In order to function properly, the eyes must be able to focus, coordinate, move and assess their surroundings. These are basic visual skills. However, some people have difficulty with one or more, leading to visual complications.
Healthy eyes have a focusing system called accommodation that allows for visual clarity. When a person looks at an object in the distance, the focusing system is relaxed. This is because the eyes are not forced to strain like they would if the object were up close. Generally, the eyes are able to easily shift between targets that are near and in the distance, and they should also be able to maintain an extended amount of focus on a target that is near.
When the eyes’ focusing system develops problems, they may be unable to switch focus between items that are near and far (accommodative infacility) or tolerate focusing on items that are close (accommodative insufficiency). Another issue may be that they overly focus on targets that are near (accommodative spasm). Any of these complications can lead to blurry vision, as well as other problems.
In children, these glitches may manifest in the following ways:
- Sluggish reading speed
- Taking an extended amount of time to complete assignments or copy material from the chalkboard
- Decreased comprehension while reading
- Poor attention, especially when the work is close
- Eye pain and/or fatigue
Academic performance, and the ability to perform daily activities, requires that the person be capable of focusing the eyes quickly and routinely to make images clear. Often, shortcomings in eye focusing are not related to the eyes themselves, rather they may be associated with the brain’s ability to control the eye focusing system. The neurological system that regulates the eye focusing system may be inept or incompetent, or poor eye focus could be the result of either visual or psychological stress.
Each eye sees a somewhat different image. Through a process called fusion, the brain merges the images into a single three-dimensional picture. Since the images that each eye sees must be practically the same, they have to maintain proper alignment, which is achieved through good eye coordination. If eye coordination is poor due to a deficiency in vision development or underdeveloped eye muscle control, the person employs additional energy in an attempt to sustain correct eye alignment. But if poor eye muscle control is severe, the muscles are not able to adjust the eyes well enough for them to see the same image, and this can cause double vision. With the brain now picking up different images, it has to compensate somehow. This often means that the brain learns, over time, to ignore the image it receives from the weaker eye. The weaker eye, because it is no longer being relied upon, can deteriorate to the point of permanent visual impairment and result in a condition known as lazy eye or amblyopia.
Aside from double vision, other signs of poor eye coordination include:
- Eye fatigue
- Difficulty reading and/or concentrating
- Poor performance of tasks
There are four types of eye movement:
- Saccades – fast, flying movements of the eyes that suddenly alter the point of fixation. These movements range in scale from the minute movements made while reading to larger movements made while looking around a room.
- Vergence movements– these movements bring into the line the area of the retina (fovea) designed for high perception
- Smooth pursuit movements– gradual tracking movements that are intended to keep moving stimulus in focus
- Vestibulo-ocular movements– helps steady the eyes when the head’s position moves
The eyes are each connected to six muscles. These muscles receive signals from the brain, and together they work to control how the eyes move. Normally, the eyes work together so that they are aimed in the same direction at the same time. However, poor eye muscle control or injury can affect the eyes’ ability to move in harmony, leading to eye movement disorders like:
- Nystagmus– quick, uncontrollable movements of the eyes. This can sometimes be referred to as dancing eyes.
- Strabismus– the eyes are misaligned and not pointed in the same direction. This may result in crossed eyes or other vision disorders.
Eye perception signifies a set of skills we use to gather and translate visual information taken in from our surrounding environment. We combine this information with our other senses and as a result of this process, we are able to derive meaning from what we see and coordinate both eye and physical movements. Therefore, eye perception is vital when it comes to learning.
Dysfunctions can lead to:
- Difficulty with rhythm
- Challenges with learning left and right
- Reversing numbers or letters when copying or writing
- Problems learning the alphabet or recognizing words
- Easily distracted or a short attention span
- Inability to concentrate
- Hard time understanding and following instructions
- Unable to recall a sequence of letter, numbers or objects in the order they were initially presented
- Unable to recognize visual clues