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25-03-2012 | Physical rehabilitation | Article

Devices such as ‘The vOICe’ effective for visual rehabilitation


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MedWire News: Over half of blind individuals using 'The vOICe', a high-resolution visual-to-auditory sensory substitution device (SSD), can achieve visual acuity levels above the World Health Organization (WHO) blindness threshold, show study findings.

The researchers say that this is "the highest acuity reported yet with any visual rehabilitation approach," and demonstrates the capacity of such devices for visual rehabilitation.

Various methods of visual rehabilitation for blind people have been investigated including retinal implants and a variety of SSDs.

Initially, tactile-to-visual SSDs seemed promising, but the maximal functional acuity achieved with them is fairly low (max 144 pixels). However, auditory-to-visual SSDs potentially offer much higher acuity with one such device -The vOICe - generating a resolution of up to 25,344 pixels.

To test the functional "visual" acuity that can be achieved by users of The vOICe, which translates a picture or view into sound using a small head-mounted camera and earpiece, Amir Amedi (The Hebrew University of Jerusalem, Israel) and colleagues recruited nine blind (eight congenitally and one early onset) adult users (55-101 hours of use in total) of the device to take part in their study.

The team used the standardized Snellen tumbling-E test to assess the functional visual acuity that could be achieved using The vOICe. This test is used by opticians to measure visual acuity and consists of rows of the letter E in different orientations decreasing in size from the top to the bottom row.

Normal vision on the Snellen test results in a score of 20/20, whereas blindness is defined by the WHO as having a score of 20/400 or worse.

In this study, the participants achieved Snellen scores ranging from 20/200 to 20/600, with five of the nine individuals achieving a score exceeding the WHO blindness threshold.

These results are significantly better than those achieved using the highest-resolution retinal prostheses (20/1000) and the most up-to-date tactile SSDs (20/860), note the authors.

"Our findings suggest that early and congenitally blind individuals using auditory SSDs can retrieve detailed visual information at a much higher resolution than previously demonstrated with any other sight rehabilitation approach," they write in PLoS ONE.

"These findings should thus also encourage the development of new SSDs with finer and additional visual detail, such as color… and direct depth cues," they conclude.

By Helen Albert

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