Intrastromal Corneal Ring Segment – Implantation by Femtosecond Laser for Keratoconus Correction

Purpose: To report the outcomes after the implantation of intrastromal corneal ring segments (KERARING) aided by femtosecond laser for the correction of keratoconus.
Design: Prospective consecutive interventional study.
Participants: Twenty-one eyes of 16 consecutive keratoconic patients with mean age 32+ -10.2 years. Forty-five percent were keratoconus grade I, 20% grade II, 15% grade III, and 20% grade IV.
Methods: Intrastromal corneal ring segments KERARING were implanted for keratoconus correction after corneal tunnel creation with the aid of femtosecond laser (IntraLase Corp, Irvine CA).
Main Outcome Measures: Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refractive outcome, complete ophthalmologic examination, videokeratography, and corneal higher order aberrations (HOA) were determined or performed before and after surgery at 1 day, 1 week, and 3 and 6 months. In addition, operative and postoperative complications were recorded.
Results: KERARING implantation significantly increased UCVA from 0.06 to 0.3 (P<0.0001), BSCVA from 0.54 to 0.71 (P<0.0003), and decreased the spherical equivalent by 2.28 diopters (D) and the average keratometric values (K value) by 2.24 D (P<0.001). There was no significant difference between the 3 and 6 months follow-up. Forty percent (8 eyes with a relatively low RMS of total HOA) showed a nonsignificant increase in the RMS of total HOA and 60% (12 eyes with a relatively higher RMS of total HOA>3.0 um) showed significant (P0.01) decrease in the RMS of total HOA due to a significant (P<0.003) reduction in coma and comalike aberrations.
The amount of change in corneal curvature (biomechanical response) ranged from a decrease of 18% from its initial value to an increase of 2.75% and was not correlated to any preoperative parameter. Localized infectious keratitis occurred in only 1 eye (4.8%), and incision opacification occurred in 8 eyes (38%).
Conclusion: Intrastromal corneal ring segment implantation with femtosecond laser is an effective method for correcting keratoconus with reduction in corneal HOA in eyes with coma aberration > 3.0 um.
Ophthalmology 2007;xx:xxx © 2007 by the American Academy of Ophthalmology.
Mohamed H. Shabayek, MD, MSc,1,2 Jorge L. Alió, MD, PhD1
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