A Case of Unilateral Blue-Yellow Color Vision Defects With a Suspicion for Functional Visual Loss

[Purpose] Acquired color vision defects are often seen in patients with functional visual loss in addition to retinal, optic nerve and cerebral disorders. Here we reported a patient with unilateral blue-yellow color vision defects suspected to be associated with functional visual loss.<BR>[Case] A 21-year-old female patient, who complained of color vision defects in the right eye was evaluated by a local doctor in November 2008. Corrected visual acuity was 1.2 in both eyes. No abnormal findings were detected in the anterior segments, media, fundus or by fluorescein angiography. The Goldmann kinetic visual field in both eyes and MRI finding of the brain were all normal. The patient was referred to the Department of Ophthalmology at the Jikei University School of Medicine in December 2009. White-on-white perimetry (Central 30-2) and blue-on-yellow perimetry (Central 24-2) on the Humphrey Field Analyzer had mean deviations (MD) of -2.07 db (right) and +0.04 db (left), and -19.19 db (right, P < 0.5%) and -2.67 db (left), respectively. Flash and focal macular electroretinograms showed normal amplitudes in both eyes. Pattern reversal visual evoked potentials (P100 components) also demonstrated normal implicit times and amplitudes. Various color vision tests were performed monocularly including: the Ishihara test with no error found, the Nagel anomaloscope Model I showing normal Rayleigh equation, the SPP-II and HRR tests demonstrating no error in the left eye but blue-yellow defects in the right eye, the panel D-15 with no error in the left eye but a tritan pattern in the right eye, and the Farnsworth-Munsell 100-hue test revealing total error scores of 8 in the left eye and 180 in the right eye indicating blue-yellow defects. The patient was followed up but the subjective symptoms did not improve two years later. The same color vision tests were performed again and almost the same outcomes as those from the initial evaluation were obtained.<BR>[Conclusion] The patient in this case was a college law student who had worked part-time for more than four days a week six months before the initial symptoms. We found that occupational and mental stress caused by her busy life and human relations might be behind the symptoms. Since no test findings indicating any organic diseases, we considered that the unilateral blue-yellow color vision defects were due to functional visual loss.