The Location of the Temporal Retinal Veins and Arteries Can Be Used to Improve the Sensitivity of the Retinal Nerve Fiber Layer Thickness Measured With Optical Coherence Tomography (OCT)

Abstract

Purpose: : Retinal nerve fiber thickness (RNFL) profiles, measured with optical coherence tomography (OCT), show inter-subject variability correlated, in part, with the location of retinal blood vessels (BVs).[1,2] Here we determine if adjusting for BV location can improve RNFL tests.

Methods: : One eye of 50 controls and 50 patients was tested with OCT (fast circular RNFL scan, OCT3, Zeiss) and scanning laser polarimetry (SLP) (GDx-VCC, Zeiss). The glaucoma group had abnormal visual fields (mostly mild to moderate with all but 3 > -5.1 dB) and optic discs. The 20 suspects had normal fields, but abnormal discs. The midpoint between the major temporal vein and artery in the superior (STva) and inferior (ITva) disc regions was marked on the SLP fundus image. The raw SLP RNFL thicknesses were exported and the profile determined for a circle of 3.4 mm dia. The average OCT and SLP RNFL thicknesses for arcuate sectors of the lower and upper optic disc [3] were obtained before and after shifting for relative STva and ITva locations.

Results: : BV locations ranged over 48° (STva) and 66° (ITva) for all 100 eyes. In fig., the average RNFL profile for the 10 control eyes with the most temporal STva (dotted), and nasal STva (dashed), locations are compared to the average of all 50 controls (solid). The RNFL profiles systematically varied with BV location. For the superior disc, a greater number of the patients’ RNFL profiles fell below a 1.96SD (5%) cutoff for the shifted [29(OCT) & 26(SLP)] as compared to unshifted [11(OCT) & 14(SLP)] profiles; the controls stayed the same at 2. There difference for the inferior disc was not significant.

Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer