Editors Selection (IGR: 8-4) | International Glaucoma Review #301

Editors Selection IGR 8-4

Clinical glaucoma: OHT

Comment by Robert Fechtner on:

15148 Inconsistency of the published definition of ocular hypertension, Tavares IM; Medeiros FA; Weinreb RN, Journal of Glaucoma, 2006; 15: 529-533

In this systematic literature review by Tavarez et al. (1166) the investigators sought to examine the variability of published definitions for ocular hypertension and evaluate the influence of the OHTS study on the published literature. A PubMed literature search returned 133 articles published between 1995 and 2005 in three ophthalmology journals with the highest impact factor. Eleven articles from the OHTS study were excluded leaving 122 studies for analysis. The studies were divided between those that evaluated the efficacy of IOP lowering medications (clinical trials) and those that evaluated diagnostic tests in different diagnostic groups. In short, they found the definitions were highly variable and the influence of the OHTS study was small. This paper is a call to action for standardizing a definition of ocular hypertension. There was no consistency in the IOP cut off level (range 18 to 26 mmHg, the number of IOP measurements, or even the reporting of methodology for measuring IOP. Central corneal thickness (CCT) was reported in 13.1% of articles and appears uninfluenced by the OHTS publications in 2001 and 2002 suggesting the importance of CCT measurement. Some visual field criteria were reported for most of the articles but only 36.9% described the criteria adopted for diagnosis. Of the 122 publications, 84 required assessment of the optic nerve but only 57 reported the method of nerve assessment and only 37 described characteristics needed to qualify a disc as glaucomatous. Ocular hypertension can be clearly defined. For the Ocular Hypertension Treatment Study and the European Glaucoma Prevention Study clear definitions were necessary for appropriate study design and analysis but may not directly reflect patterns in clinical practice. They do not seem to have informed research methodology. The first published OHTS report in 1999 of design and baseline characteristic did not result in a trend toward more standard definitions in the reviewed publications.

The authors suggest that consistency in the definition would provide a foundation for clinical investigation from which to formulate research questions. While we would likely agree that ocular hypertension is clinically defined as statistically elevated IOP in an eye with a healthy optic nerve and nerve fiber layer and with normal visual function as demonstrated by visual field testing, there has not yet been clear consensus on how to define ocular hypertension. There should be! The authors rightly propose that we should be more rigorous in defining what these concepts mean. A standardization of definition for OHT would facilitate comparison of research results and allow extrapolation of meaningful data from published work. Best of all it would bring us together speaking the same language amongst ourselves as clinicians and investigators and with our patients as we try to help them understand the risk of their disease.

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