Ocular Motor Skills:
There are three basic types of eye movements:
Fixation is the most basic eye movement skill from which other skills grow. Good fixation skills allow us to maintain a steady gaze without our eyes moving involuntarily off target. This allows images entering the eye to be centered on the fovea, the part of the retina that gives us our clearest vision. Without the ability to fixate, images will be blurry and confusing. In school, comprehension suffers as our eyes involuntarily move off the print and words jumble or jump around. Inadequate fixation skills must be addressed early in a treatment program before other oculomotor techniques are attempted because it is the foundation skill upon which others build.
Saccades are eye jumps–the sudden, quick voluntary change in fixation from one object to another. Saccades involve any shift in gaze, such as from road sign to speedometer, board to paper, and notes to computer screen. During reading, accurate saccadic movements are critical. The eyes must move left to right along a straight line without deviating up or down to the lines above or below. In addition, when we reach the end of a line, our eyes must make a difficult reverse sweep back to the beginning of the next line. If a child cannot control these eye movements, he’ll lose his place and comprehension becomes a problem. The ability to make accurate saccades involves a very precise coordination between our central and peripheral visual systems. Our central vision processes what we’re looking at in clear detail and defines what we’re seeing (“What is it?”) while our peripheral vision simultaneously locates the next target to let us know where to aim our eyes during the next saccade (“Where is it?”). If there is not a continuous, fluid, simultaneous integration between the two systems, saccadic eye movements will be poor. Pursuit eye movements are used to follow a moving target. Accurate, smooth pursuit eye movements allow us to make spatial judgments as to the speed and position of the moving target.
Pursuit eye movements are especially important in driving and sports. To evaluate pursuit movements, parents can randomly move a small target about 20 inches in front of the child’s eyes and observe the following: Does the head move with the eyes? How accurate are left-right, up-down, z-axis movements, and rotations? Does the patient falter at certain positions of gaze? How quickly do he/she correct? Is the patient tense, rigid, wiggly, or needing encouragement to complete the task, indicating the effort they must exert? Does accuracy degenerate with time?
Teaming: Controlling how we use and aim our eyes together is an importing skill that keeps us from seeing double. The ability to use both eyes as a “team,” or a single functioning pair, is what allows our brain to fuse the two separate pictures coming in from each eye into a single image with depth perception. This skill is called binocularity, or binocular fusion. Some people have difficulty aiming their eyes together, especially when looking at small images at close ranges, such as reading print. This is why eye teaming problems are especially difficult for school-aged children. As they fatigue from the strain that small print places on their visual system, they lose the ability to aim their eyes at the exact same point. If the images each eye is recording are different enough, the brain can’t fuse them, and the result is double vision. Not all children see double, however. In order to avoid double vision, the visual system will often suppress an eye, that is, “turn off” one eye by blocking the image from reaching the visual cortex in the brain, but the effort to turn off an eye is exhausting and causes the child to lose concentration. If the child doesn’t stop reading, he’ll soon become too tired to suppress and will then start to see double. Other times, the visual system tries to compensate by using the focus system to help lock eye aiming in place. By focusing too much, children can keep their eyes aimed together for a short while longer but the result is blurry vision and headaches. Most children stop reading long before they see double or get headaches. This is why eye teaming problems can look like attention issues. Because they have to stop frequently to rest their eyes, these children are often misdiagnosed with ADD.
There are two basic ways to aim or “team” our eyes:
Vision Perception is the ability to interpret, analyze, and give meaning to what we see. These skills help us recognize and integrate visual stimuli with previously stored data to form a stable, predictable, familiar world. In other words, vision perception allows us to understand, not just see. In school, visual perceptual skills are particularly important. Without good perceptual skills, we could not recognize words we’ve already seen, tell the difference between a p and q, sequence the order of letters when spelling, visualize reading content for comprehension, determine left from right, scan a busy worksheet, mentally manipulate objects in math, conceptualize relationships in science, and connect other sensory stimuli to our visual construct, such as the sound of a keyboard to a piano.Visual perception skills are generally broken down into distinctive subcategories based on their analytical function. These subsets of skills do not work in isolation but operate in combination with each other for efficient visual function. Whether considered separately or collectively, these skills are critical to learning.
Visual Motor Integration is the ability to use our hands and eyes as a team for smooth movements for tasks such as writing, drawing, coloring, throwing/catching a ball, etc. Younger children are expected to be able to copy block designs, stack block towers, snip paper, and string beads to build foundational skills for more complex task they get older such as copying from the board at school, cutting out shapes, etc.