March 2019


Device focus
Imagining the future of IOP monitoring

by Liz Hillman EyeWorld Senior Staff Writer

ICare Home is a portable tonometer that allows patients to measure their IOP at home during several parts of the day/night as prescribed by their ophthalmologist.
Source: ICare USA

Triggerfish is an external contact lens that is the only FDA-approved, wearable device for continual monitoring, but it does not directly measure IOP.
Source: Sensimed

Devices for continuous IOP monitoring might not be that far off

Intraocular pressure and its association with glaucoma dates back to the 10th century, with more widespread recognition and understanding of this association becoming established in the 19th century.1 Since then, measuring intraocular pressure to detect risk of progression has become standard of care for glaucoma patients and suspects.
Despite its long history, there are still many unknowns about IOP, said Arthur Sit, MD, professor of ophthalmology, vice chair of clinical practice, Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota. But a better understanding might not be far off with advances in the development and testing of continuous IOP-monitoring devices.
“Right now, we only measure IOP a few times a year for a few seconds when a patient is in the clinic during office hours,” Dr. Sit said, acknowledging that research has provided insight on what happens, generally, with IOP and circadian patterns. “But this still doesn’t tell us what happens to an individual patient’s IOP during activities of living.”
Marlene Moster, MD, professor of ophthalmology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, said one of the remaining mysteries in understanding glaucoma is IOP over time. What happens at night? What happens during exercise? Is it the same in every patient? What is the patient’s response to a medication change or surgery? These are all questions that continuous IOP monitoring could provide. And, according to Dr. Moster, a device that could truly provide this information is not far off.
Only one device—Triggerfish (Sensimed, Lausanne, Switzerland) —is currently approved by the U.S. FDA to provide some of these insights. The 24-hour contact lens monitoring device, however, does not measure IOP directly, rather ocular volume change. Dr. Moster also said she thinks Triggerfish is tailored more toward research situations rather than practical, clinical situations. “But it has been tremendously helpful in our understanding of what happens at night,” she acknowledged.
There is also Icare Home (Icare, Raleigh, North Carolina), an FDA-approved, externally applied, at-home tonometer operated by the patient with data retrieved by the healthcare provider. This device, though not continuous, allows patients to collect several IOP measurements throughout a time period as directed by their physician.
The ideal continuous IOP monitoring device would come in two iterations, Dr. Sit said. He said a non-invasive, well-tolerated monitoring device, like a contact lens, could be useful to learn more over a short time frame (days) about IOP patterns in glaucoma suspects or those in early stages of the disease who are not surgical candidates. For patients with established glaucoma, physicians want a more permanent monitoring device that could help detect risk of progression, and provide alerts if certain pressure thresholds are crossed, Dr. Sit said.
There has been a lot of work on this latter front thanks to advances in extreme miniaturization of electronics in order to produce a biocompatible sensor that needs little calibration, Dr. Moster said.
“I think it could be coupled with cataract surgery in the form of a capsular tension ring or perhaps embedded in an implant. It could be used as a standalone device within the sclera or perhaps attached to a shunt or any kind of MIGS device. The sky is the limit as to where this very small, biocompatible device will go. It all depends on the amount of inflammation it might cause,” she said. “The goal is to have it as inert as possible, as small as possible, and to be recharged in a way that there is little need for the patient to pay attention to this. It will need to be easily rechargeable and battery friendly so that just sleeping at the bedside near a wireless charger can enable this to last for 10–20 years.”
Some companies making headway on such devices are Implandata Ophthalmic Products (Hannover, Germany) with EyeMate, which is CE marked in Europe, and Qura (Boston) with QSmart. Implandata is currently in clinical trials with a new suprachoroidal device, with the first successful implantation in human patients occurring in December 2018. This device would be implanted as part of glaucoma filtering surgery. QSmart, which is still in development and testing in animal models, is 2.8 mm.
When asked how he thought continuous IOP monitoring could change clinical care, Kaweh Mansouri, MD, professor of ophthalmology, University of Colorado, Denver, and Montchoisi Clinic, Lausanne, Switzerland, took it a step back.
“Initially, it may not change so much because we need to learn how to interpret that data. We are used to very few data points in glaucoma management when it comes to IOP,” he said. “There will be a period where prospective studies have to be conducted to understand IOP variations, then we will be able to assess continuously and accurately how these IOP variations affect this patient’s glaucoma management.”
However, one can imagine uses for such technology, such as assessing the effect of therapy. “Let’s say Mrs. X has a sensor in her eye and the IOP is higher than the doctor would deem safe for her optic nerve,” Dr. Moster said. “They would change the therapy and be able to assess with accurate pressure readings day and night whether the IOP lowering meets the goal that was predetermined by the physician. The same would hold true for surgical procedures.”
A secondary effect of continuous IOP monitoring could be a reduction in patient visits because they would no longer need manual tonometry. This could result in not only time saved on the part of the patient and physician but cost savings as well.2 This could be a double-edged sword, Dr. Moster said. “You want patients to come in to renew their medications, to know you are still quite interested in how they are doing. You can’t do it completely from afar,” she said.
Until continuous IOP monitoring devices are easily available and more widespread, Dr. Moster said she doesn’t foresee the pattern of decision making changing among ophthalmologists caring for glaucoma patients. She does, however, expect continuous IOP monitoring devices that could dramatically change this decision-making process to start becoming available within the next 5 years.
“People have been talking about continuous IOP monitoring for decades,” Dr. Sit said, “but I think we are on the cusp of having some things that will be clinically useful.”


1. Mantzioros N. The history of the meaning of the word glaucoma. Accessed Jan. 24, 2019.
2. Dong J, et al. Potential savings from visit reduction of continuous intraocular pressure monitoring. J Curr Glaucoma Pract. 2018;12:59–63.

Editors’ note: Dr. Sit has financial interests with Injectsense (Emeryville, California). Dr. Moster has financial interests with Qura. Dr. Mansouri has financial interests with Sensimed and Implandata.

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