Corneal ectasia is a relative weakness in the structure of the cornea, which produces a progressive change in its shape which results in visual distortion. It is known that collagen cross-linking in the cornea occurs naturally with age, and in diabetes, both of which seem to prevent progressive ectasia. Corneal collagen cross-linking with riboflavin on corneas thicker than 400 microns has been shown to stabilize the cornea in keratoconus, and prevent progression of the disease.

The purpose of this study is to determine whether corneal collagen cross-linking with riboflavin in a hypotonic solution, with UV light, on corneas less than 400 microns thick, leads to stabilisation of corneal ectasia.

When cross-linking corneas of > 400 microns, riboflavin in a solution with high molecular weight dextran T500 is used to prevent corneal swelling during the administration of the drops and the UV treatment. However if riboflavin is applied to a cornea in a hypotonic solution (saline), then transient corneal oedema is created with thickening of the corneal stroma. In this way it is thought that the temporarily thickened cornea can be treated with UV whilst still providing a sufficient thickness to absorb the UV to an extent that endothelial cell damage is avoided.

Inclusion Criteria:

• Keratoconus
• Corneas thinner than 400 microns, but thicker than 250 microns

Exclusion Criteria:

• Evidence of other corneal disease in the eye to be treated (e.g., Herpes simplex keratitis)
• Women who are pregnant or nursing at the time of the initial treatment