Visual Field Loss Evaluation

What Visual Field Testing Measures

The visual field is everything a steadily fixating eye can see, center to periphery. Field loss can devastate function even when the acuity chart is normal — it governs driving eligibility, navigation, and hazard awareness — and it is a core input to impairment ratings under the AMA Guides, as described on the whole person impairment page.

The Two Main Testing Methods

Automated static perimetry — most commonly the Humphrey Field Analyzer — presents fixed points of light at varying brightness while the patient fixates centrally and presses a button when a light is seen. The common 24-2 program tests the central 24 degrees; it is the workhorse for glaucoma and neurologic disease. Goldmann kinetic perimetry uses a trained examiner moving a light from the far periphery inward while the patient signals detection, mapping the full field's outer boundaries. Goldmann testing is particularly useful for measuring overall field extent for disability rating and for evaluating suspected non-organic loss, because the examiner can vary technique in ways an automated program cannot.

Reliability Indices: Reading the Fine Print

Automated perimeters measure their own trustworthiness. Fixation losses count responses to stimuli placed in the blind spot, where a steadily fixating eye sees nothing. False positives count button presses when no stimulus was shown — the signature of a trigger-happy patient, which fabricates an implausibly good field. False negatives count missed stimuli at locations previously seen at dimmer settings, suggesting fatigue or inattention. A field with poor indices is not evidence of much, in either direction, and expert review starts with these numbers before interpreting the gray scale that juries find intuitive.

Patterns and What They Localize

Field defects follow anatomy. An arcuate defect curving around central vision reflects the nerve fiber layer architecture and is characteristic of glaucoma, discussed on the glaucoma page. A hemianopia — loss of the same half of the field in both eyes, respecting the vertical midline — localizes behind the optic chiasm and indicates brain rather than eye pathology, relevant in head trauma and stroke claims covered under neuro-ophthalmology. Generalized constriction — a field shrunken from all sides — occurs in advanced glaucoma, some retinal degenerations, and, importantly, in non-organic vision loss. Because pattern localizes the lesion, the field itself often tests the plausibility of a causation theory.

Identifying Non-Organic Constriction

Visual fields are effort-dependent, and constricted fields are the most common non-organic finding in a medical-legal setting. Several checks distinguish organic from non-organic constriction: organic constriction expands proportionally when testing distance increases, while a non-organic "tunnel" stays the same width at any distance; kinetic testing may show spiraling or crossing isopters (the mapped boundaries) that violate physiology; results may vary wildly between sessions; and the claimed field may be contradicted by observed navigation or by objective structure on OCT (optical coherence tomography), since severe true constriction has a visible anatomic cause. Identifying non-organic findings does not by itself establish malingering — anxiety and somatic conditions can produce similar results — and a careful report describes the inconsistencies without overreaching. A fuller primer for counsel is at understanding visual fields.

What Attorneys Should Provide

Every field printout in the record — full pages, not report excerpts, since the reliability indices and test parameters matter — along with OCT imaging, acuity records, and the clinical notes surrounding each test date. Serial fields are far more informative than any single study; where only one field exists, expect the expert to recommend repeat testing before firm conclusions are drawn.

Frequently Asked Questions