Ethambutol can cause optic neuritis. Which symptom requires prompt evaluation?

Ethambutol can cause optic neuritis. Which symptom requires prompt evaluation?

• A. Headache
• B. Decreased visual acuity
• C. Nausea
• D. Dizziness

Answer: (B)

Ethambutol toxicity can affect the optic nerve, causing optic neuritis. The most concerning and urgent sign is a decrease in visual acuity because it directly reflects optic nerve function and can progress to permanent vision loss if not addressed promptly. Early recognition and stopping ethambutol, often with ophthalmologic evaluation and visual testing (acuity, color vision, fields), can prevent irreversible damage. Headache, nausea, and dizziness are nonspecific symptoms and do not specifically indicate optic nerve involvement, so they don’t carry the same urgency.

Ethambutol toxicity can affect the optic nerve, causing optic neuritis. The most concerning and urgent sign is a decrease in visual acuity because it directly reflects optic nerve function and can progress to permanent vision loss if not addressed promptly. Early recognition and stopping ethambutol, often with ophthalmologic evaluation and visual testing (acuity, color vision, fields), can prevent irreversible damage. Headache, nausea, and dizziness are nonspecific symptoms and do not specifically indicate optic nerve involvement, so they don’t carry the same urgency.