Amblyopia is a condition of reduced or dim vision in an eye which appears to be normal. It is sometimes called “lazy eye”. This is a serious eye defect which often goes undetected in childhood until it is too late to have it corrected.
Amblyopia is estimated as affecting two to four percent of the population of Australia. It is a potential cause of unemployment for healthy young adults who find their vision is not adequate for certain occupations. When it is caused by a squint it is an embarrassing disfigurement.
It is important for children to have their vision tested before they start school because a successful result depends on early treatment.
Causes of Amblyopia:
1. Squint (Strabismus)
This is the most frequent cause and occurs when the eyes are not parallel when focusing on an object. Each eye looks in a different direction and the child sees either two objects or a blurry image (double vision). To avoid confusion, the child unconsciously suppresses the image from one eye causing it to become lazy or amblyopic. Some squints are not obvious to the observer and can only be diagnosed by special tests.
2. Poor vision in one eye (Refractive error)
A high proportion of children with amblyopia have eyes which look normal and appear to function normally, but they may be using one eye only. If the vision in one eye is much stronger than the other, the child habitually uses the good eye and suppresses the image from the weaker eye. Even when the refractive error in the weak eye is corrected with glasses, the eye often remains lazy and requires further treatment to overcome the amblyopia.
3. Organic Disease
This is not true amblyopia, but often appears to be, before a thorough examination is carried out. The most serious of the organic eye diseases is an eye tumour, and it is important to be sure that any child with defective vision of apparent squint is medically examined. The more serious causes of amblyopia are rare, but their possibility should never be overlooked.
Children are unaware of defective vision so routine examinations are important from an early age. The School Medical Service includes vision testing in its medical screening of school children. Any child with defective vision is referred to the General Practitioner (GP) for further investigation and treatment. But every child’s eyes should be checked before reaching school age. Parents should be aware of many characteristic actions that may indicate their child has a vision problem. They should consider it a warning if their child:
Rubs their eyes excessively
Closes or covers one eye when looking at an object
Tilts head forward when focusing his eyes, or has difficulty reading or in other efforts requiring close use of the eyes
Blinks more than usual or is irritable when doing close work
Parents should also notice if the child:
Trips over small objects
Holds books close to his eyes
Cannot participate in games requiring distance vision
Squints and frowns excessively
An involuntary turning in or out of one or both eyes at any age is an immediate problem urgently needing attention. A child will not outgrow crossed eyes.
There are three main methods of treating amblyopia. By far the most widely used is “patching”, or covering, the good eye to force the patient to use the amblyopic eye. Patching alone is often successful with children. In some instances, eyeglasses are prescribed to correct refractive errors. In others, muscle surgery may be necessary to correct the out-of-line amblyopic eye.
Orthoptics therapy retains the eyes to work together as a team by means of exercises. Some authorities believe there is no age limit for orthoptics treatment, but the therapy is most successful when the patient is treated at the earliest age possible, and preferably well before the age of seven.
Lazy eye or amblyopia often can be prevented by early detection and treatment of the conditions which cause it.
Every child should have a visual acuity test and a thorough eye examination before the fifth birthday.
Lazy eye or amblyopia should be treated promptly. The sooner the child receives proper treatment the better are his chances of regaining normal vision.
A child will not outgrow crossed eyes.
It is never too early to test a child’s eyes – it can easily be too late.
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