MDCG 2025-8: Master UDI-DI for spectacle devices, explained
How to assign Basic UDI-DIs and Master UDI-DIs to spectacle frames, spectacle lenses and ready-to-wear reading spectacles, with assignment triggers.
MDCG 2025-8 Rev.1 turns the Master UDI-DI rule for spectacles into concrete assignment logic. Basic UDI-DI groups devices by broad construction, material or lens-design parameters; Master UDI-DI adds the design values needed to identify highly individualised groups. The guidance covers labels, packaging, Eudamed and vigilance, with mandatory application from 1 November 2028.
Who this applies to
This guidance applies to manufacturers of spectacle frames, spectacle lenses and ready-to-wear reading spectacles. It is the detailed implementation companion to the timeline in MDCG 2025-7 and should be used by UDI, regulatory, product-master, labelling and vigilance teams.
Its purpose is to avoid assigning a separate UDI-DI to every highly individualised variant. Master UDI-DI groups devices that share the same essential design characteristics, intended purpose and defined design parameters.
Basic UDI-DI, Master UDI-DI and UDI-PI
The three identifiers do different jobs:
Identifier |
On the device label? |
In Eudamed? |
Role |
|---|---|---|---|
Basic UDI-DI |
No |
Yes |
Groups devices with the same intended purpose, risk class and essential design/manufacturing characteristics |
Master UDI-DI |
Yes |
Yes |
Acts as the UDI-DI for a defined group of highly individualised spectacle devices |
UDI-PI |
Yes |
The PI type is registered; individual PI values are not |
Identifies the production unit through lot, serial number, manufacturing date or other production data |
One Master UDI-DI can link to only one Basic UDI-DI, while one Basic UDI-DI can have multiple Master UDI-DIs. Brand names and catalogue numbers are not, by themselves, Master UDI-DI assignment triggers.
The assignment triggers
The guidance gives a different parameter set for each product group:
Product |
Basic UDI-DI parameters |
Additional Master UDI-DI parameters |
|---|---|---|
Spectacle frames |
Frame construction: full-rim, half-rim, rimless or other; frame material: metal, plastic, combination or other |
Horizontal boxed lens size as a discrete value, typically 40–60 mm |
Spectacle lenses |
Commercial refractive index/material, typically 1.50–1.90 and organic or mineral; design: single vision, multifocal, power variation or other |
Vision-impairment group derived from spherical equivalent power, with cylinder status, plus an addition-power group where applicable |
Ready-to-wear reading spectacles |
Frame construction, frame material and lens material |
Horizontal boxed lens size, typically 40–60 mm, plus discrete spherical power from +1.00 D to +3.50 D |
For spectacle lenses, spherical equivalent power is calculated as:
M = spherical power + (cylinder / 2)
The result is grouped by negative, zero or positive power and by whether cylinder is prescribed, corresponding to myopia, emmetropia or hyperopia with or without astigmatism. Multifocal and power-variation lenses add one of three presbyopia bands: mild/low above 0.00 D and below 1.25 D; moderate from 1.25 D to below 2.00 D; and advanced/high from 2.00 D upwards.
This is why a catalogue-driven implementation is risky. Two brands or model references may share a Master UDI-DI, while one model sold in different boxed sizes, materials, powers or impairment groups may need several.
Labels, packages and vigilance
The UDI carrier contains the Master UDI-DI plus the applicable UDI-PI and follows the normal MDR and issuing-entity rules. The label drawings in the guidance are examples, not prescribed layouts.
Higher packaging levels need their own identifier where Annex VI requires one. Packaging variants that contain different combinations of grouped devices therefore need explicit review; do not assume that the device-level Master UDI-DI can simply be copied onto every box.
For a serious incident, report the UDI — Master UDI-DI plus UDI-PI — in the Manufacturer Incident Report and Eudamed when applicable. Because one Master UDI-DI can cover many catalogue references, the QMS must retain enough internal product detail to isolate the exact device involved.
The rules apply from 1 November 2028. Spectacle frames, lenses and ready readers produced before that date are not required to carry a Master UDI-DI on the label. MDCG 2025-7 nevertheless encourages earlier voluntary implementation once issuing-entity and Eudamed functionality is ready.
What changed in Rev.1
Rev.1, published in March 2026, corrects two spectacle-lens graphics. The “Advanced” addition group is renamed “Advanced/High”, and the decision tree now correctly shows that group as at least 2.00 D, not below 1.25 D. If you built assignment logic from the original diagrams, this is a real rules-engine correction rather than a cosmetic update.
What this means for you, practically
- Convert the tables into controlled decision rules. Define allowed values and ranges for every Basic and Master UDI-DI parameter; do not rely on staff interpreting diagrams case by case.
- Test the catalogue against assignment triggers. Include brands, model references, sizes, materials, refractive indexes, design types and prescriptions to find both over-grouping and duplicate identifiers.
- Correct any pre-Rev.1 lens logic. Advanced/high addition begins at 2.00 D. Regression-test the boundary values at 1.25 D and 2.00 D.
- Preserve variant-level traceability. Master UDI-DI reduces external identifier volume; it does not remove the need to identify the exact catalogue reference and production unit during complaints, FSCA and vigilance.
- Plan labels, data and packaging together. Assignment, Eudamed registration, device labels and higher-level packaging must use the same approved mapping by the 1 November 2028 application date.
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