Amblyopia, or lazy eye, is a disorder of the eye. It is characterised by poor or blurry vision in an eye that is otherwise physically healthy and normal. The problem is caused by either no transmission or poor transmission of the visual image to the brain for a sustained period of dysfunction or disuse during early childhood. The condition will only arise at this young age because most of the visual system's development in humans is complete and "locked in" by a few years of age. more...
Amblyopia normally only affects one eye, but it is possible to be amblyopic in both eyes if both are similarly deprived of a good, clear visual image.
Amblyopia affects 2-5% of the population. Amblyopia is a developmental problem in the brain, not an organic problem in the eye. The part of the brain corresponding to the visual system from the affected eye is not stimulated properly and develops abnormally. This has been confirmed in brain specimens.
Many children who have amblyopia, especially those who are only mildly amblyopic, are not even aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. However, people who have severe amblyopia may experience associated vision disorder, most notably poor depth perception.
Amblyopia can be caused by deprivation of vision early in life, or by strabismus (misaligned eyes), vision obstructing disorders and anisometropia (different degrees of myopia or hyperopia in each eye).
Strabismus, sometimes known as lazy eye, will result in normal vision in the fixating eye, but abnormal vision in the strabismic eye due to the brain discarding certain information. Strabismus usually develops into double vision (diplopia) in adulthood, 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, getting rid of the double vision. This plastic response of the brain, however, interrupts the brain's normal development, resulting in the amblyopia.
Strabismic amblyopia is best treated by treating the strabismus through the use of prescription glasses, vision therapy, surgery or patching.
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. Refractive amblyopia 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.
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