Rehabilitation for visual disorders

State-of-the-Art

Rehabilitation for Visual Disorders
Susanne Trauzettel-Klosinski, MD

Abstract: Rehabilitation for visual disorders demands thorough assessment of many components of vision and a tailored strategy of maximizing residual function. Magnification with optical or electronic aids and the use of eccentric fixation and specific reading training exercises are helpful techniques inpatients with central scotomas. Visual exploration training is beneficial in patients with homonymous hemianopias.
Journal of Neuro-Ophthalmology 2010;30:73–84 doi: 10.1097/WNO.0b013e3181ce7e8f Ó 2010 by North American Neuro-Ophthalmology Society

any diseases of the eyes and visual pathways are associated with persisting visual deficits that require rehabilitation. There is an increasing demand forrehabilitation for these disorders (1,2), particularly in view of increased survival rates and prolonged life expectancy (3–5). A precondition for successful rehabilitation is an exact assessment of visual impairments. The World Health Organization general classification of impairments, disabilities, and handicaps (ICIDH) (6), later modified to the International Classification of Functioning,Disability and Health (7) can be well adapted to the visual system (Fig. 1). It considers 3 fields: 1) impairment, which assesses the pathologic condition and the function on the basis of the involved organ(s); 2) disability or activity limitation, which indicates the difficulties caused by the impairment; and 3) handicap or participation restriction, which stands for the resulting problems in thepatient’s environment.

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and the optimal prescription of glasses come first. Visual fields must also be determined accurately, because defects involving the central field limit the size of the reading visual field (,5° from fixation). Visual field defects in the periphery can lead to orientation difficulties. To detect small defects, one must use a dense grid or a thorough manual strategy. If perimetrycannot be performed with a standardized instrument, bedside confrontation fields are useful to detect large field defects, especially hemianopias. Tangent screen campimetry may also be used. Contrast sensitivity testing is also critical. Contrast can be improved by optimal illumination or by marking the environment with special high-contrast landmarks.

READING
In modern society, adults spendapproximately 2.5 hours per day reading, especially during work activities. Approximately 90% of all jobs require dealing with written material (8). To read newspaper print at a distance of 25 cm, a visual acuity of at least 20/50 (0.4) is necessary. Whereas visual acuity testing depends on recognizing only 1 optotype at a time, reading demands a simultaneous overview of a group of letters. The minimumreading visual field (9) is an area of approximately 2° to the right and left of fixation and corresponds approximately to the ‘‘visual span’’ or ‘‘word recognition span’’ (10,11). Within this area, letters are seen clearly. Figure 2A shows the functional and morphologic data related to a fundus image. The ‘‘minimum reading visual field’’ (turquoise oval) corresponds more or less to the area of thefovea (green oval). Parafoveal information processing can extend the total ‘‘perceptual span’’ (‘‘reading visual field’’) during 1 fixation in the reading direction up to 15 letters (11,12) (Fig. 2B, red oval). This extended perceptual span provides information about word length, capitalization, and word shape, and offers a preview benefit, which is useful in guiding the next saccade to the appropriatelanding position. For fluent reading, a total perceptual span of 5° (15 letters) to the right and 1.3–2° (4–6 letters) to the left of fixation is necessary, as shown in window experiments in 73

DIAGNOSTIC PROCEDURES IN VISUAL REHABILITATION
Determination of visual acuity for distance and near viewing, refractive error, and accommodative amplitude
Low Vision Clinic and Research Laboratory,...