Amblyopia

What is amblyopia?

Amblyopia is reduced vision in an anatomically normal eye. The term "lazy eye" is used to describe it.

When does amblypia develop?

Amblyopia develops when any of the following conditions occur:

• Squint/Strabismus (eyes not positioned straight)
• There is a difference in power between the two eyes (one eye focuses differently from the other)
• Cataract (clouding of the lens)
• High or moderate power in both eyes
• Severe ptosis (droopy eyelids)

Children under 9 years of age whose vision is still developing are at the highest risk for amblyopia. Generally, the younger the child is, greater is the risk.

Why does amblyopia develop?

Amblyopia develops because when one eye is turned, as in squint, two different pictures are sent to the brain. In a young child, the brain learns to ignore the image of the deviated eye and see only the image of the better eye. Similarly when there is difference in power between the two eyes, the blurred image formed by the eye with greater power is avoided by the brain. In order that the retina may capture an object, it needs adequate light and visual stimulus. When these factors are absent, as in the presence of cataract, amblyopia results. A moderate or high degree of refractive power present in both eyes, when not corrected early and adequately, also results in amblyopia.

What should be done?

Amblyopia can often be reversed if it is detected and treated early. Cooperation of the patient and parents is required to achieve good results. If left untreated or if not treated properly, the reduced vision or amblyopia becomes permanent and vision cannot be improved by any means.

How is amblyopia treated?

The most effective way of treating amblyopia is to make the child use the amblyopic eye. Covering or patching the good eye to force the use of the amblyopic eye may be necessary to ensure equal and normal vision. This can be achieved by:

• prescribing proper spectacles if the patient is found to have refractive error
• removal of cataract when indicated
• occluding the normal eye
• surgery, when amblyopia is accompanied by strabismus

Occlusion refers to closure of the normal eye with a patch, thus forcing the child to use the amblyopic eye. Occlusion is done from a few hours to a few days, depending upon the age of patient and the type and severity of amblyopia. In cases experiencing less severe amblyopia, partial occlusion, such as that by making one glass translucent, may be sufficient. Older children can do reading exercises at home while patching the normal eye. Those patients who are patching their eyes need periodic follow-up, which is scheduled with an ophthalmologist. Duration of treatment may extend from months to years. The ophthalmologist will decide for how long the occlusion should be continued. Loss of vision from amblyopia is preventable if treatment is begun early.

Facts on Patching

• Patching is not a pleasant thing for a child, so initially the child will be reluctant to undergo it. It is our duty to make the child understand the necessity of the procedure so that he/she will cooperate.
• In a young child patching is done for shorter periods initially; the duration is increased gradually to obtain better compliance.
• Acceptance is good as soon as vision is increased in ambloypic eye.

Method of patching should be according to the interests of the child

• Patch should be stuck directly on the face over the eye.
• If the child wears glasses, the patch should be placed on the face, not on the glasses.
• Glasses can also be used as an occluder only in older children.
• Many children try to take the patch off. This problem usually disappears as the child grows accustomed to wearing the patch.
• Older children can be encouraged to read and young children can be involved in playing interesting games during patching.
• Precautions must be taken to prevent the child from peaking around the edge of the patch.
• Patching schedules should be followed strictly.
• Patching should not be stopped abruptly. The programme should be tapered only by ophthalmologists.
• Regular follow-up visits are a must.

Source : Arvind Eye care system