[Surgery in myopic astigmatism: arciform keratotomy and PKR versus PARK]

Two surgical techniques for treatment of myopic astigmatism are compared: One technique is a combined procedure with relaxing incision and photorefractive keratectomy (RI PRK), the other one is photoreactive keratectomy done for correction of myopia and astigmatism (PARK). Fifty-nine eyes (42 patients) were operated by IR PRK. The preoperative myopia was between -1.5 and -14 D and the astigmatism between -0.75 and -6 diopters. Thirty-two eyes (20 patients) were treated with the PARK. The preoperative myopia was between -1 and -15 D and the astigmatism between -0.5 and -4. In 38 cases, relaxing incisions allowed to correct astigmatism entirely. The mean preoperative sphere of -6.8 D before PRK was 1.4 D and the spheres between -1 and -15 D. Twelve months after treatment, 26 eyes on 30 were spherical. The spherical equivalent varied between +0.75 and -1.50 D. Relaxing arciform incision presents the advantage to correct high asymmetric astigmatism without corneal thinning, as well as mixed astigmatism. At the present time, the PARK allows to correct only symmetrical myopic astigmatism.

The predictability of the results is high if the cylinder is less than 3 D and the sphere less than 6 D. Beyond this limit, there is a higher risk of regression, and haze related with the depth of photo-ablation and we prefer RI-PRK.