Amblyopia is a visual impairment resulting from abnormal visual stimulation during early childhood, the prevalence of which ranges from 1% to 4%.
Can result from strabismus, form deprivation (e.g., due to congenital cataracts or corneal opacities), and various types of refractive errors. These errors include anisometropia (unequal refractive error between the two eyes), isoametropia (high but similar refractive error in the two eyes), and high astigmatism in one or both eyes.
Amblyopia due to strabismus with or without refractive error is commonly treated with initial optical correction, and subsequent patching or atropine penalization of the better-seeing eye. Amblyopia due to refractive error alone frequently responds to optical correction alone.
Amblyopia due to form deprivation is treated initially with early surgery, to remove the visual obstruction. In unilateral or asymmetric cases, patching of the better-seeing eye is necessary after surgery.
Treatment is highly successful when instituted during the infantile and preschool years, although some children as old as 13-17 years respond to treatment, particularly if there has been no prior therapy.
Amblyopia is a reduction of best corrected visual acuity (usually unilateral, but may be bilateral) that is not attributable solely to a structural abnormality of the eye or visual pathways. For the brain to learn to see with each eye, and to develop the capacity for binocular vision, each eye must have a clear and focused retinal image, and the two eyes must be aligned. Research has demonstrated that there are critical periods for the development of normal vision, and that amblyopia is associated with structural changes in the primary visual cortex.
History and exam
Key diagnostic factors
- infant not tracking parent's face
- abnormal red reflex
Other diagnostic factors
- subnormal visual acuity for age in one or both eyes
- asymmetric corneal light reflex
- unequal behavioral response to alternate eye occlusion
- abnormal cover/uncover testing
- blurred vision
- eye strain
- congenital nystagmus
- abnormal pupil exam
- abnormal external eye exam
- age <9 years
- strabismus (misalignment of the eyes)
- opacity in the cornea, anterior chamber, lens, vitreous, or retinal surface
- severe ptosis or prolonged occlusion of one or both eyes
- family history of amblyopia or strabismus
- hyperopic anisometropia (farsightedness with unequal refractive error between the 2 eyes) of >+1.50 diopter
- myopic anisometropia
- astigmatism (cylindrical, rather than spherical, defocus of the eye) >2.00 diopter
- hyperopia >+4.50 diopter
- myopia >-3.00 diopter
- developmental delay
1st investigations to order
- visual acuity tests (by specialist)
- stereopsis (perception of depth or 3-dimensionality) and binocular vision testing
- assessment of fixation, ocular alignment and ocular motility
- anterior segment exam using a slit lamp
- dilated fundoscopy
- cycloplegic retinoscopy
- binocular red reflex test (Brückner test)
- visual evoked potentials
without form-deprivation amblyopia
- Refractive error with no amblyopia
- Functional visual impairment
- Central nervous system pathology affecting visual pathways
- Vision rehabilitation preferred practice pattern
- Vision screening for infants and children
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