However, it is accepted that loss of elasticity of the crystalline lens and loss of power of the ciliary muscles
(the muscles which bend and straighten the lens) are involved.
The focusing muscle, however, requires the availability of chromium and supporting nutrition to potentiate the uptake of adequate glucose fuel to power the ciliary muscles
inside the eye.
Positive accommodation refers to the time required for the ciliary muscle
to contract sufficiently to change the focus from distance vision to close-up or near vision.
59) Furthermore, the contraction of the chick ciliary muscle
and thus accommodation in the chick is not affected by atropine administration.
This results in a reduction of baseline ciliary muscle
length which is associated with both lens growth and increasing age.
AcrySof(R) ReSTOR(R) IOL does not rely on the ciliary muscle
, which weakens with age, to enable the eye to quickly change focus to see objects at near, intermediate and far distances.
AIOLs rely on the continued function of the ciliary muscle
with advancing age and are designed to change their power in response to physiological changes occurring in the accommodative structures.
Anterior/posterior lens movement: The primary mechanism of accommodation, resulted, as intended in the crystalens' design, from contraction of the eye's natural ciliary muscle
to which the crystalens is attached; Accommodative arching: The flexing of the lens that results in refractive power changes and provided a secondary, additive effect to the crystalens' natural focusing ability -- the first time scientific data have confirmed this hypothesis; and Sustained accommodative effect: No significant differences in near and distance visual acuities were reported between one- and three-year intervals among subjects in the clinical trial that led to FDA approval of the crystalens.
The FocusIOL and FlexOptic lenses are designed to mimic the qualities of the eye's natural crystalline lens by accommodating in response to changes in the eye's natural ciliary muscle
Anatomical and physiological mapping studies in primates suggest that neurons of the anteromedian nucleus are principally concerned with accommodation via connections with autonomic neurons of the ciliary ganglion whose post-ganglionic axons innervate the ciliary muscle
, whereas the Edinger Westphal nuclei supply other ciliary ganglion cells mediating pupillary constriction.
Zonules are the small fibers that work in conjunction with the ciliary muscle
to adjust the shape of the crystalline lens.
Many studies have shown the ciliary muscle
retains its functional ability in presbyopia, the loss of accommodation being due to increasing lens rigidity.
The IOL designs by AMO and Quest Vision are designed to mimic the qualities of the eye's natural crystalline lens by accommodating in response to changes in the eye's natural ciliary muscle
Early in his research, Cumming noted that the ciliary muscle
in the eye did not stop functioning in older patients.
The complication is thought to arise as a result of thermal injury to the short ciliary nerve, causing parasympathetic denervation of the ciliary muscle