Abstract

The crystalline lens of the human eye acts, along with the cornea, to focus an image on the retina. The cornea provides most of the eye's overall power in a fixed refractive contribution, while the lens acts in a secondary capacity, providing a variable refractive contribution that allows focus from the eye's far point to a near point which is age-dependent. The lens's ability to provide this supplementary refractive capacity is due to changes in its axial thickness, surface and internal curvature, and to shallowing of anterior chamber depth; these changes are controlled by changes in the degree of contraction of the surrounding ciliary muscle, the change in force of which is transferred to the lens through the zonular apparatus. As humans age, the location of the nearest comfortable point of focus gradually recedes, leading eventually to a coincidence of the near and far point, disregarding depth of focus, which necessitates optical prostheses [1,2].

© 1998 Optical Society of America