Learning-Related Vision Problems

Vision is a learned process.  The ability to see and correctly interpret what is seen is not fully developed at birth but develops over a lifetime.  It is estimated that 75 - 90% of all classroom learning comes to the student through their eyes. The classroom experience demands much of vision, and if a child’s visual skills are not functioning properly to meet the requirements of the classroom setting, learning can become difficult and stressful.

     It’s been well-documented that children with vision problems have difficulties learning in school.  Studies have shown that one out of four children in a standard classroom suffer from learning-related vision problems and that this percentage jumps to 50% in special education classes.  A recently completed three year vision screening of 40,000 high school students showed that 11.5% or 1.6 million teenagers in the United States may have an undiagnosed or untreated vision problem. Undetected vision problems can prevent a child from reaching his/her full potential not only in school but throughout life.  The early recognition and treatment of vision problems before they interfere with learning may prevent a child from experiencing failure in school as a consequence.

     Parents and teachers are often given a false sense of security when a child reads the bottom of the eye chart and are told that the child’s eyesight is adequate to meet the demands of the classroom.  It is also very frustrating for a child to be told that nothing is wrong with their eyes when in fact something is very wrong.  The visual skills necessary for academic achievement go far beyond the ability to see 20/20 at distance and subsequently distance visual acuity screenings miss a large population of children with significant learning-related vision problems.  A comprehensive learning-related vision examination should evaluate the following 9 areas of vision that are critical for comfortable and efficient learning in the classroom:  distance visual acuity, near visual acuity, refractive error, eye movement skills, eye focusing skills, eye teaming skills, depth perception, color vision, eye health.


     The Snellen chart is the standard eye chart used in pediatrician’s offices and school screenings to test the clarity or sharpness of sight at distance.  This test was developed in the 1860’s to determine a student’s ability to see the chalkboard from the back of the classroom.  20/20 distance visual acuity is the ability to identify a certain size letter at a distance of 20 feet.   20/20 distance visual acuity gives absolutely no information about the visual acuity at book and desk distances or if the two eyes can work together as a team.  It also gives no information as to whether or not meaning is obtained from what is seen or how much effort is needed to see clearly and singularly.


     Refractive error is the measurement of farsightedness (hyperopia), nearsightedness (myopia), and astigmatism.  It is influenced by heredity, visual development, and adaptation to environmental stress.  An eye that does not need eyeglasses or a corrective lens to see clearly at distance directs light coming from a distant object that enters the eye through the pupil and forms a clear image on the retina.   Refractive error is a defect in the structure of the eye causing the rays of light to improperly fall on the retina leading to a blurred or distorted image.  

     Hyperopia is a condition in which distant objects are seen more clearly than objects at near.  In hyperopia, light from a distant object is focused behind the retina.  A child who is farsighted needs to exert focusing effort to maintain clear distance vision and an even greater focusing effort to see clearly at near.  This extra focusing effort may cause fatigue, tension, and discomfort subsequently influencing reading comfort and efficiency.  Hyperopia is not likely to be discovered in a vision screening which only tests for distance visual acuity as a child can usually exert enough focusing effort for the short time it takes to read the eye chart.

     Myopia is a condition in which near objects are seen more clearly than objects far away.  In myopia, light from a distant object is focused in front of the retina.  There are two types of myopia, genetic and functional.  Genetic myopia is typically present at birth or shortly thereafter and is unrelated as to how one uses their eyes.  Functional myopia usually develops gradually during the school years.    The first symptom noticed may be blurred distance vision after sustained near work.  Although temporary at first, if left untreated, myopia can progress to become permanent blurred vision at distance.  Preventative treatments designed to reduce and/or eliminate the progression of myopia are available.

     Astigmatism is a condition in which images at all distances may be distorted or blurred.  The front surface of the eye, the cornea, or the internal surface of the lens is more oval than round causing light rays to not come to a single focus on the retina.  This results in images at all distances to appear distorted of blurred.  Small amounts of astigmatism may not cause distortion but are often the cause of headaches or eye fatigue.


     Visual performance skills include eye movement skills (ocular motility), eye focusing skills (accommodation), eye pointing skills (convergence/divergence) and eye teaming skills (binocular fusion).  These are learned and developed skills necessary for efficient and comfortable vision in the classroom.  Optometric treatment for a visual performance skill dysfunction includes the use of lenses, special prism glasses, vision therapy, and developmental vision guidance.  In addition, recommendations may also be made concerning general health and nutrition.  


     There are six external muscles that surround each eye.  These muscles need to work in a highly coordinated manner and require the highest degree of precision in order to establish efficient and accurate control.

     There are three types of eye movement skills:  

eye fixation = the ability to point and maintain the eyes on an object .

saccades = the ability to point the eyes quickly & accurately at a series of stationary objects, one after another, such as moving from word to word when reading or letter to letter when learning to read.

eye tracking (pursuits) = the ability to follow a moving object smoothly & accurately such as a ball in flight.

Poor eye movement skills may account for loss of place when reading, use of finger to keep place, misreading, skipping of lines or words, head movements when reading, poor handwriting, inability to stay on ruled lines, and difficulty keeping eye on the ball during sports.  


Accommodation is the ability of the eye to focus for different distances.  Accommodative facility is the ability to make rapid & accurate shifts of focus from one point in space to another.  Copying from the chalkboard requires constant shifting of focus from far to near & then near to far.  Rapid, automatic focus adjustments in addition to the ability to sustain focus are essential for efficient visual function.  

     Inadequate focusing ability may result in difficulty shifting attention from the chalkboard to the desk and back again, avoidance of close work, blurring of print after reading for short periods of time, eye fatigue, excessive blinking and reduced comprehension.  


     Eye aiming/pointing skills include the ability to turn the eyes inward (convergence) and outward (divergence) looking from objects up close to objects far away & from objects far away to up close.

These skills must be synchronized with eye focusing skills.

     Common symptoms of eye aiming/pointing skill problems include headaches, eyestrain, avoidance of close work, short attention span, closing one eye, and difficulty remembering what is read.


     In order to have good vision, the eyes must work together as a team. Eye teaming difficulties are highly corrolated with reading problems.  Binocular fusion is the ability to coordinate and align the eyes precisely so that the brain can fuse (put together) the image it receives from each eye into a clear and single percept.  Even a slight misalignment of the two images can cause double vision that can lead to suppression (the turning off of one eye for the other).  

     An imbalance in the relationship between the eye focusing, pointing and teaming systems may result in a strabismus (eye turn). Strabismus is a condition in which the two eyes are not properly aligned with each other.  One eye may point outward (exotropia), inward (esotropia), upward (hypertropia) or downward (hypotropia). It is not caused by weak muscles but rather by a lack of coordinated control.   

     When one eye is pointing at a different place than the other at the same time, different messages are sent to the brain about what is seen.  This may cause double vision and/or confusion about what is seen.  In order to make sense of what is seen and eliminate double vision, the brain learns to ignore (suppress) the image from one eye or alternate the use of one eye at a time.

     Strabismus may result in functional amblyopia (“lazy eye”) a condition in which there is reduced vision usually in one eye that is not correctable by glasses or contact lenses. Treatment exists for both strabismus and amblyopia.         


     Depth perception is the ability to judge relative distances of objects.  It is dependent on the ability of the two eyes to work together as a team.


     Color vision is the ability to perceive differences in color.  A child who is color deficient is usually unaware of their condition.  People who are color deficient often assume that everyone sees things the way they do.  A color deficiency can exist in varying degrees from minor loss to complete color blindness.  Color vision defects are usually inherited, however, it can also result from certain diseases, trauma or as a side effect of certain medications.  

     Every child should be tested for a color deficiency by age 5 for many instructional materials are color-coded, especially in the primary grades. In addition, a color vision problem can affect certain career choices.  The ability to distinguish colors is often a necessary requirement for certain vocations. 


     The eyes need to be evaluated to determine any signs of obvious defects or pathological conditions.