Using Vision to Study Poststroke Recovery and Test Hypotheses About Neurorehabilitation

Abstract

Approximately one-third of stroke patients suffer visual field impairment as a result of their strokes. However, studies using the visual pathway as a paradigm for studying poststroke recovery are limited. In this article, we propose that the visual pathway has many features that make it an excellent model system for studying poststroke neuroplasticity and assessing the efficacy of therapeutic interventions. First, the functional anatomy of the visual pathway is well characterized, which makes it well suited for functional neuroimaging studies of poststroke recovery. Second, there are multiple highly standardized and clinically available diagnostic tools and outcome measures that can be used to assess visual function in stroke patients. Finally, as a sensory modality, the assessment of vision is arguably less likely to be affected by confounding factors such as functional compensation and patient motivation. Given these advantages, and the general similarities between poststroke visual field recovery and recovery in other functional domains, future neurorehabilitation studies should consider using the visual pathway to better understand the physiology of neurorecovery and test potential therapeutics.

Keywords: cortical blindness; hemianopia; rehabilitation research; stroke; stroke rehabilitation; vision disorders.

Figure 1:

Retinotopic mapping. (A) Example of a wedge stimulus used to map polar angle visual preferences. Subjects fixate on the central dot while the flickering checkerboard wedge is presented in each of 12 non-overlapping polar angles multiple times. (B) Example of a ring stimulus used to map eccentricity visual preferences. Subjects fixate on the central dot while the flickering checkerboard ring is presented in each of 6 non-overlapping eccentricities multiple times. (C) Example of a retinotopic map from a stroke patient with a visual field cut. The map is pseudo-colored based on each voxel’s preferred wedge location.

Figure 2:

Humphrey Visual Field Analyzer. (A) The patient is positioned against the chin and forehead rest, instructed to maintain fixation on a visual target, presented with a series of bright white lights with varying intensity in different locations of the visual field, and asked to press a handheld button each time a stimulus is seen. This information is used to create visual field maps for each eye, where darker tones represent loss of vision at that location in the visual field. (B) Example of a Humphrey visual field map from a patient with right homonymous hemianopia. The focal area of darkness within the left visual field of the left eye corresponds to the anatomical blind spot, or optic disk.

Figure 3:

Optical coherence tomography. (A) Tomogram through the fovea shows the ganglion cell complex layer, which is comprised of the retinal ganglion cell layer and the inner plexiform layer. (B) Thickness of the ganglion cell complex layer. (C) Circular tomogram around the optic disc shows the retinal nerve fiber layer. (D) Thickness of the retinal nerve fiber layer.