Learning, particularly in the form of reading, requires a combination of many visual skills. A thorough eye exam is needed to evaluate these skills.
- Visual acuity refers to the clarity or sharpness of vision. Typically, distance visual acuity is measured at 20 feet, and near visual acuity is measured at 40 centimeters. A child can see 20/20 but still have issues with any or all of the skills below.
- Accomodation, or focusing, refers to the ability to keep things clear at varying distances. For instance, when a child is copying something from the board to his/her paper, the accomodative system is responsible for shifting focus quickly and easily so as to maintain clear images far away and up close. If this system is over- or under-worked, it can result in blur, headaches, and/or eyestrain. Issues with accomodation are typically addressed with appropriately prescribed glasses, or the use of vision therapy to train the system, or a combination of both.
- Eye teaming refers to the ability of the eyes to work in tandem to produce a single, fused image with depth. The most common eye teaming deficiency is called Convergence Insufficiency (CI). When doing near work, the eyes must converge, or move inwardly. In CI, a person's eyes tend to rest in an outward position, resulting in an inability to converge normally and comfortably. People with CI have to exert extra effort to keep the eyes aligned to maintain a clear and single image. This extra effort can lead to eye strain, headaches, fatigue, difficulty concentrating, and problems with comprehension when doing near work for even a short period of time. If this extra effort is exhausted, a person with CI may see double (if the eyes drift outward), or the brain may suppress the image from one eye to avoid seeing double. According to a scientific research study by the National Eye Institute, office-based vision therapy is the most successful treatment for this condition (1).
- Ocular motor skills are involved in keeping the eyes stabilized on a target, and moving the eyes quickly and accurately from target to target. The act of reading involves a series of eye movements called saccades and fixations. Saccades are the eye movements that allow us to quickly redirect our line of sight from one location to another. When reading, saccades allow us to move through a line of text. The normal reader averages about 7-9 letter spaces per saccade. Fixations occur when the eye is relatively still. Regressions are eye movements in the right-to-left direction that occur when we reread a word or section. They occur 10-15% of the time in skilled readers. Less skilled readers typically have longer fixations, shorter saccades, and make more regressions than more skilled readers (2). When these ocular motor skills are deficient, it can lead to one losing their place when reading, skipping words, and reading slowly. This is also an area that can be trained with vision therapy.
- Visual perception has to do with how we process the information we receive through the visual system. Some sub-categories of visual perception include visual memory (the ability to recall what is seen), visual-motor integration (the ability to coordinate visual input with motor output), visual closure (the ability to identify a form without its full presentation), and visual-spatial skills (the ability to perceive the position of an object relative to oneself and relative to other objects in space). There will be a separate post in the future with detailed descriptions and examples of each area of visual perception.
There are many optometrists out there that specialize in this area of optometry. To find one in your area, go to www.covd.org, or ask your primary care optometrist to recommend one close to you.
CliffsNotes: Vision and learning are very much connected!
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