what is presbyopia
Presbyopia is the loss of the eye's ability to change focus to see near objects. The ability of the eye lens to adjust its focal length according to the object distance is called power of accommodation. Presbyopia is associated with aging. The ciliary muscles gradually lose their elasticity and this makes it difficult for old people to focus on nearby objects.
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in old age due to weakening of cilliary musceles..n loosening of the flexiblty of the eye.....if a person is not able to view near-by objects clearly then hes said to hv this defect PRESBYOPIA..
in this defect near point of a person extends ie..it is more than 25cm. the image in this defect is formed behind the retina.. for correction the person needs to hv CONVEX LENS which again puts the image on the retina..n the person hs no more problems of vision....
hope this helps..!!!:)
Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age. loss of elasticity of the crystalline lens, although changes in the lens's curvature from continual growth and loss of power of the ciliary muscles (the muscles that bend and straighten the lens) have also been postulated as its cause. Like gray hair and wrinkles, presbyopia is a symptom caused by the natural course of aging. The first signs of presbyopia--eyestrain, difficulty seeing in dim light, problems focusing on small objects and/or fine print--are usually first noticed between the ages of 40-50
The power of accomadation of the eye usually decreases with ageing . For most people ,the
near point gradually recedes away .They find it difficult to see nearby objects comfortably
and distinctly without corrective eye-glasses .This defect is called Presbyopia . It
arises due to the gradual weakening of of the ciliary muscles and the diminishing
flexibility of the eye lens. the bio focal lenses consists of both concave and convex lenses . The
upper portion consists of concave lens . It facilitates distant vision vision .The lower part consists of
convex lens that facilitates near vision ....
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