Biological Feasibility Study for Implantable Continuous Intraocular Pressure Monitor

Abstract

Purpose: : To determine the biological feasibility of implantation of an anterior chamber device to continuously monitor intraocular pressure.

Methods: : A round disc of 3.3 mm diameter and 500 micrometer thickness, coated with Parylene which had been modified in order to facilitate suturing was implanted in the anterior chamber of one eye of three feline subjects. Follow up was at the slit lamp or by exam under anesthesia periodically from day 1 to 90.

Results: : In two of three subjects device stability and centration was good throughout the observed period. Focal inflammation of the cornea and fibrin in the anterior chamber were present in all three subjects. In all subjects iris synechiae developed between the iris and the device. In subject 1 there was significant diffuse corneal edema, an iron fragment was found in the endothelium on day 28 and by day 90 the device was resting on the corneal endothelium, there were significant iron and rust deposits and significant diffuse corneal pannus and opacification. Subject 1 developed a cataract. Subjects 1 and 3 developed rubeosis of the iris in the area surrounding the device. Inflammatory reaction was observed, fibrin covered the sutures. Mechanical contact between the lens and the device caused cataract formation. No clinical changes or alterations were observed in the retina. The feline anterior chamber is not an easy model for implantation due to the eye and orbit anatomy because the eyelid aperture and nictitating membrane limit globe exposure and the cul de sac is shallow.

Conclusions: : Continuous intraocular sensor placement in the anterior chamber is potentially feasible if the sensor is reduced in size such that it does not contact the corneal endothelium, iris, or lens.

Keywords: anterior chamber • clinical laboratory testing • intraocular pressure