Purchase this article with an account.
Allison Maree McKendrick, Phillip Bedggood, Bao Nguyen, Graham Lakkis, Andrew Turpin; Orientation of the temporal nerve fibre raphe in healthy eyes and those with glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4260.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Many analytical techniques applied to visual field or optical coherence tomography (OCT) data for the assessment of glaucoma assume a division between the superior and inferior hemifields due to the temporal nerve fibre raphe. The typical assumption is a horizontal raphe, or sometimes an extension of the angle between the optic nerve head (ONH) and the fovea. We aimed to characterise the orientation of the temporal raphe in glaucoma and healthy controls and to evaluate the accuracy of typical approximations to raphe orientation.
We recently described a method to automatically determine the orientation of the temporal nerve fibre raphe from OCT, using the intensity data from vertically oriented macular cube scans. Here, we used this method to measure raphe orientation bilaterally in 49 healthy participants (aged 19-81 years) and 51 participants with open-angle glaucoma (aged 51-80 years). The outcome measures were the angles measured between the fovea, disc and temporal raphe.
Fovea-disc-raphe angle did not differ between groups (p=0.28) and was 173.5 ± 3.2° (range=166–182°) in the healthy group, and 174.2 ± 3.4° (range=166–184°) in glaucoma. The fovea-disc-raphe angle was not correlated with age or axial length (p > 0.4), showed some symmetry between eyes in the glaucoma group (R2 = 0.31, p < 0.01), and little symmetry in the healthy group (p > 0.05). The fovea-disc angle was correlated with fovea-raphe angle (R2 = 0.27, p <0.01), but was not a good predictor for raphe orientation (average error = 6.8°, maximum error = 15.6°). When compared to an assumption of a strictly horizontal raphe, the average error was 3.2° (maximum error = 9.6°).
There is substantial natural variation in the orientation of the temporal nerve fibre raphe, which cannot be accurately predicted from age, axial length, relative geometry of the disc and fovea, or parameters from the contralateral eye. Raphe orientation should be measured directly for accurate mapping between visual field and anatomical data in glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only