Oculomotor Dysfunction: Why my Child Skips Words, Can’t Cross the Midline, Experiences Double Vision
This article provides helpful information about oculomotor development for reading, writing and spelling. Affiliate links are included for your convenience. Integrated Learning Strategies (ILS) is a learning and academic center. As a reminder, ILS is not a health care provider and none of our materials or services provide a diagnosis or treatment of a specific condition or learning challenge you may see in your child or student. If you seek a diagnosis or treatment for your child or student, please contact a trained professional who can provide an evaluation of the child.
Eye movements are the fastest and most frequent motions made by the human body. The eye movement control system, known as the oculomotor system, is complex and sophisticated. The function of the eyes goes beyond vision, it expounds to learning and higher thinking. Your child’s development of oculomotor eye movements can directly affect their reading ability, how they track words on a page, if they can read sentences from right to left, depth perception, and hand-eye coordination. If your child struggles with oculomotor development, they may show signs of losing their place while reading, skipping sentences or words, can’t cross the midline (pauses in the middle of sentences to adjust their eyes so they can keep reading), has difficulty copying notes from the chalkboard, has illegible handwriting, experiences double-vision, and can’t track from right to left.
In addition, if your child struggles with other types of eye movements, you may notice they have trouble at home and in school with the following:
- Spatial orientation
- Trouble with visual attention
- Poor efficiency and productivity
- Difficulty with visual perception
- Weak visual memory
- Clumsy, uncoordinated, struggles with sports
- Struggles with directionality (writes their letters backward)
- Needs a pencil or marker to avoid losing their place while they read
- Can’t focus on activities in front of them (puzzles, mazes, drawing, coloring)
6 Eye Movements for a Strong Vision System
To understand how a child needs a strong vision system, we must understand the basic structure of the eye. Light enters our eyes through the cornea and then passes through the pupil to the lens of the eye. The lens focuses the light on the back surface of the eye, which is called the retina. There is a small depression in the retina where visual acuity is the highest, which is called the fovea. This is where the center of the field of vision is focused. Depending on how far away an object is, our lens needs to change shape to keep the light focused on the retina.
When we look at an object far away, the light does not need to bend a lot to reach the retina, so ligaments pull on the lens to make a flatter shape. When we need to look at an object closely, the ligaments do not pull as much on the lens, making it a fatter shape. The ocular motor system directs both eyes to the object of interest. This requires intricate eye movements consistently working together to achieve the proper eye position. These eye movements are controlled by three pairs of muscles. Each set has a certain responsibility from moving the eye up and down, side to side and rotating around to keep an image upright.
There are three main concerns to focus on with your child’s eye movements (saccades, vergence and pursuit). These movements are controlled by the six muscles surrounding each eye. The eye muscles must work together to accurately control the six different types of eye movements that are required for a multitude of activities and tasks. Oculomotor dysfunction, when a child cannot shift their eyes from one point to another for reading and tracking, occurs when these muscles are not coordinating properly. The causes of oculomotor dysfunction range from slow development in a child to disease or problems with the central nervous system.
The following six types of eye movements hold the eyes on target:
- Saccades – very quick eye movement that allows eyes to jump from target to target accurately.
- Vergence – the angle and control of both eyes simultaneously to supply the images of the object and place them properly on the fovea.
- Vestibular ocular reflex – holds images steady on the retina during brief head rotations.
- Optokinetic – holds images on retina during gaze shifting.
- Pursuit – the ability to follow a slow moving object accurately.
- Fixation – holds the image of a non-moving object on the fovea.
The saccadic movement of the eyes is critical for quickly and accurately shifting from one target to another. This is a necessary skill for a child when they are learning to read and track words on a page. This involves very specific eye movements that make the eyes move left to right and along a straight line without deviating up or down on the lines above or below. In addition to tracking from left to right, when your child is done reading a line of words, their eyes must make a difficult reverse sweep back to the beginning of the next line without losing their visual place target. If a child cannot control the saccadic movements of the eyes, they will constantly lose their place when reading, which also affects their comprehension.
The next type of eye movement is vergence. This type of movement controls how your child moves their eyes at an angle to look at objects from different distances. For the visual system to work properly, each eye must aim at the same point so the images are identical. If the vergence movements do not aim the eyes correctly, the brain cannot fuse the images, which causes double vision. Children use vergence eye movement constantly in the classroom. When they change their gaze from the chalkboard in the front of the room to the paper at their desk and then shift their focus back to the teacher, they must use their vergence eye movement to refocus for the chalkboard then the paper at their desk.
Approximately 10 percent of children have a fusion problem related to vergence eye movement (Rouse, et al, 1999). When an older child has an issue with this type of eye movement, it can become worse with extended periods of reading or lengthy writing sessions. In addition, certain studies show immaturity and deficiency in the vergence and saccadic eye movements in children with dyslexia when compared to children without the disorder.
The final eye movement we observe with our students is their smooth pursuit motion. This enables continuous clear vision of moving objects. Reading not only utilizes the fast paced saccadic movements, but also forces our eyes to switch to smooth pursuit movements when the text moves or drifts. This occurs frequently on tablets, computers, phones, overhead projectors and movies. If your child has immature pursuit movements, his or her eyes will jump or jerk as the eyes cross the midline (for example, as their eyes cross the page while reading).
In the classroom, approximately 80 percent of all academic work requires extremely fine, accurate eye movements and 1 in 5 children have an underdeveloped vision system that is the root cause of several learning difficulties.
Some of the common visual deficiencies that can be caused by an underdeveloped vision system are as follows:
Oculomotor Dysfunction (Eye Movement Problems)
The clinical diagnosis of oculomotor dysfunction describes when a child’s eyes are not capable of performing very controlled, accurate eye movements. They will likely struggle with reading, tracking words, and do not perform well in a sports environment.
If your child struggles with Oculomotor Dysfunction, here are some of the signs you may notice:
- Choppy reader
- Slow reader
- Uses finger to keep place
- Slow at copy writing
- Skips words and lines
Accommodative Dysfunction (Eye Focusing Problems)
Sometimes a child’s visual system cannot handle transitioning their focus from near to far and far to near, or cannot relax the visual system to “clear” images at varying distances. When this occurs, we look for a diagnosis of Accommodative Dysfunction. Your child may complain of frequent headaches or blurry eyes and will constantly look down from the whiteboard to his or her paper or book and cannot seem to clearly see the words or images on the page. This problem can be a serious inhibitor and can be the cause of attention issues in school.
If your child struggles with Accommodative Dysfunction, here are some of the signs you may notice:
- Severe headaches on school days
- Blurry vision
- Says eyes are “tired”
- Difficulty copying
- Short attention span with school work
Convergence Insufficiency (Eye Teaming Problems)
This vision problem deals with vergence eye movement and your child’s ability, or lack of ability, to coordinate both eyes together. If their vision system is working properly, both eyes take in slightly different images but the brain merges them into one image. If the vergence movements do not coordinate, double vision occurs. This is extremely disruptive for your child’s learning if they see double letters or if they see the letters jump, jiggle or are blurry. If your child struggles with convergence insufficiency, sometimes they will begin to rely on only one eye for visual information and will focus or cover one of their eyes with their hand. They may also turn their head while they read to focus on the words with their dominant eye.
If your child struggles with Convergence Insufficiency, here are some of the signs you may notice:
- Difficulty with sports
- Covers an eye while reading
- Tilts head to look at something
- Frequent headaches when reading or completing schoolwork
To improve your child’s vision skills and ocular motor development, full body movement exercises, eye tracking activities and potentially vision therapy may be needed to improve their reading, tracking, handwriting and comprehension.