1、BS EN ISO 10938:2016Ophthalmic optics Chartdisplays for visual acuitymeasurement Printed,projected and electronicBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS EN ISO 10938:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN
2、 ISO10938:2016. It supersedes BS EN ISO 10938:1998 which iswithdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CH/172, Ophthalmic optics.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purpor
3、t to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 83386 1ICS 11.040.70Compliance with a British Standard cannot confer immunity fromlegal obligations.T
4、his British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 October 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 10938 October 2016 ICS 11.040.70 Supersedes EN IS
5、O 10938:1998English Version Ophthalmic optics - Chart displays for visual acuity measurement - Printed, projected and electronic (ISO 10938:2016) Optique ophtalmique - Dispositifs daffichage de tableaux doptotypes destins au mesurage de lacuit visuelle - Tableaux doptotypes imprims, projets et affic
6、hs par des moyens lectroniques (ISO 10938:2016) Augenoptik - Anzeigetafeln fr die Sehprfung - Gedruckt, projiziert und elektronisch (ISO 10938:2016) This European Standard was approved by CEN on 12 September 2016. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipul
7、ate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European St
8、andard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the n
9、ational standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
10、Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any
11、means reserved worldwide for CEN national Members. Ref. No. EN ISO 10938:2016 EBS EN ISO 10938:2016EN ISO 10938:2016 (E) 3 European foreword This document (EN ISO 10938:2016) has been prepared by Technical Committee ISO/TC 172 “Optics and photonics” in collaboration with Technical Committee CEN/TC 1
12、70 “Ophthalmic optics” the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by April 2017, and conflicting national standards shall be withdrawn at the latest by A
13、pril 2017. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 10938:1998. According to the CEN-CENELEC In
14、ternal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland,
15、 Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 10938:2016 has been approved by CEN as EN ISO 10938:2016 without any modification.
16、BS EN ISO 10938:2016ISO 10938:2016(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Requirements 24.1 Optotypes . 24.1.1 Size of optotypes 24.1.2 Luminance of background . 24.1.3 Contrast of optotypes 34.1.4 Quality of presentation . 34.1.5 Resolution 34.2 R
17、equirements specific to optically projected displays . 34.2.1 Focus range . 34.2.2 Projector screens . 34.3 Requirements specific to printed charts . 34.4 Range of compliance 34.5 Conformity to ISO 15004-1 45 Test methods . 45.1 Type tests . 45.2 Conformity 45.3 Resolution . 46 Accompanying document
18、s 47 Marking, labelling and packaging 5Bibliography 6 ISO 2016 All rights reserved iiiContents PageBS EN ISO 10938:2016ISO 10938:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing I
19、nternational 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
20、 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 Directi
21、ves, Part 1. In particular the different approval criteria needed for the different types of ISO documents 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).Attention is drawn to the possibility that some
22、of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarati
23、ons received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about
24、ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.The committee responsible for this document is ISO/TC 172, Optics and photonics, Subcommittee SC 7, Ophthalmic optics and instruments.This sec
25、ond edition cancels and replaces the first edition (ISO 10938:1998), which has been technically revised.iv ISO 2016 All rights reservedBS EN ISO 10938:2016ISO 10938:2016(E)IntroductionThe purpose of this International Standard is to provide for standardization of certain characteristics of displays
26、of optotypes used for measurement of visual acuity in general clinical practice. These characteristics include size specification, luminance, contrast, and resolution of the optotypes. It applies to displays intended for measurement of visual acuity over a limited, but clinically useful, range of ac
27、uities.The principles of standardized visual acuity measurement, including the arrangement of optotypes on the display, are presented in standards adopted by the National Academy of Sciences in the United States of America and the Consilium Ophthalmologicum Universal as referenced in the Bibliograph
28、y. This International Standard is not intended to address these principles, but they are included in an annex in ISO 8596.Due to practical design considerations and physical limitations of most general-purpose clinical visual acuity measurement systems, the chart design features specified in the ref
29、erence standards can usually be met for only a limited range of acuity presentations. Other chart display designs are often required for special clinic visual acuity measurements, such as for low-vision patients or for research purposes. ISO 2016 All rights reserved vBS EN ISO 10938:2016BS EN ISO 10
30、938:2016Ophthalmic optics Chart displays for visual acuity measurement Printed, projected and electronic1 ScopeThis International Standard applies to displays of optotypes generated by chart projectors and all other visual acuity measurement systems that use recognition of high-contrast optotypes an
31、d that are designed for general use, including optotypes printed on media (either opaque or intended for transillumination), those generated electronically, and those produced by optical projection.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this
32、 document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 8596, Ophthalmic optics Visual acuity testing Standard optotype and its presentation
33、ISO 15004-1, Ophthalmic instruments Fundamental requirements and test methods Part 1: General requirements applicable to all ophthalmic instruments3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1optotypesymbol used in the measurement of visual a
34、cuity3.2standard optotypeLandolt ring for which the gap can be oriented in eight different positionsNote 1 to entry: The Landolt ring is specified in ISO 8596.3.3Snellen fractionnotation for specifying the angular subtense of an optotype (3.1), expressed as a fraction with the numerator being the di
35、stance at which visual acuity is tested, commonly in metres or feet, and the denominator being the distance at which the critical detail (3.9) (limbs of the optotype) within the optotype subtends 1 of arcEXAMPLE A 6/6 letter has limbs that subtend 1 of arc at 6 m.Note 1 to entry: For projected chart
36、s and electronic acuity displays, it is common to calibrate the size of the optotype to subtend the desired minutes of arc at test distances other than 6 m. For example, for a short 4 m room, the letter equivalent in angular subtense to the 6/6 letter is 2/3 the size of a true 6/6 letter. However, s
37、uch a reduced letter is still labelled as 6/6. In this convention, the label 6/6 implies the limbs of the letter subtend 1 of arc at the reduced test distance.INTERNATIONAL STANDARD ISO 10938:2016(E) ISO 2016 All rights reserved 1BS EN ISO 10938:2016ISO 10938:2016(E)3.4decimal acuityreciprocal of th
38、e minimum angle of resolution (3.5) in minutes of arcNote 1 to entry: This method of noting the angular subtense of a limb of an optotype (3.1) is also found by writing the Snellen fraction (3.3) as a decimal. For example, Snellen visual acuities 6/6 and 6/12 are decimal acuities 1,0 and 0,5, respec
39、tively.3.5resolutionsmallest separation between two lines for which the lines can be distinguished as two separate lines3.6focus rangemaximum and minimum distances from a projector at which a focused image of the visual acuity chart can be displayed3.7linegroup of optotypes (3.1) having the same siz
40、e arranged in a straight row across the display3.8pixelsmallest element, or point sample, that can be individually processed on an electronic display3.9critical detailsmallest feature in an optotype (3.1) that is considered necessary to distinguish the optotype from the other optotypes4 Requirements
41、4.1 Optotypes4.1.1 Size of optotypesEach size of a set of optotypes shall be specified in terms of the size of critical detail common to that set of optotypes. For example, for the Landolt ring, the critical detail is the gap. The permissible deviation is 5 %.NOTE 1 If letters or figures are used fo
42、r visual acuity measurement, then it should be acknowledged that these normally show large differences in legibility, even if the size and width of stroke are identical. The impact of this variability can be reduced by choosing letters or figures that are comparable to one another. Comparability can
43、 be established for each letter or figure by showing that its effective resolution is equivalent to that of the standard optotype in a direct comparative test.NOTE 2 See ISO/TR 19498 for description of a method for the correlation of optotypes.4.1.2 Luminance of backgroundThe luminance of the backgr
44、ound surrounding the optotype, as viewed by the patient, shall be between 80 cd/m2and 320 cd/m2and shall be specified by the manufacturer.NOTE 1 The recommended luminance is 200 cd/m2.The luminance of the background within two character diameters of the optotype shall not vary by more than 30 %. Acr
45、oss the entire area of the illuminated field, it shall not vary by more than 50 %.NOTE 2 See Clause 6 e) for ambient illumination requirements needed to ensure compliance with background luminance specifications.2 ISO 2016 All rights reservedBS EN ISO 10938:2016ISO 10938:2016(E)4.1.3 Contrast of opt
46、otypesOptotypes shall be specified by the background luminance in cd/m2and by the luminance of the optotype as a percentage of the background luminance. The luminance of the optotype shall be not more than 15 % of the luminance of the background upon which the optotype is located. Optypes in a serie
47、s shall not differ noticeably in contrast.4.1.4 Quality of presentationOptotypes as presented shall appear with sharply defined contours to an observer with a binocular visual acuity of 1,0 to 1,25 at an observation distance of 1/3 of the distance at which the optotypes are designed to be used. Simi
48、lar optotypes in a size series shall not differ noticeably in shape or edge sharpness.For electronic displays, if anti-aliasing (i.e. modifying the brightness of pixels at the borders of optotypes) is used to smooth the naturally occurring jagged edge formed by pixels at curved edges, it shall not c
49、ause a change in the perceived size of the optotype outside of the 5 % variability in optotype size allowed by ISO 8596. Furthermore, there shall be no performance difference between the electronically displayed optotype and a printed display of standard optotypes that meets the requirements of ISO 8596.NOTE Anti-aliasing may add or subtract from the width of the detail and may change the calibration.Optotypes presented in displays for which the design prevents viewing at 1/3 the normal distance shall be observed with a magnificatio
