Vision Skills for Better Learning

Visual acuity is a measure of the sharpness of eyesight, or how clearly you see. It is influenced by eye structure, stress and the focusing system. It is the ability to identify a shape of a certain size at a certain distance, however, it gives no information on whether or not meaning is obtained from what is seen. The Snellen fraction (20/20, etc.) is most often used in an exam to measure visual acuity. Though most of the time, doctors try to get their patients to see 20/20 or better, there are particular circumstances where greater visual function is best achieved with a less clear image.

One common factor that can negatively influence visual acuity is refractive error.

Refractive error is caused by how the light is bent into the eye. Myopia (nearsightedness), Hyperopia (farsightedness), and Astigmatism occur when the shape of the eye is not ideal enough for the light rays to fall on the fovea (the only place the image can be seen sharply). To learn more, visit the refractive error section.

Other causes of decreased visual acuity are ocular disease or amblyopia (lazy eye). Even if there is no significant pathology or power difficulties, a person can have difficulty seeing clearly because of an inefficient accommodative (focusing) system.

Keeping an image clear at all distances is a factor in visual input.

Assuming the eye is healthy, it is the accommodative system that actively keeps an image clear at various distances (switching easily and effortlessly between distance and near), as well as sustaining clarity at the target, especially up close, for long periods of time.

Accommodation is difficult to “see,” just like it is difficult to see an automatic camera focus, but we can calculate how much is needed at certain distances. Remember, the nearer the distance of interest, the more power we need from our focusing system.

If a person is farsighted or nearsighted, the refractive power changes the amount of accommodation needed to see up close clearly.

The farsighted person’s eyes are typically more comfortable focused in the distance and must work much harder to focus at near. Children are expected to be a tiny bit farsighted through much of elementary school with the amount of farsightedness decreasing with age. A lot of farsightedness, however, and its known effects on accommodation, combined with hours of daily desk work, can result in signs and symptoms affecting academic achievement for students.

A person who is nearsighted needs to use less power at near than someone who is farsighted because their eyes are already “preset” to focus more closely.

Keeping an image single is another factor in visual input.

This is controlled by the vergence system. Vergence is how you move your eyes in or out to look at objects at different distances. If your eyes are not coordinated together well and pointing in the same place, you can experience double vision. This can not only cause confusion, but could lead to misalignment of the eyes (phorias), noticeable eye turns in or out (strabismus), having your brain shut down an image (suppression) and can lead to your brain disregarding most of the information coming from one or both eyes (amblyopia).

Any of these conditions can cause symptoms such as eyestrain, fatigue, avoidance and headaches. If you notice a child having these symptoms, you should refer them to a behavioral optometrist for a comprehensive developmental vision exam.

If you are suffering from double vision, dizziness, balance problems, vestibular problems, headaches, migraines, light sensitivity or other symptoms after cataract surgery, there may be help.

We treat many patients for post-cataract surgery binocular dysfunction and they are able to improve their symptoms and quality of life.

Effective management of these symptoms includes vision therapy and corrective lenses. At OPTO-MIZATION NeuroVisual Optometry, we focus on treating such post-surgical complications through personalized therapy plans.

These two systems (along with your pupil that changes size to allow the proper light to come in and helps with depth of focus) ideally work together to keep images you are attending to clear and single.

You can think of accommodation as finding the distance at which to focus (defining the plane focus), while vergence defines the point of focus within the plane. The closer we want to focus and point our eyes, the more “power” or effort we need to do so.

It is important to have effortless control over these systems so when the going gets tough and you need to work a little harder, you can! It is also important this process is automatic.

Accommodation and vergence should work hand in hand with liberal degrees of freedom between the two to help bring you clear and single images. If an individual exhibits extra effort to maintain single and clear vision, symptoms usually worsen over time. Unfortunately, some people (especially kids!) can develop adaptation strategies to cope with these problems, like avoidance or amblyopia, so they may end up not having a variety of vision symptoms.

If these two systems are not working smoothly or efficiently together and one system is working too hard or not hard enough, the result is a visual system that fatigues and basically breaks down after short periods of visual stress. Usually this results in the brain fighting between either keeping the image clear, but double or keeping the image fuzzy and clear.

Depth perception is the visual ability to perceive the world in three dimensions, (width, height, and depth). This 3D perception, or stereopsis, is our ability to see objects in spatial dimensions when the two images of the eyes are put together.

Third degree fusion (3D), or stereopsis, allows us to see where objects are in space in relation to where we are in space accurately, like a radar system. Radar systems use two trajectories to get an “X” marks the spot on a target. If you only had one trajectory, you would have to guestimate where on that line the target was sitting. If you cross reference with another line, you can accurately tell where the object is. Similarly, when our eyes coordinate together to pinpoint an object accurately, we derive meaning of how far away it is. However, with 3D vision, you are getting a much richer and fuller image compared to the images coming in through either eye.

Ocular motility is how well and efficiently you move your eyes. These are motor skills that allow us to move our eyes so we can fixate on objects (fixation), to quickly and accurately jump from one object to another (saccades), and to track moving objects efficiently (pursuits). This is a skill that gives us speed and control of our eye muscles to accurately inspect our environment.

Accurate eye movements are very important when it comes to paying attention, copying from the chalkboard or book, reading efficiently, and doing well in sports. Problems in this area can lead to all sorts of problems in school if they are not detected early.

Efficient academic and athletic performance depends on the ability to focus the eyes rapidly and automatically, regardless of the working distance to make targets clear. Activities such as reading and writing require the ability to sustain and maintain prolonged focus up close. Copying from one place to another requires a change in accommodative focus that is rapid and efficient. Visual focus is also intimately related to the ability to sustain visual attention.

*It is important to note that the visual abilities needed for sports differ from those needed for reading and focus up close. This is why many kids can excel at sports but struggle with their vision up close.