Abstract
Purpose :
Glaucoma drainage devices often fail due to scarring of the surrounding bleb, preventing outflow and intraocular pressure (IOP) reduction as pressures in the eye and drainage site equalize. We tested the efficacy of an implant-scale pump, which can pump against a pressure gradient, to reduce IOP in an ex vivo rabbit model.
Methods :
We designed and micromachined a 10 mm diameter glaucoma implant. The implant was composed of a polyetherimide body, a piezoelectrically activated silicon micropump, supplied by Fraunhofer EMFT, and a silicone inlet tube. The implant was first primed on the bench and then implanted subconjunctivally in the eye of an ex vivo rabbit. The inlet tube of the implant was inserted into the anterior chamber. Wires and an outlet tube were routed out of the surgically-formed bleb for power and explicit flow monitoring, respectively. Tested eyes were repressurized as needed with injected balanced salt solution. IOP was measured with a Tono-Vera Vet rebound tonometer with a minimum of three measurements per time point. After the devices were implanted, initial pressure measurements were made. As a control, the devices were allowed to sit unpowered for 2 minutes and IOP was measured again. Next, the pumps were activated for 2 minutes then depowered and the IOP measured a final time. This was repeated for two more eyes. Each IOP decrease was calculated with respect to the immediately prior measurement.
Results :
The pump implants fit unobtrusively under the conjunctiva after implantation. Initial IOPs spanned a common physiologic range: 20.1±0.3 mmHg, 18.4±0.2 mmHg, and 15.2±0.3 mmHg (all pressure data are mean±s.e.m.). Under control conditions (pump inactive), the IOP of individual eyes decreased by 0.6±0.7 mmHg, 2.4±0.4 mmHg, and 1.1±0.3 mmHg, respectively. Under experimental conditions (pump active), the IOP of individual eyes decreased by 4.2±0.6 mmHg, 4.5±0.7 mmHg, and 6.0±0.6 mmHg, respectively. These data represent increases of IOP reduction by 600%, 88%, and 460%, respectively, due to pump activation.
Conclusions :
The ability of an active implant to pump aqueous humor and support increased IOP reduction (versus a passive system) encourages further development towards an active glaucoma pump. Such a pump may extend the window of therapy for more late-stage glaucoma patients.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.