Ocular hypertensives with thin central corneas experience better drug efficacy with IOP-reducing medications than those with thick central corneas, according to a study published in the March issue of the Journal of Glaucoma.

The retrospective study analyzed records of 115 ocular hypertensive (OHT) patients and 97 ocular normotensive (ONT) patients. The OHT and ONT groups were further divided into groups of thick corneas (greater than 540m) or thin corneas (540m or less).

Intraocular pressure was measured after one week of treatment with latanoprost, dorzolamide, brimonidine, apraclonidine, pilocarpine or unoprostone drops in one eye and a placebo in the other.

The researchers found that IOP was significantly lower among OHT patients with thinner corneas than those with thicker corneas. There was no positive correlation found between central corneal thickness and IOP reduction in the ONT group. Also, final IOPs were markedly lower in ocular hypertensives with thin corneas who were treated with brimonidine (an alpha-adrenergic), but not latanoprost (a prostaglandin).

These results might explain why a patient may have better results in one eye than the other if there are differences in corneal thickness, says Sherry Bass, O.D., distinguished teaching professor at SUNY State College of Optometry.

However, she says, these results probably will not dramatically change how optometrists treat ocular hypertensives with thin corneas. While this study found that brimonidine was the most efficacious IOP-reducing medication in OHT patients with thin corneas, Dr. Bass says, I do not believe this information will change an O.D.s first-line drug of choice, which is a prostaglandin, because of the once-a-day dosing regimen.

Johnson TV, Toris CB, Fan S, Camras CB. Effects of central corneal thickness on the efficacy of topical ocular hypotensive medications. J Glaucoma 2008 Mar;17(2):89-99.