medskl.com is a global, free open access medical education (FOAMEd) project covering the fundamentals of clinical medicine with animations, lectures and concise summaries. medskl.com is working with over 170 award-winning medical school professors to provide content in 200+ clinical presentations for use in the classroom and for physician CME.
Ophthalmology - Amblyopia
Whiteboard Animation Transcript
with Christine Law, MD
medskl.com/mod...
Amblyopia is a leading cause of vision loss in children and young adults. It is preventable and potentially reversible if detected early. Amblyopia is diagnosed when there is reduction in best-corrected visual acuity in one or, less commonly, both eyes due to abnormal development of visual pathways during infancy or childhood. It almost always occurs during the sensitive period of visual development, from birth until about 8 years of age.
There are three causes of amblyopia that you cannot miss.
Strabismic Ambylopia: Strabismus, or misalignment of the eyes, transmits a different retinal image to the brain causing the developing brain to suppress information from the less focused eye. Chronically reduced responsiveness to input by the nonfixing eye leads to visual suppression and vision loss.
Refractive Amblyopia: This cause of amblyopia can be subdivided into anisometropia, large difference in refractive error between eyes, and high bilateral refractive errors. Anisometropia is diagnosed when each eye has a different refractive power, which can result in one eye chronically transmitting an out-of-focus image to the visual cortex relative to the other eye. Again, the brain suppresses information from one eye to improve perception. With high bilateral refractive error, both eyes are equally out-of-focus and transmitting unclear images to the visual cortex. Unlike strabismic amblyopia, refractive amblyopia usually has an insidious course because it is rarely detected without targeted screening.
Visual Deprivation: In this case, a lack of retinal stimulation leads to underdevelopment of the corresponding visual cortex. Some causes of visual deprivation include congenital cataracts and a drooping eyelid, known as ptosis. Importantly, deprivation amblyopia can be bilateral if vision in both eyes is obscured.
The majority of children during the visual development period cannot recognize or articulate a decrease in vision in one of both eyes. Therefore it is imperative all children be screened for amblyopia at a young age. As a general practitioner, this should include:
A monocular visual acuity test
Evaluation for strabismus
Fundoscopy with a direct ophthalmoscope to identify any obvious ocular abnormalities.
Children with abnormalities on any screening test should be referred to a pediatric ophthalmologist for a thorough eye examination, including refraction, and treatment for amblyopia as needed.
1 май 2017
