When it comes to treating glaucoma, the goal of eye doctors is assuring their patient don’t go blind.
That would seem relatively easy. Give them eye drops or refer them to surgery, which helps relieve what is known as intraocular pressure (IOP) inside the eye. But with current technology, it can often be difficult to measure this pressure because it fluctuates so much and those measurements have to be done in a doctor’s office.
That soon could change, thanks to a new device described in Nature Medicine.
A team of researchers from Stanford University and Bar-Ilan University in Israel has designed an implantable sensor that can be read with a smartphone camera. This allows the patient to take readings themselves and should improve the accuracy of pressure data.
“We believe this self-monitoring capabilities of the implant can significantly enhance the treatment and make it significantly better for the patient,” said Bar-Ilan’s Yossi Mandel, who co-authored the paper with Ismail Araci, Baolong Su and Stephen R. Quake of Stanford.
“Today, we think we are not treating them good enough,” he added. “They come once in a while and we take a single point in time of measurement. This probably is not good enough and we know from other studies that there is large variation in the IOP. In the same day, it can vary a lot.”
Glaucoma is a group of eye diseases that in most cases produces increased pressure within the eye and affects more than 65 million people worldwide. When the eye pressure is increased, the optic nerve becomes damaged, resulting in the death of the retinal cells, degeneration of the nerve fibers and eventually permanent loss of vision.
There are several good methods to diagnosing glaucoma but only one that monitors the disease to ensure the prescribed treatments are working. Called the Goldman applanation tonometery, or GAT, the method requires that the eye be anesthetized in a physician’s office and then a plastic prism makes contact with the cornea to measure the pressure. Not only is this uncomfortable and complex but this technique has been found in several studies to be inaccurate.
“Unfortunately, the patient can’t today measure his own IOP like he would with hypertension where you can measure your own blood pressure. Glaucoma patients have to go to their physicians,” Mandel said in a phone interview. “In one study, they measured IOP over 24 hours and saw there were large variations. In about 80 percent of the patients, they changed the treatment.”
The self-monitoring device, Mandel said, is about 50 microns in diameter and a few millimeters long. Looking much like a small tube, Mandel said the device developed in Quake’s lab is implanted in the eye.
“It looks very simple,” Mandel said. “The pressure in the eye causes a shift in the position of the fluid column in the device which then can be read much like the temperature in a thermometer.”
Glaucoma experts welcomed news of the device, saying it offers several advantages over the current methods including that it reads the pressure and does it around the clock.
“If patient comes in for cataract surgery and, if at the same time you can implant the device that would allow monitoring IOP more accurately and remotely, that has a huge benefit,” Dr. Andrew Iwach, chairman of board for the Glaucoma Research Foundation and executive director Glaucoma Center of San Francisco said. He also founded the foundation’s annual event, Glaucoma 360, which brings together researchers, industry executives and philanthropist to find a cure for glaucoma.
“So if you look at the risk benefit ratio the question wouldn’t be why did you put it in but why you didn’t put it in,” he said.
There is a similar device available in Europe to measure pressure around the clock called the Sensimed Triggerfish. But this contact lens sensor doesn’t measure the eye pressure directly, which makes it less accurate and, according to a 2012 study in Arch of Ophthalmol, caused blurred vision and other adverse reactions in over 80 percent of the patients.
Iwach said the lack of a reliable device to measure pressure in the American market has prompted a competition of sorts with at least five companies vying to be the first to get a device inserted into the eye, which transmits an electronic signal out onto the American market.
“This is an exciting a horse race,” Iwach said. “Different camps realize the first to market, the one who figures out how to do this best, is going to potentially revolutionize how we manage glaucoma and ultimately patients will be better for it.”
While showing promise to be the first, the latest device still is several years away from being commercially feasible. It has only been tested in pigs so the next step, Mandel said, is to do further research to ensure the device is safe in humans and can remain in the eye for an extended period of time.
“As scientist we are always skeptical about what we and others do,” Mandel said. “There are challenges that have to overcome but this device shows a lot of promise.”
