Enhancement techniques after incisional keratotomy

To evaluate the safety and efficacy of a four-step enhancement nomogram to reduce low residual myopia after incisional keratotomy.

Rancho Bernardo Eye Center, San Diego, California.

This retrospective study comprised 86 eyes of 60 consecutive patients who received enhancements to reduce residual myopia (mean 1.30 diopters [D] +/- 0.50 [SD]; range 0.75 to 3.00 D) after primary radial keratotomy (RK). For residual myopia of 1.37 D or less, a 0.25 mm optical zone (OZ) reduction was the preferred technique; a 0.50 mm OZ reduction was done for myopia of 1.50 [D] or more. Once a 3.00 mm OZ was reached in the primary or enhancement surgery, deepening (limbus to 5.00 mm OZ) and adding incisions were performed in some eyes for further myopic effect. All incisions were centripetal with globe fixation (Russian style). Follow-up was 6 to 42 months (mean 23.1 months).

All four enhancement techniques effectively reduced residual myopia. The 0.25 mm OZ reduction induced a mean 0.662 D of further refractive effect and was useful for myopic residuals from 0.75 to 1.37 D. The 0.50 mm OZ reduction was effective for residual myopia of 1.50 D or more and induced a mean 1.23 D of additional refractive change. Adding eight incisions (to eight at a 3.00 mm OZ) and deepening the limbus to the 5.00 mm OZ allowed mean myopic reductions of 0.695 and 0.640 D, respectively. The latter two techniques were useful for residual myopia of approximately 1.00 D. Pre-enhancement uncorrected visual acuity (UCVA) was 20/40 or better in 44 eyes and 20/50 to 20/300 in 42 eyes. Postenhancement, 83 eyes had an acuity of 20/40 or better and 71, of 20/25 or better. No postenhancement UCVA was worse than 20/50, and no eye was more hyperopic than 1.00 D (n = 1). No serious complications occurred.

Reducing the OZ by 0.25 mm for small residual myopia and by 0.50 mm for larger undercorrections was an effective initial surgical approach. Adding and deepening procedures were useful after a 3.00 mm OZ was reached. The four-step nomogram allowed an incremental reduction in residual myopia after RK without producing significant overcorrections.