Author: Claude (AI), from PubMed abstracts · Reviewed by: Dr Mina Abdelmseih · Reviewed: 2026-11-15 · Review due: 2027-11-15

Educational content only. Not personalised medical advice. Clinical decisions remain the responsibility of the treating clinician.

Drug-induced optic neuropathy: ethambutol, linezolid and amiodarone

Several systemic drugs can damage the optic nerve. Ethambutol and linezolid, both central to tuberculosis (TB) treatment, cause dose- and duration-related optic neuropathy [S5] [S11], and amiodarone has been associated with optic neuropathy, mainly in case reports and pharmacovigilance data [S1] [S2]. Early recognition and prompt stopping of the drug, in agreement with the prescriber, give the best chance of visual recovery [S9] [S12].

Key points - Ethambutol optic neuropathy (EON) had a pooled incidence of 1.54% in a 2026 meta-analysis; renal impairment and hypertension were significant risk factors [S12]. - Extending ethambutol beyond 2 months increases optic nerve toxicity [S7]; revised TB programmes using fixed-dose combinations and longer ethambutol use are expected to increase cases [S5]. - Linezolid optic neuropathy appears after long-term use, usually beyond 28 days [S3] [S11]; only 66.7% of 67 reported cases recovered complete visual function [S8]. - In the ZeNix RCT, optic neuropathy occurred in 9% of participants given linezolid 1200 mg daily for 26 weeks (all resolved), and the 600 mg for 26 weeks regimen had the best risk-benefit balance, as reported in [S6]. - For amiodarone, a large RCT found that bilateral vision loss occurs infrequently, if at all, at commonly used doses [S1], while case reports describe optic disc oedema and legal blindness in some cases [S2].

Evidence last checked: 2026-10-17 (PubMed abstracts).

Red flags

• Any new loss of vision, colour vision or visual field in a patient on ethambutol or linezolid [S5] [S8].
• Ethambutol in a patient with renal impairment or hypertension [S12].
• Linezolid for more than 28 days, at higher doses, in younger patients or with high cumulative doses [S3] [S10].
• Optic disc oedema in a patient on amiodarone [S2].

Recognise it

• Ethambutol. Toxicity is dose- and duration-dependent and may cause permanent vision loss [S5]. Younger age and earlier discontinuation were associated with better recovery [S12].
• Linezolid. Vision loss most often affects visual acuity, then visual field and colour vision [S8]. In a review of 33 cases, symptoms began after more than 28 days in 90.6% of documented cases, with a mean of 8.5 months of exposure [S3]. Peripheral neuropathy and haematological toxicity are other main adverse reactions [S11]. Pharmacovigilance data link optic nerve disorders to age under 60 and cumulative doses of 720 mg/kg or more [S10].
• Amiodarone. In 296 reports, mean duration of therapy before vision loss was 9 months; onset was insidious in 44%, nearly one third were asymptomatic, and disc oedema was present in 85% [S2]. Vortex keratopathy is the commonest ocular effect overall [S4].

Confirm it

• Use visual acuity, colour vision, visual fields, OCT and visual evoked potentials (VEP) as outcome and diagnostic measures [S7].
• VEP detected subclinical changes better than OCT in a meta-analysis [S12].
• The Indian expert consensus focuses on early suspicion through screening at the physician's office, opportunistic screening by ophthalmologists and specific clinical biomarkers [S5].

Manage it

Before acting on this section, check the national and local guidelines, product information and regulatory approvals that apply where you practise. See the medical disclaimer.

Tier A (primary care / TB programme / no specialist)

• Ask every patient on ethambutol or linezolid about blurred vision and colour change at each visit, and test visual acuity where possible [S5] [S3].
• Tell patients and health workers about vision-threatening adverse effects [S5].
• If vision symptoms appear, contact the prescriber about stopping the drug and refer [S5] [S3].
• Dosing is not covered here beyond the trial figures above: follow national TB guidelines and local formularies.

Tier B (general eye clinic)

• Examine acuity, colour vision, fields and the optic disc, and document a baseline for patients on long courses [S3] [S7].
• Recovery after ethambutol is stopped. In a cohort of 35 eyes, 77.1% recovered, with a mean estimated recovery time of 15.2 months; delay from symptom onset to discontinuation beyond 14 days was linked with slower recovery [S9]. Follow patients for 1 to 2 years or more [S9].
• Visual acuity improved significantly after stopping ethambutol, but colour vision and fields did not improve in the same way [S7].
• Linezolid. Withdrawal was followed by clinical improvement in 93.9% of 33 cases [S3], though complete recovery was less frequent in drug-resistant TB [S8].
• Report suspected cases to the national pharmacovigilance programme, as the Indian consensus describes [S5].

Tier C (specialist centre)

• Use VEP and OCT to detect subclinical toxicity in high-risk patients [S12].
• Support therapeutic drug monitoring and intensive monitoring for linezolid regimens [S11].
• Amiodarone. Annual incidence estimates from case reports were not confirmed in an RCT (837 amiodarone vs 832 placebo), in which no participant left the study because of bilateral vision loss; mean dose was 3.7 mg/kg (300 mg) daily, as reported in [S1]. Collaboration between the prescribing physician and eye care is important [S4].

Refer when

Pitfalls

• Assuming ethambutol toxicity always reverses: recovery occurred in 52.4% of clinical cases in a meta-analysis [S12].
• Delaying discontinuation after symptoms begin [S9].
• Missing linezolid toxicity because the dose is low: optic neuropathy has occurred regardless of the dose [S3].
• Attributing every optic neuropathy on amiodarone to the drug; the RCT evidence suggests it is rare [S1].

Evidence notes

• Conflict on linezolid dose: one case review concluded optic neuropathy occurs regardless of dose [S3], whereas other sources found dose- and duration-dependence [S8] [S10] [S11].
• Conflict on amiodarone: case and pharmacovigilance reports describe optic neuropathy [S2], but the RCT found bilateral vision loss infrequent, if it occurs at all [S1].
• Pooled EON incidence had very high heterogeneity (I² = 98.2%) [S12]. Much of the evidence is case-based or observational.
• The ZeNix trial was funded by the TB Alliance and others [S6].
• Not covered by these sources: ethambutol dosing per kilogram, specific screening intervals, other drugs (for example tacrolimus or PDE5 inhibitors), and treatment of established toxic optic neuropathy.

Related articles

• Nutritional and Toxic Optic Neuropathy
• Hydroxychloroquine retinopathy screening

References

See the numbered source list below. Each marker [S#] links to its PubMed and DOI record.