Acquired dyschromatopsia

Specialty: Ophthalmology.

• alteration in color vision
• loss of acquired chromatic discrimination
• acquired color blindness

Why it occurs

• Macular drug toxicity (especially induced by ethambutol, hydroxychloroquine or digitalis)
• Demyelinating or ischemic optic neuritis in acute or resolving phase
• Toxic-nutritional optic neuropathy (associated with chronic alcohol and tobacco abuse with folate deficiency)
• Progressive wet or dry senile maculopathy
• Advanced open angle glaucoma with loss of retinal fibers
• Pathology of the cortical visual pathway (e.g., infarction of the fusiform gyrus)

Initial workup

Ishihara pseudoisochromatic slide test (useful for rapid screening of the red-green axis); Farnsworth-Munsell ordering test of 100 hue (or its simplified version of 15 or 28 hue for a precise quantitative analysis of dyschromatopsia in the protan, deutan and tritan axes of confusion); Optical Coherence Tomography (OCT) of the optic nerve and macula; Visual Evoked Potentials to measure abnormalities in axonal transmission speed.

Standard management

• There is no drug that restores color perception altered by structural damage. The treatment consists of immediately removing the toxic agent
• Folic acid (5 mg orally per day) associated with Vitamin B12 (hydroxycobalamin 1000 mcg intramuscularly weekly in the attack phase, followed by monthly administration, indicated in nutritional optic neuropathy to provide metabolic support to the myelin sheath of the optic nerve).