Researchers in Turkey have found that implantation of intrastromal corneal ring segments followed by corneal collagen cross-linking (CXL) therapy provides more effective treatment of progressive keratoconus than CXL followed by corneal ring segment implantation.
Keratoconus is a progressive eye disorder characterized by thinning and bulging of the cornea into an irregular cone-shaped profile, causing blurred vision that cannot be fully corrected with eyeglasses. If left untreated, progressive keratoconus can require a corneal transplant.
In the early stages of keratoconus, vision may be adequately corrected with rigid gas permeable (GP) contact lenses, and fitting these lenses often is the first line of treatment for keratoconus.
Due to weakening of the corneal structure in keratoconus, LASIK and other corneal refractive surgery is contraindicated for anyone diagnosed with keratoconus or who shows early signs of suspect keratoconus.
In progressive keratoconus or advanced keratoconus that makes GP contact lens wear impossible, newer treatment options include implantation of intrastromal corneal ring segments (ICRS) and corneal collagen cross-linking (CXL) therapy.
In CXL, a liquid riboflavin (vitamin B2) solution is applied to the surface of the cornea and then is activated with ultraviolet light, typically for a period of 30 minutes. This noninvasive therapy has been show to successfully create stronger bonds between collagen fibers within the cornea and thereby strengthen the corneal tissue.
The researchers in this study sought to determine which sequence of these procedures works best when both ICRS implantation and CXL are employed to treat progressive keratoconus.
Patients were divided into two groups: Group 1 underwent corneal collagen cross-linking first and Group 2 underwent intrastromal corneal ring segment implantation first.
The results of the study showed that uncorrected distance visual acuity and corrected distance visual acuity improved in both groups; and myopia, astigmatism and corneal curvature decreased in both groups.
However, Group 2 (ICRS implantation followed by corneal collagen cross-linking) showed greater improvements in corrected distance visual acuity, overall myopia and astigmatism reduction and corneal curvature reduction.
The researchers concluded that ICRS implantation followed by CXL therapy is the preferred sequence for the most successful treatment of progressive myopia.
SOURCE: Effect of treatment sequence in combined intrastromal corneal rings and corneal collage crosslinking for keratoconus. Journal of Cataract & Refractive Surgery. December 2009.