Evaluation of intraocular pressure according to corneal thickness before and after Excimer laser corneal ablation for myopia

Purpose Intraocular pressure is affected by corneal thickness and biomechanics. Following ablative corneal refractive surgery, corneal structural changes occur. Our aim in this study was to determine the relation between the mean central corneal thickness and the change in intraocular pressure measurements following various corneal ablation techniques, using different measurement methods. Methods This is a prospective, nonrandomized study.200 myopic eyes undergoing laser in situ keratomileusis or photorefractive keratectomy were enrolled. Corneal parameters examined included, full ocular examination, measurement of central corneal thickness, corneal topography, corneal curvature and ocular refractivity. Intraocular pressure measurements were obtained using three different instruments: Non Contact Tonometer, Goldmann Applanation Tonometer and TonoPen XL (TonoPen-Central, and TonoPen-Peripheral). All measurements were performed preoperatively and 4 months postoperatively. differences in inter-device intraocular pressure measurements were done using ANOVA test. Results Postoperative intraocular pressure was significantly lower than preoperative values, with all instruments (p value <0.001, Student's t-test). The postoperative intraocular pressure decrease was smallest using the Tonopen-XL compared to the Goldmann applanation tonometer and Non-contact tonometer (p value <0.001,ANOVA). Conclusion Intraocular pressure readings are significantly reduced following corneal ablation surgery. We determined in our myopic patient cohort that the TonoPen XL intraocular pressure measurement method is the least affected following photorefractive keratectomy and laser in situ keratomileusis as compared to other techniques.