Visual deficits match many diagnoses and, if undetected, can be mistaken for other problems – e.g. sensory, motor, balance and cognitive deficits. It’s critical, therefore, that therapists know how to complete a basic visual screening and to interpret the results. For example, how can you tell homonymous hemianopia apart from unilateral inattention? The screening tools are virtually the same, but the screening results differ subtly.
Homonymous hemianopia is vision loss in corresponding visual fields – right nasal and left temporal, or vice versa. These types of visual deficits result from a lesion to the contralateral optic tract, optic radiations or occipital lobes. In other words, a right homonymous hemianopia may indicate a left unilateral lesion.
Unilateral inattention means reduced processing of visual information from one side of the body, and usually includes loss of motor and sensory processing. These types of visual deficits result from lesions to the contralateral parietal/temporal lobes. For example, a lesion to the right parietal/temporal lobes might result in left unilateral inattention.
Therapists must learn to detect the differences between these two visual deficits as the intervention process differs. A remedial approach is usually the best starting point for unilateral inattention while a compensatory approach may be best for homonymous hemianopia.
Below, watch the short video from my course on Evaluation and Treatment of Basic Visual Disorders for a hands-on demonstration of how to assess visual fields and screen for homonymous hemianopia and unilateral inattention.