CORRELATION OF INTRAOCULAR-PRESSURE AND CENTRAL CORNEAL THICKNESS IN NORMAL MYOPIC EYES AND AFTER LASER IN-SITU KERATOMILEUSIS

Purpose: To determine the relationship of intraocular pressure (IOP) a nd central corneal thickness (CCT) in normal myopic eyes and after las er in situ keratomileusis (LASIK). Setting: TLC The Windsor Laser Cent er, Windsor, Ontario, Canada, Methods: Intraocular pressure measured b y Goldmann applanation tonometry and CCT by ultrasonic pachymetry were determined in a group of untreated corneas:oi 120 patients (203 eyes) and in 50 patients (85 eyes) pre- and post-LASIK. Statistical analyse s were performed with the Pearson correlation coefficient and paired S tudent t test. Results: In the untreated group or 288 eyes, mean CCT w as 544.0 mu m +/- 37.3 (SD) (range 461 to 664 mu m) and mean IOP, 15.6 +/- 2.7 nm Hg (range 10 to 24 mm Hg). The correlation between IOP and CCT in this group was highly significant (r = 0.44 P < .0001). The sl ope was 0.032 mm Hg/mu m of CCT or an approximate decrease of 1 mm Hg, for a reduction in CCT of 31.3 mu m. In the post-LASIK group, mean CC T dropped approximately 73.0 mu m to 479.5 +/- 41.2 mu m (range 408 to 503 mu m) and IOP dropped to a mean of 13.6 +/- 3.3 mm Hg (range 7 to 22 mm Hg). A significant correlation was round between IOP and CCT af ter LASIK (r = 0.33; P < .002). The difference between the mean pre- a nd post-LASIK measurements of applanation IOP was 2.5 mm Hg, which was significant (P < .0001). The post-LASIK slope was 0.027 mm Hg/mu m, o r a decrease of 1.0 mm Hg per 37.8 mu m reduction in CCT. Conclusion: Central corneal thickness is an important variable in the evaluation o f applanation IOP and should be included in the assessment oi any Case of potential glaucoma or ocular hypertension, particularly in eyes wi th previous photoablative refractive surgery.