So, if the near point of an emmetrope is at 25 cm from the spectacle plane, the amplitude of accommodation is equal to − [−1/(25 ✕ 10)] = 4 D.
Accommodation is achieved by changing the degree of curvature of the internal crystalline lenses of the eyes.
In youth, these are naturally elastic and become more curved when the pull on the ligament by which they are suspended is reduced by contraction of the surrounding muscle ring (CILIARY MUSCLE). The elasticity of the lenses drops progressively with age so the power of accommodation lessens.
Consequently, myopes require more accommodation and hyperopes less accommodation when they transfer from spectacles to contact lenses.
However, this change in accommodative demand is accompanied by a similar change in convergence, so that a myope transferring to contact lenses accommodates and converges more than with spectacles and the reverse applies for a hyperope. See far point sphere.ill-sustained accommodation See accommodative insufficiency.inert accommodation See accommodative infacility.insufficiency of accommodation See accommodative of accommodation 1.
In the learning theory of Jean Piaget, the process through which a person's schema of understanding incorporates new experiences that do not fit existing ways of understanding the world.