What testing is important to detect ethambutol-related optic neuritis early?

• A. Baseline and serial visual acuity and color vision testing.
• B. Baseline and serial complete blood counts
• C. Baseline and serial liver function tests
• D. Baseline and serial blood glucose tests

Answer: (A)

Ethambutol optic neuritis presents mainly as a decline in optic nerve function, often starting with subtle changes in color perception and then visual acuity. Because these changes can be small and progressive, monitoring visual function with baseline testing and regular follow-up is essential. Visual acuity testing measures how clearly a person sees, while color vision testing detects dyschromatopsia—especially red-green deficits—that frequently signal optic nerve toxicity from ethambutol. Establishing a baseline allows you to detect even small declines over time, and serial tests can catch problems early so the drug can be stopped or adjusted before permanent damage occurs.

The other tests listed (blood counts, liver function, blood glucose) do not assess optic nerve function and therefore aren’t useful for early detection of ethambutol-related optic neuritis.