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< or =0.0001), BSCVA from 0.54 to 0.71 (P< or =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> or =3.0 microm) showed significant (P< or =0.01) decrease in the RMS of total HOA due to a significant (P< or =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 microm.