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Biocompatibility of the Ex-PRESS Miniature Glaucoma Drainage Implant

*Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, †Goldshleger Eye Research Institute, Tel Aviv University, Tel Hashomer, Israel, and ‡Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel


Purpose: Based on lessons learned from earlier attempts, a novel miniature glaucoma

implant, Ex-PRESS, was developed in 1998. The current study summarizes the

histopathologic evaluation of this device implanted in the eyes of rabbits.

Methods: The device was implanted into the anterior chamber at the corneoscleral

junction in 1 eye each of 8 white New Zealand rabbits, while the contralateral eye

served as control. Three and 6 months after implantation, the rabbits were killed and

their eyes were enucleated and processed histologically, leaving the device in situ

when sectioning.

Results: Three and 6 months postoperatively, the local tissue reaction typically

consisted of an enveloping, thin, mature, fibrotic capsule (thickness <0.04 mm), devoid

of inflammatory cells. This capsule surrounded approximately 25% of the implant

surface area present in the sections. The lumina of the devices were devoid of inflammatory

exudates or other obstructions in all specimens examined, suggesting free flow

of fluid.

Conclusions: The implantation of the Ex-PRESS miniature glaucoma shunt resulted

in minimal capsular reaction. Considering the high reactivity of the rabbit eye,

it is possible that this implant will induce a smaller cellular inflammatory reaction in

the human eye.

Key Words: Aqueous shunts—Biocompatibility—Drainage device—Glaucoma.

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