EN 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 (ISO 9342-2:2005)
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)
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.
Optik und optische Instrumente - Prüfgläser zur Kalibrierung von Scheitelbrechwert-Messgeräten - Teil 2: Prüfgläser für Scheitelbrechwert-Messgeräte für die Messung von Kontaktlinsen (ISO 9342-2:2005)
Dieser Teil von ISO 9342 legt Anforderungen an Prüfgläser zur Kalibrierung von Scheitelbrechwert-Messgeräten, die für die Messung von Kontaktlinsen verwendet werden, fest. Diese Prüfgläser werden zur Ermittlung exakter Korrekturwerte verwendet, die benötigt werden, um die gemessenen Brechwerte in Scheitelbrechwerte umzurechnen, wie in Abschnitt 3 festgelegt.
Dieser Teil von ISO 9342 gilt für Scheitelbrechwert-Messgeräte nach 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 (ISO 9342-2:2005)
Optika in optični instrumenti – Preskusne leče za umerjanje fokometrov – 2. del: Preskusne leče za fokometre, ki se uporabljajo za merjenje kontaktnih leč (ISO 9342-2:2005)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2006
2SWLNDLQRSWLþQLLQVWUXPHQWL±3UHVNXVQHOHþH]DXPHUMDQMHIRNRPHWURY±GHO
3UHVNXVQHOHþH]DIRNRPHWUHNLVHXSRUDEOMDMR]DPHUMHQMHNRQWDNWQLKOHþ ,62
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)
Optik und optische Instrumente - Prüfgläser zur Kalibrierung von Scheitelbrechwert-
Messgeräten - Teil 2: Prüfgläser für Scheitelbrechwert-Messgeräte für die Messung von
Kontaktlinsen (ISO 9342-2:2005)
Optique et instruments optiques - Verres étalons pour l'étalonnage des frontofocometres
- Partie 2: Verres étalons pour frontofocometres pour le mesurage des lentilles de
contact (ISO 9342-2:2005)
Ta slovenski standard je istoveten z: EN ISO 9342-2:2005
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN ISO 9342-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2005
ICS 11.040.70 Supersedes EN ISO 9342:1998
English Version
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)
Optique et instruments optiques - Verres étalons pour Optik und optische Instrumente - Prüfgläser zur
l'étalonnage des frontofocomètres - Partie 2: Verres étalons Kalibrierung von Scheitelbrechwert-Messgeräten - Teil 2:
pour frontofocomètres pour le mesurage des lentilles de Prüfgläser für Scheitelbrechwert-Messgeräte für die
contact (ISO 9342-2:2005) Messung von Kontaktlinsen (ISO 9342-2:2005)
This European Standard was approved by CEN on 14 November 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard 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 Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
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EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9342-2:2005: E
worldwide for CEN national Members.
Foreword
This document (EN ISO 9342-2:2005) has been prepared by Technical Committee ISO/TC 172
"Optics and optical instruments" 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 publication of
an identical text or by endorsement, at the latest by May 2006, and conflicting national standards
shall be withdrawn at the latest by May 2006.
This document supersedes EN ISO 9342:1998.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 9342-2:2005 has been approved by CEN as EN ISO 9342-2:2005 without any
modifications.
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 9342-2:2005(E)
©
ISO 2005
ISO 9342-2:2005(E)
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ii © ISO 2005 – All rights reserved
ISO 9342-2:2005(E)
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
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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
ISO 9342-2:2005(E)
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
ISO 9342-2:2005(E)
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.
ISO 9342-2:2005(E)
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 optical techniques.
A.2 Selection of glass
To manufacture spherical test lenses using this method, precision grade homogeneous optical glass shall be
used.
−5
The refractive index should be known to an accuracy of ± 5 × 10 .
A.3 The nominal back surface radius of curvature
The nominal radius of the back surface (i.e. the surface that is put on to the lens support of the focimeter) is
(8 ± 0,1) mm.
A.4 Selection of the back surface radius
Using the nominal radius of the back surface in A.3, the master test surfaces radius should be selected
closest to the desired value of A.3.
A.5 Calculation of lens thickness and selection of front surface radius
Using the selected value of the back surface radius, the desired back vertex power and a centre thickness,
that is in the range specified by Table 1, the front surface radius of curvature, r , is calculated using the
standard thick lens paraxial power formulae given in A.6. An explicit expression for r is given by
⎡⎤
rn=−11F −F+tn
()()
1bv2
⎣⎦
where
−1
F is the back vertex power of contact lens, in dioptres (m );
bv
−1
F is the back surface power of the contact lens (the surface in contact with cornea), in dioptres (m ).
This radius value i
...
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