Intraocular Pressure Sensors

Gauging intraocular pressure (IOP) during an eye exam is possible, but the eye's internal pressure changes regularly and varies throughout the day. Being able to monitor IOP at all times is important, especially for patients at high risk for glaucoma.

The second most-common cause of blindness after cataracts, glaucoma causes gradual loss of vision, typically as a result of high fluid pressure in the eye.

Our researchers are involved in the development of novel IOP sensors implanted in the eye to accurately and continuously measure IOP. Our collaborators are electrical and medical engineering experts at the California Institute of Technology (Caltech) in Pasadena, California

The miniaturized, implantable pressure sensor under development is fully wireless and highly sensitive. Smaller than a dime, the novel device is comprised of a pressure sensor, control circuitry and an antenna. It is implanted in an area on the white of the eye where it won't interfere with vision.

The implant will allow the wearer to "download" eye pressure measurements at any time with the wireless device. Having moment-to-moment data will help physicians to adjust therapy, as needed.

Prior sensing devices have been unable to overcome the issue of functioning inside the human body, where fluids can corrode electronics or cloud sensors. The Caltech researchers devised a specialized coating to encapsulate the device, using a silicone-oil bubble and a biocompatible polymer. Laboratory tests have estimated the device's functional longevity at four years.

Further tests are under way to advance the device to the clinical trial stage.

Micropump Drug Delivery

Intravitreal (into the eye) injection drugs can now maintain or improve vision in patients who before did not have treatment options. Intraocular therapy is growing for such diseases as age-related macular degeneration, diabetic macular edema and macular edema secondary to retinal vein occlusion.

However, patient adherence is an issue. Poor compliance affects treatment outcomes, and patients who miss appointments risk irreversible vision loss. In addition, patients with glaucoma must typically use prescription eye drops to control their disease. But studies show that some patients stop taking their medication after one year.

To solve this non-compliance problem and improve outcomes, our researchers are leading the development of implantable micropumps for automated, wireless drug delivery.

A small, automated, refillable ocular drug pump, now under commercial development by Replenish, Inc., is implanted under the skin of the eye. The company’s Ophthalmic MicroPump System™ features cutting-edge technology to:

• inject programmed amounts of drug at set times;
• hold up to 12 months of medication in a drug reservoir chamber;
• be refilled using a disposable 31-gauge needle, and
• recharge wirelessly.

The smart device consists of four subsystems: The Anterior MicroPump for glaucoma patients, the Posterior MicroPump for retina patients, EyeLink, a wireless programmer/charger and the Drug Refill System.

In a one-year feasibility study, reported in Translational Vision Science and Technology in 2014, 11 patients with diabetic macular edema and visual acuity of 20/40 eyesight or worse underwent surgical implantations of a MicroPump prototype.

The pump delivered the programmed dosage of ranibizumab, a blood vessel growth inhibitor, in seven subjects. The remaining four patients received a lower-than-target dose, and the treatment was complemented with standard intravitreal injections.