Ocular Toxicity Expert Witness

An ocular toxicity expert witness evaluates claims that a drug or chemical damaged the eye — and, just as often, whether the prescribing and monitoring around a known ocular toxin met the standard of care. Marc H. Shomer, MD, PhD, QME, a board-certified ophthalmologist with more than 13 years of medical-legal consulting experience, reviews these matters for plaintiff and defense counsel nationwide.

Toxicity cases differ from most ophthalmic litigation in one respect: for the major offending drugs, published screening protocols exist, so the standard-of-care question frequently becomes a concrete, documentary one — was the recommended monitoring ordered, performed, and acted upon?

The Medical-Legal Question

Two questions organize nearly every ocular toxicity case. First, causation: is the eye finding actually attributable to the exposure, or does the patient have a look-alike disease unrelated to the drug? Second, standard of care: for medications with established monitoring guidelines, did the prescriber, the monitoring ophthalmologist, and the systems between them ensure that screening happened and that early toxicity triggered a response? Responsibility in these cases is often shared across specialties — rheumatology, pulmonology, cardiology, ophthalmology — and sorting out who owed what is part of the analysis.

Drugs That Generate Litigation

Hydroxychloroquine maculopathy. Hydroxychloroquine, widely used for lupus and rheumatoid arthritis, can cause a characteristic, dose- and duration-dependent damage to the macula that is irreversible and can progress even after the drug is stopped. Established screening recommendations call for baseline examination and periodic testing — typically automated visual fields and OCT (optical coherence tomography), with additional modalities in some settings — precisely because early toxicity is detectable before symptoms. Claims commonly allege years of therapy with absent or inadequate screening, or screening abnormalities that did not prompt cessation.
Ethambutol optic neuropathy. This tuberculosis drug can injure the optic nerves, classically presenting with reduced central vision and impaired color vision in both eyes. Dose adjustment for kidney function and prompt discontinuation at the first sign of visual change are central themes.
Amiodarone. This cardiac antiarrhythmic causes corneal deposits in most users (usually visually insignificant) and is associated with an uncommon optic neuropathy; distinguishing amiodarone-associated neuropathy from the far more common non-arteritic ischemic optic neuropathy in the same vascular-risk population is a genuinely contested causation question.
Intraocular medication errors. Wrong drug, wrong dose, or wrong formulation injected or irrigated into the eye during surgery or intravitreal injection can cause immediate, severe retinal toxicity. These cases hinge on compounding, labeling, and verification procedures.
Chemical exposures. Occupational and environmental chemical injury to the ocular surface and deeper structures overlaps with the chemical eye injury page; toxicity claims add questions of exposure dose, latency, and biologic plausibility.

Causation: Association Is Not Enough

Each of these drugs has an established toxicity signature — a pattern on OCT, fields, or examination that fits the mechanism. A rigorous analysis asks whether the findings match that signature, whether dose and duration reached toxic ranges, whether the timeline fits, and whether alternatives (age-related macular degeneration mimicking hydroxychloroquine toxicity, ischemic neuropathy mimicking drug neuropathy) better explain the picture. The general approach is described on the causation page; medication-related macular disease also intersects the macular disease page.

Limitations of the Evaluation

Toxicity opinions are strongest when baseline testing exists and serial studies show evolution consistent with the exposure. Without a baseline, distinguishing drug injury from pre-existing disease may be impossible with confidence, and the report should say so. Individual susceptibility varies, and guideline adherence, while central, is evaluated against the standards in effect at the time of care — a point developed on the standard of care page.

What Attorneys Should Provide

Complete pharmacy dispensing records (dose, duration, and cumulative exposure matter), prescriber records from every involved specialty, all ophthalmic testing in image form — OCT, visual fields, fundus photographs — and, in surgical-error cases, the operative record, compounding and lot documentation, and incident reports. Records establishing vision before the exposure are frequently decisive.

Frequently Asked Questions

What must be shown to prove a drug caused eye damage?

The findings should match the drug's established toxicity signature on examination and imaging, the dose and duration should be in a range known to cause harm, the timeline should fit, and alternative diagnoses that mimic the toxicity should be reasonably excluded. Mere temporal association between a drug and vision loss is not sufficient.

Who is responsible for hydroxychloroquine eye screening — the rheumatologist or the ophthalmologist?

Screening responsibility is typically shared: the prescriber is expected to arrange baseline and periodic eye monitoring, and the examining ophthalmologist to perform appropriate testing and report toxicity signs. Many claims involve system failures between the two — referrals never made, results never transmitted, or abnormalities never acted upon. Allocation of duty in a specific case is ultimately a legal question informed by the medical facts.

Can hydroxychloroquine damage be reversed by stopping the drug?

No. Established hydroxychloroquine maculopathy is irreversible and can continue progressing for a time even after cessation, which is precisely why screening guidelines aim to catch toxicity before symptoms appear. This fact makes screening adequacy, rather than treatment choice, the usual center of these cases.

Are intraocular medication error cases hard to defend?

Each case turns on its facts. Wrong-drug and wrong-dose events implicate compounding, labeling, and verification systems, and the analysis examines where the process failed and whether the injury pattern actually matches the alleged agent. Causation is still contested territory, since surgical eyes can lose vision from recognized complications unrelated to the medication.

Educational information only. This page provides general information for attorneys and other medical-legal professionals. It is not medical or legal advice, does not address any particular case, and does not create a physician-patient, attorney-client, or expert-client relationship. Opinions in any matter are formed only after review of the specific records, examination findings, and applicable literature. Past engagements do not guarantee any result.

Authored and reviewed by Marc H. Shomer, MD, PhD, QME

Board-certified ophthalmologist; Adjunct Associate Professor of Ophthalmology, Keck School of Medicine of USC; active California Qualified Medical Evaluator. Full biography · Curriculum vitae

Published August 2, 2026 · Last substantive review August 2, 2026 · Medical reviewer: Marc H. Shomer, MD, PhD, QME