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Editors Selection IGR 14-2

Diagnostic Methods: OCT: Peripapillary choroidal thickness and glaucoma

Comment by Paul Healey on:

50203 Peripapillary Choroidal Thickness in Healthy Controls and Patients With Focal, Diffuse, and Sclerotic Glaucomatous Optic Disc Damage, Roberts KF; Artes PH; O'Leary N et al., Archives of Ophthalmology, 2012; 130: 980-986

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Does the appearance of the optic disc tell us something about the pathology of glaucoma? Roberts and coworkers have previously described a number of different morphological patterns of glaucoma damage with differing associations raising the possibility of differing pathological processes.

In this paper, Roberts et al. examined peripapillary choroidal thickness using spectral domain OCT, postulating that as the choroid supplies blood to the prelaminar optic nerve head, choroidal thinning may indicate reduced perfusion and contribute to glaucoma damage. The study design was case-control. However, cases and controls came from different longitudinal studies. Although this is a weakness, participants in both contributing studies were recruited from the same geographic area with cases recruited from clinics and controls from relatives, local telecom workers and church groups. Cases were further divided on the basis of their optic-disc morphology into three small but relatively equal groups; Focal, Diffuse and Sclerotic. Median MD and NFL thickness was lowest in the Focal and highest in the Sclerotic groups. Choroidal thickness could be measured in 86% of cases and 83% of controls. Apart from glaucoma, the major difference between the groups was age, with cases on average 15 years older than controls. This is important, as choroidal thickness was lower in older participants in both groups. But the rate of change with age was very similar in all groups.

The principal finding was that choroidal thickness was about 40 micrometres lower in the Sclerotic glaucoma group compared to controls after adjusting for age and axial length. No additional associations were found with MD of NFL thickness. While mean choroidal thickness was lower than controls in the focal and diffuse groups also, the finding was not statistically significant. The optic disc classification used in this study characterized sclerotic discs as having shallow cupping, peripapillary atrophy and visible large choroidal vessels suggesting loss of RPE pigment and choroidal vasculature. In this context it might be expected that such a peripapillary retinal morphology may be associated with a measurably thinner choroid. As with all cross sectional studies one cannot know if this association is cause or effect. But it does add to the accumulating evidence that morphological characteristics in glaucoma may guide insight into the nature of this disease.

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