Much recent attention has been paid to emerging technologies that allow for improved monitoring of glaucoma patients outside of the clinic setting. The Icare Home (Icare) is a handheld rebound tonometer designed for self-measurement of intraocular pressure (IOP) by patients (Figure 1). It was FDA cleared in 2017, and the newest iteration, the Icare Home2, received FDA 510(k) clearance in March 2022. The device offers more complete information regarding a patient’s IOP fluctuations outside the ophthalmologist’s office; however, little guidance exists for how to incorporate home tonometry into clinical practice. This article will review background information on the Icare Home device, clinical challenges it aims to solve, and considerations for incorporating it into clinical practice.

Background

Intraocular pressure (IOP) fluctuates throughout the day, with activity and position changes. Glaucoma specialists make treatment decisions based on in-office IOP measurements, which may miss IOP spikes in patients whose glaucoma is progressing despite their meeting in-office IOP targets. Traditionally, clinicians who wished to assess patients’ diurnal IOP variation had to do so in-office with the help of trained clinical staff, often using Goldman applanation tonometry (GAT). The feasibility of this sort of monitoring is limited by time and resources.

The Icare Home is designed for self IOP measurements outside the clinic setting.¹ It is similar to other Icare devices in that it uses a sterilized, disposable plastic probe and does not require use of topical anesthetic. It is battery operated with adjustable cheek and forehead supports that facilitate correct patient positioning. One of its key advantages over previous tonometers is that it stores time-stamped IOP measurements for later review by the ophthalmologist without need for real-time monitoring by eye-care staff.

To measure IOP, the Icare Home device takes 6 total measurements per eye (range of 5 mmHg to 50 mmHg), then reports the mean of the 4 central of these measurements and the standard deviation of all 6 measurements. It also uses infrared sensors to detect the laterality of the eye being measured and a circular light that turns green when the device is adequately positioned for measurement. Patients must be upright, and the probe base must be held 90 degrees to the patient’s face for accurate measurement.

Importantly, all measurements are saved to the device, but the patient is not able to view the measurements in real time. This is intended to reduce patient anxiety about measurements and maintain a strong patient-provider relationship.² The data measurements must be uploaded via USB or the Icare Clinic cloud-based software for review by a physician or eye care staff. Through this software, the clinician may view all recorded IOP data, including the time and date of each measurement, the laterality, and measurement quality.

Multiple studies have shown acceptable measurement agreement between GAT and the Icare Home, with the mean IOP difference ranging from -0.7 mmHg to 2.66 mmHg.² Of note, the Icare Home is only validated to be used in patients with central corneal thickness of 500 μm to 600 μm. Several studies have found that compared to GAT, the Icare Home device tends to overestimate at higher IOP and underestimate at lower IOP.²

Challenges the Icare Home Aims to Solve

The Icare Home may be particularly useful in certain clinical scenarios, such as identifying potential diurnal pressure spikes outside of office hours in patients with glaucoma whose disease progresses despite at-target IOP measurements.² This can be helpful when the next management decision may involve weighing the risks of glaucoma surgery. Since the device is portable, it may be used to monitor for exercise-related IOP spikes in patients with pigment dispersion syndrome.

Multiple authors have reported detection of IOP spikes outside of typical 8 AM to 5 PM office hours that they felt explained their patient’s glaucoma progression.^2-4 Icare Home tonometry has also been shown to be useful in monitoring response to therapies, such as selective laser trabeculoplasty,⁵ addition of topical medication,² and in assessing for lumen opening following ligated tube shunt insertion in children.⁶

How to Incorporate the Icare Home Into Clinical Practice

Incorporating Icare home tonometry into clinical practice may present a few key challenges; namely, need for patient training, change to clinical workflow, and device cost.

Patient Training and Clinical Workflow

Patients must be trained by an Icare Home–certified staff member prior to using the device. According to the manufacturer, to be certified for home use, the patient must meet the following criteria:

1. The first of 3 Icare Home readings and the GAT readings measured by staff must differ by 5 mmHg or less.
2. The range of the 3 Icare Home IOP readings taken by the patient must be 7 mmHg or less.
3. The positioning of the Icare Home tonometer during self-use must be correct as determined by the staff member.²

A collection of Icare Home studies have found about 73% of patients were consistently successful in being certified or trained to use the device.² Patients took an average of 20 minutes to learn to use the device, and 71% of patients rated the Icare Home as easy to use following participation in a home trial.⁷ Reasons cited for lack of success in device certification include older age, tremor, arthritis, and worse visual acuity.^7,8

After demonstrating correct use, patients are instructed to use the device according to the goals of their treating specialist. At Wills Eye Hospital, we typically enroll our patients in 1-week trials. An ophthalmic technician trains the patient and asks them to use the Icare Home device four times daily every day for 7 days at approximately 8 AM, 12 PM, 4 PM, and 8 PM. Patients are encouraged to obtain measurements as frequently as they prefer. As one advantage of the device is its portability, patients are encouraged to continue their typical life routines (including work and exercise) that may reveal intraocular pressure spikes not captured in a clinical setting.² Logging the times and dates of these activities can help the treating ophthalmologist identify triggers for pressure spikes. The patient then follows up with the technician for a brief visit, during which the IOP readings from their home trial are downloaded to the clinic computer via USB. This data is then given to the ophthalmologist for review with the patient.

Cost

Certain patients may be able to find the Icare Home device available online for purchase (from $1,200 to $2,300 per device) or for rental. However, device purchase is likely cost prohibitive for most patients. Various authors have described a system similar to library check-out and return^2,4 in which a practice loans the patient the device for the duration of the home tonometry trial. Practices may charge a flat fee for the home tonometry trial or request that the patient pay a deposit that is refunded upon return of the device. Patients wishing to purchase their own device should be advised that, at this time, the Icare Home tonometer is only FDA approved for use in partnership with an eye care professional who reviews the home tonometry data.

Utility of Home Tonometry Trials

Many clinicians may wonder whether patient participation in home tonometry trials affects glaucoma management decisions. One recent retrospective study of 96 eyes showed that glaucoma specialists advanced therapy in 58% of patients following participation in home tonometry trials.³ Of these patients whose management changed, 42% underwent surgery, 38% underwent medication change, and 20% were treated with laser trabeculoplasty.³ In this study, no clinic-based metrics such as number of glaucoma medications, central corneal thickness, or visual field mean deviation were predictive of whether change in management would be recommended. At Wills Eye Hospital, more than half of the patients who have participated in Icare Home trials have undergone changes to their glaucoma management.

Many challenges remain in expanding access to home monitoring for glaucoma care, but new home monitoring technologies present opportunities to improve patients' lives. For select glaucoma patients, the Icare Home is a valuable tool that is relatively easy to incorporate into a busy clinical practice. GP

Lauren E. Hock, MD, is a glaucoma fellow at Wills Eye Hospital in Philadelphia, Pennsylvania.

Daniel Lee, MD, is a member of the glaucoma service at Wills Eye Hospital and a clinical instructor of ophthalmology at Sidney Kimmel Medical College in Philadelphia.

Marlene R. Moster, MD, is an attending glaucoma surgeon at Wills Eye Hospital and a professor of ophthalmology at the Sydney Kimmel Medical College.

Dr. Hock reports no disclosures. Dr. Lee reports financial relationships with Allergan, Equinox, Glaukos, Mati Therapeutics, Nicox, Olleyes, Quidel Eye Health, and Santen. Dr. Moster reports no relevant disclosures. Reach Dr. Moster at marlenemoster@gmail.com

References

1. Food and Drug Administration. Icare HOME tonometer summary of safety and effectiveness. 2017.
2. Liu J, De Francesco T, Schlenker M, Ahmed II. Icare Home tonometer: a review of characteristics and clinical utility. Clin Ophthalmol. 2020;14:4031-4045. Published 2020 Nov 23. doi:10.2147/OPTH.S284844
3. McGlumphy EJ, Mihailovic A, Ramulu PY, Johnson TV. Home self-tonometry trials compared with clinic tonometry in patients with glaucoma. Ophthalmol Glaucoma. 2021;4(6):569-580. doi:10.1016/j.ogla.2021.03.017
4. Rojas CD, Reed DM, Moroi SE. Usefulness of Icare Home in telemedicine workflow to detect real-world intraocular pressure response to glaucoma medication change. Ophthalmol Glaucoma. 2020;3(5):403-405. doi:10.1016/j.ogla.2020.04.017
5. Awadalla MS, Qassim A, Hassall M, Nguyen TT, Landers J, Craig JE. Using Icare HOME tonometry for follow-up of patients with open-angle glaucoma before and after selective laser trabeculoplasty. Clin Exp Ophthalmol. 2020;48(3):328-333. doi:10.1111/ceo.13686
6. Go MS, Barman NR, House RJ, Freedman SF. Home tonometry assists glaucoma drainage device management in childhood glaucoma. J Glaucoma. 2019;28(9):818-822. doi:10.1097/IJG.0000000000001322
7. Pronin S, Brown L, Megaw R, Tatham AJ. Measurement of intraocular pressure by patients with glaucoma. JAMA Ophthalmol. 2017;135(10):1030-1036. doi:10.1001/jamaophthalmol.2017.3151
8. Dabasia PL, Lawrenson JG, Murdoch IE. Evaluation of a new rebound tonometer for self-measurement of intraocular pressure. Br J Ophthalmol. 2016;100(8):1139-1143. doi:10.1136/bjophthalmol-2015-307674