IOP measurements represent a snapshot in time, but they do not give a real-world picture of IOP. A patient’s pressure can fluctuate depending on various factors, such as time of day, activity in a given instance and postural position (for example, lying supine). Goldmann applanation tonometry (GAT), the gold standard for measuring IOP, is only conducted as an in-office procedure every few months. Because IOP is a moving target, it has prompted exploration of technologies that offer continuous measurement.

An emerging technology aimed at continuous measurement is the Icare HOME (Icare USA, Inc.), a home tonometer based on the principle of rebound tonometry. Approved for use in the US in late March, the device uses a small probe that touches the cornea. It comes equipped with automatic OD/OS recognition technology, an intelligent positioning assistant for the correct alignment of the tonometer, and an automatic measuring sequence. It also contains proprietary software that allows the health-care provider to download IOP measurements that have been recorded and time-stamped.

STUDY RESULTS

David Friedman MD, MPH, PhD, Alfred Sommer professor of Public Health Ophthalmology and director of the Dana Center for Preventive Ophthalmology at Wilmer Eye Institute, Baltimore, and colleagues found in a clinical study a mean difference of -0.33 mm Hg between the Icare HOME and GAT measurements.¹ “There was some variability, but it [IOP measurement using Icare HOME] was a good estimate,” says Dr. Friedman. Another study showed 56 of 76 patients trained to use the device correctly performed self-tonometry.²

Patients indicated the self-tonometry technology was easy to use, the reading was quick to obtain, and the measurement was comfortable. Investigators did find central corneal thickness affected agreement between an IOP measurement taken with GAT compared to Icare HOME. Patients did not have to indicate if they had used drops before or after recording their IOP.

The researchers also concluded the device’s measurements were slightly underestimated compared with GAT IOP measurements. The company website shows the product is accurate to “95% tolerance interval, relative to manometry.”

Patients can take their own measurements with the Icare HOME tonometer because the technology does not require an anesthetic to capture IOP, says Holly Swain, OD, product manager, Icare USA, Inc.

For glaucoma patients or glaucoma suspects, continuous IOP monitoring offers them and their clinicians additional information beyond a single measurement. According to the company website, the unit provides data to the clinician, not the patient, such as quality score. The unit weighs about one-third of a pound.

TRAINING, LIMITATIONS

Patients receive training on the technology and are then tested to assess whether they can use it independently. If the device malfunctions, it will not record an IOP reading, says Dr. Swain. “Patients have to be certified to prove that they can use it properly. They will not take the device home otherwise.”

The device, which requires that patients be seated or standing to use it, does not display the IOP measurement to patients, and they cannot retrieve the measurement on their own. Patients have not been instructed to note if they instilled eyedrops before or after they record their IOP with Icare HOME, and they are not instructed to take note if they have engaged in any physical activity prior to recording IOP. An app has been developed, however, that allows patients with mobile devices to troubleshoot the Icare HOME if they have challenges using it at home.

While Dr. Friedman’s study showed no adverse events or corneal abrasions,¹ he notes that 25% of patients could not use it and therefore could not complete the study. Some reasons for not completing the study included patients not recording measurements that fell within 5 mm Hg of the GAT measurements, and/or difficulty using the device.

Patients who have disabling arthritis, Parkinson’s disease or other movement disorders are not good candidates for using Icare HOME as these conditions would limit the ability to hold the device, says Iqbal Ahmed, MD, FRCPC, assistant professor at the University of Toronto and Research Fellowship director, Department of Ophthalmology, University of Toronto. Still, he says that in his clinical experience — Canada approved Icare HOME in 2014 — these patients have benefited from assistance with capturing IOP readings. “Family members have been happy to hold the device for them,” says Dr. Ahmed.

USING THE DATA

The device allows insight into how to better manage glaucoma patients. For example, with medication compliance, “if the IOP is not controlled, it might give us an idea that the drops are not going into the eye,” Dr. Ahmed says.

Also, in some instances, says Dr. Ahmed, IOP measurements recorded with the Icare HOME have caused him to modify the eye drop dosage if they showed that IOPs were not controlled, or to pursue another treatment like surgery to achieve better control of IOP. “It might be more aggressive treatment [that is required to control IOP].]

“IOP is not a single measure,” he says, explaining that 24-hour monitoring of IOP addresses the pressure’s randomness. “It is a series of measures over a patient’s day, week, or month. Emerging evidence suggests peak IOP plays an important role in determining [which] patients are at risk of progression [of disease].” OM

REFERENCES

1. Mudie LI, LaBarre S, Varadaraj V, et al. The Icare HOME (TA022) Study: Performance of an Intraocular Pressure Measuring Device for Self-Tonometry by Glaucoma Patients. Ophthalmology. 2016. Aug;123:1675-1684.
2. Dabasia PL, Lawrenson JG, Murdoch IE. Evaluation of a new rebound tonometer for self-measurement of intraocular pressure. B J Ophth. 2016 Aug;100:1139-1143.