why is image magnified by 30 ℅ with use of spectacles during aphakia?
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Answer:
Aphakia is a condition in which crystalline lens of the eye is not present in its normal position of pupillary area. Either there is no crystalline lens inside the eye or the lens is subluxated or luxated. This induces a refractive state which is not a refractive error in true sense. An emmetropic (normal refraction) eye or one having low grade ametropia (refractive error) becomes extremely hypermetropic after cataract surgery. A previously emmetropic eye requires a correction of about 10 to 11 dioptres (D) in spectacle when worn in the usual position.
Replacement of the crystalline lens with a spectacle lens causes the image on patient’s retina to be roughly 25% larger than the image formed with the crystalline lens. The exact magnification is determined by the power of the aphakic spectacles. There is about 2 % of magnification for each dioptre of power in the spectacles
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Aphakia
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Not to be confused with Aphagia or Aphasia.
Aphakia is the absence of the lens of the eye, due to surgical removal, such as in cataract surgery, a perforating wound or ulcer, or congenital anomaly. It causes a loss of accommodation, high degree of farsightedness (hyperopia),[1] and a deep anterior chamber. Complications include detachment of the vitreous or retina, and glaucoma.
Aphakia
Specialty
Ophthalmology
Babies are rarely born with aphakia. Occurrence most often results from surgery to remove congenital cataract. Congenital cataracts usually develop as a result of infection of the fetus or genetic reasons. It is often difficult to identify the exact cause of these cataracts, especially if only one eye is affected.
People with aphakia have relatively small pupils and their pupils dilate to a lesser degree.[2]
Causes
Signs and symptoms
Treatment
Etymology
References
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Last edited 28 days ago by Rdp060707
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