Mary Ann Croft, believe the reduction in the circumlental space is due to growth or relaxation of the ciliary body outwards towards the lens with age. Whether it is growth in the diameter of the lens, or growth of the ciliary body, or some combination of the two, no one in the ophthalmology industry disputes that the circumlental space is diminishing with age. More importantly, unlike any other biological change in the structures or functioning of the eye, the reduction of the circumlental space is highly correlated with the reduction in accommodation.
As Mary Ann said in a 2006 publication titled “The Zonula, Lens, and Circumlental Space in the Normal Iridectomized Rhesus Monkey Eye” in which she was the lead author: “The nonaccommodated circumlental space (CLS) decreased significantly with age in both the nasal and temporal quadrants and tended to do so at a slightly faster rate in the temporal quadrant. The CLS correlated significantly with the accommodative amplitude: the greater the CLS the greater the accommodative amplitude.” Multiple regression analysis indicated that age and CLS together are better predictors of accommodative amplitude than is age alone.” This article, which is one of more than 30 that Mary Ann has authored or co-authored on the eye and the visual system, is attached.
A graph showing the correlation with crystalline lens growth (whether at the equator or on the anterior and posterior surfaces) and Duane’s Curve (a well recognized survey of average accommodation in humans at different ages) is shown below. As seen, the correlation between lens growth and loss of accommodation is extremely high – R2 = 0.92.