The development of a new tool for testing the eyesight of children under three could mean more children receive treatment for vision difficulties earlier, leading to positive effects on learning and development.
Children under three struggle with the precise tests used for older children. With that in mind, researchers from the School of Optometry & Vision Science at the University of Waterloo created the Waterloo Differential Acuity Test (WatDAT), a new method for measuring vision equally precisely in younger toddlers.
Approximately 14 per cent of children aged two to four have vision problems such as amblyopia - often known as lazy eye - or clinically significant farsightedness or astigmatism. Young children can also have rarer problems, such as pediatric cataracts, which may prevent their vision from developing properly.
"These vision problems are not always noticeable by observing a child. Also, children will not complain about poor vision because they don't know what good vision is," said Dr. Susan Leat, the professor emeritus at the School of Optometry & Vision Science who led the research. "If this test becomes available in clinics, it will allow eye doctors to detect vision disorders earlier, leading to more effective treatment."
Currently, optometrists test the vision of babies and young toddlers by watching their eye movements. For example, babies will prefer looking at a card with a striped pattern over one with no pattern. However, this test can only tell if children see the pattern, not whether they recognize and understand the details, making the test much less effective for detecting vision disorders.
With children three and older, optometrists typically ask them to name a picture that is shown to them or to do a picture-matching task. By gradually decreasing the size of the picture, the optometrist can determine children's visual acuity, or the limit of detail they can see. But children under three tend to struggle with these tasks, making them unsuitable for testing the vision of younger toddlers.
WatDAT shows children four shapes, three of which are identical, such as a house among three circles. The tester asks them to point out the one that is different. This exercise is done at progressively smaller sizes until the child can no longer do it.
A child identifies a shape on the printed format of the WatDAT vision test, which optometrists can easily use in clinics. Video of WatDAT in use is available online. (University of Waterloo)
Because this method is cognitively easier, it works for most children as young as 18 months. All study participants 24 months and older who were meeting developmental milestones were able to complete the test with both eyes.
The Waterloo researchers found that compared to two pediatric tests currently in use, more children could complete WatDAT at younger ages. All of the tests took similar amounts of time.
The researchers also tested a smaller group of children who had significant vision or health problems or who were born pre-term. Most of these children were also able to complete the testing.
"We believe WatDAT could be a useful tool in testing the vision of people of all ages who have intellectual and developmental disabilities," said Dr. Supriya Aryal, a recent optometry graduate who participated in the research. "It could also work for low vision patients of all ages, though we need to do more research to confirm all this."
Optometrists who are currently beta testing WatDAT in Canada, the United States and the United Kingdom have reported children seem to enjoy it more because the test feels like a game.
The beta version of the vision test is being evaluated in a digital format, which gives children a cartoon reward for correctly identifying the different shape, and a printed format that optometrists can easily use in a typical exam room. The researchers intend to commercialize the test after they complete beta testing.
A paper on this work, The Waterloo Differential Acuity Test (WatDAT)-Testability and normative data, appears in Ophthalmic and Physiological Optics. The research was funded by Fighting Blindness Canada.
