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Manfred MacKeben; Kinesthetic feedback augments self-exploration of the visual field after central vision loss. Journal of Vision 2002;2(10):95. doi: 10.1167/2.10.95.
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Patients with binocular central field loss can learn to use eccentric viewing. Thus, they need to learn quickly about topographic differences of perception in th eir visual field.
We implemented two methods: 1. The high-tech solution using a personal computer, custom software and a light pen. The patient stabilizes gaze by placing the scotoma over a high contrast angle profile on the screen. The patient explores the field by moving the hand and light pen, above which a letter is displayed wherever it moves. Thus, the patient can judge where the letter target looks clearest. 2. The low-tech solution uses a cardboard card with the same pattern and letters on small handles held by the patient. Both methods were used in random order by 34 patients (69 – 84 years of age) with central scotomas.
All patients found the point with clearest vision 1.5 to 8.5 degrees away from the center using either method in less than 2 minutes. An equivalent conventional, examiner-driven method without kinesthetic feedback proved to be at least 5 times more time-consuming (Mann-Whitney-U, p < 0.0001). Comparing the high- and low-tech methods with kinesthetic feedback, absolute locations of these points differed by up to 0.5 cm, but the differences were statistically not signif icant (p < 0.5).
The low-tech “explore card” method gives patients immediate kinesthetic feedback regarding hand (and target) position in the visual field. Patients can then reverse the process and adjust gaze while pointing at a stable letter as a first step towards eccentric viewing. A further advantage of the explore card method is that it is independent of verbal communication and can be applied at home.
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