IT’S EVERY parent’s worst nightmare. A physical condition with no outward symptoms, that does not reveal itself to regular examinations. That, if untreated, can result in permanent blindness. Amblyopia, commonly known as ‘lazy eye’, is said to be one of the commonest causes of childhood blindness. It’s the focus of Vision 2020, a WHO programme for child eye care. What is amblyopia?It’s a condition in which the central vision of one eye does not develop properly. ‘‘Untreated amblyopia may lead to functional blindness in the affected eye. Although it can see, the brain ‘turns off’ this eye because vision is very blurred; the brain elects to see only with the stronger eye,’’ says Dr AK Grover, head of the department of ophthalmology at Sir Ganga Ram Hospital, New Delhi. How is it detected?Amblyopia is one of the toughest conditions to detect. Since the eyes look normal; it does not reveal itself to a regular examination. ‘‘The critical time is between one and six. Though vision can be corrected till the age of 12, the results will vary,’’ says Dr Grover. So the onus is on parents and teachers to watch out for symptoms:• Squinting or closing one eye to see better• Watching TV up close• Holding a book close to the eye• Involuntary movement in the eye LOOK INTO THESE A comprehensive eye examination for a child should include testing these visual skills: • Acuity-distant: Visual sharpness, clearness at 20 feet. • Acuity-near: Ditto, for reading distance • Focusing skills: Ability to maintain clear vision at varying distances. • Eye tracking and fixation skills: The ability to look at and accurately follow an object. • Binocular fusion: The ability to use both eyes together at the same time. • Convergence and eye teaming skills: The ability of the eyes to aim, move and work as a coordinated team. • Hyperopia: A refractive condition that makes it difficult to focus, specially at near distances. • Colour vision: Ability to distinguish colours. • Reversal frequency: Confusing letters or words (b, d; p, q; saw, was) • Visual memory: The ability to store and retrieve visual information. Why is early detection necessary?Detection and treatment should happen before the brain learns to ignore vision in the affected eye. Why does it develop?Trauma to the eye is a cause, as well as a strong uncorrected refractive error (nearsightedness or farsightedness) or strabismus. The commonest causes are:• Squint: The brain cannot coordinate different images formed by the two eyes and tends to favour one. The other turns non-functional.• Radically different power in the two eyes: The brain again prefers the image formed by the stronger eye.• Stimulus deprivation to the eye due to childhood cataract or opaque cornea. How is it treated?Amblyopic children can be treated with vision therapy, eye drops, prescription glasses for nearsightedness or farsightedness, or surgery. Vision therapy: It exercises the eye, helps the two eyes work together and trains the brain to accept the amblyopic eye’s vision. Eyedrops: Some doctors prefer placing one drop of atropine—a vision-blurring drop—in the good eye, thereby forcing the child to use and thereby strengthen the weaker eye. The constant dilation of the eyes, however, has some side-effects. Spectacles: Glasses or contacts work if the condition is due to a strong uncorrected refractive error. Surgery: For children with an underlying physical problem hampering, say, contraction of eye muscles.
