Students referred for vision therapy often have similar symptoms. Frequently the student:
· skips or adds words when reading
· loses his place when reading
· reads well for a page or two then begins to struggle
· does well in math computations but stumbles on word problems
· suffers from headaches when completing near work
But before we can understand the treatment, vision therapy, we must first understand the conditions, known as visual perceptual difficulties.
When asked to define “perfect eyesight” most people respond with the answer, 20/20 vision. Let’s take a moment to understand precisely what 20/20 means.
The number 20 on the top of the fraction states that the patient was tested 20 feet from the eye chart. The number 20 on the bottom of the fraction signifies that the patient was able to see one of the smaller letters on the eye chart. This size letter is the standard letter size that a person with very good vision can see from a distance of twenty feet.
As you can see, this shows that a student’s vision is good at long distance, for tasks such as seeing the blackboard and driving. While this is important, there are many other visual demands on a student in the classroom.
Picture this. Shortly after settling into his seat in the classroom, a student is frequently asked to read the blackboard some distance away. In this task, 20/20 vision serves the student well.
Next, however, this student must take notes and write into his notebook. This requires a shift in focus from distance to near known as accommodation. Once he records his notes he must then refocus at distance to see the next sentence. Back and forth he focuses until his notes are complete. While this visual task is easy for most students, certain individuals are born with difficulty in the ability to change focus from distance to near and back again. Difficulties with this skill may be referred to accommodative spasm or ill-sustained accommodation.
This student will also be required to read a passage from a book. Here he must align both eyes simultaneously on a word. This ability, known as convergence, must be extremely precise. As he reads, his eyes must move smoothly across the page then accurately down to the beginning of the next line. Many teachers refer to this as eye teaming. A breakdown in this skill may have names such as convergence excess, convergence insufficiency or binocular dysfunction.
