Relationship between optic disc-foveal distance and choroidal and retinal nerve fibre thickness

The optic disc-foveal distance is very important because it is an anatomical measure of the fundus. As this distance increases and the fundus tensions, there can be variability in retinal and choroidal thickness. The aim of this study was to determine the relationship between optic disc-foveal distance and choroidal and retinal nerve fibre thickness in healthy subjects.

72 people aged 20-36 participated in the study. Optic disc-foveal distance was measured with a fundus camera and choroidal and retinal nerve fibre thicknesses were measured with an optical coherence tomography (OCT) device. Littmann's formula as modified by Bennett (t = p × q × s) was applied to correct the magnification at the fundus camera imaging stage.

The thicknesses of the nasal choroid (p = 0.005; p = 0.006), subfoveal choroid (p = 0.004; p < 0.001), and temporal choroid (p = 0.001; p = 0.001) layers decreased as the optic disc-to-foveal distance (DFD) increased in both the right and the left eye of study participants, which was statistically significant. In addition, we observed that the retinal nerve fibre layer (RNFL) increased as the DFD distance increased, but this was not statistically significant.

This study demonstrated that the optic disc-foveal distance, an anatomical measure of the fundus, does not affect RNFL in healthy subjects, whereas choroidal thickness does.