ISO/FDIS 18490

ISO/DISFDIS 18490:2025(en)
ISO/TC 135/SC 7/WG 10
Secretariat: SCC
Date: 2025-XX-XX12-11
Non-destructive Testingtesting — Evaluation of vision acuity of NDT
personnel
Essais non destructifs — EvaluationÉvaluation de l'acuité visuelle du personnel END
FDIS stage
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ISO #####-#:####(X/FDIS 18490:2025(en)
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ISO/DISFDIS 18490:2025(en)
© ISO 2025 – All rights reserved
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ISO #####-#:####(X/FDIS 18490:2025(en)
Contents
Foreword . vi
Introduction . ix
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Chart print quality and marking . 2
5 Health and safety requirements . 3
6 Personnel administering the test . 3
7 Near and Far Vision Test charts . 3
8 Test procedure . 3
8.1 General. 3
8.2 Table 1 — Illumination level . 3
8.3 Table 2 — Luminance . 3
8.4 Eye to chart distance . 4
8.5 Vision Correction . 4
8.6 Tests . 4
8.6.1 General. 4
8.6.2 Near and Far Guidance . 5
9 Acceptance levels . 5
a
9.1 Table 4 — Near Vision Reading Chart (example Radner or Snellen) . 5
a
9.2 Table 5 — Far Vision (example Landolt or Snellen) . 5
9.3 Table 6 — Colour Vision (Ishihara) . 5
Annex A (informative) Radner Chart (Not to scale) . 7
Annex B (informative) Snellen Chart (Not to scale) . 10
Annex C (informative) Landolt Chart (Not to scale) . 11
Annex D (informative) Ishihara Chart (Not to Scale) . 14
Annex E (informative) Sample Colour Trade Test Exam . 15
Annex F (informative) Corresponding Reading Acuity Notations for Test Distances of 40 cm
(16 inches) and 32 cm (12.5 inches) . 18
Annex G (informative) Grey Scale Perception Testing . 19
Annex H (informative) Low Contrast Visual Acuity . 20
Annex I (informative) Verification of Trained Professional . 21
Bibliography . 23

Foreword . vi
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
iv © ISO #### 2025 – All rights reserved
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ISO/DISFDIS 18490:2025(en)
4 Chart print quality and marking . 2
5 Health and safety requirements . 2
6 Personnel administering the test . 3
7 Near and Far Vision Test charts . 3
8 Test procedure . 3
9 Acceptance levels . 5
Annex A (informative) Radner Chart (Not to scale) . 6
Annex B (informative) Snellen Chart (Not to scale) . 8
Annex C (informative) Landolt Chart (Not to scale) . 9
Annex D (informative) Ishihara Chart (Not to Scale) . 11
Annex E (informative) Sample Colour Trade Test Exam . 12
Annex F (informative) Corresponding Reading Acuity Notations for Test Distances of 40 cm
(16 inches) and 32 cm (12.5 inches) . 19
Annex G (informative) Grey Scale Perception Testing . 20
Annex H (informative) Low Contrast Visual Acuity . 21
Annex I (informative) Verification of Trained Professional . 22
Bibliography . 25

© ISO 2025 – All rights reserved
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ISO #####-#:####(X/FDIS 18490:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
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Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, SC 7, Personnel
Qualification, in collaboration with European Committee for Standardization (CEN) CEN/TC 138, Non-
destructive testing, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This second edition cancels and replaces the first edition (ISO 18490:2015), which has been technically
revised.
The main changes are as follows:
— — Farfar and Colourcolour vision acuity of NDT personnel added to the Scope;
— — updated references;
— — new terms and definitions added;
— — charts for Illumination level and Luminance added; Chart
— chart for Eye to Chart distance for Near, Far and Colour vision added;
— — additional provisions for vision correction added;
— — test instructions for Near, Farnear, far, and Colourcolour vision added;
vi © ISO #### 2025 – All rights reserved
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ISO/DISFDIS 18490:2025(en)
— — Guidanceguidance on verification of trained professional provided and sample attestation form for
NDT Vision Test Report added as Annexes (Annex I);(Annex I);
— — information for grey scale perception and low contrast acuity added as Annexes (Annex G(Annex G
and Annex H);Annex H);
— — for Nearnear vision, removed use of Tumbling E and added use of Reading Charts and Snellen chart;
— — acceptance level for Near, Far, Colournear, far, colour visions added;
— — examples of Radner, Snellen and Landolt charts added as Annexes;
— — corresponding Reading Acuity Notations for Test Distances of 40 cm (16 inches) and 32 cm
(12.5 inches) added as Annex.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
© ISO 2025 – All rights reserved
vii
ISO #####-#:####(X/FDIS 18490:2025(en)
Introduction
Standards for NDT Personnel qualification and certification require that the visual acuity of inspection
personnel is verified as being appropriate to their function. By meeting the vision acuity level defined in this
document, such requirements of ISO 9712 will be met. The purpose of this document is to provide a detailed,
standardised procedure for the evaluation of vision acuity for such personnel under defined lighting
conditions.
The tests are not medical in nature and are intended to objectively ensure adequate vision perception without
reliance on reading ability or text identification. Because it is extremely difficult to demonstrate any
equivalency in vision tests, this document has been prepared in order that an international system can be used
without any need to demonstrate equivalence and is the recommended method of determining vision acuity
for NDT Personnel.
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DRAFT International Standard ISO/DIS 18490:2025(en)

Non-destructive Testingtesting — Evaluation of vision acuity of NDT
personnel
1 Scope
This document specifies quality requirements for the chart, the test procedure and the acceptance level for
near, far, and colour vision acuity of NDT personnel. Information for grey scale perception and low contrast
can be found in the annexes. This document also specifies the qualification requirements for personnel
permitted to carry out the test.
This document is only applicable to vision acuity under defined conditions similar to those encountered during
routine NDT inspection. This document does not address an individual’s overall visual acuity and users are
advised to consider the need for a general eye examination by specialist medical personnel to ensure general
vision acuity.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
IS0 ISO 7921, Ophthalmic optics and instruments- Near reading chartsISOcharts
ISO 8596, Ophthalmic optics — Visual acuity testing — Standard and clinical optotypes and their presentation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9712, ISO 7921, ISO 8596 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 3.1
optotype
letters or symbols shown on an eye chart
3.2 3.2
eyewear
form of lens or protective transparent material placed or used between the human eye and the work piece
during routine NDT inspection operations
3.3 3.3
trade test
test performed by the employer after failure of the Ishihara Colour test to ensure a candidate can distinguish
and differentiate between the colours used in the NDT methods/ techniques concerned as specified by the
employer.
3.4 3.4
x-height
height of a lower case “x”, i.e. the middle height of a font
3.5 3.5
logRAD
logarithm of “Reading Acuity Determination” which is determined based upon the x-height
3.6 3.6
logMAR
logarithm of the “Minimum Angle of Resolution” based upon the opening, or line thickness
of a Landolt ring (i.e. one fifth of the optotypes)
3.7 3.7
decimal
reciprocal proportion of the visual angle as calculated from the test distance and one-fifth of the x-height
(3.4)(3.4)
3.8 3.8
M size
factor used to modify the print size, multiplying it by the letter height at 1 metre (= 1 M- unit)
3.9 3.9
N
desktop Publishing (DTP) point size (1 pt = 1/72 inch) of lower-case letters printed in Times Roman
approximately representing correct sizing
3.10 3.10
Snellen fraction
relationship between the test distance in feet or metres and the distance at which an optotype subtends five
minutes of an arc (for near vision 1,3/1,3 Snellen for feet or 0,4/0,4 Snellen for metre)
4 Chart print quality and marking
It is recognized that charts produced locally will have varying print quality and resolution. It is recommended
that the charts be purchased directly from suppliers or manufacturers and not printed or copied locally. The
charts supplied shall be permanently marked with a name or trade name of the manufacturer or supplier,
name and
...