Amblyopia or lazy eye
What is “lazy eye”?
“Lazy eye”, or amblyopia, is caused by low vision in one or both eyes due to lack of use during a child’s visual development (approx. before the age of eight). It is a disorder that originates in childhood, but can continue into adulthood, if it is not diagnosed and treated early.
What causes it?
The main causes are:
Strabismus: when the eyes are misaligned and point in different directions, the child’s brain, which has a great ability to adapt, suppresses vision in one eye to counter the abnormality and prevent double vision.
Refractive error: when a child has hyperopia, astigmatism or myopia, the image that reaches the brain lacks sharpness, resulting in the brain selecting the vision of the eye with less refractive error.
Cataracts, ptosis (drooping eyelid), retinal diseases: other diseases that interfere with the proper development of vision in children.
How can it be prevented?
All children should undergo an ophthalmic examination to detect for amblyopia before the age of three. Early diagnosis is vital to ensure that “lazy eye” is treated properly and to prevent the condition from continuing into adulthood.
A paediatric ophthalmologist can perform an examination to detect for this disorder at any age, however small and uncooperative the child.
Parents, teachers or caregivers may suspect that the child has abnormal vision in the following types of circumstances:
Family members cannot easily be identified over long distances.
Objects need to be held close to the eyes.
One eye deviates.
In most cases, as the child can see well with the good eye, normal development occurs, with the amblyopia remaining present until a routine eye test by a paediatrician, optician or ophthalmologist detects the problem
The treatment consists of ocular protection with sunglasses, eye drops and the application of botulinum toxin (a substance which is injected to temporarily relax the muscles and prevent them from contracting).
Although it is 90% effective, in the most severe cases, recourse to surgery called myectomy of the orbicularis muscle and the depressor muscle is required. The surgery involves the partial or complete removal of fibres from one of the muscles in the upper eyelid to prevent it from continuing to close involuntarily.
- Botulinum toxin
What is lazy eye (amblyopia)?
The amblyopic eye has not developed vision correctly, but all eye structures are in good condition. Vision develops from birth, and the eye becomes increasingly more capable of perceiving objects, which is called visual acuity. The amblyopic eye does not develop visual acuity for various reasons. The eye is anatomically correct, i.e. its structures are normal, but vision has not developed.
When is an ocular occlusion used?
Ocular occlusion is used to make the diseased eye work harder by patching the healthy one, as in amblyopia. The intensity of the patching of the good eye to develop the vision of the amblyopic eye depends on the degree of vision and the age of the patient.