Researchers are developing an implantable sensor for glaucoma that allows intraocular pressure to be read by a smartphone camera. Diagnosis and monitoring now relies on a trip to the ophthalmologist and a reading of intraocular pressure that can vary widely. The implant/smartphone combination is expected to allow at-home monitoring and a series of readings that could improve diagnosis and monitoring of glaucoma patients.
Glaucoma is the second most common cause of blindness globally. It has multiple cause, but intraocular pressure (IOP) is the primary contributing factor and key to diagnosis and monitoring. IOP fluctuates widely depending on the time of day and patient body posture, making a single measurement potentially misleading.
In the latest issue of Nature Medicine, Yossi Mandel at Bar-Ilan University in Ramat Gan, Israel and his colleagues have detailed their work toward an IOP monitoring implant that is a few millimeters long and could be embedded in the synthetic lenses used to replace the existing lenses of patients with cataracts.
Many older adults have both cataracts and glaucoma, although the two conditions are not related. This implant is designed to fit inside the standard intraocular lens prosthetics that are implanted during cataract surgery. The researchers hope to find ways to implant it on its own as well. Frequent glaucoma monitoring could allow better glaucoma treatment by physicians using laser surgery and drugs.
There were 12 million cataract operations in 2000; as the population ages, that figure is expected to balloon to 32 million by 2020, according to the World Health Organization.
|Stephen Quake, Stanford University|
The implant was developed by ophthalmologist Madel and Stephen Quake, a professor of bioengineering and of applied physics at Stanford University. It has a small tube that is open on one end to fluid in the eye and capped with a small bulb filled with gas on the other end. As the IOP increases, the intraocular fluid is pushed into the tube and the gas pushes back against it. The barrier between the gas and the fluid thus moves back and forth in the tube.
The patient then uses a smartphone to snap a photo of the implant, while an app analyzes and transmits the data. In a previous study, 24-hour IOP monitoring resulted in an altered treatment approach for up to 80% of glaucoma patients.
"For me, the charm of this is the simplicity of the device," Quake said in a statement. "Glaucoma is a substantial issue in human health. It's critical to catch things before they go off the rails, because once you go off, you can go blind. If patients could monitor themselves frequently, you might see an improvement in treatments."
The researchers expect to get the implant into clinical trials within the next few years; before they do, they need to re-engineer it with new materials to increase the length of time it can remain implanted.