What is Amblyopia?
Amblyopia (“Lazy Eye”) is reduced vision in one or both eyes caused by inadequate stimulation of the visual processing system during childhood. It does not refer to reduced vision as a result of damage or irregularity in the eye, or the visual pathway in the brain, and cannot be corrected using glasses or surgery.
Causes of Amblyopia
Strabismus (ocular misalignment)- when a child’s eye is turning this often causes double vision as the eyes are misaligned and focussing on 2 different images. To eliminate this double vision the brain is often able to ignore and shut off the image from the turned eye. This is termed suppression. Prolonged suppression of the image from one eye results in reduced stimulation of visual processing from that eye and results in amblyopia.
Stimulus Deprivation- reduction of adequate visual stimulus to one or both eyes due to factors such as refractive error (longsight, shortsight, astigmatism), cataracts or ptosis (droopy eyelid). Once the depriving factor is removed or corrected, often the vision will improve but may not return to what is considered a normal level. This remaining reduced vision is amblyopia, caused by the reduced stimulus to the eye/s.
How is Amblyopia treated?
Unilateral Amblyopia (one eye)
Stimulus deprivation amblyopia is treated by prompt removal of the cause, such as glasses correction for refractive error, removal of cataracts or ptosis repair. Following this, patching therapy is often undertaken in which the stronger eye is covered for a number of hours per day, encouraging the weaker amblyopic eye to work and improve the visual processing from this eye.
Amblyopia caused by strabismus is treated first using glasses to correct refractive error if required, followed by patching therapy. Patching therapy is undertaken before any surgery is considered to correct eye misalignment as the improved vision may lead to a better control of eye alignment and/or surgical outcome.
The amount of patching per day and the duration of patching treatment is dependent on the child’s initial level of vision and visual improvement during therapy. It is ceased on the doctor’s advice once the vision has reached the desired level (often 6/6 or better) or there is no longer improvement with patching.
Bilateral Amblyopia (both eyes)
Bilateral amblyopia is rare and is most often caused by high refractive error in both eyes. If the vision is equal in both eyes, full time wear of refractive correction is the main treatment option. If the amblyopia is asymmetrical between the eyes some patching therapy may be used to strengthen the weaker eye.
Is there an alternative to patching?
Atropine eye drops can be used as an alternative to patching in particular cases. This involves the vision in the stronger eye being temporarily blurred by the drops, encouraging the weaker eye to work.
Not all children will benefit from the use of eye drops to treat amblyopia. This is dependent on their refractive error and the doctor will advise what the best course of treatment is for your child.
When should Amblyopia be treated?
Amblyopia should be treated as soon as it is detected to encourage the most improvement in vision and is considered most effective in children 8 years and younger. In older children improvements in vision may still be made with appropriate therapy but these improvements may not be as significant and slower.
What if Amblyopia is left untreated?
If amblyopia is left untreated, the vision in the affected eye/s will remain permanently decreased. This increases the likelihood of blindness and disability in later life if the good eye becomes injured or diseased.
How can Amblyopia be detected?
Reduced vision and amblyopia can be detected in children through observation of behaviour from parents and appropriate professional vision screening. If reduced vision is suspected at any age, your child should be taken to a paediatric ophthalmologist or orthoptist for examination. If you suspect your child of having strabismus (misaligned eyes), prompt review by a paediatric ophthalmologist is advised. It is recommended that all children undergo vision screening prior to commencing school, regardless of whether or not reduced vision is suspected.