ISO 9342-2:2005
(Main)Optics and optical instruments — Test lenses for calibration of focimeters — Part 2: Test lenses for focimeters used for measuring contact lenses
Optics and optical instruments — Test lenses for calibration of focimeters — Part 2: Test lenses for focimeters used for measuring contact lenses
ISO 9342-2:2005 specifies requirements for test lenses for focimeters that are used to measure contact lenses. These test lenses are used to find the precise correction values that are needed to convert the power values measured to back vertex power values. ISO 9342-2:2005 applies to focimeters meeting the requirements of ISO 8598.
Optique et instruments optiques — Verres étalons pour l'étalonnage des frontofocomètres — Partie 2: Verres étalons pour frontofocomètres pour le mesurage des lentilles de contact
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INTERNATIONAL ISO
STANDARD 9342-2
First edition
2005-11-15
Optics and optical instruments — Test
lenses for calibration of focimeters —
Part 2:
Test lenses for focimeters used for
measuring contact lenses
Optique et instruments optiques — Verres étalons pour l'étalonnage
des frontofocomètres —
Partie 2: Verres étalons pour frontofocomètres pour le mesurage des
lentilles de contact
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
Foreword
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
technical 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 with 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 International 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 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9342-2 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 7,
Ophthalmic optics and instruments.
ISO 9342 consists of the following parts, under the general title Optics and optical instruments — Test lenses
for calibration of focimeters:
⎯ Part 1: Test lenses for focimeters used for measuring spectacle lenses
⎯ Part 2: Test lenses for focimeters used for measuring contact lenses
INTERNATIONAL STANDARD ISO 9342-2:2005(E)
Optics and optical instruments — Test lenses for calibration of
focimeters —
Part 2:
Test lenses for focimeters used for measuring contact lenses
1 Scope
This part of ISO 9342 specifies requirements for test lenses for focimeters that are used to measure contact
lenses. These test lenses are used to find the precise correction values that are needed to convert the power
values measured to back vertex power values, as defined in Clause 3.
This part of ISO 9342 applies to focimeters meeting the requirements of ISO 8598.
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 (including any amendments) applies.
ISO 7944:1998, Optics and optical instruments — Reference wavelengths
ISO 8598:1996, Optics and optical instruments — Focimeters
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
back vertex power
F
bv
reciprocal of the paraxial value of the back vertex focal length, measured in metres
−1
NOTE 1 The unit for expressing vertex power is the reciprocal metre (m ). The name for this unit is “dioptre”, and the
symbol is D.
NOTE 2 Conventionally, the back vertex power is specified as the “power“ of a contact lens.
3.2
spherical test lenses
test lenses having spherical front and back surfaces so that their back vertex power may be expressed by a
single value
3.3
reference wavelength
wavelengths specified in ISO 7944
NOTE For the purpose of this part of ISO 9342, the reference wavelength can be either the green mercury line
(λ = 546,07 nm) or the yellow helium line (λ = 587,56 nm).
e d
4 Design requirements and recommendations for test lenses
4.1 General
Test lenses should be made of homogeneous white crown glass selected to be free of bubbles and striae in
an area of 4 mm radius surrounding the centre of the free aperture.
It is accepted that other materials can also be used provided their use result in lenses with a durability and
optical reproducibility within the given tolerance over time and that can be manufactured to the same standard
of uncertainty and form, as the glass lenses specified above.
Test lenses should have a protective mount that is designed so that, when the lens is correctly placed on the
lens support, the focimeter is not obstructed.
4.2 Spherical test lens
For a complete set of spherical test lenses, the following set of nominal back vertex powers is recommended:
− 20 D, − 15 D, − 10 D, − 5 D, + 5 D, + 10 D, + 15 D, + 20 D.
Spherical test lenses should have a free aperture of at least 8 mm.
The curvature of the back surface shall approximately correspond to those of common contact lenses, which
are in the range 7 mm to 9 mm, so that the spherical aberration of the test lenses approximates that exhibited
by common contact lenses.
The nominal curvature of the back surface is recommended as 8 mm, a value meeting the requirement of
ISO 18369-3, which is approximately equal to the front surface radius of cornea for the human eye. The radius
tolerance for back surface curvature is ± 0,1 mm.
The centre thickness for a given back vertex power shall be chosen to be in the range given in Table 1.
These centre thickness value ranges are required to guarantee the durability of the test lenses during use. It is
for this reason that they are generally greater than those for common contact lenses.
Table 1 — Design range for the standard test lenses
Nominal back vertex power, F
Range for centre thickness
bv
−1
(mm)
(m )
− 20 0,5 to 1,5
− 15 0,5 to 1,5
0,5 to 1,5
− 10
− 5 0, 5 to 1,5
+ 5 1 to 2
+ 10 1 to 2
+ 15 1 to 2
1 to 2
+ 20
2 © ISO 2005 – All rights reserved
5 Tolerances for spherical test lenses
The design value of each lens shall be stated along with the reference wavelength used to determine this
−1
value. The permissible tolerances for all spherical test lenses shall be within ± 0,03 m of their stated values.
NOTE In Annex A, an example is given for the proper design of test lenses that meets this requirement and the
requirement of Table 1.
Annex A
(informative)
Manufacture of test lenses for calibration of focimeters
used for measuring contact lenses
A.1 General
Spherical test lenses, which meet the tolerances given in 4.2 and Clause 5, can be manufactured by
observing the specifications and procedure described in A.2 to A.8.
To manufacture test lenses in accordance with this annex, the manufacturer will need a selection of master
test surfaces against which the test lens surfaces can be checked, using standard precision optica
...
INTERNATIONAL ISO
STANDARD 9342-2
First edition
2005-11-15
Optics and optical instruments — Test
lenses for calibration of focimeters —
Part 2:
Test lenses for focimeters used for
measuring contact lenses
Optique et instruments optiques — Verres étalons pour l'étalonnage
des frontofocomètres —
Partie 2: Verres étalons pour frontofocomètres pour le mesurage des
lentilles de contact
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
Foreword
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
technical 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 with 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 International 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 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9342-2 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 7,
Ophthalmic optics and instruments.
ISO 9342 consists of the following parts, under the general title Optics and optical instruments — Test lenses
for calibration of focimeters:
⎯ Part 1: Test lenses for focimeters used for measuring spectacle lenses
⎯ Part 2: Test lenses for focimeters used for measuring contact lenses
INTERNATIONAL STANDARD ISO 9342-2:2005(E)
Optics and optical instruments — Test lenses for calibration of
focimeters —
Part 2:
Test lenses for focimeters used for measuring contact lenses
1 Scope
This part of ISO 9342 specifies requirements for test lenses for focimeters that are used to measure contact
lenses. These test lenses are used to find the precise correction values that are needed to convert the power
values measured to back vertex power values, as defined in Clause 3.
This part of ISO 9342 applies to focimeters meeting the requirements of ISO 8598.
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 (including any amendments) applies.
ISO 7944:1998, Optics and optical instruments — Reference wavelengths
ISO 8598:1996, Optics and optical instruments — Focimeters
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
back vertex power
F
bv
reciprocal of the paraxial value of the back vertex focal length, measured in metres
−1
NOTE 1 The unit for expressing vertex power is the reciprocal metre (m ). The name for this unit is “dioptre”, and the
symbol is D.
NOTE 2 Conventionally, the back vertex power is specified as the “power“ of a contact lens.
3.2
spherical test lenses
test lenses having spherical front and back surfaces so that their back vertex power may be expressed by a
single value
3.3
reference wavelength
wavelengths specified in ISO 7944
NOTE For the purpose of this part of ISO 9342, the reference wavelength can be either the green mercury line
(λ = 546,07 nm) or the yellow helium line (λ = 587,56 nm).
e d
4 Design requirements and recommendations for test lenses
4.1 General
Test lenses should be made of homogeneous white crown glass selected to be free of bubbles and striae in
an area of 4 mm radius surrounding the centre of the free aperture.
It is accepted that other materials can also be used provided their use result in lenses with a durability and
optical reproducibility within the given tolerance over time and that can be manufactured to the same standard
of uncertainty and form, as the glass lenses specified above.
Test lenses should have a protective mount that is designed so that, when the lens is correctly placed on the
lens support, the focimeter is not obstructed.
4.2 Spherical test lens
For a complete set of spherical test lenses, the following set of nominal back vertex powers is recommended:
− 20 D, − 15 D, − 10 D, − 5 D, + 5 D, + 10 D, + 15 D, + 20 D.
Spherical test lenses should have a free aperture of at least 8 mm.
The curvature of the back surface shall approximately correspond to those of common contact lenses, which
are in the range 7 mm to 9 mm, so that the spherical aberration of the test lenses approximates that exhibited
by common contact lenses.
The nominal curvature of the back surface is recommended as 8 mm, a value meeting the requirement of
ISO 18369-3, which is approximately equal to the front surface radius of cornea for the human eye. The radius
tolerance for back surface curvature is ± 0,1 mm.
The centre thickness for a given back vertex power shall be chosen to be in the range given in Table 1.
These centre thickness value ranges are required to guarantee the durability of the test lenses during use. It is
for this reason that they are generally greater than those for common contact lenses.
Table 1 — Design range for the standard test lenses
Nominal back vertex power, F
Range for centre thickness
bv
−1
(mm)
(m )
− 20 0,5 to 1,5
− 15 0,5 to 1,5
0,5 to 1,5
− 10
− 5 0, 5 to 1,5
+ 5 1 to 2
+ 10 1 to 2
+ 15 1 to 2
1 to 2
+ 20
2 © ISO 2005 – All rights reserved
5 Tolerances for spherical test lenses
The design value of each lens shall be stated along with the reference wavelength used to determine this
−1
value. The permissible tolerances for all spherical test lenses shall be within ± 0,03 m of their stated values.
NOTE In Annex A, an example is given for the proper design of test lenses that meets this requirement and the
requirement of Table 1.
Annex A
(informative)
Manufacture of test lenses for calibration of focimeters
used for measuring contact lenses
A.1 General
Spherical test lenses, which meet the tolerances given in 4.2 and Clause 5, can be manufactured by
observing the specifications and procedure described in A.2 to A.8.
To manufacture test lenses in accordance with this annex, the manufacturer will need a selection of master
test surfaces against which the test lens surfaces can be checked, using standard precision optica
...
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