One-year results of the intrastromal corneal ring in nonfunctional human eyes. Intrastromal Corneal Ring Study Group.

OBJECTIVE: The intrastromal corneal ring (ICR), a new keratorefractive device designed to correct myopia, was evaluated for safety and efficacy as part of a phase I Food and Drug Administration clinical trial.

PATIENTS AND METHODS: Ten patients, each with one nonfunctional eye, underwent surgical implantation of the ICR, which is a split ring composed of polymethyl methacrylate. The eyes were followed up during a 1-year period and were evaluated for wound healing, implant-related inflammation, intraocular pressure, corneal thickness, endothelial cell count, and refractive effects.

RESULTS: Wound healing was uncomplicated in all of the patients. No patient experienced implant-associated inflammation or extrusion. Intraocular pressure, corneal thickness, and endothelial cell counts were unaffected by the ICR. Non-sight-threatening intraoperative events included ring decentration and inadequate attachment of a vacuum-centering guide. The ICR reduced keratometrically determined spherical equivalence by an average of -2.5 +/- 1.1 diopters (mean +/- SD). Spherical equivalence, as determined by retinoscopy, was reduced by an average of -2.4 +/- 1.0 D. Results of corneoscopy and computerized videokeratography further confirmed this reduction of myopia.

CONCLUSIONS: The ICR may be a safe and efficacious device that offers predictable results with few side effects, and it may be a feasible alternative to current keratore-fractive procedures.