Excimer Laser Phototherapeutic Keratectomy for Granular and Lattice Corneal Dystrophy: A Comparative Study

Abstract

To compare the visual and refractive outcome after excimer laser phototherapeutic keratectomy (PTK) for superficial comeal opacities in granular and lattice dystrophy. Phototherapeutic keratectomy was performed in 62 eyes of 40 patients (granular dystrophy [n = 50] and lattice dystrophy [n = 12]) after epithelial debridement and pannus removal. Data regarding pre-and postoperative best spectacle-corrected visual acuity, changes in spherical equivalent of manifest refraction, Zeiss keratometry, astigmatism, and corneal topography were analyzed and compared between granular and lattice dystrophy. Recurrence, if any, was noted during a mean follow-up of 3.0 +/- 2.7 years. Best spectacle-corrected visual acuity improved in 79% and 62% of eyes with granular and lattice dystrophy, respectively. Spherical equivalent refraction increased by a mean of 1.3 +/- 1.7 diopters (D) (median: 1.0 D) for granular dystrophy and a mean of 1.0 +/- 1.8 D (median: 0.5 D) for lattice dystrophy. The keratometric central power decreased by a mean of -0.8 +/- 4.3 D (median: -1.6 D) for granular dystrophy and a mean of -0.3 +/- 1.6 D (median: -0.7 D) for lattice dystrophy. No significant changes were noted regarding keratometric astigmatism in either granular or lattice dystrophy. The proportion of "regular" and "mild irregular" keratometry mires increased (39% vs 67% for granular dystrophy and 0% vs 50% for lattice dystrophy). In granular dystrophy, the surface regularity index/surface asymmetry index (SRI/SAI) decreased significantly from 2.14/2.24 preoperatively to 1.31/0.80 postoperatively (P = .006/P = .01). In contrast, decrease of SRI/SAI from 1.97/1.65 preoperatively to 1.35/1.16 postoperatively did not reach statistical significance in lattice dystrophy. Recurrences were observed in 10 (20%) eyes with granular dystrophy and 2 (17%) eyes with lattice dystrophy. Our results suggest that PTK may be tried in all patients with superficially accentuated opacities in granular and lattice dystrophy before undergoing a more invasive procedure, such as lamellar or penetrating keratoplasty.