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Sowmya Srinivas, Frank Thorn, Yuri Ostrovsky, Pawan Sinha; Haptic-Visual Transfer in Children with Treatable Congenital Blindness. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5725.
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More than 300 years ago Molyneux asked the question whether after a blind man regains his sight, can he, without touching a cube and a globe be able to distinguish them purely by sight. According to a strict interpretation of the critical period, the brain is only plastic until 6 or 7 years and so visual improvement would not be expected after this age. A prior study (Held, 2009) demonstrated that newly sighted patients from underdeveloped villages in India who had their congenital cataracts removed showed little transfer from touch to vision immediately after sight onset. However, the link between touch and vision was acquired over time. The objective of the present study is to quantify this tactile-visual link in similar patients.
An object of a specific length, aspect ratio or curvature is handed to the patient who carefully touches it with both hands. Then, without touching, the patient is asked to visually identify the object among many others by pointing to it. Three patients, aged 8, 10, and 14 years, were tested prior to and after treatment. One of the patients had cataract surgery in both eyes just prior to testing. Two of the patients had surgical correction in one eye a month before the other eye was surgically corrected and testing began. There were four normally sighted control subjects.
The patient with the poorest preoperational visual acuity showed the largest haptic-visual errors with an error range of 34-51%; the other two patients had a range of 23-40%; the normal controls had errors of 1.2-10%. For visual experience, the patient who had both cataracts removed just prior to testing and the two patients who had one cataract removed a month earlier showed that the amount of earlier monocular visual experience was not a significant factor in haptic-visual skills since their estimate errors were similar. For all three patients there was a 25% improvement on postoperational day 1 and by the day 4 there was a 50% improvement in the range of errors.
After cataract surgery, patients’ estimation errors decreased by 50% in just four days. The link between touch and vision strengthened significantly after the classic critical period.
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