Anisometropia - Symptoms, Causes, Diagnosis, Treatment
What is Anisometropia?
This is a visual condition and when a person has this condition they see differently from each of their eyes. They will usually see a smaller image in one eye and a larger image in the other eye, which can cause blurring of vision. There are some cases in which anisometropia will cause another visual condition called lazy eye, which happens when you have distorted or weak vision in one eye. When a person has normal vision they see the image about the same shape and size with both eyes, which is referred to as binocular vision. Many times anisometropia is present at birth but it is usually not detected until later in life. Although it can be present at birth it can happen at any age regardless of gender or sex. It is estimated that six percent of children between the ages of six and eighteen will have this visual condition.
There are three different types of anisometropia which include:
- Simple anisometropic eye - this is when one eye gets impacted while the other eye is normal. It is also referred to as simple hypermetropic, which means a person is farsighted or simple myopic, which is when a person is nearsighted.
- Compound anisometropic eye - this is when both eyes are in the myopic stage but there is a notable difference in the refractive power, which is the improper bending of light in each eye.
- Mixed anisometropic eye - this is the last stage. It is when both of the eyes have refractive errors. One eye will myopic and the other will be hypermetropic.
- Amblyopia - this is commonly referred to as lazy eye. This is when a child has reduced vision in one of their eyes because during childhood they have not used that eye adequately.
- Strabismus - this is when a person is not able to align both of their eyes under normal conditions simultaneously and is referred as being cross eyed.
- Diplopia - this is when a person has double vision
- Eye strain
- Sensitivity to light
- Complexity in reading
- Sheer tiredness
- Their depth perception is impaired.
There are many different reasons why a person can have anisometropia, which can include:
- An uneven growth in both eyes
- During cataract surgery there is a miscalculation of lens power
- Inborn defects in the eye.
When a person has normal vision the retinal image for each eye is approximately the same shape and size. In many cases difference between the sizes of the images is less than zero point five percent. Your brain can deal with differences up to five percent before your vision is affected adversely. If you have anisometropia the difference in the images is greater than five percent and could be as much as twenty percent difference.
If a person has anisometropia it is usually detected, or diagnosed, when the child has a vision exam. If it happens in an older person they may notice that their vision is blurry and go in for an exam for a diagnosis. During the eye exam the doctor will check to see how well they see things when covering first one eye, then the other. It can also be diagnosed if it causes other conditions such as eyestrain or double vision.
It is very important that you have this visual condition treated and corrected. If you do not do this your brain will pick the better of the two images and then start to ignore the other image. In time this can lead to the development of a dominant eye. Once it has been treated and corrected your brain will have to relearn how to use the eye that is weaker. In addition, if a child has been suffering from anisometropia for a long period of time and it has been neglected and not treated they could lose their sight in that eye.
Whether to treat anisometropia all depends on how severe the case is. There are some people who develop a tolerance to it and do not require any specific treatments but this will usually only happen if there is present just a small level of difference. If the difference is prominent you may need to wear corrective lenses, contacts, or have surgery. When you have corrective lenses or contacts each lenses will have a different prescription. If it has been untreated for a long period of time and get corrective lenses or contacts you may need to gradually work up to the full prescriptions to give your eyes time to adjust to better vision.