The ability to discriminate the myriad hues that surround us transcends species, confers survival value, and is essential for veridical object detection, discrimination, and recognition.
1,2 Normal color vision depends on a normal complement of long wavelength (L), middle wavelength (M), and short wavelength sensitive (S) cone photoreceptors. Hereditary red-green color vision deficiency (CVD; 8% of Caucasian males and 1 in 200 females) is an X-linked condition resulting in a shift in peak L or M cone absorption (protanomaly and deuteranomaly, respectively) or lack of either L (protanopia) or M (deuteranopia) cones.
3,4 The importance of normal color vision has been identified for various occupations requiring accurate hue discrimination in cue-limited settings, including transportation (aviation, railway, and driving), military settings, as well as law enforcement.
5–8 Hence hereditary CVD is disqualifying for numerous occupations. Equally important, CVD can be acquired as an early clinical or subclinical sign of ocular, systemic, and neurologic disease offering potential for early diagnosis, monitoring, and treatment.
9–14 While numerous book tests of color vision are invaluable for detection of hereditary CVD, few offer qualitative (protan, deutan, or tritan) or quantitative (severity) metrics to correlate color ability with real-world demands. For hereditary red-green CVD, the anomaloscope remains a benchmark test, though newer computer-based tests offer comparable sensitivity, specificity, and require less skill to administer and interpret.
15–20 Nevertheless, all test methods described thus far require subjective responses, which precludes testing of infants, nonverbal patients, as well as cognitively impaired patients with stroke, traumatic, or senescent brain disease. Hence our purpose in this initial proof-of-principle study was to develop and validate a rapid, objective, clinically expedient visual-evoked potential (VEP) measure of cone-specific color vision to diagnose hereditary and acquired CVD.