THE ZOOMING EYE LENS: Effects of Age on Dynamic Range of Focus

DYNAMIC RANGE OF FOCUS (DRoF), or the total range of clear vision in a natural system, is an important biomechanical function of the accommodative apparatus responsible for adjusting the crystalline lens from both far to near (accommodation) and near to far (disaccommodation). DRoF is defined by true accommodation, pseudoaccommodation, and pupillary diaphragmatic changes, which work together biomechanically to selectively focus at various distances upon a neuromuscular stimulus from the brain.¹ There is an entire kinematic chain of events that lead to lens shape changes in both directions. The effects of age on the remodeling of microtissue layer interactions and collagenous structures detrimentally impact the eye’s normal biomechanical and physiological functions, which produce the symptoms of presbyopia”.² Biomechanical dysfunction increases mechanical load, shear stress, and consequential tissue strain, affecting microtissue layer interactions, collagenous structures, and tissue remodeling. These changes ultimately affect extracellular matrix chemical balance and biomechanical efficiency.³ Why is this important? Because accommodation involves more than simply changing the shape of the crystalline lens—it also involves multiple tissue and extralenticular pathways.