Quick facts
- A gonioscopy prism is a small prism, usually mounted in a handle or a lens ring, that is placed on the anaesthetised cornea so a clinician can see the drainage angle at the base of the iris.
- United States: the prism is a named entry at 21 CFR 886.1660, "Prism, gonioscopic," and the device is placed in Class I.
- Canada: the prism comes into contact with the surface of the eye, so it reaches Class II through Rule 2(1) of Schedule 1 to the Medical Devices Regulations, SOR-98-282, which clasps an invasive device that contacts the surface of the eye.
- The two columns disagree: Class I in the United States and Class II in Canada, because one side names the prism in a low-risk entry and the other acts on the contact with the eye.
- A prism used for a momentary view is not held to Class III, which Rule 2(3) reserves for a device normally intended to remain in contact with the surface of the eye for at least 30 consecutive days.
- The entry and rule text below were checked against the current CFR text and the Regulations on 2026-10-10.
A gonioscopy prism is the lens a clinician presses lightly onto the anaesthetised cornea to look at the angle where the iris meets the cornea. The angle is hidden behind the cornea, so a prism with a mirrored face is used to fold the view forward, and the prism has to touch the eye for the view to work. That contact is the fact both rulebooks act on, and it is the reason the same piece of glass reads one class in the United States and a higher class in Canada. This article sets out what the prism does, how each country files it, and what a practice should be able to point at when the prism is used and when it is reprocessed.
What is a gonioscopy prism, and what does it do?
The prism is a small block of optical glass or acrylic with a curved contact face and one or more mirrored inner surfaces. The contact face is set on the anaesthetised cornea with a coupling gel, and the mirrors fold the light so that the clinician sees the drainage angle, the trabecular meshwork and the iris root, none of which are visible through the clear cornea alone. The prism is held on the eye for seconds at a time and lifted between views.
The device is used in glaucoma assessment and in the follow-up of an angle that has been treated. It is a diagnostic device rather than a therapeutic one, it supplies no energy to the eye, and it is not worn. It contacts the surface of the eye only while the view is being taken, and that momentary contact is what decides its class in Canada.
How does the United States classify a gonioscopy prism?
The United States names the prism in its own entry. 21 CFR 886.1660 is titled "Prism, gonioscopic," and the device inside it is placed in Class I. The entry describes a prism intended to be placed on the cornea for the examination of the angle, and a Class I device of this kind is subject to general controls.
| Item | United States | Canada |
|---|---|---|
| Named entry | 21 CFR 886.1660 | No entry names the prism; the rules classify it |
| Class | Class I | Class II, by Rule 2(1) |
| Basis of the class | The named entry | The prism contacts the surface of the eye |
| Premarket route | General controls; premarket notification only if the entry is not exempt | Device licence under section 32, supported by an ISO 13485 certificate |
| Who may import or sell | Establishment registration | Establishment licence |
A buyer who reads only the class sees a low-risk article. What the entry does not say is that the class turns on the named prism rather than on the contact, and that is where the two countries part company.
How does Canada classify the same prism?
Canada reaches the answer from the Rules in Schedule 1 rather than from a name, and the Rules look at how the device meets the body. The prism comes into contact with the surface of the eye while it is used, so it is an invasive device that reaches the eye through a body opening, and Rule 2(1) places all invasive devices that penetrate the body through a body orifice or that come into contact with the surface of the eye in Class II.
The exceptions in Rule 2 do not lower the class. Rule 2(2) reaches a device placed in the oral or nasal cavities as far as the pharynx or in the ear canal up to the ear drum, which does not describe a prism on the cornea. Rule 2(3) lifts a device to Class III where it is normally intended to remain in contact with the surface of the eye for at least 30 consecutive days, and a prism is lifted away after each view, so it stays in Class II.
That is the whole contrast. The Canadian column reads the prism as an eye-contacting device; the United States column names it in a low-risk entry. The glass is the same in each case, and the class a practice records depends on the country the order ships into.
Which rules decide the class in each country?
The two lists can be put side by side, because they answer the same questions from different materials.
| Question | Canada | United States |
|---|---|---|
| What files the device | The rule for a device that contacts the surface of the eye | The named entry for the prism |
| Class | Class II | Class I |
| How long it touches the eye | Momentary, lifted between views | Momentary, lifted between views |
| What would lift it further | Rule 2(3) lifts a device worn for 30 days or more to Class III | Not applicable to this entry |
| Maker's path | Device licence under section 32, supported by an ISO 13485 certificate | General controls, premarket notification only if the entry is not exempt |
Read across, the columns agree that the prism touches the eye for a short time and disagree on what that contact does to the class. The Canadian column is a rule that catches an eye-contacting device; the United States column is a named entry that keeps it low.
Do Canada and the United States use the same optical standards?
The technical layer is shared. ISO 13485:2016 sets the quality management system behind the manufacturer's records, and ISO 14971:2019 sets the risk management process behind the design file. The optical finish of the contact face, the angle of the mirrors and the way the prism is mounted in its holder are written to the same kind of specification for either market.
The point where the two rulebooks diverge is reprocessing, not optics. A prism that touches the cornea sits between two patients, so the cleaning and disinfection step between uses is the part that matters at the bench, and it is set by the manufacturer's directions and by the infection prevention policy of the clinic rather than by the class alone. A supplier that quotes a class as a cleaning instruction is quoting something the class does not carry.
What does a practice check before it buys gonioscopy prisms?
A practice ordering prisms for an angle clinic works through three checks. First, confirm the contact face and the coupling route, because a face that is scratched or a gel left in the ring spoils the view. Second, confirm the mirror count and the field, because a single-mirror prism and a four-mirror prism cover different parts of the angle. Third, confirm the reprocessing routine, because the step between patients is the part that has to be written down.
A practice that also runs a contact lens service keeps the prism beside the trial set and the lens care stock, so the bench that cleans a diagnostic prism is the same bench that handles a worn lens. Keeping the two routines on one sheet is the simple fix that carries across both countries.
Which consumables does a diagnostic lane restock?
The prism is one line on a diagnostic shelf that turns over quickly. A practice restocks the multipurpose contact lens solution it keeps for lens work on the same bench and the Snellen and Amsler chart set it uses at the visual-acuity step. The wall-mounted eye wash station is the rinse point kept at the sink in a room where the eye is touched, and the individually wrapped cotton swabs stay there for wipe-down. Clinics that monitor their own reprocessing pair the sterilization monitoring collection with the 24-hour biological indicator 50-pack. Multi-site groups ordering at case level use the wholesale ordering page, and the B2B wholesale collection lists the lines held for institutional buyers. Reselling? become a distributor.
Sources
- 21 CFR 886.1660, prism, gonioscopic
- openFDA device classification API
- Medical Devices Regulations, SOR/98-282, full text and Schedule 1
- US FDA, medical devices
- US FDA, medical device databases
- US FDA, overview of device regulation
- Health Canada, medical devices
- Standards Council of Canada
- CSA Group
- ISO 13485:2016, medical devices quality management
- ISO 14971:2019, risk management of medical devices
- Canadian Association of Optometrists
- College of Optometrists of Ontario
- CCOHS, OSH answers
- American National Standards Institute
- US FDA, contact lenses
A diagnostic prism is used between two patients and has to be accounted for, and the printable instrument reprocessing log is a blank form with columns for the instrument, the patient, the cleaning step, the disinfectant and the date, so a practice can show the step between every pair of eyes.
The reprocessing log generator on the same page sizes the form to the number of lanes a practice runs, so a single room and a multi-lane clinic print the same sheet at two volumes.
Every clinic and every prism differ. Ask a compliance specialist and you will get a written answer specific to your equipment and province, with the regulation or standard it is based on cited.
Related reading
- Ophthalmoscopes in Canada vs the US: which device class
- Slit lamps in Canada vs the US: which class
- Corneal electrodes in Canada vs the US: which class applies
CliniEco Medical supplies eye care, laboratory and dental consumables of the kind described in this article. MDEL #35334. This article is written for optometry, laboratory and procurement professionals and is not legal advice; the class of a device and the records kept by a practice belong to the manufacturer and to the requirements that apply to it.
Frequently Asked Questions
What class is a gonioscopy prism in the United States?
It is a named entry at 21 CFR 886.1660, Prism, gonioscopic, and the device inside that entry is Class I, subject to general controls.
What class is a gonioscopy prism in Canada?
The prism contacts the surface of the eye, so it reaches Class II through Rule 2(1) of Schedule 1 to the Medical Devices Regulations.
Why is the same prism a higher class in Canada?
The United States keeps the prism in a low-risk named entry, while Canada classifies by how the device meets the body and lifts a device that contacts the surface of the eye to Class II.
Would a prism worn for a month be Class III?
A device normally intended to remain in contact with the surface of the eye for at least 30 consecutive days reaches Class III through Rule 2(3), but a gonioscopy prism is lifted between views and stays in Class II.
Does the prism supply energy to the eye?
No. It is a passive optical device with mirrored faces that fold the view of the angle; no energy is delivered to the eye and no part of it is worn.
What should a practice record for a diagnostic prism?
Record the instrument, the patient, the cleaning and disinfection step and the date, so the step between any two eyes can be shown from the log.
0 commentaire