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Editors Selection IGR 24-3
Optic Nerve Head: Gray crescent and ethnicity
Comment by Jost Jonas on:
19558 Gray optic disc crescent: Influence of ethnicity in a glaucoma population, Higginbotham L; Shafranov G; Shields MB, Journal of Glaucoma, 2007; 16: 572-576
The gray crescent of the optic disc as originally described by Bruce Shields is a mostly unrecognised feature at the border of the optic nerve head, occurring in addition to the alpha zone and beta zone of peripapillary atrophy and a conus pigmentosus. According to Shields, it is a slate-gray crescent within the peripheral tissue of the optic nerve head. The gray crescents are usually bilateral and are most often located along the temporal or inferotemporal disc margin. In their recent hospital-based study, Higginbotham, Shafranov and Shields (869) evaluated the prevalence of the gray optic disc crescent within a glaucoma population and assessed the influence of ethnicity and other variables. Out of 225 patients, the gray crescent was detected in one or both eyes of 32 patients (14.2%), with a significantly (P < 0.0001) higher prevalence in the African American group (27.3%) than in the white group (7.4%). Since the prevalence of the gray crescent did not correlate with age, sex, refractive error, intraocular pressure or the presence or degree of glaucomatous optic neuropathy, the authors concluded that the gray optic disc crescent is a common finding within a glaucoma population, especially among persons of African heritage, without showing any correlation with the presence or amount of glaucomatous optic neuropathy.
The clinical importance of the gray crescent is that one may erroneously assume that the underlying tissue is not neuroretinal rim, but parapapillary tissueThe results by Higginbotham again demonstrate the importance to the gray optic disc crescent to be included in the morphologic assessment of the optic nerve head. The clinical importance of the gray crescent is that one may erroneously assume that the underlying tissue is not neuroretinal rim, but parapapillary tissue. It will lead to a falsely small optic disc and neuroretinal rim area, and consequently, to falsely high measurements of the cup / disc diameter ratios. Additionally, it will markedly influence the assessment of the shape of the neuroretinal rim.
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