Long-term (5- to 12-year) follow-up of metal-blade radial keratotomy procedures

To evaluate the long-term stability of the refractive outcome after metal-blade radial keratotomy procedures.

A cohort of 146 patients who underwent 225 consecutive metal-blade radial keratotomy procedures that were performed under a uniform protocol between November 1979 and August 1981 was monitored prospectively, with 64% of the patients followed up for at least 5 years.

Changes in spherical equivalent and changes in average keratometry were evaluated within the following periods: 3 months to 1 year; 1 to 2 years; 2 to between 3 and 4 years (mean, 3.7 years); between 3 and 4 (mean, 3.7 years) to between 5 and 12 years (mean, 8.5 years); and 1 to between 5 and 12 years (mean, 8.5 years).

Total mean change in refraction between 1 year and the average of 8.5 years of follow-up was 1.01 diopters (D) (SD, 1.13 D). At 1 year, 31% of the cases were at least 1 D hyperopic, whereas at an average of 8.5 years, 48% were at least 1 D hyperopic. Fifty-four percent of the cases had shifted in the hyperopic direction by 1 D or more. Stepwise regression analysis failed to identify significant predictive factors for the hyperopic shifts.

The trend toward progressive hyperopic shifts within this cohort has continued with time. Other long-term studies have documented similar, although somewhat smaller, hyperopic shifts among both patients treated with metal-blade and patients treated with diamond-blade procedures. Causative factors for the hyperopic shift have not been identified. It remains to be seen if eyes undergoing current, more cautious surgical approaches to radial keratotomy will also experience this phenomenon.