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A 7-year-old boy has difficulty distinguishing red and green colors. His maternal grandfather and maternal uncle cannot distinguish these colors.
XLR; OPN1LW (red) and OPN1MW (green) on Xq28
- Red-green color blindness (most common: deuteranomaly)
- Affects ~8% of males, ~0.5% of females (homozygotes or skewed X-inactivation)
- Does not affect visual acuity
- Ishihara pseudoisochromatic plates for red-green screening
- Anomaloscope (Nagel) color matching as the reference test to confirm and classify the deficiency type
- Molecular testing of the OPN1LW/OPN1MW opsin gene array is available but rarely needed clinically
- No cure; supportive measures and counseling about the benign, stable nature of the condition
- Practical adaptations (labeling, assistive apps, color-correcting filters with variable benefit) and awareness of occupational color-vision requirements