Children born visually impaired due to cataract and who gained sight through surgery were able to differentiate faces from non-faces in about two months with over 90% accuracy, a study reports. The kids were also able to recognise by sight the objects they knew by touch in just about a week’s training. Five children aged 9-17 years thus regained sight showing that the brain retains the ability to acquire certain sensory skills even after several years of impairment.
“There is a general notion that kids who are born visually impaired [due to cataract] cannot gain sight beyond the first few years of life. But this appears not true in many cases. Current medical facilities can treat defects in lenses and corneas, and the brain can then begin to learn about the visual world,” explains Prof. Tapan K. Gandhi, Department of Electrical Engineering at IIT Delhi and first author of the paper published in the Proceedings of the National Academy of Sciences .
“We can’t call these children as totally sightless, since structurally the eye may be normal and vision potential exists. They can certainly gain vision once the cataract is removed. The quantum of improvement may depend on factors like density or position of cataract. The reason for cataract in several cases is not known, though a major part is played by intra-uterine infection in the pregnant mother due to rubella virus,” explains Dr. Sumita Agarkar, Deputy Director, Department of Paediatric Ophthalmology at Sankara Nethralaya, Chennai who was not associated with the work. “We have done such sight-restoration surgeries in infants as young as six weeks and even on a 25-year-old man.”
Treatment and testing
The children for the surgery were identified through an initiative called Project Prakash started by Professor Pawan Sinha from MIT, the corresponding author. Five children from Uttar Pradesh and Rajasthan with dense bilateral cataracts were operated upon in 2011.
The researchers examined the children’s ability to classify images as ‘faces’ or ‘non-faces’. The children were shown 300 images that ranged from non-faces and facelike images to genuine faces. The face classification performance was very poor initially. The test was repeated after a week and every month up to two years. “The face is one of the most complex objects in the world... We saw steady improvement in the facial classification skills of the children,” Prof. Gandhi adds.
This study addresses a long-standing question of whether skills can be developed later in life, after the critical early age of development, and whether the brain can meaningfully interpret the visual world.
The researchers also found that patients can quickly learn to connect touch with sight. They were made to identify shapes blindfolded and then were made to see and identify. Within weeks after the surgery, kids could connect what they touch to what they saw.
Though they do not develop vision as sharp as normally sighted people’s, the brain quickly acquired the ability to identify objects, shapes, and faces. The results were published in Nature Neurosciences .
“We found that although the brain does not possess cross-sensory mapping immediately after sight onset, it can acquire it after as little as a week of experience. We hypothesise that the brain discovers similarities in the dynamic information generated when a child is exploring objects simultaneously through touch and vision. These results have implications about brain plasticity as well as about strategies of sensory learning,” explains Prof. Sinha in an email to The Hindu.
