Amblyopia is a childhood cause of visual impairment. It occurs due to abnormal visual development in early life, particularly the cortical visual pathway. It is often described as a ‘lazy eye’. This is because of underlying pathological processes causing the brain to ‘switch off’ visual signals to the brain in the weaker eye. Over time, the brain ignores the blurry images produced from the ‘bad’ eye and the visual pathway on that side becomes weaker. It typically manifests in one eye but can in rare cases occur bilaterally.
Aetiology
There are many causes of amblyopia including strabismus (misalignment of the eyes); significant refractive errors; as well as any anatomical interference to the visual pathway (e.g. cataract (opacification of lens)/ptosis (droopy eyelid). Strabismus is the most common cause of amblyopia; here, the brain stops visual processing in the out-turning eye to prevent the patient from seeing double or having ‘diplopia’.
Clinical features
- Squinting
- Shutting one eye
- Head tilting
- Reduced visual acuity on testing
- Reduced contrast sensitivity
Referral pathway
There is a referral pathway as part of the Royal College of Ophthalmologists screening initiative, occurring between the ages of 4-5 years old. This will prompt intervention and treatment. If there is any suspicion of squint/amblyopia in a clinical setting (e.g. GP/Paediatrics), a referral to Ophthalmology/Optometry as per symptoms and local guidelines should be considered.
Treatment
The aim of treatment is to support the development of the lagging eye. Always start with the least invasive options first, especially in children. It is particularly important to commence treatment within the so-called ‘plasticity window’, which has traditionally been thought of as ages up to 8-9 years old.
Options include:
- Glasses
- Patching (of the ‘good eye’) – to re-train the brain to use the ‘bad eye’.
- Often glasses and patching are used in combination
- Medical treatment options include atropine drops – for patients who are unable to patch/struggling with compliance
- Surgery (including cataract surgery in the first instance)
If conservative methods have failed, surgical options can be considered.
Options include strabismus surgery, or repair of ptosis (droopy eyelid).
Ensure to continue to monitor children after treatment to ensure adequate visual acuity in both eyes.
References
- American Association of Ophthalmology – Amblyopia – What is lazy eye?
- American Association of Ophthalmology – Webinar on Amblyopia
- American Association of Ophthalmology – Amblyopia Introduction
- Royal College of Ophthalmology – Diagnostic Pathway following Child Vision Screening
Written by Dr Shuchi Kohli (FY3) & Reviewed by Mr Ernest Lim (Ophthalmology ST5)
