The influence of central corneal thickness on response to topical prostaglandin analogue therapy

Objective: Central corneal thickness (CCT) affects intraocular pressure (IOP) readings; however, CCT influence on topical medication efficacy is unknown. We evaluated the IOP-lowering effect of topical prostaglandin analogues (PGAs) in relation to OCT. Design: Post hoc analysis of a randomized prospective trial. Method: Subjects randomized to a PGA were followed for 24 weeks and were analyzed for relationship between COT and IOP lowering. Participants: Patients with either newly diagnosed ocular hypertension or open-angle glaucoma. Results: 75 subjects were enrolled. The mean age was 62.7 +/- 10.5 years; 48 were Caucasian. The mean OCT was 562.4 +/- 41.4 mu. At repeated measures, ANCOVA analysis showed a significant effect of both baseline IOP (p < 0.0001) and OCT (p = 0.003) on IOP. At week 12, a regression analysis of the effect of OCT on baseline IOP showed that for every 10 mu increase in COT there was 0.3 mm Hg less IOP decrease from baseline. Conclusions: We found a statistically significantly association between a lower mean IOP and a thinner cornea when baseline IOP is controlled for. The magnitude of the relationship is small but may be clinically significant in patients with either very thin or very thick corneas.