If you’re unsure whether photorefractive keratectomy (PRK) will benefit your severely myopic patients as much as those with high myopia, a new study may help you decide.

Researchers examined 120 eyes of 78 patients after multi-zone PRK for high myopia and severe myopia. Thirty-nine eyes had been severely myopic before the surgery; 81 had been highly myopic at that point. Follow-up time consisted of a mean of 18 months.

Stromal scarring, categorized as focal, semi-annular, annular and discoid, was found in 71.7% of severely myopic eyes and in 60.5% of highly myopic eyes. Discoid scars were rare and they appeared more often in severely myopic eyes than in others.

Only 50% of eyes with a discoid scar achieved final best corrected visual acuity between 6/6 and 6/9 compared to 81% of the eyes with a clear cornea. Severely myopic eyes with a discoid scar had the highest level of final undercorrection. They also had a higher number of retreatments.

In all, the researchers concluded that PRK is more efficient in correcting high myopia than it is in correcting severe myopia, in which discoid scarring occurred more frequently and was clinically more significant.