu lit is, pter ygium , an d/or early m argin al degen erat ion s. For t un ately, SEALS or ILES, are m ore con sisten t w ith con t act len s use, exten ded w ear m ore so th an daily w ear. If su perior lim bal inject ion occu rs, part icu larly bilateral, con sider oth er issues su ch as thyroid disorder or corn eal disorder.

Management

Sim p le len s discon t in u an ce is th e m ost appropriate, allow ing th e lesion to recover w ith in a few days to several w eeks. If th e SEALS or split is m in or, th e sim ple discon t in u an ce of th e len s is prop er based on th e pat ien t’s abilit y to fun ct ion w ith spectacles. As a precau t ion again st bacterial in filt rat ion , a sh or t course of topical an t ibiot ics m ay be ben eficial. In th is scen ario, a sim ple refit to a daily disposable len s w ith adequ ate an d frequ en t rehydrat ion is deem ed appropriate. Th e refit of len s sh ould n ot on ly reevaluate th e hydrat ion abilit y of th e len s but th e len s’ rela- t ion to th e corn eal topography an d asp h ericit y or corn eal con tou r. Th erefore, th e len s design sh ou ld com plem en t th e an atom y suggest ing a flat ter base cur ve or h igh er eccen t ricit y value. In conjun ct ion , sh or t-term pu n ctal p lugs can be con sid - ered an am ple adjuvan t th erapy to en h an ce epith elial h ealing an d m ain t ain len s an d corn eal hydrat ion .

If th ere is a low -grade conjun ct ival respon se, a break w ith in th e epith elium cou ld be th e p oten t ial opp or t u n it y for bacterial con t am in at ion an d/or in flam m a- tor y respon ses. As such , th e level of th e con dit ion w ill w arran t th e level of th erapy. Again , discon t in u an ce is ap propriate, yet th e addit ion of a soft steroid w ith m ild an t ibiot ics su ch as tobram ycin /lotepredn ol (Zylet , Bausch & Lom b) fou r t im es a day for 5 to 7 days w ith th e addit ion of a bacit racin oin t m en t during sleeping h ou rs is con sidered prophylact ically safe.

If th ere is a greater (m ild –m oderate–severe) ocu lar inject ion an d sign ifican t split t ing, com plete discon t in u an ce of th e len s is required w ith a m ore aggressive th erapy ut ilizing a com bin at ion steroid -an t ibiot ic drop an d oin t m en t or a separate flu oroqu in olon e drop an d oin t m en t w ith a secon dar y steroid su ch as p redn isolon e acet ate if th e con dit ion h as associated in filt rates or m ay lead to an u lcerat ive keratopathy.

On ce th e con dit ion is resolved, th e pat ien t can be refit to a low er elast ic m odulu s len s, avoiding exten ded or con t in u ou s w ear or be refit to a h igh Dk gas perm eable len s.

Dellen-Epithelial Hyperplasia

Dellen are focal areas of corn eal th in n ing t ypically located, usu ally at th e 3- to 9-o’clock lim bu s du e to dehydrat ion of th e region . Th ese form at ion s are th e ac- t ive state of m ech an ical irritat ion of a sector or por t ion of th e corn ea ju xtaposed to th e edge of th e gas perm eable con tact len s. Th ey are con sidered a t ran sien t form of corn eal degen erat ion th at resu lts from st rom al dehydrat ion secon dar y to poor w et t ing by th e tear film seen n ot on ly w ith con t act len s w ear but also p ostsu rgically (e.g., cataract , LASIK, st rabism u s). It represen t s a localized th in n ing of th e corn eal an d scleral t issu e. Epith elial hyperplasia is m ore related to th e ch ron ic dehydrat ion an d m ech an ical ch afing of th e gas perm eable len s in a specific ju xt a- posed area of th e corn ea.

Th e et iology of th e dellen is local dehydrat ion . It is th ough t th at breaks in th e oil layer of th e tear film preven t th e proper w et t ing of th e t issue, leading to devitalizing dehydrat ion of th e epith elial cells. Du e to th e lack of proper oil an d aqueou s

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A B

Fig. 16.8 (A) Corneal dellen secondary to gas permeable lens wear. (B) Epithelial hyperplasia secondary to gas permeable lens wear.

flu ids in th e locat ion , th ere is a greater ten den cy for len s bin ding an d m ech an i- cal ch afing. Mech an ical in flu en ces are in du ced by th e eyelids, w h ich are u n able to follow th e ch anging con tou r of th e len s edge forcing it to lift or bore in to th e epith eliu m . If th e len s edge creates a gap, th en th ere is a su bsequen t lack of w et- t ing an d hydrat ion of th e corn eal t issu e in w h ich m u cin s are n ot spread over th e epith eliu m , resu lt ing in an area of n onw et t ing resu lts. Fur th er dehydrat ion eith er even t u ally causes corn eoscleral th in n ing to occur, w ith th e form at ion of a dellen or long-term local epith elial hyperplasia (Fig. 16.8).

Presentation

Pat ien ts w ith corn eal dellen m ay be asym ptom at ic but often report m ild ocu lar discom fort or a foreign body sen sat ion . Th e pat ien t m ay describe a sectoral red - n ess to th e eye w ith len s aw aren ess over t im e. Th ere m ay be in creased epiph oria as w ell as n ot iceable len s decen t rat ion . Su bsequen tly, th e pat ien t m ay describe dr y eye–t ype sym ptom s an d in creasing len s in toleran ce. Addit ion ally, th e pat ien t m ay exh ibit an in com plete or errat ic blin k reflex w h en ut ilizing len ses.

Dellen appear as pale–kerat in ized w h ite “saucerlike” depression s w ith in , usu - ally th e 3- to 9-o’clock area in t ralim bal ju xt aposed to th e edge of th e len ses. Rarely are th ese lesion s larger th an 2 m m . If th e overlying epith elium is in t ake, th ey w ill n ot st ain . Th ey m ay h ave a sligh tly vascularized su rface w ith adjacen t sectoral con - jun ct ival inject ion . Flu orescein m ay appear to “gu t ter” an d surrou n d th e base of th e dellen . Th e st ain ing, at or n ear th e 3- an d 9-o’clock posit ion s, appears on or adjacen t to th e lim bu s of rigid len s w earers. Breaks in th e epith elium m ay allow for periph eral bacterial con t am in at ion leading to a kerat it is or u lcerat ion or in flam -

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m ator y in filt rat ion . Becau se of th e localized dehydrat ion , subsequ en t cell desicca- t ion occu rs an d n ecrosis of th e epith elial cells. Th is leads to epith elial hyperplasia sim ilar to corn eal scarring. Epith elial hyp erplasia is obser ved as a m ou n d of t issue th at becom es eroded an d irritated by th e len s edge due to ch ron ic dehydrat ion of t issue exposu re.

Differential Diagnosis

Several p oten t ial differen t ials n eed to be con sidered w h en obser ving a dellen or epith elial hyperplasia. If th ere is sign ifican t sectoral conjun ct ival inject ion , th en on e sh ou ld also con sider vascularized lim bic kerat it is, episclerit is, ph lycten u lit is, pin qu ecu lit is, pter ygiu m , or early m argin al degen erat ion s su ch as Terrien’s. Th e m ost im por tan t differen t ial w ould be m argin al ulcerat ion , part icu larly if epith e- lium com prom ise is obser ved . If th e adjacen t conju n ct iva is quiet , th en on e m ay con sider ru ling ou t a preexist ing scar or postoperat ive scar from cataract or ex- t raocu lar m uscle surger y, filtering blebs, an d sclerit is, obviously differen t iated by h istor y.

Management

Th erapy focuses on th e proper reepith elializat ion an d rehydrat ing th e corn ea. Copious lubricat ion ever y 1 or 2 h ours an d blan d oin t m en t at n igh t are recom - m en ded . In par t icu lar, n u t rien t-based th erapy is m ost appropriate ut ilizing an elect rolyte-balan ced or an t ioxidan t-based drop . In addit ion , a dem ulcen t su ch as Syst an e (Alcon Laboratories) or En du ra (Allergan ), w h ich form s a n et w ork gel-like con sisten cy on th e ocu lar su rface an d acts as a tem porar y ban dage en h an cing epith elial h ealing an d revitalizing th e m icrovilli an d surface glycocalyx. In it ial t reat- m en t w ill dem on st rate efficacy in 48 to 72 h ours, bu t rein sult occurs easily. Topical cyclosporin e can also be con sidered in sh ortor long-term care.

Topical an t ibiot ics are u n n ecessar y, except in ext rem e cases involving sign ifican t epith elial com prom ise to preven t in fect ion an d ulcerat ion . In th ese cases, th e in flam m ator y com pon en t is raised, an d th erefore a com bin at ion tobram ycin w ith dexam eth ason e or lotepredn ol m ay be appropriate in a sh or t cou rse of 7 days at fou r t im es a day.

On ce th ere is proper resolu t ion , th e gas perm eable len ses can be refit w ith a diligen t reevaluat ion of th e p eriph eral corn eal an atom y versu s th e periph eral cu r ve an d edge profile of th e len s. Addit ion ally, blin king exercises en couraging th e pa- t ien t to force a com plete lid closu re, on ce ever y 2 or 3 secon ds, are essen t ial. Also, con t in u e proper lubricat ion w ith rew et t ing drops com plem en t ar y to th e m aterial of ch oice. Con sider h igh er dK m aterials w ith plasm a t reat m en t for en h an ced w ettabilit y.

Ep ith elial hyp erplasia m ay resolve follow ing discon t in u at ion of len s w ear. W h en poor resolut ion occurs an d is an obst ru ct ion to len s refit t ing an d PTK excim er laser procedu re m ay be con sidered to flat ten th e area an d elevate th e devitalized cells.

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Contact Lens-Induced Corneal Warpage Syndrome

Th e syn drom e of “corn eal w arpage” im plies th at th e con t act len s h as iat rogen ically in duced an atom ical ch anges to th e corn eal surface. Th e w arpage is visu alized as an irregular ret in oscopic reflex, distort ion to topography, an d keratom et ric m ires, in duced irregu lar corn eal ast igm at ism , an d obser vable distor t ion s to th e corn eal su rface u pon len s rem oval.

Con t act len s–in du ced corn eal w ar p age is m ore frequ en tly associated w ith polym ethyl m eth acr ylate (PMMA), m ore so t h an gas-p er m eable len ses; h ow ever, ~27%of rep or ted cases of cor n eal w ar p age h ave been at t r ibu ted to hyd rogel len s w ear. Corn eal con tou r–in du ced irregu lar it ies are con sid ered th e resu lt of p robable m ech an ical deform at ion , ch ron ic m et abolic in su lt , or a com bin at ion of both . Ad dit ion ally, w ar page is seen as secon dar y to len s bin ding or st agn at ion du e to len s d ehydrat ion or a CLIDE syn d rom e. Also, som e solu t ion in teract ion s m ay ten d to in du ce len s im m obilit y du e to th e level of solu t ion viscosit y leading to len s bin d ing.

More com m on ly, h ard PMMA or rigid gas-perm eable len ses are recogn ized for th e in duct ion of corn eal w arpage or iat rogen ically in duced resh aping of th e cor- n ea w h en im properly fit or align ed to th e corn eal su rface. Th e corn eal epith eliu m , h aving a ver y “p last ic” or “m oldable” ch aracter, is easily resh aped by th e h igh m odu lus or st iffn ess of th e len s, w h ich m olds th e corn ea to th e sh ape of th e len s cur vat ure(s) un in ten t ion ally. Th is can be in ten t ion ally accom plish ed in a process called orthokeratology.

Rigid con tact len s–in du ced corn eal w arpage is easily docum en ted an d m on i- tored via obser vat ion of topograph ic abn orm alit ies. Th ere w ill be in du ced cen t ral irregu lar ast igm at ism , in ferior steepen ing or sm ile-like pat tern (pseu dokeratoco- n us-like im ages), su perior flat ten ing, loss of radial sym m et r y, h igh ly irregular pattern s w ith loss of surface sym m et r y, or an im pression of a dem arcat ion con tou r lin e con sisten t w ith th e len s edge. In du ced w arpage w ith hydrogels are con sidered m ore t ran sien t; h ow ever, gas perm eable m ay be t ran sien t to p erm an en t .

Hydrogel-in duced deform at ion s are related to a w eaken ed epith elium du e to lesser th an opt im al oxygen t ran sm issibilit y th rough various hydrogel len s m aterials. Subsequ en tly, a m isalign ed, t igh t , u lt rath in len s or ext rem e varian ts in elast ic m odu lus of len ses can in duce hydroph ilic corn eal w arp age syn drom e. In a posit ive effect , a h igh elast ic m odu lu s len s w orn in reverse can act u ally in du ce a subtle flatten ing– or th okeratological effect to th e corn ea of 0.50 to 1 diopter (Fig. 16.9).

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A B

C D

Fig . 16.9 (A) Corneal wrinkling (convolutions) induced by ultrathin hydrogel lenses.

(B) Hydrogel corneal warpage as seen with sodium fluroscein stainage. (C) Corneal im - pression ring induced by orthokeratologically fit lens. (D) Irregular keratometric mires by induced corneal warpage from a rigid gas permeable lens.

Presentation

Pat ien ts w ill com plain of poor or distor ted vision w ith len ses w ith su bsequen t reduct ion in visual acu it y. Th ey w ill ten d to u t ilize m ore rew et t ing drops th at ten d to assist in clearing th e vision m om en t arily, yet do n ot resolve th e visu al decre- m en t . Th e u n in ten t ion al m olding or w arpage of th e corn ea leads to subject ive visu al distort ion an d com plain t s of postlen s rem oval spectacle blu r or in abilit y to w ear glasses an d object ive m easu res of regression of pow er if th e len s is fit flat an d reduct ion of ast igm at ism can be m ade. In m any cases, par t icularly w ith hydrogel len ses, su btle distor t ion s can n ot be obser ved by biom icroscopy bu t m ay be m ore obviou s on topography an d aberrom et r y. In th ese cases, h istor y of p oor vision or n on opt im al vision is th e on ly descriptor by th e pat ien t . Th is w ill often occur w h en on e is refit t ing from older conven t ion al design s to frequ en t-replacem en t , th in n er len s design s th at m ay lack th e proper align m en t to th e corn eal topography.

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E

Fig. 16.9 (Continued) (E) Topography of warpage—RGP-induced corneal warpage at present and at 1 week lens discontinuance.

Clin ical sign s of corn eal w arpage are first docum en ted by redu ced, su bject ive an d object ive, visu al acu it y w ith con t act len ses an d subsequ en tly persisten t acu - it y reduct ion w ith spectacles. Th e visual redu ct ion m ay be su btle (20/20 m in us) or pron ou n ced . On ce th e len ses are rem oved for an adequate period, th e p at ien t’s m an ifest refract ion ret u rn s to n orm al w ith con sisten t im provem en t in acuit y m easures. During th e exam in at ion , ret in oscopy reflexes w ill appear “w arped” or yield a “scissor” reflex often seen in keratocon u s. Keratom et r y an d topograph ic m easures dem on st rate varian t levels of irregu larit ies. Par t icu larly, descript ive st at ist ics w ith topography w ill be h igh ly variable as com pared w ith prefit m easures, som et im es m im icking a disease st ate.

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Differential Diagnosis

Histor y of len s use an d subject ive com plain t s w ill defin e th e con cern . How ever,

en doth eliu m , part icularly w ith th e exten ded -w ear pat ien t or an older in dividu al, corn eal edem a m ay occur secon dar y to im bibem en t of flu id th rough en doth elial cell jun ct ion s an d m ay lead to associated cen t ral corn eal st riae, folds, or clouding. Th erefore, en doth elial polym egath ism , polym orph ism , an d reduced en doth elial cell cou n t m ay be th e u n derlying cau se.

Advan ced or u n con t rolled glaucom a w ith sign ifican t corn eal edem a can also cau se corn eal w arpage or distor t ion s, part icu larly w ith a low er th an n orm al (540 µm ) cen t ral corn eal th ickn ess. On ce th e IOP is con t rolled, th e distort ion of th e cor- n ea dissipates an d refract ive recover y occu rs rapidly.

High ly ast igm at ic, n on diseased, corn eal an atom y m ay also dem on st rate topograph ic irregularit ies. Th e irregu lar corn eal ast igm at ism m ay h ave a decen tered corn eal cap or a h igh asym m et r y of sup erior versus in ferior, tem poral versus n asal, sect ion s of th e corn ea. In th ese cases, a con tact len s is ver y difficult to cen ter on th e u n u su al lan dscape of th e corn eal topography an d w h en don e so, it w ill h ave a h igh er propen sit y to decen ter tow ards th e steeper m eridian an d bin d, cau sing in duced m olding to th e corn ea. Redu ced vision in th ese pat ien ts is n ot alw ays in - du ced by th e con t act len s, bu t w ill h ave an en h an ced ap preciat ion for visu al aberrat ion s an d m ay also h ave a m eridion al am blyopia.

Scarring or oth er path ologies th at in duce m ech an ical distor t ion s to th e corn ea can also m im ic corn eal w arpage. In part icular pter ygium , pulling across th e cor- n eal su rface, h as a m ore global th an localized effect , an d pan n u s or aberran t con - jun ct ival t issue m ay in du ce sim ilar m ech an ical distor t ion s.

Ect act ic corn eal degen erat ion s such as p ellu cid or keratocon u s m ay n ot h ave been determ in ed at th e in it ial len s fit t ing of th e pat ien t m any years prior. Form e fruste keratocon us (absen ce of classic an atom ical fin dings) is often m issed in th e in it ial fit if topography an d aberrom et r y are n ot properly ut ilized . Du e to th e in - creased in terest in refract ive surgical procedures, m any of th ese pat ien ts are being discovered in preoperat ive care an d ju stly den ied th e procedure. Literat u re suggest s th at PMMA an d gas-perm eable len ses at on e t im e in duced keratocon us. In fact , th e len ses did n ot in du ce th e disorder, bu t in stead cau sed a “pseudokeratocon ic” distort ion of th e corn ea, w h ich , in som e cases, is perm an en t . Pseu dokeratocon u s in du ced by con t act len ses w arping of th e corn ea produ ces a pat tern th at m im ics keratocon us eviden ced in a localized area of in ferior corn eal steepen ing. Upon len s discon t in uan ce th e in du ced steepen ing w ill regress to a n orm al “bow t ie” or “h ourglass-sh aped” topography w ith sym m et r y, m u ch un like a t ru e keratocon ic eye.

Management

Diagn osis by h istor y, refract ion , ret in oscopy, an d corn eal im aging is crit ical. Serial m easu res after len s discon t in u an ce w ill determ in e th e severit y, t ran sien ce, or p er- m an en cy an d th e fin al en d poin t prior to refit or su rgical procedu re. If con cern s of corn eal edem a arise, serial pachym et r y is a requ ired m easu re.

If th ere is sign ifican t corn eal edem a, len s discon t in u an ce is recom m en ded w ith th e in corporat ion of hyperosm ot ic agen t s w ith repeat pachym et r y t ill th e pat ien t dem on st rates refract ive recover y an d stable cen t ral corn eal th ickn ess (CCT) m easu res.

If th e corn eal distortion s are in duced by hydrogel soft len ses, th e sim ple discon - tin uance for a few days and refit to a slightly thicker or interm ediate elast ic m odu - lus, high -w ater, high -oxygen perm eabilit y, an d param eter-stable lens is appropri-