Abstract
Purpose :
Prior research suggests that binocular measures of vision equal or exceed measures obtained from each eye individually. Anecdotally, however, glaucoma patients sometimes express that a poorly-seeing eye can depress their binocular vision below the level of their better-seeing eye, a phenomenon referred to as suppression. We performed a cross-sectional, clinical study to look for evidence of suppression in a glaucoma population.
Methods :
The contrast sensitivity function (CSF), measuring contrast sensitivity at varying letter sizes to model the area under the curve log CSF (AULCSF), was evaluated in 29 primary glaucoma patients with varied disease severity using the qCSF testing device (Adaptive Sensory Technology). Testing was performed in monocular and binocular conditions. Regression models were constructed in which the binocular - better-eye AULCSF difference was the dependent variable, inter-eye AULCSF difference was the independent variable, and age was a covariate. Patients were said to have a small inter-eye difference if right and left eye AULCSF values were within 0.3 and a large inter-eye difference if the values differed by more than 0.3.
Results :
Subjects had a mean age of 69.6 (1.7) years and an average visual field mean deviation of -5.9 (1.4) and -13.1 (1.5) in the better and worse eyes, respectively. For all subjects, binocular AULCSF was 0.10 (0.12) greater than better-eye AULCSF. In the 15 patients with a small inter-eye difference, binocular AULCSF was 0.16 (0.13) greater than better-eye AULCSF, while in the 14 patients with a large inter-eye difference, binocular AULCSF was 0.03 (0.11) greater than better-eye AULCSF (p=0.003). No patient with a small inter-eye difference had worse binocular than better-eye AULCSF, while 7 of 14 patients with a large inter-eye difference had worse binocular than better-eye AULCSF (p<0.001). In regression models, each 0.1 increment in inter-eye AULCSF difference was associated with a 0.02 decrement in binocular - better-eye AULCSF difference (95% CI -0.03 to -0.002, p=0.024) and 1.43 higher odds of a worse binocular than better-eye AULCSF (95% CI 1.06 to 1.93, p=0.018).
Conclusions :
Glaucoma patients with large visual differences from a poorly-seeing eye may experience suppression of vision in their better eye and lose binocular advantage when testing CSF. Better-eye monocular visual measures may not be an accurate representation of binocular vision in glaucoma patients.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.