Ker­a­to­conus, pro­gres­sive eye dis­ease

Jamaica Gleaner - - WORLD SIGHT DAY -

WHAT IS KER­A­TO­CONUS?

KER­A­TO­CONUS LIT­ER­ALLY means a cone-shaped cornea. The cornea (the clear front por­tion of the eye) be­comes thin and pro­trudes. This ab­nor­mal shape can cause se­vere dis­tor­tion of vi­sion.

WHAT CAUSES KER­A­TO­CONUS?

Re­search in­di­cates that ker­a­to­conus may be caused by an ex­cess of en­zymes that break down the pro­teins in the corneal sur­face. Ker­a­to­conus ap­pears to run in fam­i­lies. The con­di­tion hap­pens more often in peo­ple with cer­tain al­ler­gic eye con­di­tions. The con­di­tion could be re­lated to chronic eye rub­bing. Most often though, there is no eye in­jury or dis­ease that ex­plains why the eye starts to change. Ker­a­to­conus usu­ally starts in the teenage years but it can be­gin in child­hood or in peo­ple over 30 years of age. The changes in the shape of the cornea can hap­pen quickly or may oc­cur over sev­eral years. Ker­a­to­conus is more com­mon than thought and is often not di­ag­nosed un­til in the ad­vanced stages.

WHAT ARE THE SYMP­TOMS OF KER­A­TO­CONUS?

Blurred vi­sion, dis­tor­tion, glare, light-sen­si­tiv­ity and corneal ir­ri­ta­tion are among the early signs. As the dis­ease pro­gresses and the cornea steep­ens and scars, the vis­ual dis­tor­tion will in­crease. The changes can stop at any time or they can con­tinue for decades. In most peo­ple both eyes are even­tu­ally af­fected although not al­ways to the same ex­tent. To con­firm if you have ker­a­to­conus your eye exam will in­clude the mea­sure­ment of the shape of the cornea. This can be done by us­ing var­i­ous in­stru­ments, one of which is a corneal to­pog­ra­pher.

HOW IS KER­A­TO­CONUS TREATED?

Glasses may be suf­fi­cient in the early stages of ker­a­to­conus but con­tact lenses are needed when the cornea be­comes so mis­shapen that glasses are no longer ef­fec­tive. In some cases, the corneal shape be­comes even too dis­torted for con­tact lenses to help. Scar­ring may de­velop, caus­ing the vi­sion to be cloudy. At this stage, a corneal trans­plant is usu­ally needed.

Corneal trans­plan­ta­tion is a ma­jor sur­gi­cal pro­ce­dure and car­ries cer­tain risks. There is, how­ever, a rel­a­tively new treat­ment for ker­a­to­conus called Corneal Col­la­gen Crosslink­ing with ri­boflavin.

A pro­ce­dure de­vel­oped in Europe in the late 1990s, Corneal Col­la­gen Crosslink­ing has now proven it­self in in­ter­na­tional clin­i­cal stud­ies and is ap­proved through­out the Euro­pean Union for the treat­ment of ker­a­to­conus or other corneal ec­tasias. It was ap­proved by Health Canada in 2008 and is cur­rently un­der­go­ing in­ves­ti­ga­tion by the FDA in the USA.

Corneal Col­la­gen Crosslink­ing with ri­boflavin causes the for­ma­tion of nor­mal chem­i­cal links be­tween the col­la­gen pro­tein strands in the cornea. This strength­ens the cornea, mak­ing it more rigid and can stop the ker­a­to­conus from pro­gress­ing. The treat­ment may even cause the ker­a­to­conus to re­verse to some ex­tent. Corneal Col­la­gen Crosslink­ing may pre­vent the need for con­tact lenses if per­formed early on. Even where con­tact lenses are al­ready needed, Corneal Col­la­gen Crosslink­ing can elim­i­nate the need for corneal trans­plan­ta­tion. No other treat­ment for ker­a­to­conus can of­fer these ben­e­fits.

WHO IS A SUIT­ABLE CAN­DI­DATE FOR CORNEAL COL­LA­GEN CROSSLINK­ING?

Any­one with pro­gres­sive ker­a­to­conus is po­ten­tially suit­able. Pa­tients with ad­vanced ker­a­to­conus or whose vi­sion is al­ready spoiled by scar­ring will usu­ally not be good can­di­dates for the pro­ce­dure. The ear­lier the treat­ment is done the bet­ter, but Crosslink­ing can still be ben­e­fi­cial decades af­ter ker­a­to­conus has be­gun to de­velop.

It is an out­pa­tient pro­ce­dure and is ex­tremely safe.

Based on the avail­able data, Corneal Col­la­gen Crosslink­ing of­fers a treat­ment for a dis­ease that cur­rently has no real treat­ment ex­cept corneal trans­plan­ta­tion. This treat­ment has been avail­able in Ja­maica for the past two years.

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