1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 19980:2012Ophthalmic instruments Corneal topographers (ISO 19980:2012)Incorporating corrigendum June 2012BS EN ISO 19980:2012 BRITISH STANDARDNational forewordThis Brit
2、ish Standard is the UK implementation of EN ISO 19980:2012. It supersedes BS EN ISO 19980:2005 which is withdrawn.The UK participation in its preparation was entrusted by Technical Committee CH/172, Ophthalmic optics, to SubcommitteeA list of organizations represented on this subcommittee can be obt
3、ained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012 Published by BSI Standards Limited 2012ISBN 978 0 580 ICS 11.040.70 Compliance with a B
4、ritish Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2012.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e d79207 630 June 2012 ISO second edition adds
5、Equations(7) and (8), which were missingCH/172/6, Ophthalmic instruments.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 19980 April 2012 ICS 11.040.70 Supersedes EN ISO 19980:2005English Version Ophthalmic instruments - Corneal topographers (ISO 19980:2012) Instruments ophtalmiques - Topog
6、raphes de la corne (ISO 19980:2012) Ophthalmische Instrumente - Hornhauttopographen (ISO 19980:2012) This European Standard was approved by CEN on 31 March 2012. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
7、 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, F
8、rench, 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, Bulgar
9、ia, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITT
10、EE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 19980:2012: E3 Foreword This documen
11、t (EN ISO 19980:2012) 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 DIN. This European Standard shall be given the status of a national standard, either by public
12、ation of an identical text or by endorsement, at the latest by October 2012, and conflicting national standards shall be withdrawn at the latest by October 2012. 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 s
13、hall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 19980:2005. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium,
14、Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endors
15、ement notice The text of ISO 19980:2012 has been approved by CEN as a EN ISO 19980:2012 without any modification. BS EN ISO 19980:2012 EN ISO 19980:2012 (E) ISO 2012 All rights reserved iiiContents PageForeword iv1 Scope 12 Normative references . 13 Terms and definitions . 14 Requirements . 94.1 Are
16、a measured . 94.2 Measurement sample density 94.3 Measurement and report of performance . 94.4 Colour presentation of results . 95 Test methods and test devices 95.1 Tests 95.2 Test surfaces 95.3 Data collection Test surfaces 115.4 Analysis of the data 116 Accompanying documents .137 Marking .13Anne
17、x A (informative) Test surfaces for corneal topographers (CTs) 14Annex B (normative) Standardized displays for corneal topographers (CTs) .16Annex C (normative) Calculation of area-weighting values19Annex D (normative) Test methods for measuring human corneas .21Bibliography .22BS EN ISO 19980:2012
18、ISO 19980:2012 (E)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 subj
19、ect 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 (IE
20、C) 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 International Standards adopted by the technical committee
21、s 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 may be the subject of patent rights. ISO shall not be hel
22、d responsible for identifying any or all such patent rights.ISO 19980 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 edition (ISO 19980:2005), which has been technically rev
23、ised.This corrected version of ISO 19980:2012 incorporates the following corrections:Equations (7) and (8), which were missing, have been added.iv ISO 2012 All rights reservedBS EN ISO 19980:2012 ISO 19980:2012 (E)INTERNATIONAL STANDARD Ophthalmic instruments Corneal topographers1 ScopeThis Internat
24、ional Standard specifies minimum requirements for instruments and systems that fall into the class of corneal topographers (CTs). It also specifies tests and procedures to verify that a system or instrument complies with this International Standard and thus qualifies as a CT according to this Intern
25、ational Standard. It also specifies tests and procedures that allow the verification of capabilities of systems that are beyond the minimum requirements for CTs.This International Standard defines terms that are specific to the characterization of the corneal shape so that they may be standardized t
26、hroughout the field of vision care.This International Standard is applicable to instruments, systems and methods that are intended to measure the surface shape of the cornea of the human eye.NOTE The measurements can be of the curvature of the surface in local areas, three-dimensional topographical
27、measurements of the surface or other more global parameters used to characterize the surface.It is not applicable to ophthalmic instruments classified as ophthalmometers.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated referen
28、ces, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.IEC 60601-1:2005, Medical electrical equipment Part 1: General requirements for basic safety and essential performance3 Terms and definitionsFor the purposes
29、of this document, the following terms and definitions apply.3.1corneal apexlocation on the corneal surface where the mean of the local principal curvature is greatest3.2corneal eccentricityececcentricity, e, of the conic section that best fits the corneal meridian of interestNOTE If the meridian is
30、not specified, the corneal eccentricity is that of the flattest corneal meridian (see Table 1 and Annex A).3.3corneal meridiancurve created by the intersection of the corneal surface and a plane that contains the corneal topographer axisNOTE 1 A meridian is identified by the angle , that the plane c
31、reating it makes to the horizontal (see ISO 8429).NOTE 2 The value of , for a full meridian, ranges from 0 to 180 . ISO 2012 All rights reserved 1BS EN ISO 19980:2012 ISO 19980:2012 (E)3.3.1corneal semi-meridianportion of a full meridian extending from the CT axis toward the periphery in one directi
32、onNOTE The value of for a semi-meridian ranges from 0 to 360 .3.4corneal shape factorEvalue that specifies the asphericity and type (prolate or oblate) of the conic section that best fits a corneal meridianNOTE 1 Unless otherwise specified, it refers to the meridian with least curvature (flattest me
33、ridian). See Table 1 and Annex A.NOTE 2 Although the magnitude of E is equal to the square of the eccentricity and so must always be positive, the sign of E is a convention to signify whether an ellipse takes a prolate or oblate orientation.NOTE 3 The negative value of E is defined by ISO 10110-12 a
34、s the conic constant designated by the symbol K. The negative value of E has also been called asphericity and given the symbol Q.Table 1 Conic section descriptorsConic section Value of paValue of E Value of eHyperbola p 1 e 1Parabola 0,0 1,0 1,0Prolate ellipse 1 p 0 0 1 E 1)Ee=2(4)In order to signif
35、y use of an oblate curve of the ellipse, e is sometimes given a negative sign that is not used in computations. Otherwise, use of the prolate curve of the ellipse is assumed.3.10elevationdistance between a corneal surface and a defined reference surface, measured in a defined direction from a specif
36、ied position3.10.1axial elevationelevation as measured from a selected point on the corneal surface in a direction parallel to the corneal topographer axis3.10.2normal elevationelevation as measured from a selected point on the corneal surface in a direction along the normal to the corneal surface a
37、t that point3.10.3reference normal elevationelevation as measured from a selected point on the corneal surface in a direction along the normal to the reference surface3.11keratometric constantconversion value equal to 337,5 used to convert corneal curvature from reciprocal millimetres (mm1) to kerat
38、ometric dioptres3.12keratometric dioptresvalue of curvature, expressed in reciprocal millimetres (mm1), multiplied by the keratometric constant, 337,53.13meridional planeplane that includes the surface point and the chosen axis6 ISO 2012 All rights reservedBS EN ISO 19980:2012 ISO 19980:2012 (E)3.14
39、 Normal3.14.1surface normalline passing through a surface point of the surface perpendicular to the plane tangent to the surface at that point3.14.2meridional normalline passing through a surface point of the surface, perpendicular to the tangent to the meridional curve at that point and lying in th
40、e plane creating the meridian3.15p-valuenumber that specifies a conic section such as an ellipse, a hyperbola or a parabola, with the conic section given in Equation (5):zbxa22221= (5)and the p-value defined by Equation (6):pab=22(6)Ep=1 (7)wherea and b are constants;+ indicates an ellipse; indicate
41、s a hyperbolaSee Table 1.3.16Placido ring targettarget consisting of multiple concentric rings, where each individual ring lies in a plane but the rings are not, in general, coplanar3.17radius of curvaturereciprocal of the curvatureNOTE For the purpose of this International Standard, the radius of c
42、urvature is expressed in millimetres.3.17.1axial radius of curvaturesagittal radius of curvatureradistance from a surface point, P, to the axis along the normal to corneal meridian at that point, and defined by Equation (8):rxxa=()sin (8) ISO 2012 All rights reserved 7BS EN ISO 19980:2012 ISO 19980:
43、2012 (E)wherex is the perpendicular distance from the axis to the meridian point, in millimetres;f(x) is the angle between the axis and the meridian normal at point x.See Figure 2.3.17.2meridional radius of curvaturetangential radius of curvaturermdistance from a surface point, P, and the centre of
44、the meridional curvature point, and defined by Equation (9):rKmm=1(9)See Figure 2.3.18 Surface3.18.1aspheric surfacenon-spherical surfacesurface with at least one principal meridian that is non-circular in cross-section3.18.2atoric surfacesurface having mutually perpendicular principal meridians of
45、unequal curvature where at least one principal meridian is non-circular in cross-sectionNOTE Atoric surfaces are symmetrical with respect to both principal meridians.3.18.3oblate surfacesurface whose curvature increases as the location on the surface moves from a central position to a peripheral pos
46、ition in all meridians3.18.4prolate surfacesurface whose curvature decreases as the location on the surface moves from a central position to a peripheral position in all meridians3.18.5reference surfacesurface, that can be described in an exact, preferably mathematical fashion, used as a reference f
47、rom which distance measurements are made to the measured corneal surface, and for which, in addition to the mathematical description, the positional relationship to the corneal surface is specifiedNOTE For instance, a reference surface might be described as a sphere that is the best least-squares fi
48、t to the measured corneal surface. Similarly, a plane could serve as a reference surface.3.18.6toric surfacesurface for which the principal curvatures are unequal and for which principal meridians are circular sectionsNOTE Such surfaces are said to exhibit central astigmatism.3.19toricitydifference
49、in principal curvatures at a specified point or local area on a surface8 ISO 2012 All rights reservedBS EN ISO 19980:2012 ISO 19980:2012 (E)3.20transverse planeplane perpendicular to the meridional plane that includes the normal to the surface point4 Requirements4.1 Area measuredWhen measuring a spherical surface with a radius of curvature of 8 mm, a CT shall directly measure locations on the surface whose radial perpendicular distance from the CT axis is at least 3,75 mm. If the maximum area covered by a CT is claimed, it
