THE TRUTH
Children rarely grow out of squints! The misunderstanding arises because an apparent squint due to eyelid shape (e.g. prominent epicanthic folds) frequently becomes less obvious with age, thus confusing parents and perpetuating the myth. Epicanthic fold & Squint (The child on the left of this picture has a true squint -see the light reflections- but the other child has straight eyes)
Squints can be adequately measured, assessed and corrected at any age! The importance of this early management is clear when one considers that loss of vision caused by a turned eye may become permanent!Some of the organic causes of squint (eg optic atrophy and retinoblastoma) may require early diagnosis to prevent catastrophe!click picture to enlarge
Squint and Learning Disability – Major studies have shown incidence of eye movement disorders is not increased in children with learning problems. There appears to be no correlation between squint and learning disabilities!
Eye exercises play a very minor role in the management of strabismus.
3. THE IMPORTANCE OF STRABISMUS
What causes a squint?
Sensory deprivation must always be excluded as a cause of strabismus. Potentially fatal conditions such as Optic Atrophy – resulting from an intracranial space occupying lesion (Brain Tumour) – or Retinoblastoma frequently present as a squint. As may Retinal Detachment, Lens opacity, Vitreous Haemorrhage or Toxoplasmosis Retinopathy.
All children with a unilateral squint must be fully examined to exclude these organic disorders if catastrophe is to be avoided! The possibility that a squint may be secondary to other neurological disorders (e.g. raised intracranial pressure) must also be excluded.
What effect does does a squint Have?
When one eye deviates immediate brain confusion results. There is then immediate and absolute suppression of foveal vision of the deviated eye (The eye is turned off). The object of regard projects to the wrong point on the retina – thus double vision occurs.
After visual maturity is reached (age 7 years) this diplopia is permanent. But young children are able to ignore this second image – by suppressing it – and they avoid diplopia.
They pay a price for this. Because they are not using the eye correctly in this formative period this causes loss of vision which becomes permanent if not eliminated while the patient is visually immature. i.e. Amblyopia.
4. AMBLYOPIA
-. diminished visual acuity not correctable with spectacles, in the absence of organic pathology.
Incidence of Amblyopia
– 3-5% in the general population.
Amblyopia is caused by a disturbance of foveal visual stimuli – either displacement of the image in strabismus i.e. Strabismic amblyopia or a defocused image with media opacities (vitreous, lens, or cornea) – i.e. Deprivational amblyopia or unilateral refractive error – i.e. anisometropic amblyopia.
Amblyopia is amenable to therapy provided such therapy is prompt, early and continuous until visual maturity is attained. It is rarely successful after the age of 7 years.
The earlier the onset of amblyopia the denser and the more rapid is its occurrence.
The earlier its management the more rapid and more complete its resolution.
Thus the early diagnosis and correction of strabismus will result in better prevention and control of permanent visual loss through amblyopia.
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