WHAT IS STRABISMUS AND HOW COMMON IS IT?
Strabismus is any misalignment of the eyes. It is estimated that 1-3% of the Indian population has strabismus.
ARE THERE DIFFERENT TYPES OF STRABISMUS?
There are many different types of strabismus. Is is most commonly described by the direction of the eye misalignment: common types of strabismus are esotropia, exotropia, hypotropia, and hypertropia.
Strabismus can also be described by its cause. The 3 cranial nerves (III, IV, VI) responsible for eye movement can be weak or palsied and cause strabismus. Some examples of paralytic strabismus include third nerve palsy and superior oblique palsy. Special patterns of strabismus can have unique names such as Brown syndrome, and Duane syndrome.
WHAT ARE THE COMMON TYPES OF STRABISMUS?
Esotropia is inward turning of the eyes Types of esotropia include infantile esotropia, accommodative esotropia, an d sixth nerve palsy.
Exotropia describes the outward turning of the eyes [See figures 1 and 2].
The terms hypertropia and hypotropia are used to describe vertical misalignment. Hypertropia is an abnormal eye higher than the normal eye. Hypotropia is when the abnormal eye is lower than the normal eye. The terms can generally be interchanged.
WHAT CAUSES STRABISMUS?
Most strabismus is the result of an abnormality of the poorly understood neuromuscular (including brain) control of eye movement. Less commonly, a problem with the actual eye muscle causes strabismus.
HOW IS STRABISMUS RELATED TO POOR VISION?
Eye misalignment can cause amblyopia (Lazy eye) in children. When the eyes are oriented in different directions, the brain receives 2 different visual images. The brain may ignore the image from the misaligned eye to avoid double vision, resulting in poor development of visionof in that eye. Also, an eye that sees poorly tends to be misaligned. Thus poor vision can be the result or cause of strabismus.
WHO DEVELOPS STRABISMUS AS A CHILD?
Strabismus often occurs in children who are otherwise completely normal. However, disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus and brain tumor are more likely to develop strabismus.
WHICH ADULT DISORDERS CAUSE STRABISMUS?
Stroke is the leading cause of strabismus amongst adults. Trauma, neurological problems, Graves disease (thyroid eye disorders), and Myasthenia gravis are other common causes of strabismus.
HOW DOES TRAUMA CAUSE STRABISMUS?
Trauma can cause strabismus by:
1) brain damage that impairs control of the eye movement;
2) damage of the nerves that control the eye movement, and/or
3) damage of the eye muscles, either directly or secondarily, due to trauma to the eye socket.
HOW IS STRABISMUS TREATED?
The goal of strabismus treatment is to improve eye alignment, which allows for the eyes to work better together (binocular vision). Treatment may involve eye glasses, eye exercises, prism, and/ or eye muscle surgery. Problems associated with strabismus (including amblyopia, ptosis, and cataract) are usually treated prior to eye muscle surgery.