Color Vision Testing
Color vision testing complements visual acuity assessment. Optic nerve disease, particularly demyelinating optic neuritis, may disproportionately affect color vision compared with CDVA. In macular disease, visual acuity and color vision tend to decline correspondingly. Thus, an optic neuropathy is the more likely etiology than a maculopathy in the differential diagnosis for an eye with 20/30 visual acuity but with severe loss of color vision. In optic neuropathy, persistent dyschromatopsia can occur even after recovery of visual acuity.
Color vision should be tested separately in each eye to detect unilateral disease. Because Ishihara pseudoisochromatic color plate testing is widely available, it is the commonly used method for color vision evaluation. Although the test was designed to detect congenital red-green color deficiencies, it may also identify acquired dyschromatopsia (though it may miss mild cases). Bilateral, symmetric color vision loss in men may signify congenital dyschromatopsia rather than bilateral optic neuropathies. The Hardy-Rand-Rittler (HRR) plates can be used to screen for tritan (ie, blue-yellow) defects as well as red-green defects. Blue-yellow color defects often accompany an optic neuropathy but also can occur in a maculopathy.
More detailed color testing may comprehensively characterize a color vision defect. In the Farnsworth panel D-15 test, the patient is asked to arrange 15 colored discs in order of hue and intensity. The Farnsworth-Munsell 100-hue test, which uses 85 colored discs, is the most detailed test and provides the best discrimination. This test requires a substantial amount of time to test and score, thereby limiting its use in routine clinical testing. Color vision testing is discussed further in BCSC Section 12, Retina and Vitreous.
Melamud A, Hagstrom S, Traboulsi E. Color vision testing. Ophthalmic Genet. 2004;25(3): 159–187.
Nichols BE, Thompson HS, Stone EM. Evaluation of a significantly shorter version of the Farnsworth-Munsell 100-hue test in patients with three different optic neuropathies. J Neuroophthalmol. 1997;17(1):1–6.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.