Relationship between corneal thickness and optic disc damage in glaucoma

BACKGROUND: Central corneal thickness (CCT) has been found to be a powerful predictor for the development of glaucoma in patients with ocular hypertension. This study aimed to determine whether CCT was also related to glaucoma severity.

METHODS: The vertical cup/disc ratio (VCDR) was used as a single objective measure of glaucoma severity. Vertical cup diameters and vertical disc diameters were measured using a graticule attached to a 60 D Volk lens, in consecutive patients presenting to a single ophthalmologist. Measurements were corrected for magnification. The difference between corrected VCDR and 95% probability of VCDR normality was compared to CCT, which was measured with an ultrasonic pachymeter.

RESULTS: During the study period 554 eyes from 281 patients with glaucoma were reviewed. The mean CCT was 519.0 microm, with the mean corrected VCDR being 0.71. A univariate linear regression model revealed that an increase of 10 microm in CCT resulted in a 0.009 decrease in the difference between true VCDR and the predicted normal VCDR. The R2 value for the regression was 0.04 (P < 0.0001).

CONCLUSION: There is a highly statistically significant, albeit small, negative correlation between corneal thickness and glaucoma severity. This study supports the notion that CCT should be measured in the assessment of patients with glaucoma. Progressive thinning or presence of a thin cornea may have pathogenic or prognostic roles in some types of glaucoma.