By Stanley A. Appelbaum, OD FCOVD. and Barry M. Tannen, OD FCOVD.
Nystagmus refers to abnormal movement of the eyes that is comprised of rhythmic oscillations (moving back and forth) superimposed upon one’s normal eye movements. It can be categorized as either congenital, (which is present at or within the first few months of birth), or acquired, (which has a pathological genesis and is essentially age independent). Further classification of the nystagmus eye movements themselves can be made based on whether the motion is of a “jerk” or “pendular” pattern. In the “jerk” form, the eyes cycle through a slow phase, in which they deviate relatively slowly in one direction, and a fast phase, in which they rapidly return via a corrective saccade towards the starting point. In contrast, in the “pendular” form, relatively symmetrical and slow eye movements occur in both directions.
Although nystagmus may arise from an abnormality of the eyes, it can also arise as a result of an imbalance of the eye movement mechanism within the brain Ocular albinism, optic nerve abnormalities, congenital cataracts and retinal dystrophies are common ocular anomalies that may cause nystagmus. However, the most prevalent cause is labeled as “idiopathic,” which means there is no identifiable underlying cause for the nystagmus.
There are several treatments that have tried to help control nystagmus and improve visual function. The “null zone” is a position of gaze where the nystagmus is least and therefore vision is best. Eye muscle surgery and prism glasses have tried to shift the “null zone” into primary or straight ahead position for maximum visual acuity and visual abilities with minimal head turn. Adverse side effects have oftentimes resulted, such as double vision and visual fatigue. Long-term results from surgery and prism glasses have oftentimes been disappointing, according to the medical literature.
Nystagmus may cause abnormal head posture. For an example, if the nystagmus null zone is present when looking or gazing upward, then a chin-down head posture will be present to place the eyes in up gaze. Alternatively, if the nystagmus null zone is present when looking toward the right, then a left face-turn head posture will be present to place the eyes in right gaze.
Vision Therapy, using a multi-sensory approach, has resulted in improved vision and related measures of visual function, such as the ability to sustain focus and better eye contact. in selected patients with nystagmus. For some nystagmus patients, the overall cosmetic aspect has been positively impacted. It has been documented in the medical literature that nystagmus can be volitionally reduced for specific periods of time (up to two minutes) after a vision therapy treatment program. This is especially critical in many business and social situations when eye contact is especially important.
Vision Therapy Treatment Programs involve the use of visual, auditory, tactile, & proprioceptive feedback in conjunction with visual attention, visual imagery, and relaxation techniques.
Vision Therapy is used to train and improve visual skills & abilities such as:
This is the best known visual ability. If you have 20/20 eyesight, all it means is that at twenty feet, you can see the same letters that people with normal eyes can see at twenty feet. Unfortunately, 20/20 eyesight— with or without new glasses—does not mean that during reading/computer/desk work you can see clearly for more than a few minutes. Having 20/20, does not mean you can “sustain focus,” enjoy reading, have the depth perception and localization skills to drive at night, or that you are free from vision-caused headaches and general fatigue. All 20/20 eyesight guarantees is that you can see clearly long enough to call out the small letters on a doctor’s eye chart. In addition to “20/20 eyesight” we have to consider other visual abilities, generally ignored during routine eye exams.
Using the two eyes together as a team is the second visual ability. We have fourteen eye muscles. The brain must coordinate these muscles perfectly if we are to see comfortably and efficiently. If this coordination is difficult, eyesight be clear at the times but blurred or double at others. The effort to prevent such blurred or double vision can cause premature fatigue, or loss of attention and comprehension during reading, desk or computer work. Certain types of eye muscle coordination problems can reduce depth perception for driving and sports. In extreme cases, poor eye muscle coordination can even cause crossed or lazy eyes.
Accurate Visual Tracking, allows us to quickly and accurately move our eyes across a line of print, look at the symbols (numbers, letters or words) remember what to call them, and get the sounds out of our mouths. During reading, poor Visual Tracking causes loss of place, confusing one word with another, careless errors and problems breaking words down into their parts.
Convergence or Eye Control is used for “keeping our eyes on the ball” or maintaining eye contact during conversations. When Eye Control is inaccurate, seeing is inaccurate. Our Eye Control is a direct measure of how vision is affecting our attention. Lack of efficient eye control can cause a child or adult to be mislabeled as having ADHD.
“Visual Perception” as the ability to see how things are alike and different, how the pieces fit together to make up the whole. At one extreme we have the artist who can look at a scene and “see” the relationships between the shapes and colors well enough to reproduce them with paint on canvas. On the other extreme, we have the child who cannot tell the difference between a “b” and a “d” or a “was” and a “saw”. Visual perception problems can make it difficult to recognize words, complete puzzles, align columns in math or—for adults—read a roadmap.
We can divide our ability to get our eyes to guide our hands into fine motor or”little” coordination and gross motor or “big” coordination. We need “little” coordination to copy sentences and to keep words equally spaced and on the line. We need “big” coordination to throw or catch a ball or to guide a steering wheel. The “big” type of eye-hand coordination is also very much linked with balance and general coordination.
Visualization, Visual Memory, & Visual Imagery is sometimes called, “seeing with the mind’s eye.” If visualization is good, a child or adult can “see” words in the mind to spell them. They can “see” the story when they are reading. They can picture their goals in their minds. They have the ability to picture the consequences of their actions. Visualization allows us to learn from the past and plan for the future. All Reluctant Readers should be tested for these important visual abilities.