OP1.5 | Amblyopia: Types, Prevention and Refractive Treatment — Summary & Reflection

KEY TAKEAWAYS

Key takeaways — Amblyopia: Types, Prevention and Refractive Treatment:

• Definition: reduction in BCVA not explained by structural pathology; caused by abnormal visual experience during the critical period (birth–~7 years; max plasticity 0–3 years); cortical ocular dominance shift underpins the VA loss.

• Four types:
• Strabismic: constant unilateral squint → suppression; only constant squint (not alternating) causes amblyopia
• Anisometropic: significant refractive difference (≥2–3 D); no visible squint; most commonly missed type; needs cycloplegic refraction to detect
• Deprivation: most severe; congenital cataract/ptosis/corneal opacity; bilateral congenital cataract = ophthalmic emergency (surgery within weeks)
• Ametropic (isometropic): bilateral high uncorrected refractive error; bilateral amblyopia

• Diagnosis: inter-eye VA asymmetry ≥2 lines; VA does NOT improve with pinhole or spectacles; no RAPD (RAPD = organic disease, investigate before patching!); cycloplegic refraction mandatory in children.

• Treatment:
1. Always optical correction FIRST (spectacles) — reassess VA after 3–4 months
2. If VA remains reduced → patch the fellow/dominant eye (2 h/day near activities, PEDIG evidence) OR atropine penalisation (1%, daily or weekend dosing)
- Treatment most effective <7 years; limited after 12–14 years

• Prevention: school vision screening, VA testing in all children at health checks, red reflex examination in neonates, cycloplegic refraction when anisometropia is suspected.

REFLECT

Reflect using Kolb's experiential learning cycle:

Concrete experience: Preethi from the hook is 8 years old with anisometropic amblyopia (LE VA 6/60, cycloplegic refraction LE +4.50 D). After 4 months of spectacles, LE VA improves to 6/24. You initiate patching. At age 9, after 12 months of patching (2 h/day), LE VA is now 6/12 — no further improvement over the last two visits.

Reflective observation: VA has improved from 6/60 to 6/12 over a total of 16 months — a meaningful gain, but not 6/6. At age 9, with slowing improvement, what factors would you weigh in deciding whether to continue patching?

Abstract conceptualisation: Using the concept of the critical period and PEDIG trial data, explain why treatment at age 8 is less likely to achieve a final VA of 6/6 compared to treatment started at age 4. What is the biological basis for the decreased plasticity?

Active experimentation: The family asks whether there is a surgical option to improve Preethi's left eye vision. How would you explain the difference between correcting the refractive error (spectacles/surgery) and treating the amblyopia (patching)? What would you tell them about the likely final visual outcome and the importance of maintaining spectacle wear throughout adulthood?