A comparison between Goldmann applanation tonometry and dynamic contour tonometry after photorefractive keratectomy

The intraocular pressure (IOP) could be measured by both Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT). Although these two methods have been discussed widely after laser-assisted sub-epithelial keratectomy (LASIK), there is little data in the cases undergoing photorefractive keratectomy (PRK). We aimed to compare the changes of IOP measurements obtained by GAT and DCT after PRK for myopia/myopic astigmatism. This prospective study enrolled 77 candidates (154 eyes) for PRK to correct myopia or myopic astigmatism and 30 matched patients (30 eyes) with myopia or myopic astigmatism who served as controls. Changes of the IOP measurements (Delta IOP) obtained by GAT and DCT before and at 6 months after PRK in the operated eyes, and at baseline and 6 months later in the controls, were documented. Changes of the central corneal thickness (Delta CCT) were determined in the same fashion. The mean IOP readings obtained by DCT were comparable before and at 6 months after procedure (18.34 +/- A 3.03 mmHg and 17.87 +/- A 2.61 mmHg respectively, p = 0.41); whereas the mean IOP reading obtained by GAT decreased significantly 6 months postoperatively (17.92 +/- A 3.63 mmHg and 16.25 +/- A 2.66 mmHg, p < 0.001). A significant correlation was present between the Delta IOP obtained by GAT and Delta CCT (r = 0.61, p < 0.001). Similar correlation was not significant between the DCT-obtained Delta IOP and the Delta CCT (r = 0.07, p = 0.44). The mean Delta IOP obtained by GAT was significantly higher in the operated eyes than in the controls (-1.54 A +/- 1.45 vs 0.07 A +/- 0.44 mmHg, p = 0.02). The mean DCT-obtained Delta IOP was just marginally insignificant between the operated and nonoperated eyes (-0.63 A +/- 0.59 vs 0.02 A +/- 0.38 mmHg respectively; p = 0.09). The authors recommend DCT after PRK in the cases with myopia or myopic astigmatism.