Squint eyes over the years have been looked upon as a black spot on the human beauty. Nevertheless, it has been posing the prospective brides with innumerable problems in matters of matrimony. However of a beauty she might be, one look at her eyes the boy turns her down. Such boys do not care to probe whether squint eyes can be set right.
Sometimes, on the other hand, people with squint are considered lucky in the society. But the Ophthalmologists who know the consequences of squint, do not think so. On the contrary, they stress the disadvantages and negative aspects of squints- as outlined below.
The two eyes normally should be in a definite visual axis. A manifest deviation of the visual axis of either eye is known as squint or strabismus. So one eye is deviating or squinting, the other eye takes up the visual function mainly. So it becomes a dominate eye. Most of the time, the deviating eye slowly becomes impaired functionally. Later it almost becomes blind. This hard fact will not be known to the squinting person unless he closes the good eye and tests for the other eye vision.
When the degree of squint is gross, it is very easy to recognise that. But when there is a small amount of squint, various tests have to be done to diagnose correctly the type and amount and presence of squint.
Mainly there are two types of squint -paralytic and non-paralytic. There are seven small muscles around each eye-ball, which are responsible for the various movements of the eye. These muscles are supplied by 3rd,4th, and 6th cranial nerves- which are derived from the brain.
Whenever these nerves become weak or lose their conducting capacity, the respective eye muscles become immobile. So when the other normal eye moves in a particular direction, if the affected eye cannot move in the same direction, squint becomes evident which is a paralytic squint.
Non- paralytic or concomitant deviations are for the most part, produced by anomalies of the power of convergence and divergence and the co-ordinated use of the two eyes to obtain binocular single vision. In these cases the amount and character of the deviation does not vary when the eyes are turned to the right or left.
Before going to the causes of squint, it is necessary to know the necessity of two eyes. It is the fact that when we observe a single object with both the eyes we see it as a single object instead of two. Obviously one may ask -what is the necessity of having two eyes? Even if one becomes blind, the other one can function normally - one may think.
One eye is always complement to the other eye. When we see with both eyes, the extent or field of vision is definitely wider than with one eye. Moreover, two eyes are necessary to have what we call as “ BINOCULAR SINGLE VISION” the important aspect of this being depth perception. There are 3 stages in this binocular single vision. 1. Simultaneous perception. 2. Fusion. 3. Steriopsis ( the one which gives the sense of depth )
The development of reflexes concerning the binocular single vision and the movements of eye muscles - are not complete until the child is 5 years. Usually this will be established when the child becomes 8 years old. So any disturbances during this period ( below 5years ) may hamper the relation between the movement of the two eyes and may cause a squint.
Causes of Squint : 1. Accommodation and convergence anomalies. 2. Refractive errors. 3. Weakness in the nerves supplying the eye muscles. 4. The gross difference in the vision between 2 eyes due to any reason. 5. Patching or closing of one eye for a prolonged period. 6. Defect in the development of the nerves between retina and the brain. 7. Hereditary and genetic or familial causes.
Clinically, there are two types of squints - Convergent Squint- when one or both eyes are turned in, and Divergent Squint - when one eye is turned outside the normal visual axis.
Treatment :
No case of squint can be said to be ‘cured’ unless, in addition to normality of appearance, there is restoration of binocular single vision in all circumstances. Although the latter cannot be achieved in every case, a satisfactory cosmetic result can invariably be obtained by means of operation or surgery.
In a case of squint there may be three possible defects of function which have to be remedied:
1. The loss of normal function of the squinting eye. This may not only concerns visual acuity but also visual localisation.
2. The loss of normal binocular function.
3. The physical deformity caused by the deviation of the visual axis. This is the defect which attracts the attention of parents but is the least important from the point of view of visual function.
To give complete treatment, child should be between 6 and 8 years. So the parents and school teachers have a very important role to play. They should subject these squinting children for treatment at the earliest. Because any treatment or surgical correction done after the age of 8 years is not complete or perfect because then we can only correct the physical deformity but we cannot get the very important functional part of it i.e. binocular single vision. So most of the time in persons who are treated for squint after the age of 8 years, one eye would be stronger, other eye would be weaker. They will not have binocular single vision - which can give them the exact form and depth perception.
The methods of treatment:
1. Correcting the refractive errors - by glasses whenever refractive error is found to be the cause of squint.
2. Deliberate occlusion or patching of the fixing eye so as to improve the vision of the squinting eye.
3. By special type of (orthoptic ) exercises in order to improve the binocular faculties.
4. By operation or surgery - to restore parallelism of the visual axis.
One or more of these methods or all four may be needed in any individual case.
Finally it is the dire responsibility of the parents and the teachers to detect this malady, which renders their children look ugly in the eyes, during the tender age of 6 to 8 years lest it is practically impossible to develop a squintless society.
– Dr.H.S.Mohan
