Imaging of temporal retinal nerve fiber trajectory with Transverse Section Analysis

Abstract

Purpose: Individual differences in retinal nerve fiber (RNF) trajectory patterns constitute a critical factor when we assess its correspondence between visual field change and structural change in glaucoma patients. Especially, the papillo-macular nerve fiber bundle is well-known to show individual differences up to approximately 15 degrees of leaning based on its anatomical relation with the optic disc and fovea. However, accurate assessment of horizontality of the temporal raphe is difficult with fundus photography or SLO because RNF is thin in the temporal retina. The purpose of this study was to clarify the anatomical relation of the positions of the optic disc, fovea, and temporal raphe using Transverse Section Analysis of Heidelberg Engineering SPECTRALIS, which enabled us to depict detailed image of the RNF trajectory in the temporal retina.

Methods: Eleven eyes of 11 normal volunteers (-0.38D ≤ spherical equivalent (SE)≤ -9.12D) were measured. Using SPECTRALIS, volume scan was performed covering the optic disc to the temporal raphe including the macula. Transverse Section Analysis (Version 5.7) was used to analyze RNF trajectories. The OCT image was obtained to reconstruct the plane that were fitted to the inner limiting membrane (ILM) and detailed RNF trajectory was depicted as the layer adjacent to the reconstructed plane. The reconstructed OCT image was used to measure the fovea-optic disc angle (he angle between the line connecting the fovea and the center of the optic disc and the horizontal line through the fovea). The fovea-raphe angle (the angle between the line of the temporal horizontal raphe and the horizontal line) was also measured.

Results: In all the subjects, the RNF trajectory patterns were obtained more clearly in the reconstructed OCT images with Transverse Section Analysis than the conventional SLO images. The fovea-optic disc angle ranged between 3.9 degrees and 13.4 degrees (average: 7.7± 3.1 degrees ).The fovea-raphe angles which ranged between 0.2 degrees and 5.3 degrees (average: 2.8± 1.9 degrees ) were smaller than the fovea-optic disc angles.

Conclusions: The retinal horizontal raphe has the anatomical structure closer to the horizontal line passing through the fovea regardless of the relation of its position with the optic disc and fovea.

Keywords: 758 visual fields