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Ehrlich et al. (37) studied peripapillary choroidal thickness (PPCT) in exploring the hypothesis that choroidal thickness (CT) is related to glaucoma and/or glaucoma damage. In a carefully performed and well thought out study, the authors convincingly demonstrate that they find no relationship between PPCT and either glaucoma or retinal nerve fiber layer thickness. They do find a relationship between PPCT and age, which may in fact be a confounder that contributed to the hypothesis initially.
The authors use optical coherence tomography to study PPCT. This technology allowed discrimination of the anterior and posterior borders of the peripapillary choroid. The authors show that agreement between observers in measurement of PPCT is acceptable; however, measurement reproducibility is not reported. It would be useful to know this parameter in evaluating the results of this study.
This investigation and the evidence to date suggest that there is not a relationship between choroidal thickness and glaucoma
Yin in 19971 (based on pathology specimens) and Spaide in 20092 (based on OCT findings) each proposed a link between CT and glaucoma. The current paper was e-published in January, 2011. Subsequent to this there have been other papers reporting the investigation of an association between CT and glaucoma, and these studies have similarly found no such relationship.3,4 In addition, Ehrlich and co-authors looked for the possibility of a connection between peripapillary atrophy and PPCT, but found none.
It is very difficult to prove a negative hypothesis, and neither the current study nor those with similar findings have done so; however, this investigation and the evidence to date suggest that there is not a relationship between choroidal thickness and glaucoma, or that if there is such an association it is very weak indeed.