Intrastromal corneal ring: 12-month sighted myopic eyes.

BACKGROUND: To evaluate the efficacy, predictability, and stability of the refractive effect produced by the Intrastromal Corneal Ring (ICR), the authors completed a 12-month study on 10 myopic eyes. METHODS: Ten patients with preoperative refractive errors ranging from -2.63 diopters (D) to -4.25 D (mean, -3.30 D) participated in the study. The attempted correction was -2.50 D for a 7.0-mm diameter, 0.3-mm thick ICR. One eye of each patient received an ICR. RESULTS: The average change in spherical equivalent at 12 months was -2.25 D (SD 0.54 D; range, -1.62 to -3.25 D). All patients maintained a spectacle-corrected visual acuity of 20/20 or better during the 12-month study period, with the exception of patient no. 6 who saw 20/30 at the 6-month examination. Her spectacle-corrected visual acuity returned to 20/20 a few days after the ICR was explanted and remained stable throughout the study. Uncorrected visual acuity had improved to 20/40 or better in all patients on postoperative day 1 and remained in this range for the 9 eyes (90%) during the 12 months of follow up. At postoperative month 12, 9 of 9 eyes (100%) had an uncorrected visual acuity of 20/40 or better with 3 of 9 eyes (33%) seeing 20/20 or better. The remaining patient, no. 6, experienced a tear in Descemet's membrane during the procedure and required explantation of the ring after 6 months due to induced astigmatism and deterioration of uncorrected visual acuity. Two patients developed infiltrates that resolved with the use of antibiotics. The most common postoperative ocular findings were peripheral corneal haze in all eyes that diminished over time, minute lamellar channel deposits (7 of 10 eyes, 70%), deep stromal neovascularization (5 of 10 eyes, 50%), and pannus (5 of 10 eyes, 50%). CONCLUSION: This preliminary study shows that implantation of an intrastromal corneal ring of this dimension (0.3-mm thick) can reduce approximately 1.50 to 3.00 D of myopia and maintain spectacle-corrected visual acuity.

Intrastromal corneal ring--one-year results of first implants in humans: a preliminary nonfunctional eye study.

BACKGROUND: The Intrastromal Corneal Ring (ICR) is a new investigational medical device designed to alter corneal curvature without surgical intervention in the central cornea. The ring is inserted between the layers of the stroma in the cornea's periphery at two-thirds depth through an approximately 2-millimeter incision. METHODS: To investigate the safety and refractive effect of implanting an ICR of a given thickness (0.30 mm) and outer diameter (7.70 mm) into human corneas, an ICR was implanted into one nonfunctional eye of each of three patients during the period of March to May, 1991. One predesignated ICR was successfully explanted 5 months after implantation to evaluate the feasibility of ICR removal and to observe the effect of ring removal on corneal curvature. Patients were followed for 1 year after the initial implant procedure. RESULTS: The three implant procedures and postoperative courses proceeded without any significant complications. Approximately 2.00 D of central corneal flattening was achieved in all eyes. No adverse reactions or other medically-significant complications were observed over a 1-year follow-up period. The patient who underwent ICR removal experienced no perioperative complications, and the patient's cornea has remained stable with a return to its preoperative curvature. CONCLUSION: Although this study is preliminary and limited in scope, we have demonstrated that the ICR can be tolerated safely in the human cornea and results in a flattening of the corneal curvature that is stable for up to a year after insertion. The successful removal of the ICR begins to establish reversibility of the procedure and induced refractive effect.