Hyperopic shift after 4-8 incision radial keratotomy: eight-year follow-up

To evaluate the prevalence, amount and possible factors connected with the hyperopic shift after radial keratotomy.

We studied 86 eyes (51 patients) which underwent 4-8 incision radial keratotomy (delayed technique), consecutively performed by the same surgeon between February 1983 and November 1988. The diamond-bladed knife was set at 95% of the smallest paracentral ultrasonic corneal thickness measurement and the clear zone diameter was between 3.0 and 3.5 mm. Preoperative myopia ranged from -2.00 to -7.25 diopters (D). The average follow-up was 97.4 months (range 78 to 122 months).

After eight years of follow-up, the cycloplegic spherical equivalent was satisfactory: 66.2% of the eyes showed a refractive error within 0.5 D, 17.4% were myopic by more than 0.5 D and 16.2% were hyperopic by more than 0.5 D. The mean refractive error was 0.02 D (SD +/- 0.75 D). Between six months and eight years after surgery a hyperopic shift of more than 0.5 D was found in 40.6% of the eyes. The mean hyperopic shift was higher (0.78 D) in the eyes which had keratometry less than 36 D six months after surgery. Compared to the eyes with keratometry greater than 36 D (mean hyperopic shift 0.38 D), the difference was statistically significant (p < 0.02).

These results show that keratometry, measured six months postoperatively, plays a fundamental role in the stability of postsurgical refraction, as the risk of hyperopic shift is higher in eyes with keratometry < 36 D.