Strabismus - Adult Eye Misalignment
What is Adult Strabismus?
Strabismus is a misalignment of the eyes where the eyes point in different directions. Although strabismus is often thought of as a problem of infants and children, adult strabismus is relatively common, occurring in one percent of the population.
What Causes Adult Strabismus?
Adult strabismus can result from continuing childhood strabismus, or it can be caused by a tendency for the eyes to drift during adulthood or due to neurological problems or trauma. Strabismus which occurs in adulthood without a history of childhood ocular misalignment, should be evaluated carefully for the possibility of a medical or neurological cause. Thyroid disease, myasthenia gravis, or even brain tumors can occur as strabismus.
What Are the Symptoms of Adult Strabismus?
The most common symptom is double vision (see below). Some adults with strabismus will have eye strain, discomfort with reading, headaches, or may even turn or tilt their head to use their eyes together. Children and adults whose eyes turn out (exotropia) often squint or close one eye in sunlight.
What Causes Double Vision?
In most individuals both eyes are perfectly aligned. Proper alignment allows for fusion, binocular vision and depth perception. Double vision is caused by a misalignment of the eyes. Misalignment that occurs in adults who develop strabismus in adulthood (after age 10 or 15 years) is often associated with double vision. Double vision can be avoided by closing one eye or wearing a patch. Infants and children can learn to suppress (or turn off) the images from one eye and do not see double even though their eyes are misaligned. Adults, however are unable to suppress, and acquired strabismus in adulthood frequently results in double vision.
How Is Adult Strabismus Treated?
There is a common misconception that strabismus in adulthood is difficult or impossible to treat. Using recent advances, adults with strabismus may actually have more treatment options than children. Treatment options include eye exercises, prism glasses, adjustable eye muscle surgery, and in some cases, Botulinum toxin injections.
Eye muscle exercises are rarely useful for correcting ocular misalignment, however, they may be helpful in special problems such convergence insufficiency. This is a condition where the eyes do not well for close work or reading.
Prism glasses have a limited role in strabismus therapy. Prisms align as converge the visual axis but they do not straighten the eyes. Images are displaced by the prisms to correct for the misalignment. They are most useful for correcting smaller deviations, usually when one eye is higher than the other.
Eye muscle injections with Oculinum® can be used to treat strabismus. This is a new technique under investigation. The eye muscle is injected with a medicine that temporarily paralyses the muscle. This temporary paralysis wears off in a few months, but a tightening of the opposite muscle occurs, producing a permanent change in the eye position and alignment. This technique is useful in selective cases, usually in individuals with small or moderate misalignments, nerve palsies and other conditions.
How Does Surgery Work?
The most common treatment for strabismus at any age is with surgery on the eye muscles. Tight (overactive) muscles are weakened by moving the muscle backward to produce slack and straighten the eye. Underacting muscles are tightened by removing a small segment of the muscle to shorten it and the muscle is reattached. To better understand these procedures, visualize the eye muscles as rubber bands, being either tightened or loosened.
What Anesthetic Is Used In Strabismus Surgery?
Strabismus surgery is usually performed using general anesthesia. Surgery can be performed using local anesthetic with the individual awake or slightly sedated. Local anesthesia is given by an injection of a novocaine-like anesthetic or occasionally with drops.
What Are Adjustable Sutures?
One modern adult strabismus surgical procedure uses a technique which allows for post-operative adjustment of the eye alignment. The operation is done in two stages. In the first stage, usually done under general anesthetic, the eye muscle is secured and placed on a suture which can be tightened or loosened the following day when the anesthetic has worn off. The second phase is performed using topical anesthetic with the individual awake and allows adjustment to better align the eyes. The adjustment can be somewhat uncomfortable, but it is not usually painful. This technique can be used in any co-operative adult or older child. The adjustable suture procedure is particularly useful in complicated strabismus cases and with reoperations, and may offer a better chance of straightening the eyes with one operation.
What Are The Results Of Strabismus Surgery?
The results of strabismus surgery vary depending upon the severity and complexity of the condition. Overall, we can expect successful alignment with one operation 50 to 70% of the time. Even when strabismus surgery is performed properly, 20 to 30% of patients may need additional surgery, depending on how the eyes heal after the first surgery. Even with the adjustable suture technique, there is a chance that additional surgery will be necessary.
Are There Risks With Strabismus Surgery?
As with any surgery, there are rare, but important, risks with strabismus surgery. The major risk is from complications of the general anesthetic or from bleeding or infection affecting the eye or vision. Strabismus surgery is considered safe so that both eyes can be operated on in the same surgery. The risk of strabismus surgery is extremely small, but, as with all surgeries, there are inherent risks. Specific risk depend on the nature of the surgery being done.
It is important for an adult with strabismus to realize that there are alternatives to living with misaligned eyes. Glasses, prisms, exercises and other treatments can help. Surgery can be done to align the eyes for cosmetic reasons, to eliminate double vision, or to improve binocularity. Good eye alignment results in a better appearance and self-esteem. Symptoms such as double vision, eye fatigue and head turns caused by strabismus can be improved. Advances in surgical techniques allow an excellent chance of successful alignment for most individuals.
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