[Accuracy and predictability of photorefractive keratectomy for astigmatism correction]

To study the accuracy and predictability of photorefractive keratectomy (PKR) for astigmatism correction.

53 eyes of 30 cases with compound myopia astigmatism and 33 eyes of 23 cases with simple myopia were treated with PRK and followed up for 6 months. The differences of corneal refractive power provided by corneal topography between the values at postoperative 6 months and that of the preoperative one were calculated with Holladay Ways to get real corrective degree and axis of astigmatism. The results were analyzed and compared with the preoperative predicted values.

Six months after PRK, among the compound myopia astigmatism group, the ratio of over correction or under correction of real corrected astigmatic power within +/- 0.50D was 60.4%, the ratio of axis deviation between real and predicted correction within +/- 15 degrees was 58.5%. Among simple myopia group, 48.5% appeared more than -0.50 D myopia astigmatism in real correction, and the cylinder axis position was within 180 degrees +/- 44 degrees. The ratios of uncorrected visual acuity after PRK in the two groups equal to or better than 1.0 were 77.4% and 78.8%, respectively. There was no difference between these two groups (chi(2) = 0.024, P > 0.75).

The method of myopia astigmatism correction using this PRK machine needs to be improved. After PRK treatment, the visual acuity of myopia astigmatism is similar to that of simple myopia group. It shows good efficacy. It is indicated that for myopia astigmatism lower than -2.00D, especially for the astigmatism with the rule, PRK could be performed according to equivalent spherical value.