A nurse is caring for a patient with active pulmonary tuberculosis who has been on anti-tuberculosis therapy for 2 months. The patient reports new onset of visual disturbances, including difficulty distinguishing red and green colors. Which nursing intervention should be the priority?

Ethambutol (EMB) is a first-line agent for tuberculosis, but its use carries a risk of dose- and duration-dependent optic neuropathy. The primary nursing responsibility is early detection through systematic symptom surveillance and immediate action upon suspicion of toxicity.

• Early Hallmark: Acquired red-green dyschromatopsia (difficulty distinguishing red and green).
• Progressive Signs: Blurred vision, decreased visual acuity, central scotomas (blind spots).
• Symptom Onset: Typically insidious, often after 2 months of therapy, but can occur earlier with renal impairment.

1. Immediate Discontinuation: Hold the ethambutol dose as soon as visual symptoms are reported. This is the single most critical step to maximize the chance of visual recovery, as damage is partly reversible if caught early.
2. Urgent Notification: Promptly inform the prescribing physician or advanced practice provider. The anti-TB regimen will need modification, often substituting EMB with another agent while awaiting susceptibility results.
3. Documentation: Document the specific symptoms reported (e.g., "patient states 'I can't tell red from green'"), the time of onset, baseline visual status, and the actions taken, including medication held and provider notified.

• Baseline and Monthly Screening: Visual acuity and color vision testing (using Ishihara plates) should be performed at baseline and monthly thereafter for all patients on EMB.
• Patient Teaching: Instruct patients to immediately report any changes in vision, especially color perception, blurred vision, or blind spots. Emphasize that they should not wait for a scheduled appointment.
• High-Risk Populations: Exercise heightened vigilance in patients with renal impairment, as reduced drug excretion increases toxicity risk. Older adults and those on prolonged therapy (>2 months) are also at increased risk.

Clinical Pearl: Never attribute visual complaints in a patient on ethambutol to other causes without first excluding drug toxicity. A proactive, safety-first approach prevents irreversible blindness.