ScienceDaily — A method developed at the Hebrew University of Jerusalem for training blind persons to "see" through the use of a sensory substitution device (SSD) has enabled those using the system to actually "read" an eye chart with letter sizes smaller than those used in determining the international standard for blindness.
The eight congenitally blind participants in the Hebrew University test group passed the conventional eye-exam of the Snellen acuity test, technically surpassing the world-agreed criterion of the World Health Organization (WHO) for blindness and moving them to the level of (low-vision) sighted. These results were published recently in the PLoS One journal.
The Snellen test is a standard visual test in which the patient views a chart which contains the letter E facing four different directions and in various sizes. The patient sits at a specific distance of 20 feet (6 meters) and has to determine the direction of the E's, and according to the smallest size he can read, his visual acuity is determined.
Normal vision is considered 20/20, referring to both the distance and size of the symbols on the eye chart. The congenitally blind participants in the Hebrew University test group reached a median level of 20/360, meaning they could identify letters from a distance of 20 feet that a normally sighted person (with normal vision) would be able to identify from 360 feet. The 20/360 result is better than the World health organization criterion for blindness, which is 20/400. Keep on reading...