How Well Can Glaucoma Patients Measure Their Own Intraocular Pressure?

By Will Boggs MD

September 07, 2017

NEW YORK (Reuters Health) - Self-measurement of intraocular pressure (IOP) by glaucoma patients is feasible and acceptable, but it remains to be seen whether it is sufficiently accurate to guide clinical management, according to an observational study.

"Although these initial results show patients are able to measure their own intraocular pressure, further studies are needed to determine the value to clinical practice,” Dr. Andrew J. Tatham from Princess Alexandra Eye Pavilion, University of Edinburgh, in Scotland, told Reuters Health by email. “In particular, studies are needed that examine whether having more pressure measurements from self-tonometry improves our ability to identify patients at higher risk of visual loss.”

The Icare HOME, a new device designed for home IOP monitoring, requires no topical anesthesia and has been reported to provide repeatable readings that agree well with the reference standard for measurement, Goldmann applanation tonometry (GAT).

Dr. Tatham's team investigated whether patients with glaucoma could measure their own IOP and evaluated their perceptions of self-tonometry. The study was published online August 31 in JAMA Ophthalmology.

Of the 100 study participants, 73 had “complete success” - defined as correctly using the Icare HOME and obtaining an IOP within 5 mmHg of that obtained by the investigator using the same device in both eyes. An additional 6 patients had partial success (good technique but >5 mmHg difference in patient- versus investigator-measured IOP).

Icare HOME measurements by the investigator averaged 2.66 mmHg lower than those obtained by GAT. Eyes with lower IOP generally showed greater differences between Icare HOME and GAT readings.

Only 88 of 158 (56%) self-tonometry measurements were within 5 mmHg of GAT, compared with 150 of 158 (94.9%) Icare HOME measurements by the researchers.

Thinner central corneal thickness was associated with lower IOP measurements using GAT, and even lower using Icare HOME.

Of the completely or partially successful participants, 71% reported that Icare HOME was easy to use, and 92% agreed that self-tonometry was comfortable (vs. 24% and 88% of unsuccessful patients, respectively). And 92% of successful or partially successful patients said they would be happy to perform self-tonometry in the future.

Patients took a mean of roughly 20 minutes to learn how to perform self-tonometry. Older age and worse visual acuity in the better eye were significantly associated with the inability to perform self-tonometry.

“The ability of patients to measure their own pressure has the potential to empower them, while also generating data that helps the clinician better understand their disease,” Dr. Tatham said. “The study shows the potential of remote disease monitoring. Potentially in the future, patients could send intraocular pressure measurements remotely to their doctor for analysis without the need to visit the clinic. It is conceivable that home tonometers could be linked to a smartphone app that could alert patients of high intraocular pressure and provide prompts of when medication is needed.”

“In the UK, the device costs approximately 1,500 pounds ($US1,950),” Dr. Tatham said by email. “The device uses single-use disposable probes that cost 1 (British) pound per probe.”

“This study adds to the evidence that home tonometry can be performed by many patients and is acceptable to most,” writes Dr. Kelly W. Muir from Duke University School of Medicine, Durham, North Carolina, in a related editorial. “The discrepancy between IOP measurements by Icare HOME and GAT, especially in the lower IOP range, suggests that this modality of home tonometry may not be appropriate in all scenarios.”

“But just because we can measure something, does not mean that we always should,” she concludes. “Ultimately, we need to determine whether self-monitoring leads to less vision loss.”

Dr. Clement C. Y. Tham from the Chinese University of Hong Kong told Reuters Health by email, “The results were not surprising and were largely in line with the outcomes from my research group.”

“In clinical management,” he said, “self-tonometry would be particularly useful in these situations: (1) patients with suspected normal tension glaucoma – to determine if ocular hypertension could have been missed by the IOP measurements once in a while in clinics; and (2) patients with eye diseases associated with intermittent IOP spikes (especially relatively asymptomatic spikes), e.g., uveitis, Possner-Schlossmann syndrome. Self-tonometry helps identify such IOP spikes.”

Dr. Ahti Tarkkanen from Helsinki University Eye Hospital, in Finland, told Reuters Health by email, “I have more than 10 years’ experience using rebound tonometry. The paper should be read by all ophthalmologists.”

“Self-tonometry is a must,” he said.

The FDA cleared Icare HOME for use in the U.S. in March 2017. (http://bit.ly/2eJ23Kq)

SOURCES: http://bit.ly/2j00hFT and http://bit.ly/2eCiTa8

JAMA Ophthalmol 2017.

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