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August 25, 2008
Thick CCT May Reduce Efficacy of Glaucoma Meds
Glaucoma Update
Central corneal thickness made news six years ago when the Ocular Hypertension Treatment Study showed that CCT was a risk factor for development of glaucoma independent of its effect on IOP measurement. Now CCT is making news again.
In a retrospective study, a team from the University of Nebraska reviewed its research records to determine what effect, if any, CCT had on the efficacy of topical ocular hypotensive medications in 115 patients with ocular hypertension. Data from 97 ocular normotensive volunteers were used for comparison. Corneal measurements were made by slit-lamp pachymetry and IOP by pneumotonometry. Subjects were divided into “thick CCT” (> 540 µm, n = 52) and “thin CCT” ( 540 µm, n = 63) groups, and drug-induced changes in IOP were evaluated.1
“We found that eyes with thinner corneas had significantly lower IOPs after one week of topical ocular hypotensive drug treatment than eyes with thicker corneas, even though these IOPs were statistically similar before treatment,” said Carol B. Toris, PhD, a study coauthor and professor of ophthalmology and director of glaucoma research at the University of Nebraska in Omaha.
Over the years, the team at Nebraska has conducted many studies of fluid dynamics in the eye, looking at pressure, inflow and outflow and CCT, and the effects of various IOP-lowering drugs.
“With the data readily available,” said Dr. Toris, “we decided to go back and take another look at CCT and IOP. While other researchers have looked at corneal thickness and IOP before, our study is unique in that we have baseline data on patients with ocular hypertension who are on no ocular medications, and data after one week of topical treatment with a variety of drugs.”
Within a normal range and in healthy eyes, there’s nothing wrong with thick corneas, said Dr. Toris. But, she added, “The cornea is quite a barrier. When you apply a drug to the cornea, less than 5 percent actually gets into the eye, and it appears that this is even less in eyes with thicker corneas.”
Posted by mehdi khanlari at August 25, 2008 11:02 PM