A Case of Keratectasia 5 Years after Photorefractive Keratectomy

PURPOSE: The clinically evident keratectasia has not been reported after photorefractive keratectomy (PRK) on the eyes with normal preoperative corneal topography. Herein, we present a case of keratectasia developed 5 years after PRK. METHODS: A 20-year-old man underwent the PRK for correction of myopic astigmatism in 1993. Preoperative manifest refractions were -4.00 D-0.50 D x 90degrees in the right eye and -3.75 D-0.75 D x 85degrees in the left eye. Although pachymetry was not performed, preoperative examinations including corneal topography did not show any sign of early keratoconus or forme fruste keratoconus. The operations were uneventfully performed on two eyes at an interval of one month. RESULTS: Up to 9 months after PRK, the patient's uncorrected visual acuity had been maintained 1.2 in both eyes. When the patient returned 5 years after PRK, he complained of decreasing visual acuity (0.5)in his right eye. During the next 2 years, the vision of the right eye was deteriorated to 0.04, and could not be corrected with the spectacles. The corneal topography of the right eye revealed profound steepeningjust inferior to the corneal center, and he had become contact lens intolerant. The left eye remained stable. The central corneal thickness was 419.0 micrometerin the right eye and 476.3 micrometerin the left eye.

Effect of Excimer Laser Photorefractive Keratectomy on Goldmann Applanation Tonometry

It can be speculated that the thinned and flattened central cornea after excimer laser photorefractive keratectomy (PRK) might give a falsely low Goldmann applanation tonometer(GAT) reading. We studied 353 eyes of 264 patients who underwent PRK to determine the effect of excimer laser PRK on the accuracy of Goldmann applanation tonometry. PRK was done with a VISX 20/20 excimer laser and topical fluorometholone was used after PRK. The intraocular pressure(IOP) was measured with the GAT before surgery and 1, 3, 6, 9, and 12 months postoperatively. The mean ablation depth of the cornea was 71.4 +/- 22.0 micrometer, and the eyes were divided into three groups according to their ablation depths. The mean postoperative IOP measured with the GAT decreased as compared with the mean preoperative IOP(P<0.01). The mean postoperative IOP at 9 or 12 months was lower than that at 1, 3, or 6 months(p<0.05). The mean IOP(11.9 +/- 2.5 mmHg) at 12 months was 2.8 mmHg lower than the mean preoperative IOP(14.7 +/- 2.7 mmHg). There was no statistically significant difference in the amount of postoperative IOP decrease among the three groups.