FRCOphth, CertLRS.
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Vision correction surgery @ Cleveland Clinic Abu Dhabi
+971 2 665 2051
Keratoconus
Your cornea (the clear window at the front of your eye) is normally round in shape (like a soccer ball). In Keratoconus, the cornea progressively becomes softer than normal, and therefore it thins out and becomes iirregular in shape.
When that happens, light is improperly focused within the eye, causing blurry vision, double vision or halos.
CONTACT LENSES
In early stages of keratoconus, your vision can be corrected by a change in glasses or contact lenses, however as the Keratoconus progresses, these can't correct all of the irregularities in the cornea.
As the irregularity of the keratoconus becomes worse, the first step in treatment is to try using specialized hard contact lenses which serve to mask the irregularities of the cornea and also provide optical correction. These contact lenses vary in their design and material, these include rigid gas permeable lenses (small and hard), hybrid contact lenses (hard center and soft periphery) and scleral contact lenses (large and hard, sitting on the sclera, not touching the cornea). Contact lenses usually offer quality of vision superior to that achievable by surgery. However, if the contact lenses are uncomfortable or difficult to use, then you may need to have surgery.
CROSSLINKING
Corneal collagen cross linking, is a procedure used to stabilize keratoconus, by irradiation the eye with ultraviolet light (UVA) in the presence of vitamin B2 (Riboflavin) eyedrops. These combine to cause a reaction that results in stiffening of the collagen fibers (the structural scaffolding) in the cornea. There are different techniques of doing crosslinking, but they all generally take up to half an hour to perform.
If successful, crosslinking stops keratoconus progression, and in some cases causes some flattening of the keratoconus.
It is best done in mild to moderate cases of keratoconus. This typically allows patients to continue using glasses or contact lenses as before.
However, if you are unable to reach acceptable levels of vision with glasses or contact lenses before cross-linking, then you might not be a good candidate for this treatment.
PRK LASER & CROSSLINKING
In very early cases of keratoconus, where there is a mild degree of irregularity, corneal crosslinking can sometimes be combined with PRK laser treatment to smooth out the surface of the cornea. The laser treatment serves to improve your vision, while the crosslinking treatment serves to increase the strength of the cornea.
CORNEAL RINGS
Corneal rings are offered to patients that have moderate grades of keratoconus. These are very thin semicircular segments of transparent plastic that are implanted within the cornea. These stretch out the cornea to cause some flattening, and regularisation of the keratoconus. The advantage of this procedure is that it is a quick, simple procedure that is relatively non-invasive and reversible.
CORNEAL TRANSPLANTATION
Corneal transplantation is a procedure reserved for severe grades of keratoconus, where patients are intolerant to or unable to achieve good levels of vision with contact lenses.
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When we perform a corneal transplant, we replace the weak, irregular keratoconic cornea with stronger, more regular corneal tissue from another person. This allows patients to see better with glasses afterwards, and also could open up possibilities of laser vision correction to further improve vision a year or so after surgery.
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The standard procedure for corneal transplantation is deep anterior lamellar keratoplasty. In this technique we remove between 90-99% of the corneal thickness, leaving a thin layer of recipient cells behind. The donor cornea is then placed on top of this thin layer.
Although technically demanding, this procedure eliminates the risk of endothelial transplant rejection.
This is superior to the older technique of penetrating keratoplasty, where the whole cornea is replaced, and there is a risk of your body rejecting the graft.