Accuracy of Goldmann tonometry after refractive surgery

Purpose: To assess the accuracy of Goldmann tonometry after refractive surgery. Setting: Refractive surgery center, Sherbrooke, Quebec, Canada. Methods: The charts of 824 patients who had radial keratotomy (RK) and 415 who had photorefractive keratectomy (PRK) by the same surgeon were retrospectively reviewed. Of these, 306 RK and 168 PRK patients had discontinued steroid use for at least 4 weeks postoperatively and were thus eligible for evaluation of preoperative and postoperative intraocular pressure (IOP). Only one eye per patient was used for statistical analysis. Results: Preoperative data showed that age, mean keratometry, and pachymetry were related to IOP measurement with the Goldmann tonometer. Pachymetry was related to age and mean keratometry. The mean decrease in measured IOP after RK was 1.0 mm Hg +/- 3.21 (SD) (P < .05). The only positive correlation was with the number of incisions. The mean decrease in measured PRK was 2.4 +/- 3.02 mm Hg (P < .05). Men and older patients had a larger drop in IOP measurements. There was no correlation with any corneal or operative parameter. Conclusion: Refractive surgery changed the accuracy of the Goldmann tonometer, causing it to underestimate IOP. The change was more marked in older men who had PRK.