Understanding Vision Problems -- the Basics
Crossed Eyes, Wall Eye (Strabismus), and Lazy Eye (Amblyopia)
As your baby grows and develops, so do his eyes. During the first few months of life, an infant does not have crisp, clear vision. Thereafter, the eye's focusing mechanisms and eye movements rapidly develop as the eye and brain develop the visual apparatus. By about the age of 6 months, both eyes should consistently work together, allowing your baby to see both near and far away targets. The infant's eyes should be aligned, both looking at the same object.
However, in some situations the eyes do not appear to work together. One eye may tend to drift inward or outward some or all of the time. Prompt evaluation by an eye specialist is essential to determine whether any suspected drifting is due to a muscle imbalance or an internal eye problem that interferes with good eyesight.
Simply stated, the eye doctor needs to determine how well each eye sees and why the eyes do not appear straight. Parents will be relieved to know that the eye doctor's exam can find the answers without any help from the baby! Any problems that are identified need to be addressed in order to preserve good eyesight in both eyes. Misalignment of the eyes may also be the result of the following:
- Birth trauma
- Brain injury
- Cerebral palsy
- Congenital maldevelopment
- Neurologic problems
The medical term for misaligned eyes is strabismus. There are six different muscles that are attached to each eye to help it turn and rotate. The eyes may not appear straight because one or more muscles are pulling too hard or other muscles are too weak. If the eyes turn inward leading to "crossed eyes" we call it esotropia. If they turn outward, called "wall eyes," then the condition is labeled exotropia. There are different treatments for strabismus depending on the specific cause. Some cases are managed with eye muscle surgery, some simply need glasses.
Amblyopia (Lazy Eye)
If strabismus happens to an adult, perhaps after a trauma to the head or after a stroke, the person is likely to experience double vision. Double vision occurs because the two eyes are looking at different images. In an infant or a child, the brain will not tolerate double images and will shutdown the vision in the weaker eye. This involuntary loss of vision is called "lazy eye" or amblyopia. Here's another way to say it: Amblyopia is a healthy eye that does not see. Only infants and children develop amblyopia; and the vision loss can be reversed with therapy if the contributing eye problem is corrected early enough during childhood -- typically before the age of 7.
Not every case of strabismus develops amblyopia, and not all cases of amblyopia are due to strabismus. For example, an infant with a dense congenital cataract in one eye will develop "lazy eye" unless the cloudy lens is removed