Donors Predisposed by Corneal Collagen Cross-linking in Deep Lamellar Keratoplasty for the Patients With Keratoconus

Keratoconus is a progressive ecstatic corneal disease characterized by forward bulging of the cornea, thinning of the corneal stroma, and irregular astigmatism. Corneal transplantation is necessary for patients with advanced keratoconus when spectacles and contact lens are inadequate for visual correction. Deep anterior lamellar keratoplasty is a conventional procedure for the treatment of keratoconus. However, DALK itself frequently causes abnormality of refraction, such as high degrees of astigmatism owing to irregular corneal surface for keratoconic eyes. Possible mechanisms of this progressive astigmatism include the recurrence of keratoconus in the grafts, progressive corneal thinning of the host cornea, or progressive misalignment of the graft- host interface over time, which prevents the achievement of satisfactory vision. Corneal collagen cross-linking is believed to have the ability to halt or decrease the progression of keratoconus. CXL treats keratoconus by strengthening corneal stromal collagen bonds with riboflavin activated by ultraviolet A (UVA), and is now a first-line treatment for progressive keratoconus. In this randomized controlled trial, we performed CXL on corneal donor tissues with the aim of achieving corneal stromal stiffening, thereafter DALK was conducted for the patients with advanced keratoconus using the tissues predisposed by CXL. The goal of this study is evaluating whether the strengthening grafts could reduce postoperative myopic refractive errors or arrest the progression of keratoconus for the patients with DALK.