Four-incision radial keratotomy for high myopia after penetrating keratoplasty.

BACKGROUND

High amounts of myopia can frequently produce anisometropia and limit visual rehabilitation by conventional means in eyes with clear corneal grafts. This condition is frequently coupled with large amounts of astigmatism. Four-incision radial keratotomy provides a way to reduce myopia in normal individuals. In our present study, we used the technique of four- incision radial keratotomy to reduce myopia in a group of keratoplasty patients who failed conventional visual rehabilitation. Arcuate or transverse keratotomy was used in conjunction with radial keratotomy in eyes with high amounts of astigmatism.

METHODS

This study retrospectively examined a group of 11 eyes with penetrating keratoplasty which underwent four-incision radial keratotomy for the treatment of visually disabling myopia. The radial incisions were placed in the graft, inside the graft-host interface. Seven eyes underwent concomitant arcuate relaxing incisions at the graft-host interface for treatment of associated astigmatism. One additional eye had paired straight transverse incisions for the treatment of astigmatism. The mean postoperative follow up was 16 months (range, 3 months to 5 years).

RESULTS

There was a mean reduction of the spherical equivalent refraction of 3.48 diopters (D) (range, 0.25 to 7.75 D). The eight eyes undergoing astigmatic surgery showed a mean reduction in keratometric astigmatism of 2.25 D (range, -6.75 to +6.50 D) and refractive astigmatism of 4.63 D (range, -1.50 to -9.50 D). Nine of the 11 eyes had stable or improved best spectacle corrected visual acuity. Two eyes had reduction of best spectacle corrected visual acuity--one due to development of irregular astigmatism and one due to worsening of preexisting macular edema.

CONCLUSIONS

Four-incision radial keratotomy can reduce myopia after penetrating keratoplasty when the patient is unable to tolerate spectacle or contact lens correction. It can be combined with relaxing incisions or transverse keratotomy to reduce astigmatism. There is a high amount of variability, and predictability is currently limited by the complex topographical changes occurring in corneal transplants. Complex corneal biomechanical changes may predispose these eyes to the development of irregular astigmatism.