Effect of corneal thickness on the accuracy of intraocular pressure measurement in rabbits after excimer laser photoablation

Purpose: To determine whether intraocular pressure (IOP) measurements pneum otonometry and Tono-Pen tonometry are accurate after excimer laser photoabl ation of the central cornea in rabbits. Setting: Department of Ophthalmology, Scott & White Hospital, Texas A & M U niversity College of Medicine, Temple, Texas, USA. Methods: Ten rabbits had excimer laser phototherapeutic keratectomy (PTK) i n the right eye to thin the central corneal thickness (CCT) by approximatel y 20%. The left eye served as the control. The diameter of each PTK was 6.0 mm. Four weeks later, the rabbits were examined under general anesthesia. The eyes were cannulated, and IOP was maintained at 10, 20, and 30 mm Hg an d measured using an IOP transducer Tono-Pen, and pneumotonometer at each pr essure level. The readings were compared. Results: One rabbit was excluded from the study because of recurrent erosio ns and corneal edema. There was no statistically significant difference in measurement error between the operated eye and control eye for the Tono-Pen (P = .12) or pneumotonometer (P = .35). There were significant differences in measurement error as pressure increased for the Tono-Pen (P < .01) and pneumotonometer (P < .01). The increase in measurement error with the incre ase in pressure was similar in the 2 eyes: Tono-Pen (P = .96) and pneumoton ometer (P = .55). A paired t test showed the observed CCT was comparable (P = .79) in the pre-laser right eyes (mean 400.56 mu m +/- 11.29 [SD]) and c ontrol eyes (mean 401.78 +/- 19.78 mu m). Conclusion: Photoablation of approximately 20% of the CCT in rabbits by exc imer laser PTK did not significantly after the accuracy of IOP measurements by the Tono-Pen or pneumotonometer. J Cataract Refract Surg 2000; 26:736-7 43 (C) 2000 ASCRS and ESCRS.