Cone Contrast Threshold Measurements for Compressive Optic Neuropathies

Abstract

Purpose : The cone contrast test (CCT) is a computer-based contrast sensitivity test that quantifies the type and severity of color vision deficiencies by measuring patient response to varied intensities of visual cues stimulating red, green, and blue cones. Evidence has shown that CCT has greater sensitivity in detecting color vision deficits compared to Hardy Rand and Rittler (HRR) and Ishihara pseudoisochromatic plates. It has also demonstrated clinical utility in evaluating acquired color vision deficiency in glaucoma. In this prospective clinical study, our aim is to use CCT to characterize color vision deficiency in patients with compressive optic neuropathies (ON) secondary to neurological malignancies.

Methods : CCT scores of the right eye (10 control, 8 compressive ON) were included for analysis. Patients with malignancies that led to compression and damage of the optic nerve were included. Patients with glaucoma or other causes leading to ON were excluded. Color vision assessment was performed at 20 inches under photopic conditions using the ColorDx CCT (KonanMedical, Irvine, California USA) as part of normal course of care in a neuro-ophthalmology clinic. CCT provides a numeric, whole number score for each cone class, with lower scores indicating greater color vision deficit. Scores for each group were analyzed by independent sample t-test.

Results : Mean CCT scores for red and green cones were significantly lower in the compressive optic neuropathy group than in the control group. The mean CCT scores for blue cones were also lower in the compressive optic neuropathy group, but the difference was not statistically significant.

Conclusions : This data supports that compressive optic neuropathy is associated with decreased color vision. It reinforces a correlation between optic neuropathy and color vision and the utility of quantifying color vision to follow disease onset and progression. It further highlights that blue cone color quantitation may be less reliable than green and red, as shorter wavelengths can be filtered by anterior segment pathology such as cataracts.

This is a 2021 ARVO Annual Meeting abstract.

 

Table 1. Comparison of Cone Contrast Test (CCT) Scores