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Amblyopia can be caused by deprivation of vision early in life, or by strabismus (misaligned eyes), vision-obstructing disorders, or anisometropia (different degrees of myopia or hyperopia in each eye).
Strabismic amblyopia
Strabismus, sometimes known as lazy eye, usually results in normal vision in the fixating eye, but abnormal vision in the strabismic eye due to the brain receiving poorer quality input from that eye during development. Adult-onset strabismus usually causes double vision (diplopia), since the two eyes are not fixated on the same object. Children's brains, however, are more plastic, and therefore can more easily adapt by ignoring images from one of the eyes, eliminating the double vision (suppression). This plastic response of the brain, however, interrupts the brain's normal development, resulting in the amblyopia.
Strabismic amblyopia is treated by clarifying the visual image with glasses, and/or encouraging use of the amblyopic eye with patching or pharmacologic penalization (usually employing atropine drops to the dominant eye). The ocular alignment itself may be treated with surgical or non-surgical methods, depending on the type and severity of the strabismus.
Refractive or anisometropic amblyopia
If anisometropia is present, refractive amblyopia may result. Anisometropia exists when there is a difference in the refraction between the two eyes. The eye with less refractive error provides the brain with a clearer image, and is favoured by the brain. Those with this condition are more susceptible to the development of amblyopia, which may be as severe as strabismic amblyopia. Despite its severity, refractive amblyopia is commonly missed by primary care physicians because of its less dramatic appearance and lack of obvious physical manifestation, such as with strabismus.
Refractive amblyopia is diagnosed when there is a wide disparity in visual acuity between the two eyes. It is treated by correcting the refractive error early with prescription lenses. Vision therapy and/or eye patching can also be used to develop and/or improve visual abilities, binocular vision, depth perception, etc.
Meridional amblyopia is a condition in which an individual who had an astigmatism at a young age that was not corrected by glasses will later have astigmatism that cannot be optically corrected.
Form-deprivation and occlusion amblyopia
Form-deprivation amblyopia (Amblyopia ex anopsia) results when the ocular media is opaque, such as is the case with cataracts or corneal scarring from forceps injuries during birth. These opacities prevent adequate sensory input from reaching the eye, and therefore disrupt visual development. If not treated in a timely fashion, amblyopia may persist even after the cause of the opacity is removed. Sometimes, drooping of the eyelid (ptosis) or some other problem causes the upper eyelid to physically occlude a child's vision, which may cause amblyopia quickly. Occulsion amblyopia may be a complication of a hemangioma that blocks some or all of the eye.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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