Two-year outcomes of intrastromal corneal ring segments for the correction of myopia☆

Presented in part at the American Academy of Ophthalmology annual meeting, Orlando, Florida, October 1999.

Received 27 October 1999; accepted 11 April 2001.

Abstract

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 Administration phase II and phase III clinical trials of the ICRS had best spectacle-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 measured by manifest refraction.

Intervention

Surgical correction of myopia with an ICRS.

Main outcome measures

Efficacy was assessed by predictability of refractive outcome (deviation from predicted cycloplegic refraction spherical equivalent), stability of refractive effect, and postoperative uncorrected visual acuity. Safety was assessed by adverse events, maintenance or loss of preoperative BSCVA, and induced manifest refraction cylinder.

Results

Four hundred fifty-two patients were enrolled at 11 investigational 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, respectively). First surgeries were attempted in 452 patients. An ICRS was successfully implanted in 447 initial eyes, and 5 surgeries were discontinued. Of the five discontinued surgeries, three patients subsequently exited from the study, 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. Month 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 outcome. 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% (271/358) saw 20/20 or better, and 97% (346/358) saw 20/40 or better. Although two eyes (2/358; 0.5%) lost two or more lines of BSCVA at 24 months; visual acuity in both was 20/20 or better. Intraoperative complications included anterior corneal surface perforation (three eyes) and anterior chamber perforations (two eyes, one during an attempted exchange procedure); all healed spontaneously without suturing and without loss of BSCVA. The ICRS was repositioned in five eyes to increase correction. Postoperative complications in one eye each were infectious keratitis, shallow segment placement, and loss of two lines of BSCVA at two or more consecutive examinations (subsequently regained).

Conclusions

The ICRS safely, predictably, and effectively reduced or eliminated myopia of −1.00 to −3.50 D. The refractive effect was stable over time.

Manuscript no. 99445.

1 Department of Ophthalmology, University of California San Diego, San Diego, California, USA

2 Department of Ophthalmology, University of California San Francisco, San Francisco, California, USA

3 Department of Ophthalmology, Mount Sinai School of Medicine, New York, New York, USA

4 The Sinskey Eye Institute, Santa Monica, California, USA

5 Northwest Corneal Services, Portland, Oregon, USA

6 Hunkeler Eye Centers, P.C., Kansas City, Missouri, USA

7 Department of Ophthalmology, University of South Florida, Tampa, Florida, USA

8 Lindstrom, Samuelson & Hardten Ophthalmology Associates, Minneapolis, Minnesota, USA

9 McDonald Eye Associates, P.A., Fayetteville, Arkansas, USA

10 Department of Ophthalmology, St. Louis University Health Sciences Center, St. Louis, Missouri, USA

11 Emory University Department of Ophthalmology, Emory Vision Correction Center, L.P., Atlanta, Georgia, USA

Reprint requests to David J. Schanzlin, MD, UCSD Shiley Eye Center, 0946, 9500 Gilman Drive, La Jolla, CA 92093-0946

☆ The Intrastromal Corneal Ring Segments phase II and III trials in the United States are supported by KeraVision, Inc., Fremont, California.

1 David J. Schanzlin, MD, Kerry K. Assil, MD, Daniel S. Durrie, MD, Richard L. Lindstrom, MD, George O. Waring, MD, and Terry E. Burris, MD, are paid consultants for KeraVision, Inc.

PII: S0161-6420(01)00692-3

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