Eye tests commonly used in schools and pediatricians' offices don't do a good job of finding vision errors like farsightedness and astigmatism in school-aged kids, even though they're great at catching nearsightedness. That's the news from researchers in Australia, who tested 12-year-olds with the usual eye chart test, in which children read a chart with letters in ever-smaller sizes.
School troubles could be a sign of undiagnosed farsightedness because the condition can make reading difficult, according to David Hunter, ophthalmologist-in-chief at Children's Hospital Boston. I called Hunter after reading the new study, published in the Archives of Ophthalmology, because my child has passed those eye chart tests with flying colors, but I've had farsightedness and astigmatism my whole life. So I asked Hunter: How can parents tell if a child needs more than that test?
Parents need to think about vision testing at two points in a child's life, according to Hunter: in the preschool years, when children can lose vision permanently due to amblyopia (lazy eye), and in the school years, when vision problems can interfere with reading the board, books, and computer screens.
The Australians tested 4,497 children with both the "visual acuity" eye chart test, and autorefraction, in which eyes are dilated with eye drops, and a machine measures the amount of correction needed to focus light on the retina at the back of the eye. The eye chart test caught more than 90 percent of children with myopia, or nearsightedness. But children with farsightedness, or hyperopia, can read a wall chart just fine. (About 5 to 10 percent of people are farsighted, compared to 25 percent who are nearsighted.) A farsighted child might even be able to squint and do OK in a close-vision test, Hunter says. But they're not going to be able to maintain that level of focus through the day without hurting.
"If a child is struggling at school for no obvious reason, and just seems to be having trouble, then I think [he or she is] entitled to a complete eye exam by a pro," Hunter added. That includes dilating pupils, and using machines to measure visual acuity both near and far. He was less worried about the fact that the Australian researchers found the eye test to be crummy at detecting astigmatism, in which variations in the eye's lens can cause blurry vision. If the astigmatism is bad enough to cause blurry vision, Hunter says, you're going to have trouble reading both near and far, and common eye tests will pick that up.
Farsightedness symptoms to look for include:
Children should have their eyes tested in infancy, around age 3, and during their school years, according to the American College of Ophthalmology. Not all children need to see an ophthalmologist, Hunter says, but it's good for parents to know that eye problems can persist into elementary school and beyond, and aren't always identified by the big "E" on the eye chart.