Association of acquired color vision defects in blue cone monochromatism.

The retinal functions of a 43-year-old man with diabetic retinopathy in a family affected by blue cone monochromatism were studied. While changes in visual acuity and color vision were similar to those seen in patients affected by rod monochromatism, and his spectral sensitivities on high intensity background and his threshold versus intensity curve indicated only suggestive blue cone function, mass electroretinograms (ERG) findings demonstrated well preserved blue cone function. The disparity in blue cone function between psychophysical and mass electroretinographical evaluation may be caused by the difference in how much the fovea influenced each testing. Diabetic retinopathy most likely caused significant reduction of the psychophysical blue cone function and resulted in clinical findings similar to rod monochromatism. The mass blue cone ERG was useful to differentiate blue cone monochromatism from rod monochromatism in this diabetic patient.