Efficacy of IOP lowering drugs dependent on CCT

Intraocular pressure (IOP) lowering drugs are more effective in eyes with low central corneal thickness (CCT) than those with high CCT, according to a study published in the March issue of Journal of Glaucoma.

Thomas V. Johnson of the University of Nebraska Medical Center, Nebraska, US, and colleagues conducted a retrospective study of 115 ocular hypertension (OHT) patients and 97 ocular normotensive (ONT) volunteers to determine the effect of CCT on the efficacy of topical IOP-reducing treatments.

Patients were divided into Thick (CCT >540 µm) and Thin (CCT ≤540 µm) categories (OHT, n=52, n=63 respectively; ONT, n=34, n=63 respectively). Measurements in the OHT group were made after washout of all IOP-lowering drugs and at one week of treatment with latanoprost 0.005%, dorzolamide 2%, brimonidine 0.2%, apraclonidine 0.5%, pilocarpine 2%, or unoprostone 0.15% to one eye and vehicle contralaterally.

One week following treatment, IOP was significantly lower in the OHT Thin group than the OHT Thick group (16.0±3.0 mmHg and 17.4±2.8 mmHg, respectively). Drug-treated eyes showed a positive correlation between IOP and CCT, which was not evident in vehicle-treated or untreated (ONT) eyes.

As the OHT Thin group demonstrated lower IOPs than the OHT Thick group following treatment, the researchers concluded that eyes with thinner corneas respond more positively to IOP lowering drugs than do eyes with thicker corneas.