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Editors Selection IGR 9-4

Medical treatment: Chronic use and ocular surface

Comment by Christophe Baudouin on:

17187 Effects of glaucoma medications on corneal endothelium, keratocytes, and subbasal nerves among participants in the Ocular Hypertension Treatment Study, Baratz KH; Nau CB; Winter EJ et al., Cornea, 2006; 25: 1046-1052

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This study by Baratz and collaborators (20) deals with cornea, a tissue rarely explored in glaucoma, in a series of 47 patients enrolled in the OHTS in one center, and followed for a long period of time. The OHTS design allowed to compare the group receiving treatment with that only observed, which gives this study a highly relevant impact. The follow-up was 6 to 9 years and the tools used for exploring the cornea were specular microscopy and in vivo confocal microscopy, a well-validated technique for non-invasively examining corneal cells and structures at a histologic-like level. Special attention was focused on endothelial changes, keratocyte number and subbasal nerve density. Even though no endothelial or keratocytes changes were noted in the treated group compared to the control observational one, the authors found significant decrease in nerve density and number in the treated group. The conclusion is that chronic use of medications may affect some regulatory elements of the ocular surface. Whether this is a toxic effect or the result of continuous stimulation of the cornea by the medications and/or their preservative will have to be further evaluated.

Chronic use of medications affect some regulatory elements of the ocular surface

Concerning the methodology used in this study it is useless to discuss the quality of a large, well-designed clinical trial like OHTS, and confocal microscopy is a well established method for evaluating corneal structures. Even though the full follow-up was only conducted in a limited number of patients, the information given by this study is important. Indeed it shows that cornea may be damaged by long-term use of treatments and these data illustrate that the whole ocular surface may be directly influenced by topical treatments. The authors also observed in a separate study on superficial cornea of the same patients a decrease in epithelial thickness in the treated group compared to the observation group and relate all those findings to neurotrophic keratitis. Many reports have shown that the ocular surface of glaucoma patients may present tear film instability, subclinical inflammation with proinflammatory cytokine release, and corneal epithelial changes. The ocular surface of glaucoma patients should deserve in the future a higher interest for clinicians, scientists, pharmaceutical companies, and… regulatory authorities.

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