Study of the force dynamics at the capsular interface related to ciliary body stimulation in a primate model

To study the mechanical dynamics between the zonuli-capsular complex and an accommodating intraocular lens mechanics simulator using pharmacological stimulation of the ciliary body in a primate eye.

Following phacoemulsification removal of the lens, force/movement gauges simulating the accommodating intraocular lens mechanics were implanted in 8 primate eyes (4 positioned in-the-bag and 4 on-the-bag). The gauge readings were taken under full effect of pilocarpine 4% or atropine 1% starting 6 weeks after surgery and following 3-month intervals for 30 months.

An average movement of 390 µm for on-the-bag gauges and 145 µm for in-the-bag gauges was documented at 3 months postoperatively. The mechanical compliance of in-the-bag gauges rapidly deteriorated with capsular fibrosis developing inside the gauge and the capsular bag shrinking around it. On-the-bag gauges remained functional but the initial compliance was compromised over time by the pressure build up caused by the fibrotic capsular bag.

Following phacoemulsification, capsular fibrosis causes disappearance of the mechanical forces detected by an in-the-bag gauge. An on-the-bag gauge detects active forces at the sulcus lasting at least 5 years, although the contracting capsule pressure compromises its compliance. These findings have important implications for future accommodating intraocular lens designs.