Technology overview

This briefing describes the regulated use of the technology for the indication specified, in the setting described, and with any other specific equipment referred to. It is the responsibility of healthcare professionals to check the regulatory status of any intended use of the technology in other indications and settings.

About the technology

CE marking

The Icare tonometers are CE marked as class IIa devices under the medical device directive 93/42/EEC. CE marks were awarded in 2003 for TA01i, 2010 for Icare PRO, and 2015 for Icare ic100. Icare ic100 is functionally similar to Icare TA01i, which is expected to be discontinued in 2017. Icare ONE received CE marking in 2010. In 2014, the Icare ONE was updated (removing the display and adding positioning assistant technology, automatic left or right eye recognition and automated measuring sequences) and received CE marking as the Icare HOME. The 4 devices are manufactured by Icare Finland Oy. In the UK, Icare tonometers are supplied by Mainline Instruments.


Icare tonometers are portable, handheld devices used to measure IOP. They assess the deceleration and rebound time of a small, lightweight probe, which makes brief contact with the cornea and can be used without local anaesthesia.

There are 4 Icare models, all of which use the same rebound technology: Icare TA01i, Icare ic100, Icare PRO and Icare HOME (previously known as Icare ONE; see table 1). Each model has a built‑in adjustable forehead support and is supplied with single‑patient use probes, a spare probe base and a container for cleaning the probe base (recommended every 3–6 months). The probes are disposable and must be changed for each patient, but can be used for both eyes assuming there is no eye infection. Several additional accessories are supplied with each model, including a USB cable and a USB memory stick with Icare LINK software for the Icare PRO and Icare HOME, and a USB charger (for rechargeable battery) for the Icare PRO. Icare HOME is also supplied with a carrying case.

Icare PRO and Icare HOME can be connected to a computer. Icare LINK software can be installed on the computer and used by healthcare professionals to transfer, analyse and store measurement data from the handheld device.

Table 1 Features of Icare TA01i, Icare ic100, Icare PRO and Icare HOME

Icare TA01i

Icare ic100

Icare PRO

Icare HOME

Approximate dimensions (mm)





Approximate weight, with batteries (g)






Monochromatic 7‑digit liquid crystal display (LCD)

128×128 pixel organic light‑emitting diode (OLED) display

128×128 pixel organic light‑emitting diode (OLED) display

No display

Data transfer

No data transfer

No data transfer

USB port for data transfer to PC with Icare LINK software

USB port for data transfer to PC with Icare LINK software

Data storage

Stores previous 10 readings

Stores over 1000 readings

Stores over 1000 readings

Stores over 1000 readings

Position of the person during the measurement

Standing or sitting

Standing or sitting

Standing, sitting or lying down in the supine position

Standing or sitting

Notification of incorrect device position

Two short beeps and an error message on the display

Red light on probe base for incorrect positioning or green light for correct positioning

Two short beeps and an error message on the display

Red light on probe base for incorrect positioning or green light for correct positioning

Eye recognition



User can manually select 'left' or 'right' depending on which eye is being measured

Automatic eye recognition to identify left or right eye

Probe material(s)

Wire pin with a plastic tip

Wire pin with a plastic tip


Wire pin with a plastic tip

Power supply

4 AA non‑rechargeable lithium batteries

4 AA non‑rechargeable batteries

Rechargeable internal lithium‑ion battery

2 CR123 non‑rechargeable batteries

Icare tonometers are used as follows:

  • The tonometer is switched on by pressing the 'measurement' button (or 'main' button for Icare PRO). A new single‑patient use probe is inserted into the probe base and the button is pressed again to activate the probe.

  • The person is positioned appropriately according to the tonometer in use: standing or sitting for all devices, or supine for Icare PRO only. The person looks straight ahead and the tonometer is brought close to the eye with the probe perpendicular to the centre of the cornea. The forehead support should be positioned against the forehead. The distance between the tip of the probe and the cornea should be 4–8 mm for Icare TA01i, Icare ic100 and Icare HOME and 3–7 mm for Icare PRO. The person taking the measurements can move the forehead support by turning the adjustment wheel to ensure the probe is correctly positioned.

  • The IOP reading is based on 6 individual readings (1 measurement sequence, which takes about 2 seconds). The user must press the 'measurement' button to perform 1 individual IOP measurement. Both Icare ic100 and Icare HOME also have a 'series' mode, in which the user only needs to press the 'measurement' button once and keep the button pressed down to activate 6 automatic measurements. Each device calculates the final IOP measurement by discarding the highest and lowest readings and displaying the average of the remaining 4 readings. The probe moves to the cornea and back during every measurement and a short beep sounds after each measurement has been taken. The Icare TA01i, ic100 and PRO tonometers show results and measurement reliability on the display. The Icare HOME tonometer does not display the final IOP, but measurements can be transferred to a computer directly from the device by a healthcare professional using the Icare LINK software during routine monitoring assessments.

Setting and intended use

The Icare TA01i, Icare ic100 and Icare PRO devices are intended to measure IOP. They would be used by optometrists or ophthalmologists in primary, secondary or tertiary care settings. Although professionals should read the user manual before using Icare, no additional training is needed. However, a training session is offered by the manufacturer, if needed.

Icare HOME is intended to be used by adult patients or adult carers in the home to monitor IOP. According to the instructions for use, an eye care professional should observe the patient using the tonometer and provide certification before the device can be used in the home. Certification should be provided if the readings taken by the patient and the healthcare provider fall within 5 mmHg of each other, the range of the (3) readings taken by the patient is 7 mmHg or less and the position of the tonometer during the measurement is judged to be correct.

The manufacturer does not list contraindications for these devices; however, they state that their safety and effectiveness have not been evaluated in people with a variety of eye pathologies, including (but not limited to) corneal scarring, dry eyes, or corneal or conjunctival infections.

Current NHS options

NICE's guideline on glaucoma recommends that Goldmann applanation tonometry (GAT) should be used to measure IOP in people with ocular hypertension (OHT) or chronic open‑angle glaucoma (COAG), and in those who are suspected of having COAG. GAT is a contact technique for measuring pressure in the eye, in which the patient is given anaesthetic eye drops before the pressure inside the eye is measured by applying force directly to the cornea. Optometrists use both contact and non‑contact (such as air‑puff) tonometry to detect glaucoma (College of Optometrists and Royal College of Ophthalmologists 2013).

The NICE guideline on glaucoma also recommends the following tests, in addition to GAT, for people with OHT, COAG, or suspected COAG:

  • central corneal thickness (CCT) measurement

  • peripheral anterior chamber configuration and depth assessments using gonioscopy

  • visual field measurement using standard automated perimetry (central thresholding test)

  • optic nerve assessment, with dilatation, using stereoscopic slit lamp biomicroscopy with fundus examination.

The results of these tests estimate the risk of progression to glaucoma (CCT measurement, visual field measurement and optic nerve assessment) and assess for angle closure (peripheral anterior chamber configuration and depth assessments), thus indicating the level of clinical supervision and treatment needed. The guideline recommends that people with OHT or suspected COAG are monitored at regular intervals (every 4–6 months for people at high risk and 12–24 months for people at low risk of COAG). Monitoring intervals for people with confirmed COAG are based on their risk of progression to sight loss, and range from every 2–6 months to every 6–12 months. NICE recommends that an optometrist or ophthalmologist should perform GAT at every monitoring assessment for all people with OHT, or COAG, or those suspected of having COAG.

Icare tonometers are the only devices that currently use rebound tonometry to measure IOP. NICE is aware of the following CE‑marked devices that appear to provide alternatives to GAT:

  • Pascal Dynamic Contour tonometer (Swiss Microtechnology)

  • Perkins Mk3 (Haag‑Streit UK)

  • Tono‑Pen (Reichert Technologies)

  • Triggerfish (SENSIMED); NICE has produced a medtech innovation briefing on Triggerfish

  • Diaton tonometer (TGDc‑01 Ryazan State Instrument, Ryazan)

  • Ocular response analyser (Reichert Technologies)

  • Corvis ST tonometer (Oculus).

Costs and use of the technology

Information on the cost of using the technology has been sourced from the manufacturer. The capital components of each Icare tonometer system have the following prices, excluding VAT:

  • Icare TA01i: £2,195

  • Icare ic100: £2,395

  • Icare PRO: £3,695

  • Icare HOME: £1,595

The probe bases for each system have the following prices (excluding VAT):

  • Icare TA01i and ic100: £40

  • Icare PRO: £50

  • Icare HOME: £40

The disposable probes for each system cost (excluding VAT):

  • Icare TA01i and ic100: 100 for £70

  • Icare PRO: 100 for £50

  • Icare HOME: 50 for £50

A staff training session is included in the price of an Icare tonometer if needed.

No other practical difficulties have been identified in using or adopting the technology.

The manufacturer suggests that the lifespan of these 3 technologies is 'tens of years'; a lifespan of 15 years has been assumed in this briefing. Both the Icare TA01i and Icare ic100 use 4 AA batteries, which cost an average of £1.06. The Icare HOME needs 2 CR123 batteries, which cost about £3.23. No routine maintenance or calibration is needed for any of the Icare tonometers, but the probe base and batteries should be replaced every 12 months for Icare HOME, Icare TA01i and Icare ic100. The probe base (and connected probe holder) should be replaced every 6 months for Icare PRO.

If a monitoring session with a healthcare professional takes 15 minutes, up to 30 Icare TA01i, ic100 or PRO measurements could be taken per day (7.5 hours), and 7,200 taken in 1 year (240 annual working days). Icare HOME measurements (self‑monitoring) are typically taken 5 times per day (Asrani et al. 2011). Assuming that the Icare HOME is loaned to a different patient each week, this leads to 1,825 monitoring sessions per year. Using the standard annuity method with a discount rate of 3.5% gives the following costs per IOP assessment (inclusive of capital cost and costs of regular replacement of probe base, batteries and disposable probe):

  • Icare TA01i and ic100: £0.70

  • Icare PRO: £0.60

  • Icare HOME: £1.10

No unit cost for GAT is reported in nationally representative sources. The NICE guideline on glaucoma uses the national tariff figure for follow‑up visit to an outpatient ophthalmology clinic as the cost for a monitoring session. It notes that these monitoring sessions can include measurement of IOP with GAT. This method gives a cost of £59 (NHS National Tariff 2014/15; WF01A, 130), which may indicate the unit cost of GAT and includes a variety of resource uses (for example, the ophthalmologist's time).

Likely place in therapy

Icare rebound tonometers would be used for measuring IOP as a replacement, or addition to, existing tonometry methods.

Specialist commentator comments

Two specialist commentators stated that Icare tonometers may be most useful in paediatric and community care settings; one of the commentators noted that Icare tonometers could also be useful in secondary care ophthalmology clinics. Two commentators stated that fast pressure measurement is particularly important in paediatric ophthalmology and one of these commentators also noted that Icare tonometers could be useful for paramedics. Two commentators noted that anaesthetic eye drops are not needed when using Icare tonometers, which one commentator felt would be preferred by most children, and it also allows them to be used by trained non‑medical personnel. However, according to another specialist, the Icare tonometer is unreliable when used in children's glaucoma clinics because the results do not correspond to those obtained with GAT. One commentator added that there is evidence that Icare is useful in the neonatal setting, specifically in the special care department, citing the study by Rodrigues and Chan (2014). Two commentators stated that Icare tonometers can also be used in patients with disabilities, and are easy to use.

Two specialist commentators stated that Icare may not be useful in clinical settings already using GAT, which is likely to be the preferred measurement method. One of the commentators considered that GAT may be used to supplement IOP results if the Icare reading is unusual or a more accurate reading is needed. Another commentator reiterated this point, stating that in the hospital setting, Icare should only be used for patients in whom GAT measurements are unobtainable, whereas in primary care, the indication for using Icare should be similar to that of other non‑contact tonometers.

Two specialist commentators stated that Icare is useful as a screening tool, whereas a third specialist noted that additional technologies would be needed alongside Icare for screening in a hospital clinic. A fourth specialist commentator stated that more research should be done to evaluate the effectiveness of Icare for screening. One specialist commentator noted that GAT is the preferred tool for monitoring IOP in people who have confirmed glaucoma.

One specialist commented on the poor repeatability reported in the published Icare studies discussed in the briefing, stating that it may be a result of users not positioning the device in the centre of (or perpendicular to) the cornea. This was supported by another specialist who stated that ensuring the centre of the cornea is 'hit' with the probe is more difficult to guarantee with Icare than with a conventional tonometer. The commentator explained that rebound tonometry is affected by corneal hysteresis (a biomechanical property of the cornea relating to its elasticity), which is why peripheral measurements can give erroneous results (although these will not necessarily be clinically significant).

Two specialist commentators noted that other potential causes of incorrect Icare IOP readings include biomechanical changes to the cornea caused by medicated eye drops to treat glaucoma, and 'stiff' corneas associated with diabetes. These specialist commentators also noted that Icare readings may be affected by different corneal biomechanics and other visual pathologies (including myopia), and such inaccuracies can often result in false referrals for these people. One of the commentators stated that this problem can also happen with non‑contact tonometers, but less often. Three commentators emphasised the importance of measuring CCT, because this influences IOP measurement and will vary across a population. One of the commentators specified that Icare will overestimate GAT where CCT is high and underestimate it where CCT is low.

One commentator discussed costs, stating that it is unlikely that monitoring sessions will take place every day of the week and there will be high variability in the frequency of tonometer use depending on the setting. They also noted that it is unlikely that Icare HOME would be used as often as 5 times per day every day of the year. A second commentator stated that Icare is affordable and a third commentator noted that Icare may be associated with a reduction in costs because, unlike GAT, it does not need clinically qualified staff time (clinical assistants can use the device). Additionally, the commentator stated that the cost per measurement of the Icare devices (about £1 based on the cost of the disposable probe) is similar to the cost of using GAT with a disposable prism and topical anaesthetic.

Equality considerations

NICE is committed to promoting equality, eliminating unlawful discrimination and fostering good relations between people with particular protected characteristics and others. In producing guidance, NICE aims to comply fully with all legal obligations to:

  • promote race and disability equality and equality of opportunity between men and women

  • eliminate unlawful discrimination on grounds of race, disability, age, sex, gender reassignment, marriage and civil partnership, pregnancy and maternity (including women post‑delivery), sexual orientation, and religion or belief (these are protected characteristics under the Equality Act 2010).

Vision loss may be classified as a disability depending on its effect on the ability to carry out normal day‑to‑day activities. Disability is a protected characteristic defined in the Equality Act (2010). People who are registered as blind or partially sighted are automatically considered to be disabled under the Act.

People with diabetes are more likely to develop OHT and glaucoma and, therefore, may particularly benefit from Icare devices. Diabetes is a chronic disease. Chronic disease is treated as a disability if it has a substantial and long‑term adverse effect on a person's ability to carry out normal day‑to‑day activities. Older populations and people of African and African‑Caribbean family origin are also at increased risk of developing OHT and glaucoma. Age and race are protected characteristics defined in the Equality Act 2010.