Quick facts
- A corneal electrode is the contact lens-shaped electrode placed on the anaesthetised eye during an electroretinogram (ERG), where it picks up the tiny electrical response the retina produces when it is stimulated by light.
- In the United States a corneal electrode is a named Class II entry at 21 CFR 886.1220, under its own product code.
- Canada lists no corneal electrode by name. A device the Regulations describe as coming into contact with the surface of the eye is an invasive device, and Rule 2 of Schedule 1 to the Medical Devices Regulations places that device in Class II.
- The two countries reach the same class from different directions: the United States from a named entry, Canada from the rule that catches a device touching the eye.
- A corneal electrode is a reusable or single-use contact device, so the cleaning and storage routine matters as much as the class, and it sits with the diagnostics rather than with the instruments.
- The entries and rule text quoted here were checked against the openFDA device classification API and the Regulations on 2026-10-10.
A corneal electrode is the part of an electroretinogram that touches the patient. The retina generates a small voltage when light hits it, and the electrode is the sensor that reads that voltage, so an ERG laboratory lives or dies on how well the electrode couples to the eye. For a clinic buying them, there are two questions: what the device has to clear before it is sold, and which type to stock. This article answers the first from both rulebooks and the second from how the test is run.
What does a corneal electrode do?
Electroretinography measures the electrical response of the retina to a flash of light. The signal is on the order of a few microvolts, so the electrode has to sit against or near the eye, and the conductive path has to be stable for the seconds the recording takes. A corneal electrode is shaped like a contact lens or a small shell so it can rest on the anaesthetised cornea, and it is filled or coated with a conductive medium so the signal passes cleanly.
The test is used where a clinician needs to know whether the retina itself is working, which includes the investigation of inherited retinal disease, the assessment of a patient who cannot describe their vision, and the monitoring of retinal toxicity from certain medicines. The electrode is the first link in that chain, and a loose or dry electrode shows up as noise on the trace rather than as a clear reading.
How does the United States classify a corneal electrode?
The United States files the device by name. Regulation 21 CFR 886.1220 is titled "Corneal electrode," and the device inside it is Class II. It sits in the ophthalmic family of the code, in the same part as the perimeter and the ophthalmoscope, and it carries a product code of its own so that a filing names the electrode rather than the whole ERG system.
| Item | United States | Canada |
|---|---|---|
| Basis of the class | Named entry, 21 CFR 886.1220 | Rule 2, Schedule 1, MDR |
| Class | Class II | Class II |
| Why that class | The named entry | The device contacts the surface of the eye |
| Market path for the maker | Premarket notification, unless the product code is exempt | Device licence under section 32, supported by an ISO 13485 certificate |
| Who may import or sell | Establishment registration | Establishment licence |
| Related ophthalmic entries | Perimeter 886.1605, ophthalmoscope 886.1570 | Rule-based, no named entries |
A Class II entry reaches the market with the controls the regulation attaches to it, and premarket notification applies unless the specific product code is exempt. The practical effect for a buyer is that the electrode carries a filing, and the filing survives only as long as the manufacturer keeps the quality system behind it.
How does Canada classify the same electrode?
Canada starts from the eye rather than from a name. The Medical Devices Regulations define an invasive device as a device intended to come into contact with the surface of the eye or to penetrate the body, and a corneal electrode is squarely inside that definition because it rests on the cornea. Schedule 1 then places an invasive device of that kind in Class II under Rule 2.
That is the same number the United States reaches, and the route is what differs. A Canadian buyer asking for a corneal electrode is asking about a device licence and an establishment licence; a United States buyer is asking about a clearance number. Both are asking for evidence, and the evidence is different paperwork for the same physical object.
Which electrode type does a laboratory stock?
The choice follows the protocol rather than the country. A contact lens electrode is worn on the cornea and gives a stable signal, so it suits the full-field ERG used for inherited retinal disease and for toxicity monitoring. A fibre or thread electrode rests on the lower lid or the conjunctiva and needs no anaesthetic drop, which is why it is used where a patient cannot tolerate a lens on the eye, including some paediatric work. A single-use electrode removes the cleaning step at the cost of a consumable per test, while a reusable one needs a defined disinfection routine between patients.
| Electrode type | Where it sits | Typical use | Cleaning step |
|---|---|---|---|
| Contact lens electrode | On the anaesthetised cornea | Full-field ERG, toxicity monitoring | Defined disinfection between patients |
| Fibre or thread electrode | Lower lid or conjunctiva | Paediatric work, patients who cannot wear a lens | Wipe and store per the instructions |
| Single-use electrode | On the cornea, used once | High-volume screening | None, disposed after the test |
| Reusable shell electrode | On the cornea, reused | Referral laboratory work | Reprocessing routine on file |
Two checks keep a purchase clean in either country. First, ask the distributor which entry or rule the electrode is filed under and keep that answer on file. Second, ask for the conductive medium the electrode is specified with, because an electrode run with the wrong gel reads a shifted signal, and no filing corrects that.
Do Canada and the United States use the same testing standard?
The technical layer is shared. ISO 15004-1 sets the fundamental requirements for ophthalmic instruments, including the electrical and environmental conditions a device is built to meet, and ISO 13485 sets the quality management system a manufacturer of either market works to. A recording made in a Toronto laboratory and a Denver laboratory follows the same international convention for which wave is analysed, so a trace can be read across the two.
The point where the two rulebooks diverge is not the electrode but the trace. The class of a device does not set a normal range, and a laboratory's reference values come from its own protocol and its own reference material, not from the supplier. A supplier that quotes a diagnostic threshold is quoting a clinical judgement it does not own.
What does a clinic check before it buys electrodes?
The purchasing decision turns on the protocol. A laboratory that runs a full-field ERG for toxicity monitoring buys a contact lens electrode because it gives the lowest noise against the trace. A paediatric service buys a fibre electrode because it does not need a drop and a child tolerates it. A high-volume screening service buys single-use electrodes because it values the removed cleaning step over the unit price.
A practice also has to decide what happens between patients. A reusable electrode needs a defined disinfection routine and a place to dry, and the routine belongs in the same written procedure as the rest of the room. Keeping the electrodes with the rest of the reusable contact devices, rather than beside the single-use stock, is the simple fix that stops the two being mixed up.
Which consumables does a diagnostic lane restock?
The electrode is the device; the lane around it runs on consumables. A diagnostic room restocks the smooth examination table paper it replaces between patients and the occlusion eye patch set it keeps for patients who need one eye covered during a test. A practice that also monitors its own steriliser pairs the sterilization monitoring range with the 24-hour monitoring five-pack. Clinics and 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 886.1220, Corneal electrode
- 21 CFR 886.1605, Perimeter
- 21 CFR 886.1570, Ophthalmoscope
- Medical Devices Regulations, SOR/98-282, full text
- openFDA device classification API
- ISO 15004-1:2020, fundamental requirements for ophthalmic instruments
- ISO 13485:2016, medical devices quality management
- ISO 14971:2019, risk management for medical devices
- ISO 10940:2009, ophthalmic instruments and fundus cameras
- Health Canada, medical devices
- CCOHS, OSH answers
- Public Health Ontario, infection prevention and control
- Opto, eye health library
- American Academy of Ophthalmology, eye health
- Royal College of Dental Surgeons of Ontario
- Canadian Dental Association
- WHO, Laboratory biosafety manual
- American Optometric Association
- eCFR, Title 21, Food and Drugs
- Minnesota Department of Health
A record of when a reusable electrode was last disinfected, and by whom, is the part of a diagnostic room that is hard to rebuild after the fact. The printable device disinfection log is a blank form with columns for the device, the date and the initials of the person who ran the step. The disinfection log generator on the same page sizes the form to the number of rooms a practice runs. No account and no sign-up are needed to open either one.
Every diagnostic room is set up differently. 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
- Eye Test Charts in Canada vs the US: Which Optotype Standard?
- Retinal Diagnostic Software in Canada vs the US: Which Route Applies?
- Corneal Topographers in Canada vs the US: Which Class?
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
Is a corneal electrode a Class II device in the United States?
Yes. A corneal electrode is a named Class II entry at 21 CFR 886.1220, which is the regulation titled Corneal electrode, and it carries a product code of its own.
How does Canada classify a corneal electrode?
Canada lists no corneal electrode by name. A device the Regulations describe as coming into contact with the surface of the eye is an invasive device, and Rule 2 of Schedule 1 places an invasive device of that kind in Class II.
Which corneal electrode type should a clinic stock?
The protocol decides. A full-field ERG for inherited retinal disease or toxicity monitoring uses a contact lens electrode, a paediatric service uses a fibre electrode that needs no anaesthetic drop, and a high-volume service buys single-use electrodes.
What conductive medium does a corneal electrode need?
The electrode is specified with a conductive medium, and the recording is run with that medium. Running an electrode with the wrong gel shifts the signal, and no refiling corrects a recording made through the wrong conductive path.
Do Canada and the United States use the same ERG standard?
Both markets build on the shared ISO layer, including ISO 15004-1 for ophthalmic instruments and ISO 13485 for quality management, so a trace is read under the same international convention in either country.
Is a corneal electrode reusable?
It can be either. A single-use electrode removes the cleaning step at the cost of a consumable per test, while a reusable electrode needs a defined disinfection routine between patients and a place to dry.
What paperwork should a clinic keep for an electrode?
Ask the distributor which entry or rule the electrode is filed under, keep the conductive specification on file, and record when a reusable electrode was last disinfected.
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