Certain refractive errors may not be caught on a vision screener (remember vision screenings can miss around 60% of vision conditions). Hyperopia, also known as far-sightedness, is a common refractive status in children. Far-sighted is a bit of a misnomer because it implies that an individual can see far and not near. Individual's who are far-sighted have the ability to see clearly at all distances but regardless of what they are focusing on their eye muscles have to do a specific amount of work. When looking at a distance target the eye muscles work less. The closer the viewing distance becomes the harder the eyes have to work. This amount of work can be so high that it causes headaches, eye strain, and fluctuating vision.
The American Academy of Ophthalmology published a recent study from the Vision in Preschoolers group. This study evaluated the effects of uncorrected hyperopia and early literacy. Previously it was thought that children had focusing abilities similar to adults at a young age; however, it is found that a child's focusing abilities becomes more variable depending on the visual stimulus.
Children with varying amounts of hyperopia were compared to their peers without a refractive error, it was found that children presenting with higher amounts of hyperopia had significant decreases in their ability to identify letters and sounds. There was also a deficit in definitional vocabulary in children with lesser degrees of hyperopia. Higher amounts of hyperopia can cause intermittent blur, secondary to focusing deficits, which can lead to inconsistency between visual stimuli when learning letters, numbers, etc. Remember with hyperopia the child may be able to see clearly at certain times so they may not complain of blurred vision.
While the Vision in Preschoolers group was researching hyperopia and its effects on early literacy, there was research that evaluated the effects of astigmatism on reading fluency. The American Academy of Optometry recently published research that evaluated the effects of bilateral astigmatism on reading fluency in school-aged children as well as the impact of spectacles on reading fluency in children with bilateral astigmatism. Astigmatism causes blur in a specific meridian of vision. Many people with astigmatism have heard it has to do with the shape of the eye (ex “your eye looks like a football instead of a soccer ball). While this is true, it doesn't explain how astigmatism affects vision. Astigmatism causes blur in a meridian of vision. For example if a person is looking at a letter H, maybe the horizontal bar is clear and the vertical lines are blurry or vice versa. Now the meridian of blur can vary depending on how the meridian is located but you can understand the general idea. These meridional discrepancies have been shown to disrupt accuracy of focus and can even cause meridional amblyopia (see our amblyopia blog - AVTC). A previous study conducted by the Pediatric Eye Disease Investigator Group have indicated that amblyopia reduces reading performance.
The “Reading Fluency in School-Aged Children with Bilateral Astigmatism” study assessed individuals from third grade to eighth grade. It was found that students with uncorrected astigmatism had decreased oral reading fluency compared to their peers without an associated refractive status. When the student was wearing the appropriate refractive correction their oral reading fluency was comparable to their peers. Students with higher amounts of astigmatism showed the most improvement in oral reading fluency as well as students in higher grades.
This school year make sure your child is ready to learn by scheduling an annual comprehensive eye examination with one of our doctors.