Home Tonometry-Can We? Should We?

Lowering intraocular pressure (IOP) is the only intervention that has been proven to reduce the risk of visual loss from glaucoma, but as clinicians, we often have few IOP measurements available on which to base our decisions. We know that IOP varies throughout the day, but traditional IOP measurements performed in the clinic only provide us with a snapshot picture of a continuously changing variable. If patients with glaucoma could accurately measure their IOP at home, physicians could make their decisions based on more IOP data points. With that goal in mind, Pronin and colleagues1 report on the reproducibility and acceptability of selfmonitoring of IOP with the Icare HOME device. The study included 100 participants with glaucoma or ocular hypertension. Participants underwent Goldmann applanation tonometry (GAT) by a physician, Icare HOME tonometry by a physician masked to the GAT reading, and, after receiving education regarding device use, performed Icare HOME tonometry on themselves in the office. Participants were queried about their acceptability of using the device. Most of the participants (73 of 100) recorded IOP measurements with the Icare HOME tonometer that was 5 mm Hg or less different from the readings with Icare HOME performed by the physician. Readings for IOP by Icare HOME were consistently lower than IOP measurements by GAT, and the difference appeared to be more pronounced in the lower IOP range. Most participants reported the act of self-monitoring of the device to be acceptable when performed once in this way in the office. The investigators note important caveats to their findings. Being able to perform the Icare HOME test in the office immediately after receiving instruction may not translate into successful testing in the home environment. Also, a difference of 5 mm Hg or less met the criteria for success in this study but might be a difference too great to usefully inform decision making in the clinical environment. This study adds to the evidence that home tonometry can be performed by many patients and is acceptable to most. The discrepancy between IOP measurements by Icare HOME and GAT, especially in the lower IOP range, suggest that this modality of home tonometry may not be appropriate in all scenarios. In keeping with the increasing popularity of devices to measure physical activity, sleep, dietary intake, and other personal health metrics, patients with glaucoma may not only find self-monitoring of IOP acceptable, but also soon demand it. But just because we can measure something, does not mean that we always should. Ultimately, we will need to determine whether self-monitoring leads to less vision loss. It is unclear that incorporating technology into self-monitoring results in better clinical outcomes in other chronic diseases such as non– insulin-dependent diabetes, as evidenced by a recently published report from a study comparing remote blood glucose monitoring with traditional in-clinic visits.2 We will not know the role of home IOP monitoring in glaucoma management without carefully designed studies, but research such as this by Pronin and colleagues1 adds to our understanding in the field. Because of the ability to take multiple measurements, and the ability to look at the mean of these measurements, such studies could assess how frequently these multiple measurements are an even better representation of a person’s IOP than infrequent physician measurements, which have their own inherent variability.