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BLOG: Hemianopia or spatial neglect – can you tell the difference?
by Penelope S. Suter, OD, FCOVD, FNORA
Visual spatial neglect is a disturbance in the perception of space due to inattention to that area of space. If we cannot attend to an area of space, then not only can we not “see” that area of space, we cannot even know that it exists.
If you enjoy reading, the novel, Left Neglected, by Lisa Genova, provides some fictional insight into what a patient with a severe case of visual spatial neglect (VSN) experiences.
Spatial neglect is surprisingly common in patients hospitalized for stroke, occurring in up to 82% of assessable right hemisphere stroke and 65% of left hemisphere stroke patients (Stone et al.). Neglect can also be found in neurodegenerative disease, such as Alzheimer’s disease, or following traumatic or other brain injury. Many of these patients improve on their own, but a large percentage do not.
Patients with VSN are frequently discharged home without ever being tested or treated for the condition. It is not uncommon, therefore, for someone to bring in their elderly parent and say, “Mom had a stroke a few months ago and she’s been bumping into things ever since. I think she doesn’t see well anymore.”
There may be significant visual field loss on one side, and the temptation is to diagnose this as hemianopia. However, hemianopia is a sensory deficit in vision due to damage to the primary visual pathway from the retina up through primary visual cortex. Patients with hemianopia will know they have lost vision and will turn their head or eyes into the blind field to try to compensate. In VSN, the ability to attend is what is impaired, and those patients have extreme difficulty even recognizing that there is a problem. This obviously creates a significant safety risk.
VSN can be body-centric (following the midline of the head or torso) or object-centric. Someone with object-centric VSN may complete only half the picture when asked to draw or copy something. I once had a patient with dense peripersonal left neglect (affecting only the space within arms’ reach). When asked to walk to his wife at the other end of a hallway, he walked directly to her until he got within arms’ reach and then would suddenly veer to the side so that she ended up on his right. When asked why, he had no idea he was doing it.
VSN can cause difficulty in almost all activities of daily living, including navigation, balance, personal care, spatial memory, reading and eating. To screen for it, combine a visual field test, a cross-out task, a line bisection and a drawing task. Neuro-optometric interventions include treatment with Peli peripheral prisms, the Pisella prism adaptation technique, or other yoked prism applications. Educating the patient, consistent cuing, as well as teaching them how to scan into the affected field are also critical parts of rehabilitation.
In the examination room, patients who skip the first letter of the row when reading the distance or near eye charts should be suspects for neglect. Patients who show any sort of visual field loss or evidence of broad functional difficulties with navigation, reading or generalized confusion about their surroundings following brain injury may be patients with visual spatial neglect who would benefit from neuro-optometric evaluation and treatment.
Reference:
Stone SP, et al. Age Ageing. 1993;doi:10.1093/ageing/22.1.46.
For more information:
Penelope Suter, OD, FCOVD, is in private practice in Bakersfield, Calif. She is first editor of the only comprehensive text/reference book on vision rehabilitation following brain injury, Vision Rehabilitation: Multidisciplinary Care of the Patient Following Brain Injury, (Suter & Harvey, CRC Press, 2011). In addition to her private practice, Suter served as co-director of the CSU Bakersfield Vision Laboratory for more than 20 years and spent 17 years as the primary vision consultant to the Centre for Neuro Skills brain injury rehabilitation center in Bakersfield.
Disclosure: Suter receives royalties from sales of Vision Rehabilitation: Multidisciplinary Care of the Patient Following Brain Injury.
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