Eye Disorders - Amblyopia and Presbyopia
Amblyopia
Lazy eye, or amblyopia, is the loss or lack of development of central vision (straight ahead vision) in one eye that is unrelated to any eye health problem and is not correctable with lenses. It result from a failure of the brain to develop the uses of both eyes together. Lazy eye is often associated with crossed-eyes or a large difference in the degree of nearsightedness or farsightedness between the two eyes. It usually develops before age six and it does not affect side vision.Symptoms may include noticeably favoring one eye or a tendency to bump into objects on one side. Symptoms are not always obvious. Treatment for lazy eye may include a combination of prescription lenses, prisms, vision therapy and eye patching. Vision therapy teaches the two eyes how to work together, which helps prevent lazy eye from re-occurring.
Early diagnosis increases the chance for a complete recovery. This is one reason why the American Optometric Association recommends that children have a comprehensive optometric examination by the age of six months and again at age three. Lazy eye will not go away on its own. If not diagnosed until the pre-teen, teen or adult years, treatment takes longer and is often less effective.
In the animation linked below, a child with amblyopia is sending unequal signals from each eye to the brain. As shown in this animation, neuro-electrical signals travel along pathways from the eye to the brain. The unaffected right eye is sending strong signals. The eye with amblyopia, the left eye, is sending fewer neuro-electrical signals. If untreated, the pathways through which these signals travel may weaken and not develop properly, damaging the child’s vision.
Placing a patch over the unaffected eye for several weeks will stimulate and strengthen the signals from the eye with amblyopia leading to more normal nerve function in the brain, which improves vision in that eye.
View Animation (14 second MPEG)
View Animation (14 second Quicktime)
View Animation (30 second Quicktime)
Presbyopia
Presbyopia is a vision condition in which the adjustable-focus crystalline lens of your eye loses its flexibility, becoming rigid and non-adjustable. This usually makes it difficult for you to focus on both near and far objects without relying on some type of eyeglass to adjust your focus for you.
Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-forties. Presbyopia is a natural part of the aging process of the eye. It is not a disease and it cannot be prevented.
Some signs of presbyopia include the tendency to hold reading materials at arm's length, blurred vision at normal reading distance and eye fatigue along with headaches when doing computer work or close work. A comprehensive eye examination will include testing for presbyopia.
To help you compensate for presbyopia, your optometrist can prescribe reading glasses, bifocals, trifocals or contact lenses. Since presbyopia can complicate other common vision conditions like nearsightedness, farsightedness and astigmatism, your optometrist will determine the specific lenses to allow you to see clearly and comfortably. You may only need to wear your glasses for close work like reading, but you may find that wearing them all the time is more convenient and beneficial for your vision needs.
Because the effects of presbyopia continue to change the ability of the crystalline lens to focus properly, periodic (usually about once per year) changes in your eyewear are necessary to maintain clear and comfortable vision.