Monitoring the highs and lows of IOP

A new tonometer, designed for use by patients, allows doctors to track IOP fluctuations throughout the day.

Intraocular pressure (IOP) fluctuations during a 24-hour period, or diurnal fluctuations, complicate glaucoma management strategies. Normal IOP is considered 21 mmHg or less, but at what time of day? Does the pressure spike at times throughout the day or night, leading to silent progressive nerve damage?

In-office IOP readings are a snapshot in time. Even when patients present to their ophthalmologist’s office at 8 a.m. and again at 4 p.m., fluctuations in IOP occurring at other times during the day or night may be missed.

The Icare HOME tonometer received FDA clearance in March 2017, providing a method to precisely track IOP over time, thus revealing the unknown.1

The ICare HOME tonometer can identify IOP fluctuations that occur outside the ophthalmologist’s office.

Using the tonometer

The Icare HOME tonometer is a compact, hand-held, no-puff, anesthetic drop-free device, which is designed for use by the patient outside the office. It uses a replaceable rebound probe, calculating IOP based on the deceleration and rebound time over a series of six consecutive measurements.2 The instrument stores the final IOP, date, time, eye (OD or OS) and measurement quality for subsequent retrieval, but the IOP measurement is not visible to the patient. When the device is returned to the office, the IOP measurements are uploaded via a USB cable to the companion Icare Link software for review.

Learning how to operate the tonometer (and subsequently teach a patient to use the device) is straight forward and takes only about 20 minutes, says Holly Swain, OD, product manager for Icare USA. The unit has two adjustable supports, one for the forehead and a second for the cheek, to ensure accurate alignment and to prevent the housing of the instrument from contacting the patient’s eye. The tonometer has an automatic eye recognition system using LEDs to identify which eye is being tested and an alignment guide to ensure probe centration.

Icare offers a comprehensive training guide on its website, as well as instructional videos for eye-care providers and ophthalmic allied health professionals. A more succinct guide is offered to pass on to patients. All cover how to load and remove the probe and acquire measurements. Icare-certified representatives train and qualify ophthalmic staff members on how to correctly use the device. Once certified, staff can train patients and fellow colleagues. In addition, an Icare HOME educational app, available for Apple and Android devices, was designed to help patients use the device without direct supervision. The app contains a quick guide, brief training video, and a troubleshooting section. 


The cost of the Icare HOME tonometer falls within the range of most hand-held tonometers on the market. Icare offers a one-year manufacturer’s warranty. An additional service plan may be purchased to cover damage or theft, with a reasonable deductible. Probes, costing approximately $1 a piece, are blister packed and available in boxes of 50.

The tonometer is designed to be loaned to patients for home use of IOP monitoring, four to six times per day for five consecutive days, for a rental fee that the practice sets. This fee would include the probes, which the patient changes after each binocular measurement. Also, the practice may take a deposit to encourage timely return of the device.

Medicare does not cover home IOP monitoring, and there is no associated Current Procedural Terminology (CPT) code, so patients are not reimbursed. Ophthalmic staff may be responsible for providing an Advance Beneficiary Notice of noncoverage to patients to sign and date prior to receiving the device, acknowledging that they are responsible for payment, either personally or through another insurance plan.3

The Icare HOME tonometer received FDA clearance in March 2017.

Utility and Accuracy

There are numerous reasons for self-monitoring of IOP, according’ to David S. Friedman, MD, MPH, PhD, professor and director, Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine. At-home monitoring can demystify these scenarios:

  • A glaucoma suspect with borderline IOPs, to determine if there are possible IOP spikes, particularly in the early morning hours.
  • In normal tension glaucoma, it may appear as though a patient’s IOP is well controlled, yet visual field continues to decline.
  • When initiating therapy to acquire a baseline measurement, then subsequent measurements to determine that the new anti-glaucoma drops are working adequately to lower the IOP.
  • To determine the necessity of adding a second drop or to justify referral for surgical intervention.
  • To postoperatively determine whether selective laser trabeculoplasty or minimally invasive glaucoma surgery was successful.
  • To determine if patients are using their anti-glaucoma drops correctly or missing instillations.

According to an abstract presented at ARVO in 2015 and subsequently published in the Journal of Glaucoma in 2016, Icare HOME tonometer results are generally consistent, whether measured by the doctor, allied health professional or the patient, and congruent with Goldmann applanation tonometry (GAT).4 Additionally, patients deemed the device satisfactory with respect to operability with an average single eye series measurement time of approximately 45 seconds with a standard deviation of ± 43 seconds.5 According to Dr. Friedman and his colleagues, 16% of patients could not be certified to use the Icare HOME tonometer because their IOP measurement was not within 5 mmHg agreement of that obtained by GAT. An additional 6% had difficulty using the device even after training and could not be certified.6


At-home IOP monitoring has the potential to change the management landscape for glaucoma suspects, refractory glaucoma cases and postsurgical monitoring. Ophthalmic allied health professionals will be the keyholders for this technology, confirming that patients are adequately trained to use the device and convincing them that the cost of rental far outweighs the unknowns of glaucoma. OP


  1. Icare. News and Events. March 22, 2017. . Accessed August 22, 2017.
  2. Icare HOME Instructional Manual for Health Care Professionals. Page 6. . Accessed August 22, 2017.
  3. Corcoran Consulting Group. Reimbursement for Self-Tonometry. March 2017. . Accessed August 22, 2017.
  4. TermChlen J, Mihailovic N, Alnawaiseh M, Dietlein TS, Rosentreter A. Accuracy of Measurements With the Icare HOME Rebound Tonometer. J Glaucoma. 2016;25:533-538.
  5. Mihailovic N, TermVehlen J, Eter N, Dietlein TS, Rosentreter A. Operability of rebound tonometers designed for self measurement of intraocular pressure. ARVO Annual Meeting Abstracts, 2015.
  6. Mudie, L, LaBarre, S, et al. The Icare HOME (TA022) Study: Performance of an Intraocular Pressure Measuring Device for Self-Tonometry by Glaucoma Patients. Ophthalmology. 2016;123:1675-1684.