WHAT CAUSES STRABISMUS?
Although family history should be considered, the exact cause of childhood strabismus is not completely clear. Most strabismus is the result of poor control of the eye muscles responsible for eye movement and optical conditions such as hyperopia.
Other causes of strabismus are ocular diseases affecting the retina, the optic nerve, the crystalline, etc. There are general diseases which secondarily affect the eye. Among them we can mention diabetes, thyroid disease, miastenia gravis, cerebrovascular accidents (CVA), brain tumors, cranial or orbital trauma.
WHAT ARE THE SYMPTOMS AND SIGNS?
Strabismus may be evident since birth or it may appear at age 3 or 4 due to hyperopia.
Normally, the child’s ocular deviation is detected by his parents or relatives, or by the pediatrician and sometimes by the ophthalmologist during a routine examination. However, it should be known that newborns until 6 months of age have no control over ocular movements. If after this age a baby still has strabismus, he must be examined by an ophthalmologist immediately. This is very important also to rule out other causes of strabismus such as tumors or retinal lesions.
HOW IS IT DIAGNOSED?
Parents should visit their ophthalmologist as soon as possible when they suspect the child might suffer of strabismus. The ophthalmologist will examine the visual acuity of each eye using the appropriate method depending on the age of the child and he will evaluate the ocular movements by means of the Cover Test.
He will also perform the dilated fundus examination and ocular refraction applying the drops which dilate the pupil and paralyze the eye’s accommodation system. In this way, it shall be possible to determine the existence of an organic lesion or refractive defect (myopia, hyperopia, astigmatism). With this information the ophthalmologist may diagnose and recommend the corresponding treatment.
WHAT ARE THE CONSEQUENCES OF STRABISMUS ON CHILDREN?
If strabismus is not treated before age 7, the deviated eye will not receive the correct image in the appropriate place of its retina. This will lead to an irreversible visual reduction called Amblyopia (loss of vision in one or both eyes due to abnormal visual development).
GLASSES, EYE PATCHES OR SURGERY?
The appropriate treatment depends on the type of Strabismus.
1- In case of strabismus due to unbalanced ocular muscles with no optical defects or eye fundus alterations, the treatment is generally surgery.
2- If strabismus is due to unbalanced ocular muscles with an optical defect, the treatment will combine surgery and eyeglasses.
3- Finally, there is another type of strabismus caused exclusively by an optical defect (Accommodative Strabismus). Permanent eyeglasses may be prescribed to achieve the eye alignment.
In any of the above mentioned cases, if there is a visual deficit in one eye, it shall be treated by means of a “patch”, eyeglasses or both.
WHICH ARE THE AIMS OF THE TREATMENT?
The treatment is aimed mainly at:
Avoiding Amblyopia: Eyeglasses for the optical problem (if any) will be prescribed and the healthy eye will be covered with a patch so that the other one may develop a better vision. Sometimes children don't want to wear the patch but it is the only way of avoiding Amblyopia. During the development of the visual system, the brain must receive clear and sharp images from the retina of both eyes. If untreated, the brain area corresponding to the vision of the defective eye will suffer an abnormal development and permanent loss of vision.
There are other causes responsible for Amblyopia such as: refractive alterations (hyperopia, astigmatism), eye opacity (congenital cataracts), trauma, etc. The sooner the cause for the abnormal visual stimulation starts, the most serious the visual deficit is.
This is the leading cause of loss of vision in childhood.
Eye Alignment: Strabismus associated to hyperopia can be corrected completely or partially with eyeglasses, but the surgery is more frequent. In this way it is possible to “realign” the eyes and achieve an aesthetically acceptable look.
Restoring Binocular Vision: The former treatments help to restore binocular vision. When both eyes have the same vision level and they are aligned it is possible to achieve an almost normal binocular vision.
WHAT IS STRABISMUS SURGERY LIKE?
Surgery may involve the deviated eye, the aligned eye or both.
The surgical procedure involves either a recession or resection of eye muscles. Recession is a “weakening” of the “strong” eye muscles. In contrast, resection is the “strengthening” of the “weak” eye muscles removing a portion of their fibers.
Although modern surgical techniques such as adjustable sutures offer excellent results, further surgery is sometimes necessary in order to realign eyes and achieve an aesthetically acceptable and functional look. This surgery requires of general anesthesia.