EN ISO 8596-2018 Ophthalmic optics - Visual acuity testing - Standard and clinical optotypes and their presentation.pdf

1、BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06Ophthalmic optics Visual acuity testing Standard and clinical optotypes andtheir presentation (ISO 8596:2017)BS EN ISO 8596:2018National forewordThis British Standard is the UK implementation of EN ISO 8596:2018. It is

2、identical to ISO 8596:2017. It supersedes BS EN ISO 8596:2009, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CH/172/6, Ophthalmic instruments.A list of organizations represented on this committee can be obtained on request to its secretary.This publi

3、cation does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2018 Published by BSI Standards Limited 2018ISBN 978 0 580 93833 7ICS 11.040.70Compliance with a British Standard cannot confer immunity

4、 from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2018.Amendments/corrigenda issued since publicationDate Text affectedBRITISH STANDARDBS EN ISO 8596:2018EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO

5、8596January 2018ICS 11.040.70 Supersedes EN ISO 8596:2009EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGCEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2018 CEN Ref. No. EN ISO 8596:2018: EAll rights of exploitation in any form and

6、by any means reserved worldwide for CEN national MembersOphthalmic optics - Visual acuity testing - Standard and clinical optotypes and their presentation (ISO 8596:2017)Optique ophtalmique - Mesure de lacuit visuelle - Optotype normalis et optotypes cliniques et leur prsentation (ISO 8596:2017)Auge

7、noptik - Sehschrfeprfung - Normsehzeichen und klinische Sehzeichen und ihre Darbietung (ISO 8596:2017)This European Standard was approved by CEN on 20 November 2017.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Stand

8、ard 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 Standard exists in three official versions (English,

9、 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 national standards bodies of Austria, Belgium, Bulga

10、ria, 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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerl

11、and, Turkey and United Kingdom.English VersionEN ISO 8596:2018 (E)European forewordThis document (EN ISO 8596:2018) has been prepared by Technical Committee ISO/TC 172 “Optics and photonics” in collaboration with Technical Committee CEN/TC 170 “Ophthalmic optics” the secretariat of which is held by

12、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 July 2018, and conflicting national standards shall be withdrawn at the latest by July 2018.Attention is drawn to the possibility that some of t

13、he elements of this document may be the subject of patent rights. CEN shall not be held responsible for identifying any or all such patent rights.This document supersedes EN ISO 8596:2009.According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countri

14、es 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, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Polan

15、d, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.Endorsement noticeThe text of ISO 8596:2017 has been approved by CEN as EN ISO 8596:2018 without any modification.2BS EN ISO 8596:2018ISO 8596:2017(E)Foreword iv1 Scope . 12 Normative referenc

16、es 13 Terms and definitions . 14 Requirements 24.1 Specifications of the standard optotype 24.2 Visual acuity grades and standard optotype grades . 34.3 Test area and spacing between standard optotypes 44.4 Positions of the optotype . 44.5 Quality of presentation 44.6 Luminance 55 Test methods . 65.

17、1 Viewing distance for distance visual acuity testing 65.2 Criteria for determination and assignment of visual acuity grade 66 Test report . 6Annex A (informative) Optotypes for clinical investigations 7Bibliography .10 ISO 2017 All rights reserved iiiContents PageBS EN ISO 8596:2018ISO 8596:2017(E)

18、ForewordISO (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 te

19、chnical 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

20、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 documents should be noted. This documen

21、t 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 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

22、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 declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does n

23、ot constitute an endorsement.For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (T

24、BT) see the following URL: www.iso.org/iso/foreword.html.This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 7, Ophthalmic optics and instruments.This third edition cancels and replaces the second edition (ISO 8596:2009), which has been technically rev

25、ised.The main changes compared to the previous edition are as follows:a) restructuring of technical content into the Clauses 4 and 6 has been applied;b) terms and definitions with the terms standard optotype, clinical optotype, visual acuity, and the systems decimal visual acuity, Snellen fraction,

26、LogMAR acuity, and visual acuity grade have been added;c) Snellen fraction values in Table 1 have been added;d) Figure 2 has been added;e) Annex A has been added.iv ISO 2017 All rights reservedBS EN ISO 8596:2018Ophthalmic optics Visual acuity testing Standard and clinical optotypes and their presen

27、tation (ISO 8596:2017)1 ScopeThis document specifies a range of Landolt ring optotypes and describes a method for measuring distance visual acuity under photopic conditions for the purposes of certification or licensing.This document is neither intended as a standard for clinical measurements nor fo

28、r the certification of blindness or partial sight.Other optotypes used for clinical investigations are described in Annex A for information.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this docum

29、ent. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 3:1973, Preferred numbers Series of preferred numbers3 Terms and definitionsFor the purposes of this document, the following terms a

30、nd definitions apply.ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at https:/www.iso.org/obp 3.1standard optotypeLandolt ringNote 1 to entry: The

31、Landolt ring is specified in Table 1 and Figure 1.3.2clinical optotypeoptotype other than the standard optotype (3.1) used for measuring visual acuity (3.3) Note 1 to entry: This definition does not exclude the standard optotype from being used for the same purposes as a clinical optotype.Note 2 to

32、entry: Since clinical optotypes can differ greatly in legibility, it is crucial to refer to the standard optotype whenever the comparability of the results is important. ISO/TR 19498 provides a method for correlation of clinical optotypes to the standard optotype.3.3visual acuitynumber characterizin

33、g the ability of the visual system to recognize optotypesNote 1 to entry: Currently, three different scaling systems are used to describe the visual acuity of a patient. These are decimal visual acuity, Snellen fraction, LogMAR acuity. See Table 1.INTERNATIONAL STANDARD ISO 8596:2017(E) ISO 2017 All

34、 rights reserved 1BS EN ISO 8596:2018ISO 8596:2017(E)3.3.1decimal visual acuityreciprocal of the minimum recognizable gap width of a Landolt ring measured in minutes of arcEXAMPLE A visual acuity of 1,0 is assigned when the smallest Landolt ring recognized by a patient has a gap width of 1 min of ar

35、c measured from the patients viewing distance.3.3.2Snellen fractionnotation for specifying the angular subtense of an optotype, expressed as a fraction with the numerator (test distance) being the distance at which visual acuity (3.3) is tested, commonly in m or ft, and the denominator (normal dista

36、nce) being the distance at which the critical detail (limb) of the smallest recognizable optotype subtends 1 min of arc VDDSntn= whereVSnis the visual acuity, measured as Snellen fraction;Dtis the test distance, measured in m or ft;Dnis the normal distance, measured in m or ft.EXAMPLE A Snellen frac

37、tion of 6/6 is assigned to the visual resolving power of a patient, when the smallest recognizable Landolt ring has a gap size of 1 min of arc from a viewing distance of 6,0 m.Note 1 to entry: The decimal visual acuity can by calculated from the Snellen fraction by evaluating the above quotient (e.g

38、 Snellen fraction 6/6 = decimal visual acuity 1,0).3.3.3LogMAR acuitylogarithm (base 10) of the minimum angle of resolution measured in minutes of arcNote 1 to entry: LogMAR acuity can be converted to decimal visual acuity (3.3.1) by: Decimal visual acuityLogMAR acuity=()10 3.4visual acuity gradenu

39、mber assigned to an optotype that is equal to the minimum visual acuity of a patient necessary to recognize the optotype from a specified distanceNote 1 to entry: The standardized visual acuity grades used in the three different scaling systems are given in Table 1.4 Requirements4.1 Specifications o

40、f the standard optotypeThe Landolt ring is detailed in Table 1 and shown in Figure 1.The decimal visual acuity grade 1 shall be represented by a Landolt ring whose outer diameter, d, subtends an angle of 5 min of arc and whose width, as well as the gap in its continuity, subtends an angle of 1 min o

41、f arc at the designated viewing distance.2 ISO 2017 All rights reservedBS EN ISO 8596:2018ISO 8596:2017(E)The Landolt ring shall be capable of being presented with eight different gap orientations, including left and right horizontal orientations, upper and lower vertical orientations, and the four

42、principal diagonal orientations.4.2 Visual acuity grades and standard optotype gradesThe visual acuity grades shall be as given in Table 1. The gap size of the standard optotype shall be graduated logarithmically. The quotient of the size of the optotype and that of the next smaller one shall be10 1

43、 258910= , (series of preferred numbers R10 from ISO 3:1973)Optotypes of decimal acuity grades 0,05, 0,06, 0,08 and 2,0 may be omitted if necessary. Use of additional decimal acuity grades, either larger or smaller than those listed in Table 1, is permitted.Table 1 Visual acuity grades, Landolt ring

44、 sizes and minimum number of presentationsVisual acuity grades (nominal values)dGap size of Landolt ring(minutes of arc)Minimum number of presentationsdDecimal visual acuityaLogMAR acuitySnellen fraction for test distance 6 m0,05 +1,30 6/120 20,0b20,063 (0,06) +1,20 6/95 15,8b20,08 +1,10 6/75 12,6b2

45、0,10 +1,00 6/60 10,0b20,125 +0,90 6/48 7,94b30,16 +0,80 6/38 6,31b30,20 +0,70 6/30 5,01b30,25 +0,60 6/24 3,98b50,32 (0,30) +0,50 6/19 3,16b50,40 +0,40 6/15 2,51b50,50 +0,30 6/12 2,00b50,63 (0,60) +0,20 6/9,5 1,58b50,80 +0,10 6/7, 5 1,26b51,00 0 6/6,0 1,00b51,25 0,10 6/4,8 0,794b51,60 0,20 6/3,8 0,63

46、1b52,00 0,30 6/3,0 0,501c5aThe values in parentheses shall be used only for the purpose of identifying the acuity grade.bThe gap size is accurate to 1 %. The permissible deviation is 5 %.cThe permissible deviation is 10 %.dThe recommended number of presentations is at least 5 presentations. ISO 2017

47、 All rights reserved 3BS EN ISO 8596:2018ISO 8596:2017(E)Keyd diameterFigure 1 Landolt ringTable 2 Spacing between standard optotypes (border to border)Decimal visual acuity grades Minimum spacing between standard optotypesless than 0,06 0,4 diameter of Landolt ring0,06 to 0,125 1,0 diameter of Land

48、olt ring0,16 to 0,32 1,5 diameter of Landolt ring0,40 to 1,00 2 diameter of Landolt ringgreater than 1,00 3 diameter of Landolt ring4.3 Test area and spacing between standard optotypesThe field shall extend at least 0,5 in all directions from the contour of the optotypes to the border of the test fi

49、eld. If more than one standard optotype is used in the same test area, the spacings given in Table 2 shall apply. If more than one acuity grade is used on the test area, the spacing for the largest optotype shall apply.Table 2 applies to both horizontal and vertical spacing.The background to the optotypes shall appear uniformly bright and without any variation of colour or texture which could indicate the orientation of the symbols. If the different orientations are achieved by rotation of the optotypes, this rotary moveme