Mechanical model of human eye compliance for volumetric occlusion break surge measurements

Session Details

Session Title: Cataract Surgery Equipment/Instrumentation/Surgical Devices I

Session Date/Time: Monday 12/09/2016 | 14:00-15:30

Paper Time: 14:24

Venue: Hall C5

First Author: : K.Miller USA

Co Author(s): :    D. Dyk                    

Abstract Details

Purpose:

To develop a mechanical model of human eye compliance for volumetric studies of the occlusion break surge response.

Setting:

Alcon Laboratories Lake Forest, CA

Methods:

Compliance curves were obtained from 15 eyes. Each eye was subjected to a maximum 12 pressurization/depressurization cycles with 60 to 100 mmHg peak IOP. A piezoresistive transducer measured anterior chamber pressure. Volume change was measured from an ultrasonic flow sensor’s integrated output. Each eye’s average net volume change curves were calculated as a function of IOP after a boxcar filter and two-term exponential fit were applied to each pressurization cycle. Overall mean volumes were computed from each eye’s average at pressure points extrapolated over 5 to 90 mmHg. A two-term exponential function was fitted to these results.

Results:

Individual eye compliance curves varied greatly. The fitted function took the form, V=C1∙exp(C2∙P)+C3∙exp(C4∙P)-V0, where V is the volume (cc) and P is the IOP (mmHg).V0 was a chosen reference volume such that V=0 cc at 110 mmHg IOP. C1 through C4 were -0.07141, -0.23055, -0.14972, and -0.02006 respectively. The fitted results were modeled using a piston system employing three parallel springs with staged engagement. A test fixture was constructed that incorporates the mechanical model and enables timed occlusion of the end of a phaco needle. A laser confocal displacement meter measures piston displacement after an occlusion break. Surge volume is calculated from displacement of the piston.

Conclusions:

A novel apparatus for reliably measuring the volumetric surge response following an occlusion break has been developed using compliance data from human cadaver eyes. The fixture will establish a new standard for evaluating an important safety issue of phacoemulsification/aspiration systems.

Financial Disclosure:

... is employed by a for-profit company with an interest in the subject of the presentation, ... research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented