Estimation of the Relative Amount of Hemoglobin in the Cup and Neuroretinal Rim Using Stereoscopic Color Fundus Images

Abstract

Purpose:To calculate the amount of hemoglobin (Hb) in sectors of the optic nerve head (ONH) from stereoscopic color fundus images using the Laguna ONhE method and compare the results to the visual field evaluation and optical coherence tomography (OCT). Methods:Healthy eyes (n=87) and glaucoma eyes (n=71) underwent reliable Oculus Spark perimetry and Cirrus OCT. ONH color images were acquired with a non-mydriatic stereoscopic Wx Kowa fundus camera. Laguna ONhE program was applied to these images to calculate the Hb amount in the cup and 6 sectors of the rim. Receiver operating characteristic (ROC) analysis and correlations between parameters were calculated. Results:We did not observe any variations in the amount of hemoglobin in relation to age in normal subjects (R2=0.033, P>0.05). Maximum ROC area confidence intervals were observed for a combination between perimetric indices and the Laguna ONhE Glaucoma Discriminant Function (0.970-0.899) followed by rim area (0.960-0.883) and mean deviation (MD) (0.944-0.857). In glaucoma cases, Hb amount presented significant reduction in all rim sectors, especially 231-270º and 81-120º (P<0.001), except in the temporal 311-40º (P=0.11). Perimetry mean sensitivity by sectors was better correlated with respective hemoglobin levels than with rim areas or the corresponding nerve fiber thickness, especially the superior and inferior sectors (p<0.05). Conclusions:Visual field sensitivity was better correlated with hemoglobin levels than with rim sector areas or the corresponding nerve fiber thickness. In many cases the remaining rim showed insufficient perfusion, especially in the superior and inferior sectors.