Diseases of the Eye
Our eyes are complex organs we rely on every moment we are awake. Like any organ in our body, our eyes are also susceptible to disease. This section of our website provides a comprehensive list of common eye diseases as well as known treatments to these eye problems.
Amblyopia (Lazy Eye) Can Lead to Permanent Decreased Vision if not Treated Early in Life
Amblyopia, sometimes referred to as "lazy eye", is poor or blurred vision in an eye that is otherwise physically normal with no pathological condition. Many people confuse the term "lazy eye" with strabismus (an eye turning in or out). Amblyopia can be associated with strabismus but it can also exist without strabismus.
Amblyopia is a developmental disorder of the brain involving the part of the brain that deals with the visual system.
Amblyopia (lazy eye) affects about 2-5% of the population.
Amblyopia is caused by either no transmission or poor transmission of the visual image to the brain for a sustained period of time during early childhood. Amblyopia occurs because the neural pathways from the eye to the brain develop at an early age and if either eye is not getting a clear image, the pathways to the brain will not develop correctly and the eye could lose the ability to see clearly even with glasses or contact lenses.
Amblyopia usually affects only one eye so if it is mild there may not be any symptoms because the good eye will take over. If the amblyopia is severe there may be deficits in...
- Depth perception: The ability to judge depth may be impaired since the eyes are not working together.
- Visual acuity: The small lines on a vision chart may be difficult to read even with both eyes open and with visual correction in place.
- Binocular summation: The fact that vision, contrast sensitivity, and depth perception are better with both eyes open. People with amblyopia may actually see worse with both eyes open and better when just viewing through the good eye.
- Contrast sensitivity: The ability to perceive differences between an object and it's background. So something like a newspaper which has black print on a gray background would be much harder for someone with amblyopia to see. It would be a lot easier for them to see something with high contrast like black print on a white background.
- Sensitivity to motion: A normal visual system is very sensitive to something moving in the visual field. A person with amblyopia may be less sensitive to the same movement.
- Crowding Effect: This means a person with amblyopia may be able to read smaller letters on the vision chart if the letters are singled out. If the whole chart is showing it is much harder for them to read letters from the smaller lines.
Types of Amblyopia
There are several types of amblyopia and they are categorized based on the cause.
Strabismus is a misalignment of the eyes. When the eyes are misaligned the brain gets two conflicting images. So in order to deal with the double vision it suppresses one of the images and it's usually the blurrier image that gets suppressed. Since that eye is not being used the corresponding part of the brain never develops correctly. Strabismic amblyopia can be treated by clearing the blurry image as much as possible with glasses then putting a patch over the good eye in order to force the other eye to work. The frequency and length of time patching is different in each case and it is very important to do this under a doctor's supervision so that the good eye does not develop occlusion amblyopia from the patching. The alignment can be corrected by surgery or vision therapy depending on the amount and type of misalignment.
This occurs when the two eyes have very different refractive errors so that one has much clearer vision than the other. The difference must be significant and the better eye becomes the dominant eye so the brain begins to ignore the bad eye. Refractive amblyopia is usually less severe than strabismic amblyopia and it is actually common for the two to occur together. The treatment is to correct the vision as much as possible in the amblyopic eye and patch the good eye. Once again, it is very important to consult with your optometrist and follow a specific patching treatment so as not to damage the vision of the good eye.
This occurs when both eyes have very high refractive errors and are not treated with glasses. The amblyopia is in both eyes and the treatment is to correct the vision as much as possible with glasses or contacts. It also helps to do small detail work in order to speed up the progress. This form is usually the least severe.
Occlusion amblyopia is caused by something physically obstructing the vision. Some examples are cataracts (opaque lens), a corneal scar, or a drooping eyelid. The amblyopia will persist after the object is removed and must be treated with vision therapy like the previous two types.
Treatment For Amblyopia
Vision therapy has been shown to be most effective if started before age twelve. There have been small improvements shown with adults but it is much less common. If started before age 12 there is a good chance the vision will reach 20/30 or better depending on the case. However, the earlier the treatment the better the prognosis to improve vision. Treatment started before age seven or eight results in a much better prognosis.
As mentioned previously, the treatment includes correcting the vision as much as possible, patching the good eye and doing some kind of detailed near work while patched. Often things like beading, word puzzles, or even small video games are part of the therapy.
The prognosis depends on what age treatment is started and on the severity of the amblyopia as well as how well the patient adheres to the treatment protocol. Treatment should be started as soon as amblyopia is diagnosed and no age is too young.