A study performed by the National Eye Institute (NEI) in the United States has demonstrated that uncorrected hyperopia, commonly called longsightedness, in preschool children is closely linked with diminished performance on literacy tests.
The Vision in Preschoolers-Hyperopia in Preschoolers (VIP-HIP) study, which focused on comparing literacy rates in 4 and 5 year old children, found that those with uncorrected hyperopia (3-6 diopters) did significantly worse than those with normal vision. Diopters are a measurement of lens power, where a greater number means more correction is needed to see clearly.
"This study suggests that an untreated vision problem in preschool, in this case one that makes it harder for children to see things up-close, can create literacy deficits that affect grade school readiness," said Maryann Redford, D.D.S., M.P.H, a program director in Collaborative Clinical Research at NEI.
The majority of children affected by hyperopia only experience mild symptoms, with very little change in visual acuity. High hyperopia, with measurements above 6 diopters, affects very few children, is very easily diagnosed, and is often corrected with eye glasses. In between those groups are children with moderated hyperopia, who often go undiagnosed, and don't receive proper treatment. It's estimated that between 4-14% of children fall into this category.
"Prior studies have linked uncorrected hyperopia and reading ability in school-age children," said Marjean Taylor Kulp, O.D., M.S., distinguished professor in the College of Optometry at Ohio State University and lead author of the study. "But large-scale investigations looking at reading readiness skills hadn't been conducted in preschool children. This study was necessary to determine whether or not, at this age, there was a link between the two."
In the study, 492 4-5 year old children were divided into two groups and examined by researchers. Each group, equal in size, was given the Test of Preschool Early Literacy (TOPEL). One group was comprised of children with moderate hyperopia, the other of children with normal vision. Those administering the test were unaware of the children's visual acuity.
The results of the TOPEL showed that the children with hyperopia performed far worse than the children with normal vision. Those with reduced near visual function, including clarity of binocular vision and depth perception, performed exceptionally poorly. The skills most affected were those pertaining to the print knowledge section of the exam, which is intended to measure the children's ability to identify written letters and words.
More research is required to determine if correcting hyperopia in children with the use of eyeglasses can prevent the development of deficits in early literacy skills.