Study of the Force Dynamics at the Capsular Interface Related to Ciliary Body Stimulation in a Primate Model

PURPOSE: 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. METHODS: 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. RESULTS: An average movement of 390 mu m for on-the-bag gauges and 145 mu m 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. CONCLUSIONS: 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.