Simultaneous Comparison of Relative Damage to Chromatic Pathways in Ocular Hypertension and Glaucoma: Correlation with Clinical Measures

Abstract

PURPOSE: To use a new methodological approach, based on luminance noise, to assess without bias the relative damage of blue-yellow and red-green pathways in ocular hypertension and glaucoma and to correlate obtained measurements with clinical markers of disease progression. METHODS: A psychophysical procedure modified from Cambridge color test was used to assess color discrimination in three different groups: patients with primary open-angle glaucoma (n = 51 eyes), patients with ocular hypertension (n = 95 eyes), and control subjects (n = 46 eyes). Viewing conditions were such that the function of the macula was being tested, using a discrimination task under noisy conditions. Confusion vectors, and parameters obtained from discrimination ellipses were correlated with perimetric and clinical data taken from the same groups. RESULTS: The lengths of the major axis of chromatic discrimination ellipses and all confusion vectors were significantly different between the groups. These measures followed a significant gradient of worsening performance from the control to hypertensive and glaucoma groups, which was steeper for the tritan axis. There was a significant global positive correlation between test parameters and cup-to-disc ratio and a significant negative correlation with the perimetric mean deviation index. Ellipse length in patients with ocular hypertension correlated significantly with the duration of their hypertensive state. CONCLUSIONS: This psychophysical test can detect visual dysfunction in a significant subset of patients with long-term hypertension with preserved visual fields. Macular function is damaged earlier than previously believed, in both the blue-yellow and red-green pathways.