Homonymous Hemianopia After AVM Resection: Visual Field Exception
Ms. S is a 29-year-old graphic designer, 7 months after resection of a right occipital arteriovenous malformation. She has a complete right homonymous hemianopia, visual acuity 20/20 in each eye, normal color vision, and no neglect on testing. She has no motor, sensory, or cognitive deficits; MoCA is 29/30. She wants to drive her automatic sedan. She lives in a city with light rail and has a 20-minute commute. Her state requires a 120-degree horizontal binocular visual field for unrestricted licensing but allows an exception with an on-road evaluation and specialist recommendation. Her binocular field is approximately 90 degrees. She has no bioptic telescope and does not need one for acuity.
1. Does Ms. S meet the state's visual field standard? Explain and describe how you would assess functional seeing.
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She does not meet the 120-degree standard; her binocular field is about 90 degrees because of the complete right homonymous hemianopia. She may still qualify for the exception if the state accepts an on-road evaluation and specialist recommendation. Functional assessment should go beyond the visual field printout: I would test target detection in the blind and seeing fields, scanning into the right side, reaction to pedestrians entering from the right, lane position, and mirror use. I would also assess whether she turns her head reliably and whether she can integrate mirror and direct views. Because acuity and cognition are intact, her main risk is detection, not recognition. The on-road evaluation should include right-side hazards at intersections, driveway pullouts, and lane changes. A passing result must show consistent scanning and detection under increasing traffic demand, not a single quiet drive.
2. What training and vehicle strategies would you use, and what evidence would show they work?
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Training should teach systematic scanning toward the blind side, with head movements large enough to bring the right field into view, and should integrate mirror checks before lane changes and turns. I would practice in a closed course with targets placed at the right edge and then progress to low-traffic roads. Vehicle strategies may include an extra wide-angle interior mirror or cross-view mirror, but these do not replace scanning and can distort distance; they should be trialed, not assumed helpful. I would not recommend a bioptic telescope because her acuity is normal and the device does not restore field. Evidence of effectiveness would be fewer missed targets, more consistent head turns, improved lane position, and safe responses to right-side hazards across repeated drives. If she only succeeds with verbal cues from an instructor, she is not ready for independent driving.
3. What recommendation would you give to the licensing authority, including restrictions and review?
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I would recommend the visual field exception only if she passes a structured on-road evaluation and demonstrates independent scanning without prompts. The recommendation should state her measured field, acuity, cognitive status, on-road performance, and the specific compensatory strategies she uses. If approved, I would suggest initial restrictions: daylight only, familiar routes, no freeway driving for the first 3 months, and a review at 6 months with repeat on-road testing. The restrictions should be tied to the demonstrated risk, which is right-side detection, rather than to her diagnosis. I would also document that she was counseled about the limits of the exception and the need to avoid fatigued or night driving. If she fails, I would recommend alternative transportation and re-evaluation only after further training. The licensing authority should receive objective findings, not a vague statement that she is 'safe.'