Committees responsible for this British Standard

The preparation of this British Standard was entrusted by the Health Care Standards Policy Committee (HCC/-) to Technical Committee HCC/78, upon which the following bodies were represented:

Association for Consumer Research (ACRE)
Association of British Dispensing Opticians
Association of Contact Lens Manufacturers
British College of Optometrists
British Contact Lens Association
British Medical Association
British Spectacle Frame Makers' Association
British Universities Committee of Contact Lens Educators
College of Ophthalmologists
Consumer Policy Committee of BSI
Department of Health
Department of Trade and Industry (National Physical Laboratory)
Federation of Manufacturing Opticians
Federation of Ophthalmic and Dispensing Opticians
Flat Glass Manufacturers' Association
OPTIC (UK)

Foreword

This Part of BS 3521 has been revised under the direction of the Health Care Standards Policy Committee and, together with BS 3521‑2:1991, supersedes BS 3521‑1:1962 & BS 3521‑2:1962 which is withdrawn.

The first edition of this Part of BS 3521 was published jointly with Part 2 in 1962. Since that time, the terminology relating to spectacle lenses (and ophthalmic optics in general) has changed, mainly because of the development of increased international trade. This development has encouraged participation by many countries in the work of the International Organization for Standardization (ISO) and, in particular, in the work of ISO Technical Committee 172. That Committee has been and is being instrumental in the preparation of a number of International Standards and, in this revision of BS 3521‑1 & BS 3521‑2, the terms and definitions have been updated in order to align with current international usage.

In addition to publishing Parts 1 and 2 of the 1962 edition of BS 3521 separately, the recommended method of writing prescriptions for ophthalmic lenses that appeared as Appendix A is also published separately as BS 2738‑3.

The purpose of this British Standard is unaltered from that of the first edition: it is to assist the mutual understanding of manufacturers, purchasers, users and others that have connections with the production, specification and sale of spectacle lenses. The use of an identical meaning for a word is all-important in such transactions.

This Part of BS 3521 presents a glossary, with a numerical classification, listing most of the terms in common use by those who design, teach the theory of, make or handle spectacle lenses. The initial numeral "0" or "1" in a reference to a classified term indicates that that term is included in this Part of BS 3521 (i.e. Part 1); the initial numeral 2 in a cross-reference to a term indicates that that term is included in BS 3521‑2. An alphabetical index to this Part is provided for ease of reference.

The preferred term, where more than one term exists, is given first in bold type. Other terms, which are at present acceptable but which it is hoped will fall into disuse, are set in medium type below the preferred term. Certain terms in current use are objectionable for various reasons (for example, they are confusing, imprecise or ambiguous); these terms are followed by the word "deprecated".

Italicized words indicate terms that are defined elsewhere in this Part of BS 3521.

In preparing this edition of BS 3521‑1, it was decided 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.

A number of definitions have been amended editorially and some terms, which are now in current use (some of which are taken from BS 2092 and BS 3199) have been introduced.

A minor restructuring of this Part of BS 3521 has also been carried out, although the titles of sections 1 to 11 of the 1962 edition are unaltered. However, because of the publication of BS 3521‑3 (which resulted in the deletion of section 14 by amendment in 1972) and because of other changes, such as the amalgamation of the sections dealing with defects, the numbering of section 12 and onwards has been amended.

At the time of publication, the British Standards that relate to ophthalmic subjects include the following:

BS 2092, Specification for eye-protectors for industrial and non-industrial uses.

BS 2724, Specification for sun-glare eye protectors for general use.

BS 2738, Spectacle lenses.

BS 3062, Specification for ophthalmic lens materials.

BS 3162, Specification for ophthalmic trial case lenses.

BS 3172, Specification for screw threads for spectacle frames.

BS 3199, Method for measurement of spectacles including a glossary of terms.

BS 3521, Terms relating to ophthalmic optics and spectacle frames — Part 2 Glossary of terms relating to spectacle frames — Part 3 Glossary of terms and symbols relating to contact lenses.

BS 3668, Specification for red and green filters used in ophthalmic dichromatic and dissociation tests.

BS 4110, Specification for eye-protectors for vehicle users.

BS 4274, Specification for test charts for determining distance visual acuity.

BS 6625, Specification for spectacle frames.

BS 6903, Specification for graduated dial scales for ophthalmic instruments.

BS 7017, Specification for reference wavelengths for optics and optical instruments.

BS 7208, Contact lenses.

BS 7394, Complete spectacles.

NOTE The 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 with a British Standard does not of itself confer immunity from legal obligations.

Section 1. Basic and general terms

1.1 Reference points, lines and dimensions

1.2 Distances and fields

1.3 Power

1.4 Lens theory and prescribing

Section 2. Types of surfaces

Section 3. General classes of lenses

3.1 Classification according to purpose

3.2 Classification according to lens form

3.3 Classification according to refractive properties

3.4 Classification according to stage of completion

3.5 Classification according to material

Section 4. Focal properties

Section 5. Prismatic properties

Section 6. Spherical lenses

Section 7. Astigmatic lenses

Section 8. Image defects and best-form lenses

Section 9. Lenticular lenses

Section 10. Bifocal, multifocal and progressive power lenses

10.1 General terms

10.2 Types of bifocal and multifocal lenses

10.3 Terms relating to fused bifocals and multifocals

10.4 Terms relating to solid bifocals and multilocals

Section 11. Tinted and coated lenses

Section 12. Protective lenses

Section 13. Magnifying devices

Section 14. Miscellaneous lenses and spectacles

14.1 Miscellaneous lenses

14.2 Miscellaneous spectacles

Section 15. Trial case accessories

Section 16. Manufacturing processes

16.1 Manufacture of lenses

16.2 Glazing processes and terms

Section 17. Defects

17.1 Defects of materials

17.2 Surface defects

Section 18. Verification

Section 19. Miscellaneous terms

Publication(s) referred to

BS 3521-1:1991

Terms relating to ophthalmic lenses and spectacle frames - Glossary of terms relating to ophthalmic lenses

Current

Published:

30 Sep 1991