For how long can regression continue after photorefractive keratectomy for myopia?

The presence and degree of regression were assessed from 18 to 30 months after photorefractive keratectomy (PRK).

A total of 449 eyes (449 patients) were treated with an Aesculap Meditec 193-nm Arf Excimer laser. These 449 eyes were followed during the first 24 months after PRK, and 252 of these eyes were followed for 24 to 30 months.

Thirty (6.7%) of the 449 eyes followed for up to 24 months showed good refractive results during the first year and a half but regressed thereafter and required retreatment. Late regression was confined to subjects with pretreatment myopia above -4.0 diopters (D) and was the same in low- and high-myopic eyes between 18 and 24 months post-PRK. However, between 24 and 30 months, regression was higher in low-myopic eyes, where it reached -0.55 D, than in high-myopic eyes, where it was -0.21 D. This lower frequency of regression in high-myopic eyes is attributed to the relatively high rate of retreatment in this group during the first 18 months after PRK.

Although the findings indicate a fairly low rate of regression after 24 months, there still are insufficient data on which to predict when regression post-PRK stabilizes.