Progressive hyperopia in radial keratotomy. Long-term follow-up of diamond-knife and metal-blade series.

In an earlier report, the authors demonstrated a trend toward progressive hyperopia in radial keratotomy (RK) patients examined between one and three to four years postoperatively. In those 109 cases, the surgeries were performed using a metal-blade instrument. In the following study, the metal-blade series was updated to a total of 225 procedures, and a more recent series of 300 procedures performed on 228 patients was examined in which a diamond-knife cutting instrument was used. Patients had uncorrected visual acuity determination, cycloplegic refractions with best corrected visual acuity measurements and keratometry measurements. The authors demonstrated a hyperopic shift in the distribution of postoperative spherical equivalent (SE) values across time such that higher proportions of cases in both metal-blade and diamond-knife series were at least 1.0 diopter (D) away from emmetropia at 24 and 48 months than was the case at 12 months after surgery. Regression analysis determined that none of the preoperative or surgical variables known to affect refractive outcome of RK (alone or in combination) could account for the changes in refraction seen during the course of postoperative time. In general, changes in keratometry paralleled refractive changes, but were somewhat smaller in magnitude.