1、BS 7394-2:2007Complete spectaclesPart 2: Specification for prescription spectaclesICS 11.040.70NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when the document was
2、 last issued. BSI 2007ISBN 978 0 580 53601 4The following BSI references relate to the work on this standard:Committee reference CH/172Draft for comment 07/30082138 DCPublication historyFirst published May 1994Second edition August 2007Amendments issued since publicationAmd. no. Date Text affectedBS
3、 7394-2:2007 BSI 2007 iBS 7394-2:2007ContentsForeword ii1 Scope 12 Normative references 13 Definitions 14 Lens characteristics 45 Frame characteristics 66 Mechanical characteristics 67 Marking and instructions for use 7AnnexesAnnex A (informative) Recommendations on mounting, material and surface qu
4、ality 8Annex B (informative) Classification of lenses 11Annex C (normative) Lens retention test 13Annex D (normative) Test for enhanced robustness lenses 15Annex E (normative) Test for lenses of increased robustness 16Bibliography 17List of figuresFigure A.1 Recommended system for visually inspectin
5、g a lens for defects 9Figure A.2 Front view of round lenses illustrating marks (exaggerated) on back surfaces 10Figure C.1 Test lever 14Figure C.2 Location of the test lever on the test specimen 14Figure D.1 Holding device for testing lenses of enhanced and increased robustness 15List of tablesTable
6、 1 Classification of robustness 7Table B.1 Classification by refractive index 11Table B.2 Classification by Abbe number 11Table B.3 Classification of tinted lenses 12Table B.4 Classification by UV transmittance 12Summary of pagesThis document comprises a front cover, an inside front cover, pages i a
7、nd ii, pages 1 to 17 and a back cover.BS 7394-2:2007ii BSI 2007ForewordPublishing informationThis Part of BS 7394 was published by BSI and came into effect on 31 August 2007. It supersedes BS 7394-2:1994, which is withdrawn. It was prepared by Subcommittee CH/172/3, Spectacles, under the authority o
8、f Technical Committee CH/172, Ophthalmic optics. A list of organizations represented on CH/172 can be obtained on request to its secretary.BS 7394 was prepared to establish a means of specifying the attributes necessary for complete spectacles. Information about this documentThis Part of BS 7394 has
9、 been revised to take account of the change in name and number of various referenced standards where British Standards have been replaced by European standards, and to take account of improvements in lens technology and changes in terminology. The method for specifying surface-dyed tints is now in B
10、S 2738-3.BS 7394-1, relating to ready-to-wear near vision spectacles, has been withdrawn and replaced by BS EN 14139.Product certification/inspection/testing. Users of this British Standard are advised to consider the desirability of third-party certification of product conformity with this British
11、Standard. Appropriate conformity attestation arrangements are described in BS EN ISO/IEC 17025. Users seeking assistance in identifying appropriate conformity assessment bodies or schemes may ask BSI to forward their enquiries to the relevant association.Use of this documentThe provisions of this st
12、andard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.Contractual and le
13、gal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations. BSI 2007 1BS 7394-2:20071 Scope1.1 This Part of BS 7394 speci
14、fies requirements for complete spectacles incorporating a pair of prescription lenses.1.2 This Part of BS 7394 is not applicable to the following:a) ready-to-wear spectacles (see 3.2 and also BS EN 14139);b) spectacles to be used for eye protection (these spectacles are specified in BS EN 166) or sp
15、ectacles intended for use in high activity or contact sports;c) spectacles without optical power to be used as non-prescription sun glare eye protectors (these spectacles are specified in BS EN 1836).1.3 This Part of BS 7394 defines several terms that may be used when dispensing or which will help i
16、n describing the numerical attributes of various lens characteristics. It also includes a lens retention test which has been developed by the Association for Consumer Research (ACRE) with the assistance of the Federation of Manufacturing Opticians (FMO), the Department of Trade and Industry and the
17、Department of Health.1.4 This part of BS 7394 is applicable to a product at the point of supply to the intended wearer. NOTE Annex A contains recommendations for the mounting of lenses and on material and surface quality characteristics that are subjective and which, therefore, cannot be specified.2
18、 Normative referencesThe 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 (including any amendments) applies.BS 2738-1, Spectacle lenses P
19、art 1: Specification for tolerances on optical properties of mounted spectacle lensesBS EN 166: 2002, Personal eye protection SpecificationsBS EN ISO 8980-3, Ophthalmic optics Uncut finished spectacle lenses Part 3: Transmittance specifications and test methodsBS EN ISO 12870:2004, Ophthalmic optics
20、 Spectacle frames Requirements and test methodsBS EN ISO 14889:2003, Ophthalmic optics Spectacle lenses Fundamental requirements for uncut finished lenses3 DefinitionsFor the purposes of this Part of BS 7394, the definitions given in BS EN ISO 13666, BS 3521-1, BS 3521-2 and BS EN ISO 12870 apply, t
21、ogether with the following.NOTE If the definitions in BS EN ISO 13666 differ from those quoted below, the definitions in BS EN ISO 13666 take priority.BS 7394-2:20072 BSI 20073.1 prescription spectaclesspectacles glazed in accordance with a prescription1)written for a particular individual wearer3.2
22、 ready-to-wear spectaclesspectacles intended only for near vision and reading use having or incorporating a pair of single vision lenses of equal positive spherical power in which the glazing has not been carried out in direct response to a written prescription by a qualified practitioner BS EN 1413
23、9NOTE The term “ready-to-wear spectacles” (also known as “ready-made spectacles”) as defined in BS EN 14139 is restricted to spectacles having or incorporating single vision lenses. The rationale for this restriction is that spectacle lenses other than single vision lenses (e.g. bifocal, multifocal,
24、 progressive power lenses) are not recommended for use in ready-to-wear spectacles due to the need of a qualified practitioners prescription and dispensing for such lenses.3.3 Abbe number mathematical expression for determining the correction for chromatic aberration of an optical BS EN ISO 13666NOT
25、E This is expressed as either:where: Id is the Abbe number for the yellow helium d-line (wavelength: 587.56 nm);ndis the refractive index of the yellow helium d-line (wavelength: 587.56 nm);nFis the refractive index of the blue Hydrogen F-line (wavelength: 486.13 nm); andnCis the refractive index of
26、 the red Hydrogen C-line (wavelength: 656.27 nm).or:where: Ie is the Abbe number for the green mercury e-line (wavelength: 546.07 nm);neis the refractive index of the green mercury e-line (wavelength: 546.07 nm);nF is the refractive index of the blue cadmium F-line (wavelength: 479.99 nm); and nCis
27、the refractive index of the red cadmium C-line (wavelength: 64 385 nm).These reference wavelengths are given in BS EN ISO 7944:1998.1)The presentation of prescriptions and prescription orders for ophthalmic lenses is specified in BS 2738-3.dnd1nFnC-=ene1nFnC-= BSI 2007 3BS 7394-2:20073.4 refractive
28、index of a medium, for a monochromaticradiation of wavelength 2 in vacuum, n(2) ratio of the velocity of the electromagnetic waves in vacuum to the phase velocity of the waves of the monochromatic radiation in the medium IEC 60050-845:1987, 04-101NOTE 1 For technical applications the refractive inde
29、x is given against air instead of against vacuum.NOTE 2 Wavelengths to be used for the characterization of optical glasses, all kinds of optical systems and instruments together with spectacle lenses are specified in BS EN ISO 7944.3.5 luminous transmittance (LT)ratio of the luminous flux transmitte
30、d by the lens or filter to the incident luminous flux BS EN ISO 13666NOTE The terms “light transmission factor” (LTF) and “luminous transmission factor” (LTF) are deprecated.%where:(2) is the spectral transmittance of the tinted spectacle lensV(2) is the spectral luminous efficiency function for day
31、light (see BS ISO/CIE 10527)SD652(2) is the spectral distribution of radiation of CIE standard illuminant D 65 (see BS ISO/CIE 10526).3.6 design reference point point or points, stipulated by the manufacturer, on the finished surface of the lens blank or front surface of the finished lens at which t
32、he design specifications apply BS EN ISO 13666NOTE Examples are the distance design reference point and the near design reference point.3.7 distance design reference pointpoint, stipulated by the manufacturer, on the front surface of a finished lens or the finished surface of a lens blank at which t
33、he design specifications for the distance portion apply BS EN ISO 136663.8 near design reference point point, stipulated by the manufacturer, on the front surface of a finished lens or the finished surface of a lens blank at which the design specifications for the near portion apply BS EN ISO 13666v
34、100()V ()SD65() d 380mm780mmV ()SD65() d380mm780mm-=vBS 7394-2:20074 BSI 20074 Lens characteristics4.1 MaterialsThe materials used for the lenses of the spectacles shall conform to BS EN ISO 14889.NOTE Recommendations regarding optical characteristics that are subjective (and cannot therefore be spe
35、cified), as well as glazing recommendations, are given in Annex A.4.2 ThicknessExcept at the bevel, if any, the thickness of each lens shall exceed 0.9 mm. (See also A.3.1.)4.3 TolerancesThe tolerances on the lenses as prescribed in the prescription2)shall conform to BS 2738-1.4.4 Tinted lensesNOTE
36、1 As an example, consider an untinted lens made of clear material with a refractive index of 1.5 and having an actual transmission of 92% due to the 4% of light lost by reflection at each surface (total lost approximately 8%). Since this untinted lens has no absorption, the LT would be approximately
37、 92%.The addition of a tint to the same lens will reduce the LT, while the application of an anti-reflective coating will increase the LT.A lens made of material having a higher refractive index, but identical in all other respects, will have a lower LT due to the increased surface reflectance.NOTE
38、2 In BS EN ISO 13666:1999 a “tinted lens” is defined as “a lens having a noticeable colour in transmission”. Such a lens can be manufactured by surface dyeing or permeation (of resins), by surface coating or as solid tints (where the tint is dispersed throughout the material during its manufacture).
39、NOTE 3 It is recommended that when a tint is required for cosmetic purposes only, it should be ordered by reference to a manufacturers identification code, name or reference number. The person dispensing the spectacles should note the effect of additional surface treatments as described in Note 1.If
40、 particular transmission or absorption characteristics are required for clinical purposes, specific values (see 4.4.2) should be quoted in the prescription or prescription order. To avoid ambiguity, BS 2738-3 recommends that such requirements be specified by reference to the LT.2)The presentation of
41、 prescriptions and prescription orders for ophthalmic lenses is specified in BS 2738-3. BSI 2007 5BS 7394-2:2007NOTE 4 As the colour of spectacle lenses is not conducive to independent assessment, colour is not specified in this Part of BS 7394. The accurate measurement of colour requires complex eq
42、uipment which is not available generally. Moreover, the assessment of accuracy has to be made visually under daylight conditions or under artificial lighting which is equivalent to a daylight source. Agreement on colour is generally based on comparison with manufacturers samples and should be subjec
43、t to agreement at each interface in the supply chain (see 7.3).NOTE 5 This Part of BS 7394 does not specify prescription spectacles fitted with lenses of graduated tint because of the difficulty of measuring graduated tints with any accuracy. The guidance for checking and agreeing colour given in No
44、te 4 is applicable.4.4.1 Suitability of tinted lenses for road usersTinted lenses that are stated by the manufacturer as being suitable for road users and particularly for use when driving shall conform to the signal and colour recognition requirements of BS EN ISO 14889:2003, 4.5.2.WARNING. The sup
45、plier should warn the purchaser or wearer see 7.2b) if the luminous transmittance of the tinted lenses makes their use inadvisable when driving a motor vehicle, especially under dull light conditions. 4.4.2 Determination of LTIf specified, the luminous transmittance shall be determined in accordance
46、 with BS EN ISO 8980-3.NOTE 1 In most practical situations, an approximate value of the LT for a tinted lens may be obtained by the following method.Using a simple photometer commonly available in prescription laboratories and with no lens inserted, adjust the calibration to read 100%. Insert the le
47、ns to be measured into the photometer and record the displayed transmittance reading T. This reading is approximately the value of the LT.NOTE 2 It should be noted that the accuracy of an LT determination can be affected if the lens has strong positive or negative power.If, for a specific reason, th
48、e value of the absorptance is quoted in the prescription or prescription order, the specified value shall be expressed as a percentage and should be accompanied by the letter A (see Note 3).NOTE 3 The approximate relationship between LT (T), luminous absorptance (A) and luminous reflectance (R) is a
49、s follows:100 = T + A + RThusT = 100 R A and A = 100 R TThat is, the LT is reduced by the absorption of the lens material and by surface reflections, which, in turn, are dependent on the refractive index, and which can be diminished by any anti-reflective coatings.BS 7394-2:20076 BSI 20074.4.3 Toleranc
