Amblyopia or lazy eye syndrome is one of the common ophthalmic conditions found in children. It develops during early childhood. Following article provides the basics and detection strategies of amblyopia for pediatricians.
Amblyopia is a functional reduction in visual acuity that is caused by abnormal visual development early in life. It is the most common cause of pediatric visual impairment, occurring in 1 to 4 percent of children around the globe. Early detection and treatment of amblyopia improve visual outcomes.
Amblyopia is generally unilateral, meaning most of time only one eye gets affected. It also shows very close association with impaired or absent depth perception (stereoacuity).
Two common types of amblyopia are:
Unilateral amblyopia: which is defined as ≥2-line difference in visual acuity between eyes.
Bilateral amblyopia: which is defined as visual acuity worse than 20/40 in either eye (in children ≥4 years) or visual acuity worse than 20/50 in either eye (in children ≤3 years).
The classification under the above mentioned types is not so straightforward in pediatric patients using traditional methods. Most of the guidelines recommend complete eye examination by an ophthalmologist.
Classification of Amblyopia:
The classification of amblyopia is done on the basis of the cause of a visual disturbance. The classification is as following:
Strabismic amblyopia: It is caused by an abnormal alignment of the eyes. It results from abnormal binocular interactions. It is most common type found in about 50% percent of cases.
Refractive amblyopia: It is caused by unequal focus between two eyes. It is also known as anisometropic amblyopia. In this condition foveas of two eyes are presented with different image clarity. It is found in approximately 15-20% of the cases.
Deprivational amblyopia: It is caused due to structural abnormalities of the eye those inhibit clear image reception. It is found in less than 5% of the cases.
In many patients (about 30% cases) combination of both strabismic and refractive amblyopia is found.
How Can Pediatricians Detect Signs of Amblyopia?
Pediatricians and family physicians are first in line for consultation for almost all the symptoms presented by a child. Pediatricians can suspect amblyopia if they find vision in the two eyes unequal. The testing used to diagnose amblyopia depends upon the age of the child. In preverbal children, asymmetry of vision may be indicated by an abnormal fixation reflex or occlusion objection test. In older children, asymmetric vision is detected through formal visual acuity testing.
What are the Referral Indications for Amblyopia?
The pediatricians or family physicians should refer their patients to ophthalmologists experienced in pediatric patients if following symptoms are found.
Visual acuity worse than 20/40 in a child three to five years of age or worse than 20/30 in a child ≥6 years
Visual acuity difference of ≥2 lines between eyes
Abnormal ocular alignment (i.e. strabismus)
Abnormal red reflex)
Asymmetry of vision (eye preference)
Unilateral ptosis or other lesions obstructing the visual axis (e.g. eyelid hemangioma)
Alternative causes of reduced visual acuity should be considered in children with apparent amblyopia who do not have an associated amblyogenic condition (i.e. strabismus, refractive error, or structural obstruction of the visual pathway).
Alternative causes of vision loss should also be considered if a child with amblyopia fails to demonstrate improvement in visual acuity despite adherence to the treatment regimen prescribed by an ophthalmologist.
Our upcoming article will focus on the differential diagnosis and management of amblyopia in children.
Williams, C.; Northstone, K.; Harrad, K. A.; Sparrow, J.M.; Harvey, I.; Alspac Study, Team (2002). “Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial”. BMJ.
Solebo A.L., Cumberland P.M., Rahi J.S.,”Whole-population vision screening in children aged 4-5 years to detect amblyopia”. Lancet 2015.
Journal of Pediatric Ophthalmology and Strabismus.