Two-year outcomes of Intrastromal Corneal Ring Segments for the correctionof myopia

Objective: To evaluate the safety and efficacy of Intrastromal Corneal Ring Segments (ICRS) for the correction of myopia. Design: Nonrandomized, comparative trial. Participants: Patients enrolled in the United States Food and Drug Administ ration phase II and phase III clinical trials of the ICRS had best spectacl e-corrected visual acuity (BSCVA) of 20/20 or better, myopia of - 1.00 to - 3.50 diopters (D), and a cylindrical correction of 1.00 D or less as measur ed by manifest refraction. Intervention: Surgical correction of myopia with an ICRS. Main Outcome Measures: Efficacy was assessed by predictability of refractiv e outcome (deviation from predicted cycloplegic refraction spherical equiva lent), stability of refractive effect, and postoperative uncorrected visual acuity. Safety was assessed by adverse events, maintenance or loss of preo perative BSCVA, and induced manifest refraction cylinder. Results: Four hundred fifty-two patients were enrolled at 11 investigationa l sites in both studies. Of the 454 surgical attempts, 449 received an ICRS in one eye (0.25, 0.30, and 0.35 mm in 148, 151, and 150 eyes, respectivel y). First surgeries were attempted in 452 patients. An ICRS was successfull y implanted in 447 initial eyes, and 5 surgeries were discontinued. Of the five discontinued surgeries, three patients subsequently exited from the st udy, and two patients went on to have the ICRS implanted in the second eye, bringing the total number of successful implants to 449 patient eyes. Mont h 24 postoperative follow-up was completed on 358 patients (80%). At month 24, 328 of 354 eyes (93%) were within +/-1.00 D of predicted refractive out come. Refraction changed by 1 D or less in 97% of eyes (421/435) between 3 and 6 months after implantation and in 99% (343/348) between months 18 and 24. Before surgery, 87% of eyes (390/448) saw worse than 20/40 uncorrected; 24 months after surgery, 55% of eyes (196/358) saw 20/16 or better, 76% (2 71/358) saw 20/20 or better, and 97% (346/358) saw 20/40 or better. Althoug h two eyes (2/358; 0.5%) lost two or more lines of BSCVA at 24 months; visu al acuity in both was 20/20 or better. Intraoperative complications include d anterior corneal surface perforation (three eyes) and anterior chamber pe rforations (two eyes, one during an attempted exchange procedure); all heal ed spontaneously without suturing and without loss of BSCVA. The ICRS was r epositioned in five eyes to increase correction. Postoperative complication s in one eye each were infectious keratitis, shallow segment placement, and loss of two lines of BSCVA at two or more consecutive examinations (subseq uently regained). Conclusions. The ICRS safely, predictably, and effectively reduced or elimi nated myopia of -1.00 to -3.50 D. The refractive effect was stable over tim e.