HISTORY OF EYE ASSOCIATES OF NEW MEXICO

Strabismus

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Understanding Strabismus and Amblyopia

Basic information about how the eye works:  light rays enter through the front of the eye, are refracted or bent by the cornea and the crystalline lens and come to a point of focus on the retina.  The retina is the innermost layer inside of the back of the eye and is composed of sensitive nerve tissue.  The retina changes the light into electrical impulses, which are transmitted via the optic nerve to the brain.  In order for us to see, however, more is required than just a healthy eyeball; the eyes must also move properly and they must be able to look at the same subject at the same time.  When this “working together” process does not occur, the condition is called STRABISMUS, a term referring to any kind of extra-ocular muscle imbalance.

Strabismus may become apparent at almost any time in life from infancy to adulthood.  It is, however, most common in childhood.  It may be present all of the time or it may be obvious only during periods of fatigue, stress, illness or when an individual is attempting to concentrate on very close objects.  Newborns often seem to have strabismus, but the condition usually disappears in a few months as muscle control and coordination develop.  If strabismus is present at birth and does not disappear in early infancy, the prompt attention of an ophthalmologist is needed to prevent the development of amblyopia.  AMBLYOPIA occurs when the brain “turns off” the signal received from the wandering eye because the signal produces blurred and/or double vision.  The eye thus ceases to function. 

To understand strabismus better, it’s helpful to understand how the eyes move.  Six pairs of muscles, one of each pair attached to the eye, control our ocular movements.  While one pair of muscles pulls or tightens, the corresponding pair loosens or relaxes allowing the eyes to move and work together.  Normally, when both eyes work together, each sees an object from a slightly different angle.  A process called fusion occurs when the brain blends the two slightly different images into one three- dimensional object. 

When the paired muscles fail to function as a team, the brain receives visual messages so different that it cannot merge them into one image.  The visual message from the properly aligned eye is accepted while the visual message from the wandering eye is rejected.  This sets the stage for the development of amblyopia in children and double vision in adults. 

Fortunately, strabismus and amblyopia, if diagnosed in time, can be corrected.  However, if amblyopia goes unchecked until the age of 6 or 7, no type of treatment will restore proper vision in the affected eye.  Even though the eye may be surgically straightened, the eye will never see properly. 

Treatment of strabismus focuses on three goals:  to make the eyes work together, to preserve vision and to straighten the eyes.  Treatment can consist of a singular measure or may involve a combination of techniques.  None of the treatments are quick or simple, but with patience and cooperation with your ophthalmologist, the goals are attainable. 

Very mild cases of strabismus may be treated with ORTHOPTICS.  Here, eye exercises are used to strengthen weak muscles allowing the eyes to move together and fostering the fusion process.  Orthoptic procedures are also helpful as a diagnostic tool and in training the eyes to work together after surgery.

For cases of strabismus resulting in amblyopia, patching has historically proven to be a very effective form of treatment.  The theory is that by covering the “good” eye, the lazy eye will be forced to function and amblyopia will be discouraged.  The sooner that patching is started the move effective it will be. In some instances, eyeglasses can be prescribed to assist in the straightening of the eyes.  Generally speaking, strabismus is easier to treat if the patient’s vision is otherwise sharp.  To review, light entering the eye is refracted or bent by the cornea and the crystalline lens and is brought to a focal point on the retina.  The crystalline lens automatically alters its shape to facilitate focusing on any object, near or far.  This adaptive process is known as ACCOMMODATION.  If a patient is farsighted, the point of focus occurs behind the retina producing a blurred, distorted image.  As the eyes struggle to accommodate to achieve a single clear image they may actually cross.  With eyeglasses, the focusing responsibility is transferred to the corrective lenses, thus allowing the eyes to relax and straighten. 

Surgery is a corrective option that is often used in combination with patching and/or eyeglasses.  The procedures performed are designed to correct only the amount of strabismus that other treatment methodologies could not eliminate.  Surgery to correct strabismus is most often done on an out patient basis with minimal discomfort.  Muscles to be weakened are “recessed”; their point of attachment to the eyeball is moved back.  If a muscle is to be strengthened, a small piece of the muscle will be removed, those ends sewn together and the muscle reattached to the eyeball.  This process is called “resection”.  The operated eye will be red and sore for a week or so after surgery but these conditions will subside as healing progresses. 

It is important to remember that strabismus runs in families.  Once past infancy, children with strabismus will not “outgrow” the condition.  A child is never too young to have an eye exam and all children should undergo an ophthalmic examination before starting school.  If there is a family history of strabismus, children should be examined by the age of two. 

Eye Associates’ ophthalmologist Frank Durso, MD, provides specialized care in the areas of pediatric ophthalmology and ocular motility disorders.  Dr. Durso has practiced with Eye Associates since 1981.