Can Mean Central Corneal Thickness and Its 24-hour Fluctuation Influence Fluctuation of Intraocular Pressure?

Abstract

To evaluate the influence of central corneal thickness (CCT) and its 24-hour fluctuation on 24-hour intraocular pressure (IOP) fluctuation in primary open-angle glaucoma. Forty consecutive patients underwent 24-hour evaluation (8 PM, midnight, 4 AM, 8 AM, noon, and 4 PM) of supine and sitting IOP, measured with handheld Perkins and Goldmann tonometer respectively, and of CCT measured using ultrasonic pachymeter. Thirty patients were treated with timolol 0.5% twice daily and latanoprost 0.005% once daily; 10 patients were untreated. Measurements were taken in both eyes, but only one eye per patient was used for analytical purposes. Three IOP curves were drawn: sitting position, supine position, and habitual body position (diurnal sitting measurements and nocturnal supine measurements). Fluctuation was calculated as the SD over the 24-hour curve. Differences in the 2 groups were inspected by means of t test; the correlations between IOP fluctuation and mean CCT, respectively, and its fluctuation were evaluated by means of regression analysis. Untreated patients had higher IOP than the treated group (habitual body position: 22.1+/-5.1 mm Hg vs. 16.0+/-3.0 mm Hg, P=0.004), but no differences were found for IOP fluctuations (habitual body position: 2.5+/-1.2 mm Hg vs. 2.3+/-0.8 mm Hg, P=0.32), mean CCT (542+/-38 microm vs. 534+/-39 microm, P=0.44), and CCT fluctuation (8.7+/-5.6 microm vs. 6.5+/-3.0 microm, P=0.09). The correlation between IOP fluctuation and mean CCT and its fluctuation was not statistically significant at supine, sitting and habitual body positions (P>or=0.07; R<or=0.20). Twenty-four-hour IOP fluctuation was independent from CCT parameters in both treated and untreated glaucoma patients, regardless of body position at which IOP was measured.