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Effects of Central Corneal Thickness on the Efficacy of Topical Ocular Hypotensive Medications

Johnson, Thomas V. BA; Toris, Carol B. PhD; Fan, Shan MD; Camras, Carl B. MD

doi: 10.1097/IJG.0b013e31814b9938
Original Studies
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Purpose To determine the effect of central corneal thickness (CCT) on the efficacy of intraocular pressure (IOP)-reducing drugs in patients with ocular hypertension (OHT).

Methods This retrospective study analyzed research records of 115 OHT patients and 97 ocular normotensive (ONT) volunteers. CCT was measured by slit-lamp pachymetry and IOP by pneumatonometry. The OHT patients were divided into Thick (>540 μm, n=52) and Thin (≤540 μm, n=63) Cornea groups. Measurements in the OHT group were made after washout of all IOP-lowering drugs and at 1 week of treatment with latanoprost 0.005%, dorzolamide 2%, brimonidine 0.2%, apraclonidine 0.5%, pilocarpine 2%, or unoprostone 0.15% to 1 eye and vehicle contralaterally. ONT volunteers also were divided into Thick (n=34) and Thin (n=63) Cornea groups. Results were compared between groups using unpaired t tests or nonparametric Wilcoxon tests and within groups using linear regression analyses.

Results Baseline IOPs were not different between CCT groups of OHT patients or of ONT volunteers. After 1 week of drug treatment, IOP was significantly (P=0.02) lower in the OHT Thin Cornea group (16.0±3.0 mm Hg, mean±SD) than the OHT Thick Cornea group (17.4±2.8 mm Hg). There was a positive correlation between IOP and CCT (R 2=0.06, P=0.007) in OHT drug-treated eyes, but not OHT vehicle-treated or ONT untreated eyes. The final IOP was significantly lower in the Thin than the Thick Cornea group treated with brimonidine (P=0.02) but not with latanoprost (P=0.91).

Conclusions When dosed with IOP lowering drugs, eyes with thinner corneas had lower IOPs than eyes with thicker corneas. This suggests a reduced efficacy of some glaucoma medications in ocular hypertensive patients with thick corneas.

Department of Ophthalmology, University of Nebraska Medical Center, Omaha, Nebraska

Supported by an unrestricted grant from Research to Prevent Blindness, Inc, New York, NY. Dr Camras was a Research to Prevent Blindness Senior Scientific Investigator.

Correspondence: Carol B. Toris, PhD, Department of Ophthalmology, 985840 Nebraska Medical Center, Omaha, NE 68198-5840 (e-mail: ctoris@unmc.edu).

Received for publication September 19, 2006; accepted June 30, 2007

Presented in part at the Association for Research in Vision and Ophthalmology annual meetings in May 2003 and April 2004 and at the American Glaucoma Society annual meeting in March 2004.

© 2008 Lippincott Williams & Wilkins, Inc.