Childhood amblyopia: current management and new trends

Abstract

Introduction or background: With a prevalence of 2-5%, amblyopia is the most common vision deficit in children in the UK and the second most common cause of functional low vision in children in low-income countries.

Sources of data: Pubmed, Cochrane library and clinical trial registries (clinicaltrials.gov, ISRCTN, UKCRN portfolio database).

Areas of agreement: Screening and treatment at the age of 4-5 years are cost efficient and clinically effective. Optical treatment (glasses) alone can improve visual acuity, with residual amblyopia treated by part-time occlusion or pharmacological blurring of the better-seeing eye. Treatment after the end of the conventional 'critical period' can improve vision, but in strabismic amblyopia carries a low risk of double vision.

Areas of controversy: It is not clear whether earlier vision screening would be cost efficient and associated with better outcomes. Optimization of treatment by individualized patching regimes or early start of occlusion, and novel binocular treatment approaches may enhance adherence to treatment, provide better outcomes and shorten treatment duration.

Growing points: Binocular treatments for amblyopia.

Areas timely for developing research: Impact of amblyopia on education and quality of life; optimal screening timing and tests; optimal administration of conventional treatments; development of child-friendly, effective and safe binocular treatments.

Keywords: amblyopia*/diagnosis; amblyopia*/therapy; child; humans; treatment outcome; vision screening; visual acuity.

Fig. 1

Children with amblyopia can have straight eyes (left, anisometropic amblyopia), strabismus (strabismic amblyopia) or both. Small degrees of strabismus can go unnoticed and may only be discovered by orthoptic assessment (centre). In the UK, commissioning of vision screening at primary school entry is variable (right); commissioning in England has recently changed from Clinical Commissioning Groups to Local Authorities, resulting in boundary changes and further development of local protocols. An updated map is currently in preparation. Purple: pre-school orthoptic-led and delivered with orthoptic assessment, pre-school in community clinics; yellow: orthoptic-led and delivered with orthoptic assessment, in school at age 4–5 years; blue: orthoptic-led, other profession delivered, visual acuity assessment in school at age 4–5 years; green: other profession-led and delivered, visual acuity assessment only in school at age 4–5 years; blue: orthoptic-led visual acuity assessment only; red: no primary screening commissioned; white: unknown, no response to British and Irish Orthoptic Society questionnaire

Fig. 2

Left: The visual acuity, measured on a logMAR chart, of an amblyopic eye is two or more lines (=0.20 logMAR, red line) less than the acuity in the better-seeing eye (green line: 0.00 logMAR, normal visual acuity expected from the age of around 6 years on a crowded logMAR test). Right: Here, the reader can simulate the effects of amblyopic vision on acuity and crowding, using their peripheral vision. By fixating on the innermost grey cross in the top row, the isolated Landolt-C element should be reasonably identifiable. The effect of acuity losses can be experienced by fixating the increasingly distant crosses (though the magnitude of losses will depend on viewing distance). Fixating the crosses in the lower row allows visualization of the effects of crowding. Here, the same Landolt-C is flanked to either side by ‘distractor’ elements. Where previously the isolated element was visible (e.g. when fixating the innermost cross), it should now be considerably more difficult to identify. Crowding can also be increased by fixating the more distant crosses and moving the central target further into peripheral vision.

Fig. 3

In 1583, Bartisch documented the first conservative treatment of strabismus; in 1839, Dieffenbach first published a surgical method. Glasses for children were introduced at the end of the 19th century (images of spectacles courtesy of the College of Optometrists, London). Current amblyopia treatment includes glasses, occlusion or pharmacological blurring of the better-seeing eye (atropine paralysis of the ciliary muscle/accommodation, with dilation of the pupil as associated effect), and occasionally strabismus surgery. Future treatment may involve binocular strategies balancing the input from the two eyes to the visual cortex.

Fig. 4

Current management of amblyopia in childhood (black) and areas of controversy (red).