Amblyopia refers to reduced vision in one or both eyes caused by visual deprivation. Normal vision develops in the first years of life and if there is any interruption in this process such as the development of strabismus “squint”, optical defocusing or cataract amblyopia will occur.
What is Amblyopia?
Amblyopia is reduced vision in one or both eyes caused by abnormal visual development in childhood. Even with glasses the eye is unable to see clearly. It is often treatable with glasses and patching. The term “lazy eye” is often used to describe amblyopia. Amblyopia affects 2% – 4% of all children. There is frequently a family history of amblyopia or strabismus in the family. Amblyopia may be mild or moderate or severe.
What Causes Amblyopia?
The causes are varied and include: Strabismus (crossed eyed squint). This is a misalignment of the eyes, i.e one eye is oriented straight ahead and the second is pointed towards the nose (inwards) or the temple (outwards). When the eyes are not aligned, the child’s brain will often use the correctly aligned eye to see with and the other will be “shut off” or “suppressed”. This prevents the child from seeing two images. The eye that is crossed is therefore not used and the part of the brain dedicated to vision in this eye becomes dormant and amblyopia develops. Anisometropia. This refers to an unequal optical focusing power of each eye.
The eye with the most defocused image is used less and amblyopia can develop. This is treated with glasses and occasionally patching. This type of amblyopia often responds well to treatment. Visual deprivation. Any condition that blocks light getting into the back of the eye and stimulating the retina (the photographic camera at the back of the eye) can cause amblyopia. Such conditions include congenital cataracts, corneal opacities or droopy eyelids (ptosis). Even if the underlying disease is corrected with the appropriate surgery, amblyopia may persist.
How is Amblyopia detected?
The presence of strabismus (squint) or a droopy eyelid will often be associated with amblyopia and needs an examination by an ophthalmologist. Amblyopia however may not be obvious if the child’s external eye appearance is normal and is only detected by visual acuity testing of each eye separately.
Making the diagnosis
The ophthalmologist performs all of the necessary tests to confirm that your child has amblyopia. Vision testing is accomplished with the appropriate methods for your child’s age. An examination with eye drops that dilate the pupils is generally performed. This permits an evaluation of the internal ocular structure and allows a determination as to whether or not there is a need for eyeglasses.
Treatment may consist of glasses, patching and occasionally surgery depending on your child’s individual condition.