The interpretation of results of 10-2 visual fields should consider individual variability in the position of the optic disc and temporal raphe

Aims

To clarify the anatomical relation between the optic disc and temporal raphe and to examine how these are related to test points in the 10-2 visual field test pattern.

Subjects and methods

For 22 eyes of volunteers with normal vision (+0.75 D spherical equivalent 7.88 D), a volume scan was used to obtain en-face images from a plane fitted to the inner limiting membrane using optical coherence tomography (OCT). The clearest en-face retinal nerve fibre (RNF) image was chosen for each subject and superimposed on fundus photographs using blood vessels for alignment. Individual landmarks (disc, fovea and visual field blind spot) were then used to superimpose the Humphrey Field Analyzer 10-2 visual field on the OCT image to compare with the RNF image.

Results

The average disc–fovea–raphe angle was 169.4°±3.2°. Both the disc and temporal raphe were located above the horizontal midline (ie, were inferior in visual field space). For the 10-2 test pattern superimposed on the OCT image, in 54.5% of eyes, the temporal inferior test points adjacent to the horizontal midline mapped to the anatomical inferior hemifield. In 22.7% of eyes, nasal inferior test points adjacent to the horizontal midline mapped to the anatomical inferior hemifield. This mapping is opposite to typically assumed.

Conclusion

The position of the disc and raphe affects the mapping between structure and function with respect to superior and inferior hemifields. Individual differences in the position of the temporal raphe should be considered when mapping between structure and function for the 10-2 test pattern.

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