Two eyes of an individual maintain an alignment with respect to each other as they gaze around in various directions. Each eye has six muscles and the balance between twelve extraocular muscles of two eyes maintain this equilibrium. Under certain circumstances this alignment can breakdown leading to the appearance of a squinting eye. This can occur for a variety of causes and in the children this is usually a congenitally acquired disbalance of the eye muscles which might manifest even by the 3rd or 4th year of life or could be due to an uncorrected high power of glasses. Sudden onset of squinting in the adult is usually due to neurological disease which can happen in patients of diabetes, hypertension or even in viral infections.
Fig : Extraocular muscles
of the eye (courtsey Pharmacia )
Top
What does the eye specialist look for in squinting eyes ?
In the children the first thing to look for is whether they need glasses or not. The ocular movements are then carefully assessed and in case some of the eye muscles are found to be under acting or over acting, the balance of eye muscles are examined by a series of tests called orthoptic tests which includes the cover test, the prism bar tests, the red green diplopia tests, the Hess's or the Lees Screen test and the synaptophore examination. The retina is also carefully examined since certain retinal disorders rarely manifest as squint in children.
In the adult with sudden onset squint, besides a test for diabetes and hypertension , a careful neurological assessment is ordered.
Do squinting eyes improve by themselves ?
Sudden onset squint in in adults especially in those with diabetes usually correct spontaneously over months . Many other neurological causes of squint in the adult are known to correct themselves spontaneously over months once the underlying cause is treated. In children, rarely a type of squint called the intermittent exotropia is known to correct itself . However, most of the squinting eyes in children do not correct themselves.
Can squinting eyes be corrected by glasses ?
Often when a child has a eye power called hypermetropia and is not wearing his glasses, the eyes begin to squint inwards. A child requiring a high minus power glasses can also start squinting outwards alerting the parents to have the child's eyes examined. Most of theses cases are corrected simply by the use of the appropriate power of glasses.
This squint is completely
corrected by the glasses.
What about surgery for squinting eyes?
When a child continues to squint even after wearing glasses or when he does not need glasses at all, a surgery is usually called for. The muscle balance is carefully assessed before the surgery to find out the muscles which are under acting or over acting. In the course of the surgery the over acting muscles are weakened by shifting away their insertion ( recession ) or strengthened by shortening the muscles by cutting out a piece ( resection ). This is a relatively safe procedure since the eye ball does not need to be penetrated. Undercorrection or over correction of squint can infrequently occur and may be corrected by a subsequent surgery. Constant squints in adults are treated by similar surgeries.
Residual squint after surgery can also be managed by eye muscle exercises or by incorporating prisms in glasses.
Can squinting recur after a correcting surgery ?
Certain types of squints i.e. . some of the exotropias or when the vision in one eye is poor, is known to recur although they rarely reach the previous degree. When the vision in both the eyes is good, and in most of the common types of squint , the squinting generally does not recur after surgery .