1、BS EN ISO 8596:2009ICS 11.040.70NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDOphthalmic optics Visual acuity testing Standard optotype and its presentation (ISO 8596:2009)This British Standardwas published under theauthority of the StandardsPolicy and Strateg
2、yCommittee on 31 July 2009 BSI 2009ISBN 978 0 580 65275 2Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 8596:2009National forewordThis British Standard is the UK implementation of EN ISO 8596:2009. Itsupersedes BS EN ISO 8596:1996 which is withdrawn.This standard is not to be u
3、sed for clinical measurements. For clinicalmeasurements please refer to BS 4274-1.The UK participation in its preparation was entrusted to TechnicalCommittee CH/172/6, Ophthalmic instruments.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publica
4、tion does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 8596July 2009ICS 11.040.70 Supersedes EN
5、 ISO 8596:1996 English VersionOphthalmic optics - Visual acuity testing - Standard optotypeand its presentation (ISO 8596:2009)Optique ophtalmique - Essai dacuit visuelle - Optotypenormalis et sa prsentation (ISO 8596:2009)Augenoptik - Sehschrfeprfung - Das Normsehzeichenund seine Darbietung (ISO 85
6、96:2009)This European Standard was approved by CEN on 27 June 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical
7、references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN membe
8、r into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latv
9、ia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 20
10、09 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 8596:2009: EBS EN ISO 8596:2009EN ISO 8596:2009 (E) 3 Foreword This document (EN ISO 8596:2009) has been prepared by Technical Committee ISO/TC 172 “Optics and optical instrument
11、s“ in collaboration with Technical Committee CEN/TC 170 “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 January 2010, and conflicting
12、national standards shall be withdrawn at the latest by January 2010. 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 sup
13、ersedes EN ISO 8596:1996. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
14、 Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 8596:2009 has been approved by CEN as a EN ISO 8596:2009 without any modification.
15、 BS EN ISO 8596:2009ISO 8596:2009(E) ISO 2009 All rights reserved iiiForeword 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 technic
16、al 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 wi
17、th the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft Inte
18、rnational Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document ma
19、y be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8596 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 7, Ophthalmic optics and instruments. This second edition cancels and replaces the first
20、edition (ISO 8596:1994), which has undergone minor revision to take into account the withdrawal without replacement of ISO 8597:1994, Optics and optical instruments Visual acuity testing Method of correlating optotypes. BS EN ISO 8596:2009BS EN ISO 8596:2009INTERNATIONAL STANDARD ISO 8596:2009(E) IS
21、O 2009 All rights reserved 1Ophthalmic optics Visual acuity testing Standard optotype and its presentation 1 Scope This International Standard specifies a range of Landolt ring optotypes and describes a method for measuring distance visual acuity under daylight conditions for the purposes of certifi
22、cation or licensing. It is neither intended as a standard for clinical measurements nor for the certification of blindness or partial sight. For the purposes of measuring visual acuity, the standard optotype should be used. For clinical use, see the recommendation prepared by the Visual Functions Co
23、mmittee of the International Council of Ophthalmology1. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (inclu
24、ding any amendments) applies. ISO 3:1973, Preferred numbers Series of preferred numbers 3 Standard optotype The standard optotype shall be the Landolt ring as detailed in Table 1 and as shown in Figure 1. The visual acuity grade 1 shall be represented by a Landolt ring whose outer diameter, d, subte
25、nds an angle of 5 and whose width, as well as the gap in its continuity, subtends an angle of 1 at the designated viewing distance. The Landolt ring shall be capable of being presented in eight different positions (see 6.2). 4 Visual acuity grades and standard optotype grades The visual acuity grade
26、s shall be as given in Table 1 and shall be expressed as the reciprocal of the gap width measured in minutes of arc. The acuity values for the size of the optotype shall be graduated logarithmically. The quotient of the size of the optotype and that of the next smaller one shall be: 1010 1,258 9= (s
27、eries of preferred numbers R10 from ISO 3:1973). Optotypes of acuity grades 0,05, 0,06, 0,08 and 2,0 may be omitted if necessary. Addition of further acuity grades is permitted. BS EN ISO 8596:2009ISO 8596:2009(E) 2 ISO 2009 All rights reservedTable 1 Visual acuity grades Optotype size Angle for gap
28、 and ring width Acuity gradeaLog gap size Minutes of arc () Permissible deviation% Minimum number of presentations 0,05 0,063 (0,06) 0,08 0,1 +1,3 +1,2 +1,1 +1 20 16 12,5 10 2 0,125 0,16 0,2 +0,9 +0,8 +0,7 8 6,3 5 3 0,25 0,32 (0,3) 0,4 0,5 0,63 (0,6) 0,8 1,0 1,25 1,6 +0,6 +0,5 +0,4 +0,3 +0,2 +0,1 0
29、0,1 0,2 4 3,2 2,5 2 1,6 1,25 1 0,8 0,63 5 5 2,0 0,3 0,5 10 5 aThe values in parentheses shall be used only for the purpose of identifying the acuity grade. Figure 1 Landolt ring Table 2 Spacing between standard optotypes (border to border) Acuity grades Minimum spacing between standard optotypes les
30、s than 0,06 2 width of gap in Landolt ring 0,06 to 0,125 diameter of Landolt ring 0,16 to 0,32 1,5 diameter of Landolt ring 0,4 to 1,0 2 diameter of Landolt ring greater than 1,0 3 diameter of Landolt ring BS EN ISO 8596:2009ISO 8596:2009(E) ISO 2009 All rights reserved 35 Test area and spacing betw
31、een standard optotypes The field shall extend at least 0,5 in all directions from the contour of the optotypes to the border of the test field. 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 te
32、st 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 orien
33、tations are achieved by rotation of the optotypes, this rotary movement shall not be observed by the subject. 6 Presentation of the standard optotype 6.1 Quality of presentation The standard optotype as presented shall appear with sharply defined contours to an observer with a visual acuity of at le
34、ast 1,0 at an observation distance of 1/3 of the distance at which the test types are designed to be used. Test types presented in instruments shall be observed with a magnification of 3. The optotypes in a series shall not differ noticeably in contrast and contour. 6.2 Positions of the optotype The
35、 optotype shall be presented in at least the number of different positions per acuity grade as shown in Table 1. In 50 % of these positions, the gap shall be either vertical or horizontal but, in the case when there is an odd number of presentations, this value shall be rounded to the next larger in
36、teger. The sequence of presentations shall be as diversified as possible and shall be randomly ordered. If the standard optotype is presented singly, this fact shall be specifically mentioned in the test report. 6.3 Viewing distance for distance visual acuity testing The test shall be performed with
37、 a minimum viewing distance of 4 m between the entrance pupil of the subject and the optotype. 6.4 Criteria for determination and assignment of visual acuity grade When testing for visual acuity, the performance level at which the presentation of optotypes shall be terminated is dependent upon the n
38、umber of optotypes used for each size. For a “Pass” assessment: at least three shall be called correctly if the total number of optotypes used is five; at least four shall be called correctly if the total number of optotypes used is six or seven; at least five shall be called correctly if the total
39、number of optotypes used is eight or nine; at least six shall be called correctly if the total number of optotypes used is ten. NOTE Preferred numbers of presentation are five, eight or ten. In each case, the minimum called correctly represents approximately 60 % of the total. The test shall be term
40、inated at the first grade at which the number called correctly falls below the “Pass” level. The visual acuity shall be assigned, by reference to Table 1, as one grade lower than the grade at which the test is terminated. BS EN ISO 8596:2009ISO 8596:2009(E) 4 ISO 2009 All rights reserved7 Luminance
41、The luminance of the test area shall be as given in Table 3 and shall apply to all methods of presentation. The luminance of the standard optotype shall be not more than 15 % of that of the test area, taking into account the room illumination. The surrounding field (test room) shall be darker than t
42、he test area. However, within an area of 10 diameter, the luminance of the surrounding field shall be not less than 1/10 nor more than 1/4 of the luminance of the test area. There shall be no direct or indirect glare source (e.g. light source, reflected image of a light source, glossy or very bright
43、 matt surface) within the field of view. White light within a colour temperature range of 2 500 K to 7 000 K shall be used. NOTE In measuring the visual acuity, the luminance and contrast conditions should be such that consistent results can be expected for a normal eye. Table 3 Luminance General su
44、rrounding luminance as a fraction of the luminance of the test area Luminance range cd/m2field u 10 field 10 80 to 320 not less than 0,1 not more than 0,25 not less than 0,01aaNo brighter than 10 field. 8 Test report The test report shall include the following information: a) reference to this Inter
45、national Standard, i.e. ISO 8596:2009; b) identification of the acuity grades of the optotypes used in the test (see Table 1); c) the instrument used, if any; d) the number of different positions for each acuity grade (see 6.2); e) the viewing distance used (see 6.3); f) the assigned visual acuity g
46、rade (see 6.4); g) the date of the test. BS EN ISO 8596:2009ISO 8596:2009(E) ISO 2009 All rights reserved 5Bibliography 1 International Council of Ophthalmology Visual Functions Committee, Visual Acuity Measurement Standard. Ital. J. Ophthalmol., ll/l, pp. 5-19, 1988 BS EN ISO8596:2009BSI GroupHeadq
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