Biology Questions and Answers
object can be placed and its image is
still focused, i.e., maximum relaxation oit is the situation of the ciliary f
muscles. The zone between the near
point and the far point is called thaccommodation zone. e
- How can the visual
deficiencies known as myopia
and hypermetropia be
optically explained?
Myopia is ththe images are e visual conformed before (in frontdition in which (^)
of) the retina. Hypermetropia is the
visual conimage formation is bdition in which eyond (behind) thethe point of (^)
retina. Actually myopia is due to an
increase in retina and the crystallinethe distance b lens, maietween thenly (^)
caused by a slight flattening of the
eyeball. In hypermetropia ttoo close to the crystalline lens due tohe retina is
slight shortening of the eyeball.
In myopia the near point and the far
point of vision comrefractivity of the crystallinee closer (t lens thathe (^)
corresponds to the maximum distension
capacityenough to provide visual of the ciliary muscles is not
accommodation). In hypermetropia the
ciliary musclesmore to compensate th are not able to contracte inadequate
position of the retina, i.e., the near
point becomes more distant.
- What are presbyopia and
astigmatism?
Presbyopia is the visual impairment in
which thestrength thus reducing the capare is loss of the cililary musclebility of
the crystalline lens to adjust images of
near objects onto the retina. Inpresbyopia the near point of vision (^)
becomes more distant. The disease
generally occurs in old people.
Astigmatism is caused by irregular
shape of the refractive structures,mainly the cornea. In astigmatism (^) a
single object-point may produce more
than one image onto the retina anthe vision becomes distorted. d so
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