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 ferntosecond 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 1, 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 <= 50.0003), and decreased the spherical equivalent by 2.28 diopters (D) and the average keratornetric 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 RIVIS of total HOA and 60% (12 eyes with a relatively higher RIVIS of total HOA >= 3.0 mu m) showed significant (P <= 0.01) decrease in the RIVIS 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 Jim. Ophthalmology 2007,-114:1643-1652 (c) 2007 by the American Academy of Ophthalmology.