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Deaf adults have highly tuned vision

U. SHEFFIELD (UK) — Children born deaf are slower to react to objects in their peripheral vision than hearing people, but teens and adults who have been deaf since birth react faster than their hearing peers.

A new study, published today in Development Science, is the first to test how peripheral vision in deaf people develops from childhood to adulthood.

Profoundly deaf children aged 5 to 15 years were tested using a visual field test. Children between 5 and 10 had a slower reaction time to light stimuli in their peripheral vision than hearing children of the same age.

By the age of 11 and 12, however, hearing and deaf children reacted equally and by the age of 13 and 15, the deaf adolescents reacted more quickly than their hearing peers.

The children tested sat with their head positioned in the center of a gray acrylic hemisphere into which 96 LEDs were implanted.  The participants then had to watch a central glowing ring in which a camera was hidden to monitor their eye movements.

The LEDs were each briefly illuminated at three different light intensities all in random order.  The test was designed to be like a computer game called the Star Catcher.  If the LED flash occurred above, the child had to ‘catch the star’ by moving the joystick upward, and if it occurred to the left they would have to move the joystick to that position.

In this way, the team was able to verify that the child had seen the light and not just guessed, as has been the problem with previous visual field tests in children.

“We found that deaf children see less peripherally than hearing children, but, typically, go on to develop better than normal peripheral vision by adulthood, says Charlotte Codina, of the Academic Unit of Ophthalmology and Orthoptics at the University of Sheffield.

” Important vision changes are occurring as deaf children grow up and one current theory is that they have not yet learned to focus their attention on stimuli in the periphery until their vision matures at the age of 11 or 12.

“As research in this area continues, it will be interesting to identify factors which can help deaf children to make this visual improvement earlier.”

“This research shows that adults who have been deaf since birth may have advantages over hearing people in terms of their range of vision,” says Joanna Robinson, program manager at the Royal National Institute for Deaf People, which funded the study.

“For example, deaf people could be more proficient in jobs which depend on the ability to see a wide area of activities and respond quickly to situations, such as sports referees, teachers, or CCTV operators.

“On the other hand, the findings suggest that parents of deaf children need to be aware that their child’s initially delayed reaction to peripheral movements may mean they are slower to spot and avoid potential dangers such as approaching traffic.”

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