Corneal Collagen Cross-Linking (CXL)

CXL is a breakthrough procedure used primarily to treat keratoconus and corneal ectasia (bulging of the cornea). The technique was introduced in the 1990s and first performed on human eyes in 2003.

The cornea is made of collagen fibers interconnected with cross-links of which their primary function is to provide mechanical support. In keratoconus there is a reduced number of these links and as a result the corneal shape becomes more conic. CXL works by increasing these collagen cross-links and therefore strengthening the cornea.

The links are seen as red lines-number of red links increased after CXL

CXL uses riboflavin (vitamin B2) and ultraviolet-A (UVA) radiation to increase the biomechanical and biochemical stability of the stromal collagen fibers. Riboflavin has a  dual purpose: to induce crosslinks between the collagen fibers and to protect the underlying tissue from the effects of UVA.

Research has shown that CXL can produce significant flattening of corneal topography as well as improvements in best-corrected vision.

Patients between the ages of 10 and 35 years who have progressive keratoconus, corneal thicknesses of at least 400μm, and minimal corneal scarring can be treated with CXL. CXL should be considered in patients under the age of 18 years, as keratoconus progresses more rapidly in young people than in any other group.

Improvements have also been achieved in patients older than 40 years of age who were treated, but the improvements are more modest than those observed in younger patients. These data suggest that even patients who have stable keratoconus may achieve improved vision and corneal flattening after their corneas have stabilized.

Whether improved vision is a sufficient reason to cross-link older patients is debatable, particularly if they are seeing well with contact lenses or eyeglasses. Further studies are necessary to assess potential complications of treating older patients.


Corneal Graft

Corneal transplantation is a surgical procedure by which the damaged cornea is removed and replaced by the donor clear cornea.

PK (Penetrating Keratoplasty) is a full thickness graft, where the entire thickness of the central part of your cornea is removed.

DLK (Deep Lamellar Keratoplasty) is a partial thickness graft leaving the bottom half of your own cornea intact and replacing the top half with the new one.

The most common diagnosis eventually leading to corneal transplantation is keratoconus;
15-20% of the keratoconic patients will progress to a point where vision correction is no longer possible, thinning of the cornea becomes excessive, or scarring as a result of contact lens wear causes problems of its own, and corneal transplantation or penetrating keratoplasty is the only option.  Corneal transplantation for keratoconus is highly successful.

Despite advances in surgical techniques, high irregular astigmatism, myopia and hypermetropia still remain common after surgery.

Up to 25% of these patients may require a contact lens correction after surgery, usually a rigid gas permeable lens for optimum vision.