Good vision is vital to reading well. And although vision may not be the only cause of reading difficulties, it is one that is sometimes overlooked.
Eight vision skills needed to read
Reading requires the integration of eight different vision skills. Only one is checked by the typical school eye chart test. Quick eye examinations may cover only one or two. Since a comprehensive eye examination will cover the eight vision skills, it is a must for anyone having trouble reading. The eight skills include:
Visual acuity, or the ability to see objects clearly at a distance. Visual acuity is sometimes measured in a school vision screening. Normal visual acuity is referred to as 20/20 vision (or 6/6 vision in the metric system) -- a measure of what can normally be seen at a distance of 20 feet, or six meters. If a problem is discovered in the screening, a thorough optometric examination should follow.
Visual fixation, or the ability to aim the eyes accurately. One type of fixation, called direct, has to do with the ability to focus on a stationary object or to read a line of print. The other type, called pursuit fixation, is the ability to follow a moving object with the eyes.
Accommodation, or the ability to adjust the focus of the eyes as the distance between the individual and the object changes. Children frequently use this skill in the classroom as they shift focus between books and blackboards.
Binocular fusion, or the brain's ability to gather information received from each eye separately and form a single, unified image. Eyes must be precisely aligned or double vision (diplopia) may result. If it does, the brain often subconsciously suppresses or inhibits the vision in one eye to avoid confusion. That eye may then develop poorer visual acuity (amblyopia or lazy eye).
Stereopsis, a function of proper binocular fusion enhancing the perception of depth, or the relative distances of objects from the observer.
Convergence, or the ability to turn the two eyes toward each other to look at a close object. Any close work, such as deskwork, requires this vision skill. If convergence is poor then reading becomes uncomfortable after a relatively short period of time and double vision may result.
Field of vision, or the area over which vision is possible. It is important to be aware of objects on the periphery (left and right sides and up and down) as well as in the centre of the field of vision.
Perception, the total process of receiving and recognizing visual stimuli. Form perception is the ability to organize and recognize visual images as specific shapes. A reader remembers the shapes of words, which are defined and recalled as reading skills are developed.
Treating reading-related vision problems
When a vision problem is diagnosed, the practitioner will prescribe glasses or contact lenses, vision therapy or both. Vision therapy involves an individualized program of training procedures designed to help develop or sharpen vision skills and possibly develop the eye muscles involved in focusing.
Because reading problems usually have multiple causes, treatment must often be multidisciplinary. Educators, psychologists, optometrists and other professionals often must work together to meet each person's needs. The optometrist's role is to help overcome any vision problems interfering with the ability to read. This may require the use of corrective spectacles and/or the implementation of a variety of eye exercises. Once any vision problems are addressed, the student is better prepared to respond to special reading education efforts.