Tip of the Month
Publishing date: January 2014
Tip Editors: John Salmon and Gordana Sunaric Mégevand
Tip reviewer: Roger Hitchings
The Science behind the Tip
Recent studies using spectral domain ocular coherence tomography (SD OCT) measurement of the optic disc margin show that current methods of measuring the optic disc margin are not accurate (1). The disc margin is not the true anatomical outer border of the neuro-retinal rim because of variable, invisible extensions of Bruch's membrane (2). The opening in Bruch's membrane represents the logical outer border of the rim.
Current regional data acquisition and analysis algorithms assume the same anatomical location in different individuals, potentially yielding errors in regional rim or peri-papillary nerve fibre quantification. SD OCT imaging of the Bruch's membrane opening has been shown to detect changes in the glaucomatous optic nerve head more accurately than disc margin-based assessment (3). It can also detect progressive optic nerve head change in experimental glaucoma in primates (4).
By incorporating these new SD OCT-detected anatomical quantitative features of the optic nerve head, glaucoma should be diagnosed at an earlier stage in future and glaucoma progression should be more accurately detected than with present techniques.
Contributor: Gordana Sunaric-Mégevand, Geneva
1. Chauhan BC, Burgoyne CF. From clinical examination of the optic disc to clinical assessment of the optic nerve head: a paradigm change. Am J Ophthalmol 2013; 156:218-227.
2. Reis AS, O'Leary N, Yang H, et al. Influence of clinically invisible, but optical coherence tomography detected, optic disc margin anatomy on neuroretinal rim evaluation. Invest Ophthamol Vis Sci 2012; 53:1852-1860.
3. Chauhan BC, O'Leary N, Almobarak FA, et al. Enhanced detection of open-angle glaucoma with an anatomically accurate optical coherence tomography-derived neuroretinal rim parameter. Ophthalmology 2013;120:535-543
4. Strouthidis NG, Fortune B, Yang H et al. Longitudinal change detected by spectral domain optical coherence tomography in the optic nerve head and peripapillary retina in experimental glaucoma. Invest Ophthalmol Vis Sci 2011; 52:1206-1219