Astigmatism following photorefractive keratectomy for myopia.

Background: Astigmatism following photorefractive keratectomy for myopia has been reported as stable as early as 2 to 3 months. The authors report 36 out of 60 consecutive eyes with variations in the cylindrical component of their refraction at 6 months after laser treatment.

Method: A standard photorefractive keratectomy was carried out on 60 consecutive eyes in 52 patients over a 7-month period. The manifest refraction of these eyes was followed for 6 months.

Results: Thirty-six eyes demonstrated a change in the cylindrical element of their refraction manifested as a change in cylinder power or axis, or both. The mean pretreatment cylinder power in the group that underwent a change in the cylindrical element was significantly higher than the mean of the group where this did not take place. The mean cylinder power change was 0.75 diopters (D) and in 9 eyes this change was 1.00 D or more. The corrected and uncorrected postoperative visual acuities were the same in the two groups.

Conclusions: This observation implies meridional variability in the healing process of the anterior cornea following photorefractive keratectomy.