Improving Vision in a Patient With Homonymous Hemianopia

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A 54-year-old woman has a right occipital stroke that causes a complete left homonymous hemianopia. Six months after the stroke, her ophthalmologic and neurologic examinations are entirely normal except for the persistent hemianopia, which, on Humphrey perimetry, shows no macular sparing. She reports that her reading has slowed down and that because of her visual field defect, she has been forbidden by her doctor from driving a car.Is there any intervention that would help her?Bernhard A. Sabel, PhD:A closer examination is first indicated to determine if the patient has a presumed “complete” hemianopia or whether the visual field examination actually shows some visual sparing, “areas of residual vision” or “relative defects” (1). I would recommend re-evaluating the patient for residual vision with additional repeated suprathreshold high-resolution perimetry to hunt for such areas of residual vision. If some are present, vision restoration therapy (VRT), a computer-based training program, might improve residual vision (2,3). Even small improvements in visual function offered by VRT can be beneficial to the patient.If VRT proves ineffective or when no further improvements after VRT are noted, saccadic training could be tried. This might improve the patient's ability to scan visual scenes with the intact hemifield and this, in turn, might improve visual orientation (4) but not reading or driving.Susanne Trauzettel-Klosinski, MD:Six months after the stroke, the patient still has a chance of spontaneous recovery of at least parts of the field defect. After 1 year, spontaneous recovery can no longer be expected. After that point, any improvements could be attributed to training. However, except in the research setting, I suggest that training begin within the first few months of onset of the hemianopia.There is yet no evidence that any intervention will enlarge the visual field defect in a relevant way. Reports of visual field enlargement after training (3,5) have not been confirmed in controlled studies (6,7). Therefore, I would suggest training to improve saccadic exploration toward the blind hemifield, which has been shown to be effective in compensating for the visual field defect (4,8) and in improving the functional visual field essential in everyday life activities. However, the chance of regaining the prerequisites for driving is low.To overcome the reading disorder, training of predictive saccades during the return sweep can reduce the difficulties in finding the beginning of the next text line. The use of a slightly eccentric fixation locus improves reading by increasing the perceptual span toward the blind hemifield (9,10). Some have recommended that the patient be taught to read vertically by turning the text although there are no scientific studies to support that recommendation.Are there any studies that compare the outcomes in patients who have undergone saccadic training to patients who have not undergone such training?Bernhard A. Sabel, PhD:No studies are available yet in which two independent groups have been compared-one with saccadic training and the other without. Instead, within-subject experimental designs have been used. Thus, the role of the patients' expectations and the general effect of working on a computer monitor cannot be separated from a specific “saccadic training” effect. Rigorous experimental standards would mandate a double-blind, randomized, placebo-controlled clinical trial before establishing efficacy of “saccadic training.”Saccadic training can follow different strategies. One strategy is to train patients to make broader searches (“visual search field”) in the blind hemifield. A second approach is to train patients to make large-scale eye movements toward the blind hemifield.

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