| Written by: Md Oliullah Abdal, Clinical Optometrist & COO, Bynocs
| Medically reviewed by: Dr. Gul J. Nankani, Ophthalmologist & Founder, Bynocs
| Originally published: 16 August 2021
| Last updated: 29 September 2026 | 8 min read
| Quick answer: The three main types of amblyopia are strabismic (caused by misaligned eyes), refractive (caused by unequal or high prescriptions) and deprivation (caused by something blocking vision). Doctors also classify amblyopia by severity — mild, moderate or severe — and by whether it affects one eye or both. The type guides the treatment plan. |
How do doctors classify amblyopia?
Amblyopia (lazy eye) is reduced vision that develops when the brain does not learn to use one or both eyes properly in early childhood (National Eye Institute). Eye care professionals describe it in four ways:
- By cause — what disrupted normal visual development
- By severity — how much vision is reduced
- By laterality — one eye (unilateral) or both eyes (bilateral)
- By treatment status — new, residual or recurrent
If you want a simple explanation of the root causes and risk factors first, read what causes a lazy eye. This guide goes deeper into how each type is defined and managed.
Types of amblyopia by cause
Strabismic amblyopia
Caused by strabismus (a squint), where one eye turns in, out, up or down. The brain suppresses the turned eye to avoid double vision. It usually affects one eye and may be noticed as a visible eye turn.
Refractive amblyopia
Caused by blurred focus. It has three subtypes:
- Anisometropic amblyopia — one eye has a much stronger prescription than the other, so it sends a blurrier image. The eyes look normal, which is why it is often found late.
- Isoametropic (bilateral refractive) amblyopia — both eyes have high, uncorrected prescriptions, so both develop reduced vision.
- Meridional amblyopia — caused by uncorrected astigmatism, which blurs lines in certain directions.
Deprivation amblyopia
Caused by something that blocks light from reaching the back of the eye early in life, such as a congenital cataract, a droopy eyelid (ptosis) covering the pupil, or corneal scarring. It is the least common type but the most urgent, and it can affect one or both eyes (AAO).
Mixed amblyopia
Some children have both strabismus and a prescription difference. This combined type may need more than one treatment approach.
Types of amblyopia at a glance
| Type | Cause | Eyes Usually Affected | How It’s Often Found | Usual First Steps in Treatment |
|---|---|---|---|---|
| Strabismic | Eye misalignment (squint) | One | Visible eye turn | Glasses if needed, then patching, drops or binocular therapy; surgery for large turns |
| Anisometropic | Big prescription difference | One | Eye test or screening | Full-time glasses first, then patching, drops or binocular therapy |
| Isoametropic (Bilateral) | High prescription in both eyes | Both | Eye test; child may sit close to screens | Glasses, often with gradual improvement over months |
| Meridional | Uncorrected astigmatism | One or both | Eye test | Glasses correcting astigmatism |
| Deprivation | Cataract, ptosis or scar blocking vision | One or both | Abnormal red reflex, white pupil, droopy lid | Urgent removal of the cause, then vision rehabilitation |
| Mixed | Strabismus + prescription difference | One | Eye turn plus eye test | Combination of the above |
Note: Treatment depends on the type, severity and age of the patient. A comprehensive eye examination is necessary to determine the appropriate treatment plan. Signs such as a white pupil or abnormal red reflex require urgent medical evaluation.
What is the most common type of amblyopia?
Refractive (anisometropic) and strabismic amblyopia — or a mix of the two — make up the large majority of cases. Deprivation amblyopia is rare. Globally, about 1.44% of children have amblyopia (Fu et al., British Journal of Ophthalmology, 2020).
Types of amblyopia by severity
Severity is based on the best-corrected visual acuity in the weaker eye. Exact cut-offs vary slightly between studies, but these ranges are commonly used:
| Severity | Weaker-Eye Vision (Feet) | Weaker-Eye Vision (Metres) | What It Means |
|---|---|---|---|
| Mild | 20/30 to 20/40 | 6/9 to 6/12 | Slight blur; often found only on testing |
| Moderate | 20/50 to 20/100 | 6/15 to 6/30 | Clear difference between the eyes; the most-studied group in trials |
| Severe | 20/125 or worse | 6/38 or worse | Large loss of vision in the weaker eye; usually needs more intensive treatment |
Note: Severity is based on best-corrected visual acuity. Classification thresholds may vary between clinical studies. An eye care professional should evaluate visual acuity and recommend appropriate treatment.
Large trials by the Pediatric Eye Disease Investigator Group (PEDIG) used severity to set treatment dose — for example, 2 hours of daily patching for moderate amblyopia (AAO — PEDIG studies).
Unilateral vs bilateral amblyopia
- Unilateral amblyopia affects one eye. It is the most common form and is usually caused by strabismus, anisometropia or one-sided deprivation.
- Bilateral amblyopia affects both eyes. It usually results from high uncorrected prescriptions in both eyes or from bilateral cataracts. Because both eyes are affected, treatment focuses on correcting the prescription or removing the cause, rather than patching one eye.
Residual and recurrent amblyopia
- Residual amblyopia — vision improves with treatment but then stops improving before it matches the other eye. Binocular (dichoptic) therapy is one option clinicians use for residual amblyopia.
- Recurrent amblyopia — vision slips back after treatment stops. PEDIG research showed recurrence is common in the first year, which is why doctors often taper treatment gradually and schedule follow-ups.
Symptoms by type
Many children with amblyopia have no complaints — they do not know their vision is different. Signs vary by type:
- Strabismic: an eye that turns, especially when tired; closing one eye in bright light
- Refractive: squinting, sitting close to the TV, tilting the head, poor depth judgement
- Deprivation: a white or cloudy pupil, a droopy eyelid, or an abnormal red-eye reflection in photos
- All types: bumping into things on one side, difficulty with ball games, poor school screening results
How is the type of amblyopia diagnosed?
A comprehensive eye exam checks vision in each eye, eye alignment (cover test), an accurate prescription with dilating drops (cycloplegic refraction), the health of each eye and how well both eyes work together. The combination of findings tells the doctor the type, severity and laterality. See what to expect at a comprehensive eye exam.
Treatment timelines by type
- Refractive amblyopia: glasses alone may improve vision over the first few months; further treatment is added if vision plateaus.
- Strabismic amblyopia: often needs glasses plus patching, drops or binocular therapy; eye-muscle surgery may straighten the eyes but does not treat the vision loss on its own.
- Deprivation amblyopia: the cause (e.g. cataract) must be treated quickly, followed by months of vision rehabilitation.
- Residual amblyopia: binocular therapy can target suppression that patching did not resolve.
Treatment works best in early childhood, but improvement is also possible in older children and adults (Tsirlin et al., 2015). Compare options in vision therapy games vs patching and read about new developments in lazy eye treatment.
Questions to ask after an amblyopia diagnosis
- Which type of amblyopia is it — strabismic, refractive, deprivation or mixed?
- How severe is it, and what is the vision in each eye?
- Does it affect one eye or both?
- What is the first step, and when will we review progress?
- What vision goal is realistic for this type and age?
- What signs of recurrence should we watch for after treatment ends?
Writing down the answers helps you track progress and compare notes at each follow-up.
Where Bynocs fits in
Bynocs is a cloud-based dichoptic therapy used by eye care professionals for refractive, strabismic and residual amblyopia once any blur is corrected. Patients play prescribed games with special glasses, typically around 30 minutes a day, and the clinician tracks progress online. A peer-reviewed study of 161 children with anisometropic and isometropic amblyopia reported significant vision improvement with the platform (Abdal et al., Brain Sciences, 2022). Explore lazy eye treatment for kids or lazy eye treatment for adults, and read adult lazy eye treatment options.
PERSONALISED AMBLYOPIA CARE
Know the Type — Then Choose the Right Plan
Not all types of amblyopia need the same treatment. A binocular vision assessment at a Bynocs partner clinic can help identify the type and severity of amblyopia and determine whether dichoptic therapy may be suitable for you or your child.
Book an Amblyopia Assessment →Professional eye evaluation | Personalised treatment guidance
Frequently Asked Questions
What are the 3 types of amblyopia?
The three main types are strabismic amblyopia (from misaligned eyes), refractive amblyopia (from unequal or high prescriptions) and deprivation amblyopia (from something blocking vision, such as a cataract). Some children have a mixed type.
What is the most common type of amblyopia?
Refractive (anisometropic) and strabismic amblyopia, or a combination of both, account for most cases. Deprivation amblyopia is the least common.
Which type of amblyopia is the most serious?
Deprivation amblyopia is usually the most urgent, because blocked vision in infancy can cause significant vision loss quickly. The cause, such as a congenital cataract, needs prompt treatment.
Can amblyopia affect both eyes?
Yes. Bilateral amblyopia can occur when both eyes have high uncorrected prescriptions or when both are affected by a problem such as cataracts. It is treated mainly by correcting the prescription or removing the cause.
What is residual amblyopia?
Residual amblyopia is when vision improves with treatment but stops improving before it matches the other eye. Clinicians may change the treatment plan, for example by adding binocular or dichoptic therapy.
What is meridional amblyopia?
Meridional amblyopia is a refractive type caused by uncorrected astigmatism in early childhood, which blurs lines in certain orientations. It is usually treated with glasses that correct the astigmatism.
Can anisometropic amblyopia be treated in adults?
Improvement is possible for many adults with modern binocular and perceptual-learning therapies, although results are usually smaller and less predictable than in young children. An assessment helps set realistic goals.
Sources
- National Eye Institute — Amblyopia (lazy eye)
- American Academy of Ophthalmology — What is amblyopia?
- Fu Z, et al. Global prevalence of amblyopia and disease burden projections through 2040. British Journal of Ophthalmology, 2020.
- American Academy of Ophthalmology — PEDIG studies and amblyopia treatment
- Tsirlin I, et al. Behavioral training as new treatment for adult amblyopia: a meta-analysis. IOVS, 2015.
- Abdal MO, et al. Evaluation of the efficacy of a new dichoptic digital platform to treat anisometropic and isometropic amblyopia. Brain Sciences, 2022.
Medical disclaimer: This article is for general education and does not replace a consultation with a qualified eye care professional.