Single-Segment Intacs Severe Keratoconus 80% Stromal Depth Insertion With a Femtosecond Laser for Asymmetric Keratoconus: A Case Series.

PURPOSE: To study the efficacy of inferior, single-segment, 80% stromal depth Intacs severe keratoconus (SK) intracorneal ring segment implantation. DESIGN: A prospective case series. METHODS: Eighteen eyes from 15 patients with asymmetric keratoconus underwent 80% stromal depth Intacs SK single inferior segment implantation, using an IntraLase femtosecond laser for tunnel creation. Parameters studied included preoperative and postoperative uncorrected and best-corrected visual acuity (VA), manifest refraction and elevation-based computerized corneal topography. RESULTS: Patients' VA was tested with Early Treatment Diabetic Retinopathy Study (ETDRS) chart. All the eyes demonstrated a significant ETDRS line improvement of 5.4 ± 2.0 after a follow-up period of 8.9 ± 3.9 months. Thirteen eyes (72%) showed a line improvement of 4 or more. Best-corrected VA remained unchanged in 8 eyes (44%) while 7 eyes (39%) showed a line improvement of 1 to 8. Sixteen eyes (89%) had a significant change in manifest cylinder [3.0 ± 2.2 diopters (D)]. Of the 18 eyes, astigmatism reduction was 3.44 ± 1.98 D, from 5.6 ± 2.2 D preoperatively to 2.5 ± 1.5 D postoperatively (P < 0.05). Implant placement reduced both preexisting hyperopic and myopic spheres in 14 cases (78%). Although one case showed a significant postoperative regression of the obtained correction, Intacs SK implantation was safe and effective in all the other cases. CONCLUSIONS: Femtosecond laser-assisted single-segment Intacs SK (80% depth intrastromal placement) is a safe and effective technique for improving uncorrected and best-corrected VA and correcting both spherical and cylindrical refractive errors in eyes with severe asymmetric keratoconus.