Quick facts
- A tonometer is the instrument that measures intraocular pressure, and the probe or tip is the only part that touches the cornea.
- United States: the instrument and its accessories are classified together. 21 CFR 886.1930 covers a tonometer and accessories and places them in Class II.
- The tonometer sterilizer has its own entry. 21 CFR 886.1940 covers an AC-powered device that heat sterilizes a tonometer, and places it in Class I.
- Canada: a probe that contacts the surface of the eye is Class II under Rule 2(1) of Schedule 1 to the Medical Devices Regulations, SOR/98-282.
- The rule that separates the two countries is Rule 13(b): a device intended to disinfect or sterilize a medical device is Class II in Canada, so the tonometer sterilizer is Class I in the United States and Class II in Canada.
- The purchase decision is not the instrument; it is the contact surface, the fitting it goes into, and how that surface is cleaned between patients.
A tonometer is one of the few ophthalmic instruments that touches the eye every time it is used, and the pressure it reports depends on a tip that sits against the cornea. Two clinics can run the same tonometer and record different numbers because the tip, the cover and the way the tip is handled between patients are not interchangeable. This article sets out what the probe does, how each country files the instrument, the probe and the sterilizer, and what a clinic should be able to point at when it buys or reorders.
What is a tonometer probe, and why is the contact surface the whole story?
A tonometer measures intraocular pressure. The applanation type presses a small flat surface against the cornea and measures the force needed to flatten a fixed area; the indentation type measures how far the cornea is pushed in by a known weight. 21 CFR 886.1930 describes the instrument as a manual device intended to measure intraocular pressure by applying a known force on the globe of the eye and measuring the amount of indentation produced, or to measure intraocular tension by applanation, and notes that accessories may include a tonometer calibrator or a tonograph recording system.
The probe, tip or prism is the part that carries the contact. Three properties decide whether it does the job:
- Optical flatness and fit. An applanation tip that does not seat squarely against the instrument changes the area it flattens, and the pressure reading moves with it.
- Single use or reusable. A disposable tip is discarded between patients; a reusable tip has to be cleaned, disinfected and, where the maker requires it, sterilized between patients.
- Where the cover sits. Some systems use a probe cover or cone cover over the tip, and the cover becomes the part that touches the eye.
That last point is why the regulatory question is not theoretical. The instrument, the tip and the cover can each sit in a different regulatory position, and the pressure to keep them separate comes from infection control as much as from the device rules.
How do the Canadian and United States rules classify a tonometer and its accessories?
Both countries place the instrument in Class II, but they reach that class through different structures, and the accessory and the sterilizer do not follow the instrument.
| Item | Canada | United States |
|---|---|---|
| Entry that catches the instrument | None; class derived by rule | 21 CFR 886.1930, tonometer and accessories, Class II |
| What drives the class | Contact with the surface of the eye under Rule 2(1) | The device definition itself |
| Calibrator or tonograph accessory | Rule 7(2)(a) if sold as a calibrator, tester or quality control support, Class II | Named inside the same Class II entry |
| Tonometer sterilizer | Rule 13(b), Class II | 21 CFR 886.1940, Class I |
| Premarket position of the sterilizer | Licence where the derived class requires one | Exempt from premarket notification, subject to 21 CFR 886.9 |
| Who holds the licence or registration | Manufacturer, importer or distributor | Manufacturer or repackager |
| Wording that decides the case | Comes into contact with the surface of the eye | The identification in the section |
The United States section is compact and names the accessory inside the instrument entry: a tonometer calibrator or a tonograph recording system is part of 21 CFR 886.1930. Canada derives the same result by different steps. Rule 2(1) sends all invasive devices that penetrate the body through a body orifice or that come into contact with the surface of the eye to Class II, and a probe that rests on the cornea meets that wording. Rule 7(2)(a) is the clause that catches a calibrator sold on its own: a device intended to act as a calibrator, tester or quality control support to another medical device is Class II.
Does a tonometer sterilizer sit in the same class in Canada and the United States?
No, and this is the clearest difference in the whole category. In the United States the sterilizer is split out from the instrument and placed in Class I. 21 CFR 886.1940 describes a tonometer sterilizer as an AC-powered device intended to heat sterilize a tonometer, and classifies it as Class I, exempt from the premarket notification procedures in subpart E of part 807, subject to the limitations in 21 CFR 886.9.
Canada does not have a named tonometer-sterilizer entry, and the general rule does not leave it at Class I. Rule 13(b) of Schedule 1 states that a medical device that is intended to be used for disinfecting or sterilizing a medical device is classified as Class II. A bench unit whose stated job is to heat sterilize a tonometer between patients meets that wording, so the same appliance that is Class I in the United States is Class II in Canada.
Two consequences follow for a buyer. First, the appliance can change the class of the task even when the instrument does not, which is why a Canadian clinic should be able to name the sterilizer as a device in the file rather than treat it as generic bench equipment. Second, the reusable tip and the sterilizer are a matched pair: the cleaning, disinfection and sterilization instruction the maker publishes for the tip is the instruction the clinic has to be able to follow, and a sterilizer that was not qualified for the tip does not satisfy that instruction.
Which probe formats fit which work?
| Format | What it is | What a buyer should confirm |
|---|---|---|
| Reusable applanation tip | A solid tip that returns to the instrument after cleaning and disinfection | The maker's cleaning and sterilization instruction for the tip |
| Disposable tip | A single-use tip discarded between patients | Fit on the specific instrument model |
| Probe cover or cone cover | A cover that becomes the contact surface | Whether the cover is part of the cleared or licensed configuration |
| Calibration or verification accessory | A reference device used to check the tonometer | Whether it is sold as a calibrator or quality control support |
| Tonometer sterilizer | A heat sterilizer for reusable tips and probes | The temperature and time the maker states, and the record kept |
The format choice is a workflow decision. A disposable tip removes the between-patient reprocessing step and its record; a reusable tip keeps the cost per patient down but adds cleaning, disinfection, sterilization and a log. Neither is wrong, but the two are not interchangeable inside the same clinic without changing what the record has to show.
What should a clinic verify before it reuses a tonometer tip?
Five checks keep a reusable tip from becoming a source of unexplained variation:
- Fit on the labelled instrument. Test a tip on the model it was bought for before the box goes into rotation.
- The maker's reprocessing instruction. Cleaning, disinfection and sterilization steps are stated by the maker, and the clinic follows that instruction rather than a house preference.
- The sterilizer record. Where a sterilizer is used, the cycle and the result belong in a log that names the device.
- One change at a time. A tip change and an instrument change made in the same week cannot be separated afterwards.
- The calibration date. A calibration or verification accessory has a check interval, and the record belongs in the equipment file, not the purchase file.
Which consumables does an eye examination room go through?
An examination room restocks table paper, swabs, gloves, disinfectant and hand-hygiene supplies in the same cycle as its instruments. For clinics buying at case level, the wholesale ordering page sets out account and case terms, and the B2B wholesale collection lists the lines held for institutional buyers. The perforated examination-table paper roll is the kind of line we hold for treatment rooms, and clinics that also run an in-house sterilizer can start with the biological indicator 5-pack trial and read the sterilization monitoring collection for the monitoring lines.
Sources
- 21 CFR 886.1930, tonometer and accessories
- 21 CFR 886.1940, tonometer sterilizer
- 21 CFR 886.9, limitations of exemptions from section 510(k)
- Medical Devices Regulations, SOR/98-282, full text, Schedule 1
- Health Canada, medical devices
- Public Health Ontario, laboratory test information index
- Public Health Ontario, infectious diseases
- Canadian Centre for Occupational Health and Safety, OSH answers
- CCOHS, personal protective equipment
- College of Optometrists of Ontario, standards of practice
- Canadian Association of Optometrists, eye health library
- American Academy of Ophthalmology, glaucoma
- American Association for Pediatric Ophthalmology and Strabismus, glaucoma glossary
- National Eye Institute, glaucoma
- ISO 15004-1:2020, ophthalmic instruments, general requirements
- openFDA device classification database
- FDA device classification database search
- US OSHA bloodborne pathogens standard, 1910.1030
- World Health Organization, blindness and visual impairment
- World Health Organization, laboratory biosafety manual
Related reading
- Ophthalmic Eye Shields in Canada vs the US: Which Device Rules Apply
- Comprehensive Eye Check-Up in Canada vs the US: Which Exam Interval Applies
- Eye Wash Solution in Canada vs the US: Which Flushing Fluid Rules Apply
- Newborn Eye Tests in Canada vs the US: Which Red Reflex Rules Apply
CliniEco Medical supplies eye care, laboratory and clinic consumables of the kind described in this article. MDEL #35334. This article is written for clinic, procurement and infection-control professionals and is not clinical guidance; instrument handling and reprocessing belong to the treating professional and the clinic's infection-control lead.
Frequently Asked Questions
Is a tonometer a Class II device in the United States?
Yes. 21 CFR 886.1930 covers a tonometer and accessories and places the device in Class II. The same section names the tonometer calibrator and the tonograph recording system as accessories inside the entry.
Is a tonometer Class II in Canada?
Yes, by rule rather than by a named entry. Rule 2(1) of Schedule 1 to the Medical Devices Regulations classifies invasive devices that come into contact with the surface of the eye as Class II, and an applanation tip that rests on the cornea meets that wording.
What class is a tonometer sterilizer in each country?
It is Class I in the United States and Class II in Canada. 21 CFR 886.1940 places the AC-powered tonometer sterilizer in Class I, while Rule 13(b) of Schedule 1 classifies a device intended to disinfect or sterilize a medical device as Class II in Canada.
Is a tonometer calibrator a different device from the tonometer?
In the United States it is an accessory named inside the tonometer entry, so it is Class II. In Canada a calibrator sold on its own is caught by Rule 7(2)(a), which classifies a device intended to act as a calibrator, tester or quality control support to another medical device as Class II.
Does a disposable tip change the device class?
No. The class follows the instrument and the accessory, not whether the tip is single use. What a disposable tip changes is the between-patient reprocessing step and the record the clinic keeps for it.
What should a clinic keep on file for a reusable tonometer tip?
The maker's cleaning, disinfection and sterilization instruction for the tip, the record of the cycle where a sterilizer is used, the calibration or verification date for any reference accessory, and the identity of the instrument the tip was fitted to. The record belongs in the equipment file rather than the purchase file.
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