Four-Year Update on Predictability of Radial Keratotomy

We present an update on the predictability of radial keratotomy for both steel and diamond knife cases. A predictability model is developed 4 years after surgery for steel knife cases and compared with earlier reported results. The R p 2 value for the 4-year model is 57%, which is similar to results of 6, 12, and 24 months. The predictive factors of planned incision depth, age, number of incisions, redeepening, sex, and central pachymetry are consistent with earlier results. A 2-year model for diamond knife cases yielded an R p 2 value of 78% with predictive factors of incision depth, redeepening, age, number of incisions, and optical zone size similar to earlier models. Corneal microperforations and preoperative average keratometry are new long-term predictive factors. An analysis of inaccurately predicted results is presented and shown to relate to high myopia, redeepening, using 16 incisions, incision depth greater than 90%, perforations, and a 3.0 mm optical zone.