Academic journal article Journal of Visual Impairment & Blindness

A Computer Program for Training Eccentric Reading in Persons with Central Scotoma

Academic journal article Journal of Visual Impairment & Blindness

A Computer Program for Training Eccentric Reading in Persons with Central Scotoma

Article excerpt

Macular lesions result in vision loss in the central visual field, disabling the performance of activities that require good acuity, such as reading, while leaving intact the performance of activities that depend more on peripheral vision, such as mobility. Some macular dystrophies affect younger individuals, but the term generally refers to age-related macular degeneration (AMD) in older people (Park, 1999). Several studies have shown that many of these persons developed a preferred retinal locus for seeing, located outside the lesion (see, for example, Crossland, Culham, & Rubin, 2004; Frennesson, Jakobsson, & Nilsson, 1995). Some persons have several such retinal loci which are sometimes used under different lighting conditions (Lei & Schuchard, 1997; Schuchard, 2005). Usually this extrafoveal seeing is helpful for orientation in daily living, but only some persons are able to read (Cummings, Whittaker, Watson, & Budd, 1985). Therefore, Nilsson and Nilsson (1986; see also Nilsson, Frennesson, & Nilsson, 2003) developed a technique for eccentric reading training (EVT). A practical method was developed by Oertel-Verweyen; this method requires a considerable number of sessions with a therapist.

For home training, we developed a computer program--Xcentric viewing--to optimize this method. In our small study, we investigated whether this program increases the reading capacities of individuals with macular degeneration. Instead of a control group, we compared the data with the results of Schreckenbach's (2006) study, which used the same scientific design of EVT with 21 persons without using a computer.

METHODS

The computer-based training program Xcentric viewing was programmed by the first author. It contains the following parts: search of a prime position, training, home exercises, and the move-the-text technique.

Search of prime positions

Usually the eye with better visual acuity is selected to choose the prime viewing position. The person is asked to fixate the gaze of their better eye at a red fixation mark or a crosshair on the screen; a chin support helps to hold the person's head stable. The fixation is controlled by observing the person's eyes during training. The therapist can present letters or words in different sizes on the screen with the arrow keys on the keyboard. The person tells the therapist when he or she is able to read the letters or words. In most cases, several positions are found, and the program allows the locations to be stored. Five hot keys enable the therapist to compare these positions. The same letter or word can be shown in a short sequence in these stored positions, and the person decides which one is the best. Finally, in interaction with the person, the therapist recommends a prime viewing position for home training (see Figures 1 and 2).

Training

During training, an optimal stimulation is performed with marquees; the words run from the right to the left side through the area of the prime position. It is crucial for the person to hold his or her head and eyes in a firm position by looking stably at the crosshair and to try to read the marquee letter by letter. Later, the size of the letters is reduced, and the lengths of the words are extended.

Home exercises

Xcentric-viewing can store the individual adjusted level of difficulty on a memory stick. For home training, a simplified version of the program is available. In the study, the therapist explained the usage of the program to the participants (or relatives), which usually took about 1 hour, and gave them a copy of the software. In addition, the participants received magnifying lenses (reading microscopes); the optical power was adapted to their needs, but was almost stable in most participants (average magnification: 11.6 diopters before and 10.8 after the training). The program was designed to load the current data from the USB stick and automatically adjust the program for the particular level of difficulty required. …

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