1、BRITISH STANDARD BS3521-1: 1991 Terms relating to ophthalmic optics and spectacle frames Part 1: Glossary of terms relating to ophthalmic lensesBS3521-1:1991 This British Standard, having been prepared under the directionof the Health Care Standards Policy Committee, waspublished under the authority
2、of the Standards Boardand comes into effect on 30 September1991 BSI10-1999 First published June1962 as BS3521-1 these terms are followed by the word “deprecated”. Italicized words indicate terms that are defined elsewhere in this Part of BS3521. In preparing this edition of BS3521-1, it was decided
3、that a number of terms (given below) should be deleted. Either these terms were obsolete and no longer in common use or they had meanings little different from their dictionary definitions. bad metal cut circle periscopic bi-nasal notation cut piece prism degree bi-temporal notation cut square rimle
4、ss fitting bloomed lens datum centre a scalloped edge b blank number degree of deviation Stanhope lens break globular lens Steinheil cone centrad goggles step down solid bifocal Coddington lens mi-coquille varifocal lens crescent segment nose graph Wollaston lens a See01113 b Replaced by “faceted ed
5、ge”.BS3521-1:1991 BSI 10-1999 iii A number of definitions have been amended editorially and some terms, which are now in current use (some of which are taken from BS2092 and BS3199) have been introduced. A minor restructuring of this Part of BS3521 has also been carried out, although the titles of s
6、ections1 to11 of the1962 edition are unaltered. However, because of the publication of BS3521-3 (which resulted in the deletion of section14 by amendment in1972) and because of other changes, such as the amalgamation of the sections dealing with defects, the numbering of section12 and onwards has be
7、en amended. At the time of publication, the British Standards that relate to ophthalmic subjects include the following: BS2092, Specification for eye-protectors for industrial and non-industrial uses. BS2724, Specification for sun-glare eye protectors for general use. BS2738, Spectacle lenses. BS306
8、2, Specification for ophthalmic lens materials. BS3162, Specification for ophthalmic trial case lenses. BS3172, Specification for screw threads for spectacle frames. BS3199, Method for measurement of spectacles including a glossary of terms. BS3521, Terms relating to ophthalmic optics and spectacle
9、frames Part2Glossary of terms relating to spectacle frames Part3 Glossary of terms and symbols relating to contact lenses. BS3668, Specification for red and green filters used in ophthalmic dichromatic and dissociation tests. BS4110, Specification for eye-protectors for vehicle users. BS4274, Specif
10、ication for test charts for determining distance visual acuity. BS6625, Specification for spectacle frames. BS6903, Specification for graduated dial scales for ophthalmic instruments. BS7017, Specification for reference wavelengths for optics and optical instruments. BS7208, Contact lenses. BS7394,
11、Complete spectacles. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance wi
12、th a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1to40, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendme
13、nts incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS3521-1:1991 BSI 10-1999 1 Section 1. Basic and general terms No. Term Definition 1.1 Reference points, lines and dimensions NOTESee also10164. 01 101 vertex Point of intersection of the optical axis w
14、ith a surface of a lens. 01 102 meridian A direction line across the surface of a lens. 01 103 back Relating to the surface of a lens nearer to the eye. 01 104 front Relating to the surface of a lens remote from the eye. 01 105 optical centre (O) That point (real or virtual) on the optical axis of a
15、 lens which is, or appears to be, traversed by rays emerging parallel to their original direction. NOTEWhen applied to an ophthalmic lens, the optical centre is commonly regarded as coinciding with the vertex of either surface. 01 106 visual point Point of intersection of the eyes visual axis with t
16、he back surface of a lens. 01 107 distance visual point(DVP) An assumed position of the visual point on a lens which is used for distance vision under given conditions, normally when the eyes are in the primary position. 01 108 near visual point (NVP) An assumed position of the visual point on a len
17、s which is used for near vision under given conditions. 01 109 lens shape Outline of the lens periphery with the nasal side and the horizontal indicated. (See Figure 1.) 01 110 boxed lens size Size of the rectangle containing the lens shape (see01109) and formed by the horizontal and vertical tangen
18、ts to the lens shape. (See Figure 1.) 01 111 shape difference Difference, in millimetres, between the horizontal and vertical dimensions of the boxed lens size. (See Figure 1.) 01 112 horizontal centre line(HCL) datum line deprecated The line midway between, and parallel to, the horizontal tangents
19、at the highest and lowest points of a lens. 01 113 boxed centre a The mid-point of the rectangle containing the lens shape. a The term “datum centre” is now deprecated. However the following definition of that term is included for information: datum centre (dat C) The midpoint of that part of the da
20、tum line which is bounded by the lens shape. Key HHis the horizontal centre line (see 01 112) WXYZis the limiting rectangle defining boxed lens size NOTEThe letter N denotes the nasal side of the lens shape. Figure 1 Boxed lens size, lens shape and shape differenceBS3521-1:1991 2 BSI 10-1999 No. Ter
21、m Definition 01 114 standard optical centreposition A reference point specific to each lens shape, situated on the vertical line passing through the boxed centre (or situated at the boxed centre if the manufacturer has published no contrary indication as to its height). (See note to01115.) 01 115 ce
22、ntration point (CP) Point at which the optical centre is to be located in the absence of prescribed prism or after any prescribed prism has been neutralized. NOTEIf the centration point is not specified, it is located at the standard optical centre position. 01 116 pantoscopic angle The angle betwee
23、n the optical axis of a lens and the visual axis of the eye in the primary position, usually taken to be the horizontal. 1.2 Distances and fields 01 201 optical centre distance(OCD) optical PD, optical centres(OCs) both deprecated The actual horizontal distance between the optical centres of a pair
24、of mounted lenses, with any prescribed prisms being neutralized. 01 202 centration distance (CD) The specified horizontal distance between the right and left centration point. NOTEIf an inter-pupillary distance only is stated this is taken to be the centration distance. 01 203 decentration (dec) Dis
25、placement, horizontal and/or vertical, of the centration point from the standard optical centre position. 01 204 bodily decentration 1) Of lenticular lenses. Decentration which is applicable to the lenticular aperture as well as to the centration point. 2) Of multifocal lenses. Decentration which is
26、 applicable to the segment as well as to the centration point. 01 205 vertex distance Distance from the visual point of a lens to the corneal apex or the closed eyelid. NOTEIt should be stated whether the vertex distance has been measured from the corneal apex or the closed eyelid. 01 206 working di
27、stance Distance to the object plane from a specified point or plane. 01 207 field of view A general term denoting the maximum angular extent of vision through an optical appliance under given conditions. (Seealso01208,01209 and01210.) 01 208 apparent macular field of view Angle subtended by the effe
28、ctive diameter of an optical appliance at the eyes assumed centre of rotation. 01 209 real macular field of view Angular field of view in object space of an optical appliance at the eyes assumed centre of rotation. (See01208.) 01 210 linear field of view The linear extent of the real field of view a
29、t the stated working distance. 01 211 apparent peripheral field of view Angle subtended by the effective diameter of an optical appliance at the assumed centre of the eyes entrance pupil. 01 212 real peripheral field of view Angular field of view in object space of an optical appliance at the assume
30、d centre of the eyes entrance pupil.BS3521-1:1991 BSI 10-1999 3 No. Term Definition 1.3 Power 01 301 curvature (R) Reciprocal of the radius of curvature. NOTECurvature is sometimes expressed in terms of dioptres (when the radius of curvature is measured in metres). This use of the dioptre as a unit
31、of curvature is deprecated because of the confusion which would arise between curvature and surface power. In ophthalmic optics, the appropriate unit is the reciprocal metre(m 1 ). 01 302 power Capacity of a lens or surface to affect incident wave-fronts by refraction. NOTEThis term includes both fo
32、cal power (see01303) and prismatic power (see01305). 01 303 focal power The measure of a lens or surface to affect the curvature of incident wave-fronts by refraction. 01 304 deviation The change in direction imposed on a ray of light (the normal to a specified element of a wave-front) as a result o
33、f refraction. 01 305 prismatic power The measure of the deviation of a ray of light as a result of passing through a specified point on a lens or prism. 1.4 Lens theory and prescribing 01 401 thin lens A lens whose centre thickness has a negligible effect on its focal properties. 01 402 lens form Th
34、e combination of surface powers chosen to produce the given focal effect. 01 403 sphere (Sph) A term commonly used for brevity to denote: a) the spherical element either of a prescription or of the power of a lens; or b) a spherical lens. (See03303.) 01 404 cylinder (Cyl) A term commonly used for br
35、evity to denote: a) the cylindrical element either of a prescription or of the power of a lens; or b) a plano-cylinder lens. (See07006.) 01 405 transposition 1) A change of lens form without change of back vertex power. (See04006and08004.) 2) One of the customary methods of writing a prescription; f
36、orexample the plus cylinder transposition. 3) Process of converting a prescription from the original to an alternative formulation, especially from the plus to the minus cylinder and vice versa. 01 406 thin lens transposition simple transposition A change of form without change of lens power, with t
37、he effects of thickness being ignored for simplicity. 01 407 correction Power of a lens or lenses for correcting, or prescribed to correct for, a refractive error. 01 408 prescription (Rx) Specification, produced by the prescriber, giving essential details of the lens or lenses required for a partic
38、ular patient. NOTEThe method of presenting a prescription is described in BS2738-3. 01 409 prescription order Document that provides sufficient information for suitable uncut or mounted ophthalmic lenses to be manufactured or supplied which comply with the prescription. (See01408.) NOTEThe method of
39、 presenting a prescription order is described in BS2738-3.BS3521-1:1991 4 BSI 10-1999 Section 2. Types of surfaces No. Term Definition 02 001 plane flat, plano both deprecated when applied to a “surface”, see03302 Of zero curvature. 02 002 concave (Cc) Relatively depressed at the centre as compared
40、with a plane surface. 02 003 convex (Cx) Relatively raised at the centre as compared with a plane surface. 02 004 spherical Forming part of the surface of a sphere. 02 005 cylindrical Forming part of the surface of a cylinder. 02 006 aspherical Of a surface of revolution having continuously variable
41、 curvature from the vertex to the periphery. 02 007 toroidal Forming part of the surface generated by a circular arc rotating about an axis which is in the same plane as the arc but which does not pass through its centre of curvature. NOTE 1It is desirable to restrict the term “toroidal” to a surfac
42、e and the term “toric” to a lens or object. (See03210.) NOTE 2Three different types of toroidal surface are used in ophthalmic lens manufacture as illustrated in Figure 2, Figure 3 and Figure 4. The axis of rotation RR and the vertex V of the generating arc AA are on the opposite sides of the latters centre of curvature C. Figure 2 Tyre formation
