Computer-Based Training of Stimulus Detection Improves Color and Simple Pattern Recognition in the Defective Field of Hemianopic Subjects

Abstract

In a previously conducted randomized placebo-controlled trial, we were able to demonstrate significant visual field enlargement induced by restitution therapy in patients with cerebral lesions [Kasten, E., Wuest, S., Behrens-Bamann, W., & Sabel, B. A. (1998c). Computer-based training for the treatment of partial blindness. Nature Medicine, 4, 1083-1087.]. Visual field training was performed on a computer monitor for 1 hr per day over a period of 6 months. Since the procedure included only stimulation with white light, in the present study we investigated if this simple detection training had a transfer effect on color or form recognition in the trained area (i.e., in the absence of modality specific training). Answering this question would be crucial for planning optimal restitution therapy: In case there is no transfer of training effects to other visual modalities, a specific treatment of each visual function must be performed in order to achieve maximum benefit. Therefore, we analyzed the data from 32 patients with visual field defects who had participated in the original trial and whose form and color recognition had been investigated. The experimental group (n = 19, restitution training) experienced not only an increase of 12.8% correctly detected stimuli (PeriMa program, p <.05), but also an improvement of 5.6% in pattern recognition (PeriForm) and of 6.1% in color perception (PeriColor), respectively. In contrast, the placebo group (n = 13, fixation training) showed no significant changes from baseline to final outcome in any of the visual modalities (PeriMa: 0.3%; PeriForm: -0.3%; PeriColor: 0.4%). Conventional perimetry yielded an increase of 7.8% detected stimuli in the experimental group, but only of 1.2% in the placebo group (p <.05). For form recognition and color perception, the differences between the results of the experimental and the placebo groups narrowly missed significance. However, correlations of diagnostic results showed that mainly those patients who had achieved visual field enlargement also improved in color and form perception: r =.67 (p <.05) between PeriMa and PeriForm and r =.32 between PeriMa and PeriColor. We conclude that visual restitution training using a simple white light stimulus has at least some influence on improving other visual functions such as color and pattern recognition. This result supports the "bottleneck theory" of visual restitution, i.e., training effects can be explained as a process of perceptual learning and increased processing of information by residual structures surviving lesions of the primary visual pathways.

The rehabilitation of hemianopic dyslexia

“…46-57 treatmentinduced visual field enlargement in patients seldom exceeds 5°, although a few cases have shown remarkable and stable restitution of the visual field. [48][49][50][51][52][54][55][56] this enlargement might be sufficient to improve the reading abilities of some patients with visual field defects; however, the degree of change is too small to reduce the visual exploration impairment. normal reading performance only requires a visual field sparing of 3° to the left and 5° to the right of a fixation, 11,26,58 but the critical left-sided and right-sided visual field requirements in visual exploration are at least 20°.…”

Using Reaction Time to Assess Patients With Unilateral Neglect and Extinction

“…While it is true that patients suffering from primary sensory damage can often compensate for their de®cits via appropriate eye and head movements, estimates of the percentage of hemianopic patients that exhibit spontaneous visual recovery have only ranged between 12 and 30% (see Chapter 2, Zihl, 2000). In contrast, two recent studies by Kasten and colleagues have shown that 1 hr of visual ®eld training per day over a 6-month period in patients with visual ®eld defects resulted in signi®cant enlargements of the visual ®eld, as tested via conventional perimetry, as well as some bene®ts in color and form recognition (Kasten, Poggel, & Sabel, 2000;Kasten, Wuest, Behrens-Bamann, & Sabel, 1998). Nonetheless, a substantial number of stroke patients suffer from cortical damage that compromises higher order visual and attentional abilities as well, particularly when the right hemisphere is affected (De Renzi, 1982;Posner, Walker, Friedrich, & Rafal, 1984;Robertson & Rafal, 2000;Zihl, 2000).…”

Participatory Design of Therapeutic Video Games for Young People with Neurological Vision Impairment

“…Restitution aims to either restore function to the primary visual cortex or improve visual detection in nearby extra-striate visual pathways. This is typically undertaken with visual stimulation using extremely bright, high contrast stimuli [17]. Compensation aims to change behavior to compensate for lost visual function.…”