what type of a defect that you will get when the ability of accomodation will come down?define it
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Answer:
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies. In this, distances vary for individuals from the far point—the maximum distance from the eye for which a clear image of an object can be seen, to the near point—the minimum distance for a clear image. Accommodation usually acts like a reflex, including part of the accommodation-vergence reflex, but it can also be consciously controlled. Mammals, birds and reptiles vary their eyes' optical power by changing the form of the elastic lens using the ciliary body (in humans up to 15 dioptres). Fish and amphibians vary the power by changing the distance between a rigid lens and the retina with muscles.[1]
Minimum (top) and maximum accommodation (bottom).
Duane's classical curves showing the amplitude or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown.[2]
The young human eye can change focus from distance (infinity) to as near as 6.5 cm from the eye.[3] This dramatic change in focal power of the eye of approximately 15 dioptres (the reciprocal of focal length in metres) occurs as a consequence of a reduction in zonular tension induced by ciliary muscle contraction. This process can occur in as little as 224 ± 30 milliseconds in bright light.[4] The amplitude of accommodation declines with age. By the fifth decade of life the accommodative amplitude can decline so that the near point of the eye is more remote than the reading distance.