Ophthalmology Causation Expert
Causation is the question that decides many vision cases: is the claimed visual loss actually the result of the incident or treatment at issue, or of pre-existing disease, natural progression, or something else entirely? Dr. Marc H. Shomer provides independent causation analysis built on objective ophthalmic evidence — imaging, visual fields, and the documented clinical course — rather than on assumption in either direction.
Why causation is frequently the real battleground
Vision loss after an event is not the same as vision loss from an event. The eye is subject to common, slowly progressive diseases — cataract, glaucoma, macular degeneration, diabetic retinopathy — that can surface or be first documented coincidentally after an injury or a procedure. Conversely, genuine traumatic damage is sometimes dismissed as pre-existing because no one assembled the baseline evidence. Rigorous causation analysis protects both sides from the wrong answer.
The analytical framework
- Baseline. What was the documented vision and ocular status before the event? Optometry records, prior refractions, DMV vision screenings, and old imaging often establish it.
- Mechanism. Is the proposed mechanism medically plausible for the claimed injury — can blunt trauma of the described force produce this finding?
- Temporal course. Does the timing of documented findings fit the proposed cause? Some sequelae are immediate; others, such as angle-recession glaucoma or traumatic cataract, characteristically appear late — a point that cuts in different directions in different cases.
- Objective correlates. Does structural evidence — OCT, photographs, visual fields, electrophysiology — corroborate the claimed functional loss?
- Alternative explanations. What else could produce these findings, and can the alternatives be excluded or apportioned on the evidence?
Association is not causation. "The patient's vision was worse after the surgery" is a temporal observation, not a causal conclusion. An opinion that does not engage the alternatives is advocacy, not analysis — and it rarely survives a well-prepared cross-examination.
Where causation analysis is decisive
- Claimed vision loss after trauma with disputed pre-existing disease
- Post-surgical visual loss attributed to alleged negligence vs. known complication or disease progression
- Workers' compensation claims requiring apportionment between industrial and non-industrial causes — see Apportionment in Ophthalmic Injury
- Toxic exposure claims involving the eye — see Ocular Toxicity
- Disputed non-organic or exaggerated visual loss, assessed with objective testing rather than accusation — see Evaluating Vision-Loss Claims
The honest limits of retrospective analysis
Some causation questions cannot be answered to a reasonable degree of medical probability from the available record, and a credible expert says so. Where the evidence supports a conclusion, the report explains the reasoning transparently; where it supports only a range of possibilities, the report says that instead. This discipline is what makes the opinions that are given defensible under oath.
What to provide
Everything that bears on baseline and course: pre-incident eye and optometry records, all post-incident treating records, and diagnostic imaging in native format. A precise statement of the causation questions counsel needs answered focuses the review. See What Records to Provide.
Frequently Asked Questions
What does a causation expert do in an eye case?
A causation expert determines whether the claimed visual loss is medically attributable to the event at issue — trauma, treatment, or exposure — or to pre-existing disease, natural progression, or other causes, using baseline records, mechanism analysis, the temporal course, and objective testing.
Can pre-existing eye disease defeat causation?
Not automatically. Pre-existing disease may explain all, part, or none of the current impairment. The analysis frequently apportions: it identifies what the objective evidence attributes to the event versus the underlying condition, with the reasoning stated explicitly.
What if there are no baseline records?
Baseline can sometimes be reconstructed from indirect sources — optometry files, prior refractions, driver's license screenings, or the structural characteristics of findings themselves, since some changes take years to develop. Where baseline genuinely cannot be established, the opinion states that limitation candidly.
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.
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
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