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Abstract #5640 Published in IGR 2-1
Effects of central corneal thickness on measurement of intra-ocular pressure in keratoconus and post-keratoplasty
Patel S; McLaughlin JMOphthalmic and Physiological Optics 1999; 19:236-241
PURPOSE: To measure and compare central corneal thickness (CT) and intraocular pressure (IOP) in keratoconus and post-keratoplasty subjects and examine the CT-IOP relationship. METHODS: 22 keratoconus (category I: six females, 16 males; average age, 27.0 years; range, 12-47) and 19 post-keratoplasty (category II: ten females, nine males; average age 34.6 years; range, 16-54) patients without other anterior segment conditions were recruited. Only one, non-contact lens wearing, eye of the patient was included for analysis. Cornea was anesthetized with non-preserved 0.4% benoxinate hydrochloride. Using a randomized approach, CT was measured using a standard ultrasonic pachymeter. IOP was then measured using a standard Goldmann tonometer. At all times, the tonometrist remained unaware of the corneal thickness values. RESULTS: The mean (± SD) values for CT and IOP respectively in the two categories were: (I), 445 (45) μm and 9.8 (2.3) mmHg, (II), 564(44) μm and 15.8 (3.9) mmHg. Differences between I and II for both CT and IOP were significant (t test, p=0.01). Within each category, a significant correlation between CT and IOP was not found. Pooling all pairs of data (n=41), a significant relationship between CT and IOP was detected (r=0.635, p=0.0001). CONCLUSIONS: The results confirm the hypothesis that an eye with a thicker cornea tends to present with a higher measured IOP. In the management of keratoconus and other corneal surgical procedures, changes in CT will contribute to any apparent changes in measured IOP.
Dr. S. Patel, Academic Unit of Ophthalmology, Birmingham and Midland Eye Centre, City Hospital NHS Trust, Birmingham, UK Dr_SPatel@compuserve.com
Classification:
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
