Simulated Capsule Dynamics During Phacoemulsification Using An Adjustable Compliance Eye Model

To evaluate the behavior of the retro lenticular space, surge volume and posterior lens capsule dynamics using a combination of surgical observations and a bicameral mechanical eye model with adjustable eye compliance using a handpiece with and without pressure sensing capability.

Phacodynamics Laboratory, Clinica Oftalmologica Pasteur, Santiago, Chile.

A bicameral eye model was built having anterior and posterior compartments separated by an impermeable membrane mimicking the posterior capsule. The model also including adjustable compliance to match different human eye response curves: low, medium and high. The fluidic communication between the anterior and posterior compartments was adjusted to emulate a detached and an attached hyaloido-capsular ligament of Wieger. Pressure, vacuum and flow were measured . Surge volume and capsule displacement were observed at different intraocular pressure (IOP) using a handpiece where the built-in pressure sensor capability was enabled and disabled.

Surge volume and simulated central posterior capsule displacement were more noticeable when the handpiece pressure sensor was disabled. When the handpiece pressure sensor was enabled, the measured and set IOPs were more closely matched where the surge and displacement were generally more stable and lower with a potential decoupling from preset simulated eye compliance. Observed variability in the degree of communication between the anterior and posterior chamber may be related to retro lenticular space features surrounding Wieger´s ligament. Computer video simulations based on surgical experience illustrate that high IOP may increase disturbance to the space between the posterior capsule and the anterior hyaloid.

An eye model was designed to mimic the complete fluid mechanical system and differences in compliance of human eyes. High IOP may increase retro lenticular space disruption. Posterior capsule stability as well as capsule reaction to post-occlusion surge may relate to the status of attachment of Wieger´s ligament to the posterior capsule. A handpiece with an enabled pressure sensor allows operating using low IOP to preserve Wieger´s ligament together with high vaccum for efficiency still while providing good anterior chamber stability.