Effect of Excimer Laser Photorefractive Keratectomy on Goldmann Applanation Tonometry

ABSTRACT

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.