Keratoconus

KERATOCONOUS and DD

1. DR. Anupama Manoharan JR Dept of ophthal UGMCH ooty KERATOCONUS

2. KERATOC O NUS It is a clinica l en t ity cha r acterized by nonin fl a mmatory and nonin fect i ve, progr e ssive, bilatera l t hinn ing o f th e corne a wi t h ectasi a of conica l sha p e. This is mo s tl y bilatera l condition , girl s be t we e n 1 5 - 20 y e ars affected more, ov e ra l l incidence rate es t imated t o b e 0.15 t o 0.20 p erce n t. It manif e st s b y adolescenc e , resulting in consider a bl e visu a l impairment owin g t o the de v elo p ment o f high de g ree irre g ul a r myo p ic astig matism.

3. Keratocon u s is cl a s si f ie d in t o fo u r s t ag e s b y Kr u mei c h et al. STAGE 1 Eccentri c cornea l st e e p n e ss Myop i a and / o r astig matism < 5D Corne al radi u s ≤ 4 8D Vogt’s striae - no cornea l scar STA GE 2 Myop i a and / o r astig matism > 5D < 8D Corn eal radius ≤ 53 D No co r n eal scar Corne al t hickness ≥ 4 00 µm

4. STA G E 3 M y op i a and/or as t i g matism > 8 D < 1 0D Cornea l radius > 5 3D N o cor n ea l scar Cornea l t h ick ne s s 20 - 400 µm STA G E 4 Re fract i ve erro r not measurable Co r neal radius > 5 5 D Cornea l scar/p e rforation Cornea l t h ick ne s s 200 µm

5. ETIOLOGY D e fini t e e t iology is unknown . 9 5 % o f p a ti e nts d o not show evidenc e o f sp e cific her e ditar y pa t t e rn. P a tt e rn of inheritance is va r iable. Several theorie s hav e bee n put forwar d to ex p l a in th e e t iology o f keratoconu s . E NZYME TH EORY A l t e ration in th e l e vels o f fo l lowin g e nzy m e s hav e be e n not e d: Inc r e a s ed l e vel o f e pith e li al lysosoma l enzymes. Decrease d l e vel o f alph a -1 proteinas e inhibitor in the e p ith e li u m. D e c r e a s ed l e vels o f g l ucos e -6 phosph a te dehy d rogena s e in th e e pith e li u m.

6. C ONNE C T I VE T I SSUE A B NORMALI T Y THEO RY There is association o f ker a toconu s with som e c o nn e ctive tissue dis orders. G E NETI C T H EO R Y Due to th e occasi o nal association o f trisom y -21 with ker a toconu s, ge n eti c a b norma l ity may b e th e ca u se. HORMONAL THEORY It i s pr o p o sed bec a us e o f the man i festation s o f th e disease in adole sce n ce. E YE R U B BI N G Ha b itual ey e ru b bin g in som e diseas e s like v e rnal cat a rrh, Dow n syndrom e and p o orly s i ghte d patient s o f L e b e r ’ s tapetoret inal de g en e ration are associated with ker a toconu s.

7. AS S OCIATIONS S Y STE MIC DIS E AS E S C onn e ctive tissue a n d m e soderm a l dyspl a sia Marfan ’ s syndrome E h l e rs - Dan lo s syndrome Ost e ogen e si s im p erfecta C ong e nital h i p dyspl a sia Oculodent o dig i ta l syndrome Rie g er ’ s syndrome      Cr o uzon’ s syndrome Flo p p y eyel id syndrome Dow n syndrome Tur n er s syndrome Ato pic der m atitis Atopic der m atitis Do w n s y nd r o m e Ehler s -D a nl o s s y nd r o m e Marfan s y nd r o m e C r ou z on s y nd r o m e O steogenesis i m perfecta

8. ASS O CIATED OCULAR DI S ORDERS Retin i ti s pi g mentosa Le b er s con g enita l am a uros i s Blue sclerae Con g eni t al c ataract An i ri d ia Retino path y o f prematu r ity Fu c h s d y str o phy Posteri o r pol y morpho u s d y str o phy Granula r and latti c e d y str o phy ALLERGIC COND I TIONS Spring catarrh Asthma

9. CL I NI C AL FEATURES Gra du a l decreas e in vision, pho t ophobia, mono c u l ar diplopi a o r mon o cu lar polyopi a . Sever e pho t ophobi a and wat e ring is see n in c a ses o f hydrop s . Pa r ticul a rly ad o lescen t female s are a f fected There is c o nical protrusio n o f th e co r nea with centra l thinnin g and th e apex o f th e c o ne is u s u a l l y directe d inferona s a l l y .

10. Muns on’s s i gn is a V-s haped c o n f orma t ion o f th e lowe r li d produc e d b y th e ectati c corn e a in do w nga z e . Rizzuti’s s ign is a s harpl y fo c us e d bea m of ligh t near th e n a sa l limbus , produc e d by late r al illumin a t ion o f th e c o rnea in p a t ients with advanced kera t oc o nu s .

11. Sl i t l a mp ex a mina t ion Pr o minent c o rneal nerv e s

12. Sli t l a mp ex a mination Fleisch e r' s Ring  The Flei s che r ring is a yel l o w - brow n to olive - gree n ring o f pigmen t whic h m a y or may not comple t el y s urroun d th e bas e of th e cone  Forme d whe n hemo s ide r in (iron) pigme n t is deposite d dee p in th e epithelium Flei s che r ' s ring ofte n become s t h inner and more dis c rete wit h progres s ion

13. Seen ap p roximate l y 50 % o f a l l cases. Locating thi s ring ini t ial l y may b e made easi e r by usin g a cobal t filte r and carefu l l y focu s ing on the sup e rior hal f o f th e co r nea's e p ith elium. Onc e loc a t e d , t h e ring shoul d b e vie w e d in wh i te ligh t t o as s es s its e x t e nt.

14. Lines of V og t : Smal l and brus h lik e lines , g enerally vertica l bu t the y ca n be o b liq u e. F o un d in th e d e e p layer s o f th e strom a and f o rm a lon g the mer id i an o f gr e ate s t curvatur e. Disappea r w h e n gentl e pres s ur e is exerte d o n th e globe throu g h th e li d .

15. Cornea l Thinning: Si g nificant thin n ing (up to 1/5th c o rnea thick n e s s) in th e advan c e d stag e s o f th e dis e ase and a diag n o s tic cri t erion based on c o mpar i s o n of c e ntral an d p e r i p h era l c o rneal thick n e s s has be e n prop o s e d. Additional l y , as th e di s ea s e pro g re s s e s , th e c o ne is o f ten disp l aced inf e r i orly . The ste e pe s t p a rt o f the c o rnea (apex) is g e n e r a l l y t he thin n e s t.

16. Cornea l Scarring: Su b -e p ith e li a l c ornea l sc arring, not g e neral l y seen early , may occu r as k eratoconu s pro g resses b e cau s e o f r upture s in Bowm a n's membrane whic h is th e n fil l e d with connec t ive tissue D e e p opac i t y o f t h e corn e a are also commo n i n k e ratoconus.

17. Corne al Hydro p s : C o rneal h y drop s oc c ur s in advanced case s, wh e n D e sc e met's membrane rupture s , aque o u s f l o ws i n to th e corne a and reseals K e r a toc o n us pa t ients wh o a r e havin g an acute epis o d e o f c ornea l h y drop s report a s udd e n l o s s of vision and a visible whit e sp ot on th e c o rnea. C o rneal h y drop s cause s e d em a a nd opacificat ion .

18. As Descemet's regenerates, ed e ma and opa c ific a tion decr e ases. Occ a sional l y , hydrops can ben e fit k e ratoconus pati e nts wh o hav e ex t remely ste e p corneas . If th e co r ne a s c ars, a flatt e r c o rnea oft e n results, making it easi e r t o fi t wi t h a con t act lens. An increased incidence o f hydrops ha s also b e e n re p orte d in k e ratoconus pati e nts wit h Down's syndrom e .

19. Di a gnosis Ear ly ker a toconu s usuall y m a nifests as a sma ll islan d o f i r reg ula r astigmat i s m in th e inf e r ior par a c e ntral corn e a. As th e c o rnea bul g e s outward , th e amount of astigmat i s m increas e s du e to th e progr e ssi v e dist o r t ion o f th e corn e al surfac e. Th e s e chan ge s can easil y b e se e n as i r regular mi r es on keratometry readings and on corneal topograph y .

20. Man y objec t ive sign s a r e pr e sen t in ke rato c onus . Retinosc o p y sh o w s a sci s so r ing ref l ex. O n direc t oph tha l mo s cop y ther e is a dar k round shado w in t h e c o rneal m idperi p hery du e to t otal internal re f l e ction o f th e ligh t sur rou n din g the ce nt r al b r ight red fun d u s reflex and s e pa r a t ing it fro m th e n o r m al red periphera l reflex. It is c alled a C ha r l e u x oi l drople t refl ex.

21. The photokeratoscop e o r to p ograph e r pla c ido disc can p rovide an ov e rview o f th e co r ne a and can show th e relative st e e p ne s s o f any cornea l area. There is ev e n se p aration o f th e rings in t h e s p he rical corne a .

22. In astigmatic corne a uneve n spacin g o f the rings,espe c ia l l y inferi o r l y - in th e keratoc o nic co r nea sho u l d b e not e d The centra l rings may sh o w a t ea r -dro p configuration terme d " keratokyphosi s ".

23. With th e handhel d keratos c opes , s u c h a s t h e K l ein k e ratoscop e , earl y ke rato c onu s is cha r acterized b y a down w ard deviatio n o f th e horizonta l a x is o f the Pla c ido dis k reflection

24. The Keratome t e r al s o aids diagnosis. o C l a s s i f i c ation bas e d on kerato m etr y- Mi l d - < 4 5D in bot h m eridians Mod erat e - 4 5- 52D in b o th meri d ians Advance d - > 5 2D in bo t h meridians S e vere- >62D in bot h m e ridians The initial keratometric sig n o f keratoconus is absence of para l l e li s m and inclin ation o f t h e mire s . Th e s e ca n e a si l y b e missed in mild o r e arly c as e s.

25. COMPUTE R ASSISTED VIDEO K E R AT O S C OPY It i s o n e o f th e m o s t impor t ant diagn o stic aids f o r v e ry earl y as w e l l as abor t ive f o rms o f kera t oc o nus in th e oth e r ey e o f th e patie n ts with u nilateral k e r a toc o n us o r in th e famil y members. Dat a o f vide o kera t o s copi c im a g e a r e analyzed by c o mputers and d e picted as c o l o r c o d e d maps. Red c o l o r indicates my o pi c refract i on o r ectasi a and blu e c o l o r indicates hyper m et r opi c refr a ction or flatte ning o f th e corn e a.

26. PACHYMET R Y Sli t l amp pac h y m etr y s h ow s thin n ing in th e c e ntre o f the apex. Ultrasoni c pach y metry s h ow s exa c t thicknes s of c o rnea a t d i ffer e nt plac e s. Thinning in th e infer i o r quadrant ca n b e d i agnostic of kerat o c onu s. C entra l o r parac e ntral corn e al t h ickness of les s tha n 450 µ m is abnorm a l. If th e reading d e cr eases b y nearly 20 µ m towar d s the inf e rior per i pher y o n succ e s s ive pach y metric read ings, it is su s pi c i o u s o f ke r at o c on u s . Increase i n th e pro g ressive thinn i ng o f th e c o rnea i s a tru e in d e x o f keratoc onus .

27. Cornea l t opography P r ovi de s a c o lo r c o de d map of th e c or n ea l s urfa c e. The pow e r in d i op t e r s o f the ste e p e s t a n d flattes t me r i dia n s a n d th e ir a x e s are c a lcula t ed a n d displayed S t e e p c u r va tu re s are mark e d ora n g e o r r e d Fla t curvature in blu e o r vi o let Norma l curvatur e s in gr e e n or yellow

28. Keratoconu s is a cli n ic a l diagno s is a nd For m e Fruste K C is a subtl e topographi c abno r ma l ity before clinica l manifestat ion o f th e disease. The aim o f to p ogra p hy and tomo g raphy in refractive surger y clini c is t o ru l e ou t keratoectatic disease ei t he r in for m o f f r ank k e ratoconus o r subtl e FFKC as th e y are c ontraindic a tion s t o th e procedure.

29. The su s piciou s sign s fo r keratoc o nus inc l u d e: Ax i al map abnorm alities K greate r than 48 D . Skewe d r a di a l axis greate r tha n 21 de grees. Inferior -Superio r ratio great e r than 1.42D . C o rneal astigmatism greate r than 6 D. Against th e r u l e a s ti g m a tism. Superio r - Inf e r i o r differe n c e at th e 5 - mm zone >2 .5 D.

30. On t h e elevation maps Iso l a t e d isla n d o r to n gu e - lik e ex t ensi o n o n eithe r s urfa c e Elevat i o n values gr e a t e r than 12 mi cro n s o n th e a n terio r el e va t i o n map in th e cen tral 5 mm. Elevat i o n values gr e a t e r than 15 mi c rons o n th e poste r i or el e va t i o n map P achymetr y /corneal th ick n ess map: On Schei m pfl u g devices Thi n nest lo c a t i o n le s s than 470 m i crons. Displa c em e nt o f th e thi n nest poi n t >50 mi c rons fro m th e cen t e r . Pa c hyme t ry d iffere nc e asymmetry in tw o ey es at th inn e s t poi n t >30 mi c rons. S -I d i ff e r e n c e at th e 5 mm c i rcle > 3 mi c rons. Con e - lik e pat t e r n o n th e thi c knes s map.

31. The most elevate d poin t s o n t h e ant e rior and t he p osterio r el e vation maps shoul d b e co r related t o the hi g he s t p ow e r on A xial / Saggital cu r vature map a nd th e thi n ne s t p oin t o n th e g loba l pachyme t ry map. If all th e above match, it is c a l l e d as the “fo u rpoint touch” and is a hal l ma r k o f s uspec t co r nea, esp e cia l ly if th e ap e x is decen t ere d b y mo r e than 50 microns and t h e p eri p he r al thic k ness readings o f th e up p er and lowe r hal f at th e 7 - mm zone al s o sho w a sig n ificant differ e nce o f grea t e r than 100 microns.

32. Swir l sta i ning In pati e nts wh o hav e never wor n c ontac t lense s . Occ u r du e t o basa l e p ith elia l cel l dro p ou t as a r e su l t th e e pith e li u m s l ides f r o m th e p eriphe r y as the corne a re g e n erat e s. Thus a hurric a ne, vortex o r swir l stai n may occ ur.

33. Rabinovitz crite r ia fo r diagnosi s o f keratoco n us Centr a l co r neal powe r >47.2D Inferior superio r dioptri c as s yme t ry ove r 1.2 D Skew e d ra d ial axes o f a sti g matism b y mo r e than 21D e grees Difference in centra l powe r o f m or e than 1D be t we e n th e fel l o w eye.

34. DIF F ERENTIA L DIAGNOSIS 1 . KERATO G LOBUS This is du e to th i nning o f peri p her y o f th e corne a w hich grad u a l ly pr o gr e sse s toward s th e c e ntr e . It i s prese n t at or so o n after birth . So it is th ough t to b e a d e ve l o p m e ntal anoma l y. Perforation ca n o ccu r i n thi s condition with minimal ocular tra u ma. 2. POSTE R IOR KERATO C ONUS It i s nonprogressiv e , dom e sha p e d p osterio r e x cavat io n in the cornea w hich may b e sma l l and c i rcu m scrib e d ( ker a toconus p o sticu s circumscriptu s ) o r may b e di f fuse ( ker a toconus p o sticu s tota l i s ). It is consid e r e d to b e a cong e nital d e fect. Origin is prior to 5 t h o r 6 t h month o f ges tation . Tra u matic etiology is also reported.

35. 3. PELLUCID M A RGI N AL DE GENERATION It is a bilater a l p er i p h era l corn e al ect a ti c d i sorder charact e rize d b y a ban d o f thinnin g o f 1- 2 mm width ty p ically in th e inferior cornea . M aximum corneal protrusio n oc c ur s superio r t o th e area o f thinning. There i s no othe r abnormality and it oc c ur s in 2 n d t o 5 th de c ad e .

36. Management G l a s ses C o ntact lenses C o l l agen cro s s linking Intra c o r neal rings LASIK Xtra D e e p anterior l a mell ar Keratopla s ty Penetrating Ker a topla s ty

37. Specta c les M i l d ke rato c onu s can b e c or r ect e d wit h spectacles. Re t i noscopy is dif f icu lt ; a norm a l subjec t ive refr a ctio n is r equired. Mo n ocu l ar k e ratoconus is us u a l l y bes t deal t with usin g s p ec t ac l e cor r ec t ion. In t h is grou p o f pati e nts, motivation fo r contac t lens w e ar t e nds t o b e p oor.

38. Contac t lenses Contac t lense s are consid e red w h e n vi s ion is not correct i ble t o 6/9 b y spectacl e s and pat i ent s b e c ome s y mptoma ti c . Rig i d ga s perm e able (RGP) c ontact lense s are th e lense s of firs t choic e . The aim i s t o pr o vide th e b e s t vision possibl e wit h the maxim u m c omfort s o tha t th e lense s c a n b e wor n fo r a long per i o d o f tim e .

39. Base d on sha p e of cone Nipple c one : smal l d i am e t e r (5 mm.); ro u nd shap e ; e a si e st t o f it wit h conta c t lenses Ova l larg e d iameter(>5 mm.); oft e n disp l ac e d infer i orly; more d i ffi c ul t t o f it wit h lenses Glo b u s larges t d iamete r (>6 mm.); 7 5 % o f corn e a affec te d ; most diff i cul t t o f it wit h lens

40. Ni p pl e cone ova l cone glob u s

41. Fi t tin g methods 1 . Thre e -point- t o u c h des i gn Three- poin t- to u c h actua ll y refe rs t o th e ar e a o f ap i cal centr a l c ontact and tw o o the r are a s o f be a ring o r c ontact at th e mid- per i p h er y in th e h or i zontal d irec ti o n. The thre e- poin t - touc h desig n is th e m os t popula r and the most wid e l y fitt e d d e sign The aim i s t o distrib ut e th e we i gh t o f th e c ontact len s a s evenl y a s possibl e b e twee n th e con e and th e per i pheral c o rnea.

42. The ideal fi t shou l d sho w an a p ical contac t area o f 2 - 3mm wit h mi d -p e ripher a l contact. Adequate edg e clea r ance is required t o ensur e t ear e x chan g e.

43. 2 . A p ical cle a rance In thi s t y p e o f f i ttin g techn i que , th e len s vaults th e con e and cle a rs th e centr a l c o rnea, resting o n th e parac e ntral c o rn ea. These lense s ten d t o b e sma l l in d iameter and ha v e s m all opt i c zo nes The pot ential a d vantages o f re d uc i ng centr a l corn e al scarrin g are outweighe d b y th e disadvantage s lik e poor te a r film , c o rneal o e dem a , and po o r visual acuity as a result o f b u bbl es b ec o ming trapp e d un d e r th e lens.

44. 3. F la t f it t ing T h e fla t f it t ing method pl a ce s alm o s t th e en t i r e weigh t o f th e le n s on th e con e . T h e l e ns t e nds t o b e held in po s iti o n b y th e to p lid. Goo d visual acuity is ob tained as a result o f apical tou ch Alig n m e nt ca n b e o bt ai n ed in early k eratoco n u s; however , fla t fit ting le n se s ca n lea d t o p r og r ession / a cce l eratio n o f a p ical change s and cornea l abrasions. T h is typ e o f f it t ing is usefu l w h er e th e a p e x o f th e con e is displaced. .

45. Pigg y back lense s - R G P - C L ove r a SOF T CL Ca n b e use d in pt s wh o are uncomf o rtable wit h RGP wear, more s o in pt s pr o ne t o e pith e lia l er o sio n at apex o f c o ne ROSE -K design R G P - are spec i ally desi g ned for kerat o c o nic eye s wit h a di a gnosti c se t o f 26 len s e s w ith base curve s rangi ng fro m 5 .1 t o 7.6 mm in 0.1 in c reme nts, a std len s diam e te r o f 8.7mm

46. Scleral len s es Scleral lense s pla y a v e ry significan t ro l e in ca s e s of advanced keratoc o nus wh e re co r neal le n se s d o not wor k a nd cornea l surg e ry is contr a -indicated. Scleral lense s co m plet e l y neutr a li s e any c o r neal irre g ul a rity and can he l p patients maintain a n ormal quality o f l ife

47. Soper lens Custo m made lens Two zones in th e p e riph e r al p osterio r curvature Centra l zone : to v a u l t ste e p centra l corne a .It is of varying ste e pn e s s de p endin g o f th e pati e nts co r nea. Periphe ral zone is wit h a 45D cu r vature designe d to vau l t th e mid p e riphery and limb a l co r nea

48. Bos t on scler a l len s pro s the t ic devi c e (BSL P D) Flui d ve nti late d sc l era l lens D esi g ned t o e n clo s e a bubbl e fre e reserv oi r o f f l uid ov e r th e co r neal surf a ce Seri e s o f breache s are creat e d b e t w e e n haptic b e aring sur f ace o f th e le n s and und e rlying sc l era.

49. This wi l l faci l itate th e a s piratio n o f s ur f ace tear s into th e reservoir s o tha t intrusion o f air bubbl e durin g a blin k is prev e nt e d. Sha p e o f haptic confi r ms exactl y t o tha t of underlyi n g sc l er a t o maintain functionalit y and prev e nts intrusion o f air bubbles. Very e x p e n si v e

50. C o lla g e n cro s s lin k ing A newer and les s invasive techn i que tha t s h ow s prom i s e in kerato c onus manag e ment is com b in e d rib oflavin - ultraviolet typ e A ray s ( UV A ) collag e n cros s - linking. This pro c e d ur e consist s o f phot o polym e r i z a t i o n o f corn e al strom a b y c ombin i ng vitamin B2 (photosen s it i zi ng sub s tance ) wit h UVA. This pro c es s in c reases rig i d ity o f c o rneal c o llage n and thus re d uc e s th e likel i hood o f furth e r ect a si a .

51. • U sin g topica l a n a e sthesi a , 7 mm ci r cl e is ma r k ed o n the co r n e a usin g a tho r nton ma r k e r . • Ep i th e liu m o f th e mar k ed area is scrap e d of f usin g a blun t s pa t ula. • A corn e al abrasion is c r ea t ed t o f a cilit a t e r ibof l a v in diffusio n into th e co r n e a. • O n e dr o p o f r ibof l a v in 0.1 % an d 20% de x tran o p hthalmi c so l utio n is in stil led to p ical l y in th e e y e e v e r y 2 minut e s f o r 30 minut e s. • At th e end o f th e 3 - minute pre t r ea t ment p e r iod, th e e ye is e xamined wit h blu e lig h t fo r t h e pres e nce o f a y e llow fl a r e in th e an t e r ior chamber , indic ati n g ad e quate r ibof l a v in s a tur a t ion o f th e cor n e al tis s ue. Technique

52. When th e yello w flar e in th e ante rior chamb e r is conf i rmed , th e ey e is aligned un d e r th e U V - A ligh t wit h th e tr e atment plan e at 5 mm fro m th e U V - A bea m aperture . Fo c us s e d on th e ape x o f c o rnea a t a d i stanc e o f 1 - 12m t o obtai n a rad i ant en e rgy o f 5.4 J /cm2 fo r 5 min The corr e c t aperture s ett i ng is s ele c te d fo r th e siz e o f the eye ; th e ey e is irrad iat e d fo r 30 min u tes , d u ring whic h time instillati o n o f ri b o flavin is cont i nued (one dr o p ever y 5 minutes).

53. After completio n o f th e proc e dure,ey e is w a she d with BSS , an an t ibiotic dro p is instilled and a b andage contac t len s is ap p lied. The contac t len s is remove d onc e the abr a sion has healed. Posto p era t ive med i cat i on s include an ant ibio t ic and a s t eroi d fo r 2 we e ks p osto p erati ve l y.

54. Compli c at i on s o f C 3 R Co r neal h aze D iffuse lamel l ar keratitis Re activati on o f viral keratitis and iritis Infective keratitis Cornea l scarring Persistent c ornea l e dema Co r neal me lt

55. LA S IK Xtra LASIK X tra basi c ally means LAS I K c ombi ned wi t h C3 R t o treat K e r a t o c o n u s a n d also fo r ec t asia fol l o w i n g LA S IK su r gery. LASIK X tra embod i e s a prop e r evolutio n o f LAS I K t echni qu e , t he r e frac tive s u rge ry tech n ique whic h ha s r e ceive d th e most enthu s iast i c a c cl a im worldwi d e . This tech n ique u s e s t he exc i mer lase r t o rem od e l th e c urv e o f th e c or n e a a n d s urgi c ally c orrect myop ia, hype rme trop ia, asti g ma t ism a n d pr e sbyopi a in a rapid a n d saf e ma n ner. J u s t lik e LASIK pro c edu r e , th e LASIK X tra tech n ique is also s u cc e s sf u ll y e mpl o ye d t o r e - trea t previou s i n tervent i on s th a t were partl y o r i n c o mple tel y satisfa c t ory. G e nerally, th e pro c edu r e is bil a teral , i .e . th e sigh t def e c t is c orre c t e d in bo t h ey e s in a single operati n g s e s s i on.

56. Advantag es It is p a in-fr e e , bot h durin g and af t e r th e pro c edur e. In addition to sta n dar d L A SIK res u l t s , th e L A SIK X t ra t e chniqu e rest ore s th e stre n gt h o f cornea s weak e n e d by L A SIK. It e n abl e s normal activity to b e res u med immedia t e l y: e.g . wor k a n d sp ort. F u rthermore, bila t era l cor r ectio n al s o notably faci l itat es po s to p era t ive adj u stm ent.

57. WHO C AN US E LAS I K XTR A ? T h e ideal candidat e fo r LAS I K Xtr a ha s a stab le refra ct i on, hea lth y cornea s and certai n p h ysiol o gica l characteristics (essent i all y , an adequate co r neal thickness) ; in addition the candidat e must b e hig h l y motivated t o r e duc e o r eliminate any de p endenc e o n gl a sse s and lenses. T h er e must b e no ot h e r e y e diseas e s p r es ent. F o r w om e n at an advan c e d stag e o f pr e gnancy , it is p r efer ab le tha t the y d o not underg o las er sigh t co r rection un t il their e y esigh t stabilises , af t e r th e birth. Prev i ou s surg e ry is n o t a contraindic ation. Indeed, LAS I K Xtr a ofte n p erfects u nsat i sfactor y res ult s o f p r eviou s surge r y.

58. L A SIK Xtr a streng t heni n g ef f ec t al l ow s to b r oade n the incl u sio n c r iteria fo r po t e n tia l pa t ien ts , op e ning the po s sibili t y f o r many i n e ligible L A SIK p a ti e nts to become candidat e s fo r LA SIK Xtr a – al thoug h t hi s eva l ua t ion is sp e cifi c al l y car r ied ou t b y th e surg e o n o n a cas e- b y - case basis. To ass e s s s uitabi l ity fo r th e proced u re and th e nat u re of the eye s ight d e f e ct , it is indis p e n sabl e tha t th e pa t ient u n derg o a thoro u g h pr e op e rative check . O n th e basi s of this the sp e cialis t ca n p l an a tai l o r -made tre a tmen t .

59. R I SK S AND COM P LICATI O NS Wi t h th e LAS I K t ech n ique, n o ma j o r o r s e r i o u s ev e n t s hav e ev e r be e n r e ported , i n volv i ng los s o f th e e y e o r o f ey e sight . Infect i o n is extrem e l y rare, bu t c a n b e re solv ed wit h a n t i bi o t i c treatment. O n r are oc c asio n s it may b e th e c ase tha t wh e n vis i o n has s e t t led, th e re s u l t s ob t a in e d d o n o t full y meet expec t a t i on s . Th i s d ep e nd s on th e n a tura l r e a c t ivi t y o f th e ey e which , if th e treatment s are e qual, d i ff e rs fro m p e r s o n t o p e r s o n . In the s e rare cases, term e d “ u n d e r - c o rr e c t i o ns” or “ove r - c orrec t i on s”, the ex t reme flexi b il i ty of the LAS I K X t ra te c hn i que all o w s fo r a s u bs e qu e nt i n terv e n t i o n t o p erf e c t t he r e s u lt s o bt ai n ed, wit h no risk fo r th e pat i ent

60. Intracorneal stroma l rings Act as passive spaci n g ag e nts w h ich flatt e n the cornea Made o f PMMA Amount o f corr e ction d e pend s o n th e ring t h ickn e ss , more thicker th e ring more correc t ion. O n insertion th e y s h orten the a rc o f ant cornea l surface , iro n out gros s i rr e g u l a rities and in effec t c r e ate a secon d lim b us . Vario u s cornea l ring - ker a ring s , intac s .

61. An im p ortan t p ot e ntial b ene fi t o f treati n g k e ratoconus wit h INTACS inserts is t o del a y or elimina t e the ne e d fo r a corn e al g raft. Patients w i t h mild t o moder a t e keratoc o nus appear t o b e th e bes t c andidate s.

62. Complications Undercorrection Overcorrecti on Migration o f rings E x t rusion o r pr o gr e ssive thinn i ng Ne w vess e l f o rmation glare / h alos

63. Penetra tin g Ker a topla s ty The g ol d sta n dar d s u rgery Succes s r ate is mo re than 90%. In thi s procedure , th e k e ratoconi c co r nea is pre p ared b y removing th e cen t ral a r e a o f th e cornea, and a ful l - thic k ness co r neal but t on is sutu r e d in its place. Usuall y tr e p hin e s b e t w e e n 8. -8. 5 mm are u sed.

64. Fleischer’s ring can be used a s t he limit o f the conic a l cornea. Conta c t lense s a r e ofte n required after this procedure fo r b e s t visual rehabili t ation.

65. Dee p Anterior Lamellar Kera t opla s ty Par t ial c orn e al t ransplan t . T h e corne a is removed t o t h e dep th o f post e rior stroma , a nd th e donor bu t to n is suture d in place. T h is te c hniqu e is t e chni cally difficul t , a nd visual acuity is inferior to tha t ob t ained after p e n e t r a ti n g kerat opla s t y . As a result, us e o f lame l la r k eratoplast y is largel y confin e d t o t he treat m e n t o f larg e con e s o r k eratoglo b u s whe n t e c t oni c su p po r t is n e ed e d. T h is t e chni q u e r equ i r e s les s r ecover y time , and p o se s les s chanc e for co r neal g r a f t r ej e ctio n o r f a ilure. I t s d i sad v an t ag e s i n c l u de vascula r ization and ha z in e s s o f t h e gr a ft

66. Thermokeratopla s ty Rare proced u re It involv e s p l acing a ho t ring ( Holmi u m ya g l a s er, 2100 n m) al on g t h e bas e o f th e con e to h e at a n d tra u matize th e co r n ea, res u l t ing in a co r n eal sca r which reduces th e c ornea l cur v ature. It al low s a f l att e r contac t l e ns to b e fi t t e d.. The disa d vantages o f th e pro c edure o tr a ns i tor y corn eal haze o deve l opm e nt o f corne al scarr ing

67. Phakic iols Use d t o co r rect high myopia and asso c iated astig matism o f s el e ct ed ke rato c onu s pati e nts. Ant e rior chambe r phaki c intra o c u l a r len s hav e a l s o b e e n combin e d wit h intacs wit h goo d r esults. The Intacs implantation is f ol l owe d b y tori c phakic intraocul a r l e ns im p lantatio n t o correc t th e residual myo p ic and astigmatic refractive error.

68. “Five point” m an a geme n t alg o r i thm for ker a toconus

69. TH A N K YOU