EN ISO 10338:1997
(Main)Optics and optical instruments - Contact lenses - Determination of curvature (ISO 10338:1996)
Optics and optical instruments - Contact lenses - Determination of curvature (ISO 10338:1996)
Specification of a uniform test procedure in order to achieve comparable test results.
Optik und optische Instrumente - Kontaktlinsen - Bestimmung der Krümmung (ISO 10338:1996)
Diese Internationale Norm beschreibt Verfahren zur Bestimmung der Krümmung von Kontaktlinsen.
Optique et instruments d'optique - Lentilles de contact - Détermination de la courbure (ISO 10338:1996)
Optika in optični instrumenti - Kontaktne leče - Ugotavljanje ukrivljenosti (ISO 10338:1996)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 10338:2000
01-januar-2000
2SWLNDLQRSWLþQLLQVWUXPHQWL.RQWDNWQHOHþH8JRWDYOMDQMHXNULYOMHQRVWL ,62
Optics and optical instruments - Contact lenses - Determination of curvature (ISO
10338:1996)
Optik und optische Instrumente - Kontaktlinsen - Bestimmung der Krümmung (ISO
10338:1996)
Optique et instruments d'optique - Lentilles de contact - Détermination de la courbure
(ISO 10338:1996)
Ta slovenski standard je istoveten z: EN ISO 10338:1997
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
SIST EN ISO 10338:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 10338:2000
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SIST EN ISO 10338:2000
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SIST EN ISO 10338:2000
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SIST EN ISO 10338:2000
ISO
INTERNATIONAL
STANDARD 10338
First edition
1996-07-I 5
Optics and optical instruments - Contact
lenses - Determination of curvature
Optique et instruments d’optique - Lentilles de contact - Détermination de
la courbure
Reference number
10338 :1996(E)
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SIST EN ISO 10338:2000
ISO 10338:1996(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide fed-
eration 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 rep-
resented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO col-
laborates closely with the International Electrotechnical Commission (IEC)
on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are cir-
culated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 10338 was prepared by Technical Committee
ISO/TC 172, Optics and optical instruments, Subcommittee SC 7, Oph-
thalmic op tics and instruments.
Annexes A to C form an integral part of this International Standard. Annex
D is for information only.
0 60 1996
All rights reserved. Unless otherwise specified, no part of this publication may be repro-
duced or utilized in any form or by any means, electronic or mechanical, including photo-
copying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Genève 20 l Switzerland
Printed in Switzerland
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SIST EN ISO 10338:2000
INTERNATIONAL STANDARD @ Iso ISO 10338:1996(E)
Optics and optical instruments - Contact lenses - Determination
of curvature
ISO 5725-4: 1994, Accuracy (trueness and precision) of
1 Scope
measurement methods and results - Part 4: Basic
methods for the determination of the trueness of a
This International Standard describes methods for the
standard measurement method.
determination of curvature of contact lenses.
ISO 5725-6: 1994, Accuracy (trueness and precision) of
measurement methods and results - Part 6: Use in
practice of accuracy values.
2 Normative references
ISO 8320:1986, Optics and optical instruments -
The following standards contain provisions which,
Con tact lenses - Vocabulary and symbols.
through reference in this text, constitute provisions of
this International Standard. At the time of publication,
ISO 10344: -11, Optics and optical instruments -
the editions indicated were valid. All standards are
Contact lenses - Saline solution for contact lens
subject to revision, and parties to agreements based
tes ting.
on this International Standard are encouraged to in-
vestigate the possibility of applying the most recent
editions of the standards indicated below. Members
of IEC and ISO maintain registers of currently valid In-
ternational Standards.
3 Definitions
ISO 5725-l : 1994, Accuracy (trueness and precision) of
For the purposes of this International Standard, the
measurement methods and results - Part 1: General
definitions given in ISO 8320 apply.
Princip/es and definitions.
ISO 5725-2: 1994, Accuracy (trueness and precision) of
measurement methods and results - Part2: Basic
method for the determination of repeatability and re-
4 Test methods
producibility of a standard measurement method.
The test methods specified in detail in annexes A to C
ISO 5725-3: 1994, Accuracy (trueness and precision) of
to this International Standard are listed in table 1, to-
measurement methods and results - Part 3: Inter-
gether with a statement of their reproducibility when
mediate measures of the precision of a standard
applied to either rigid or hydrogel contact lenses.
measurement method.
1) TO be published.
1
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SIST EN ISO 10338:2000
ISO 10338:1996(E) @ ISO *
Table 1 - Test methods
Annex
lest method/application Reproducibility, R (ISO 5725)
A Optical microspherometry
Spherical rigid lenses t 0,015 mm in air
B Ophthalmometry
Spherical rigid lenses + 0,015 mm in air
Spherical rigid lenses + 0,025 mm in saline solution
Spherical hydrogel lenses (38 % water content, + 0,050 mm in saline solution
t, > 0,l mm)
C Sagittal height method
Hydrogel lenses (38 % water content, t, > 0,l mm) + 0,050 mm in saline solution
Hydrogel lenses (55 % water content, t, > 0,l mm)
+ 0,100 mm in saline solution
Hydrogel lenses (70 % water content, t, > 0,l mm) + 0,200 mm in saline solution
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SIST EN ISO 10338:2000
@ ISO ISO 10338:1996(E)
Annex A
(normative)
Determination of radius of curvature using the optical microspherometer
A.2 Principle
A.1 Scope
This annex specifies a method for determining the ra- The optical microspherometer consists essentially of a
dius of curvature of rigid contact lenses using the op- microscope fitted with a vertical illuminator. Light
tical microspherometer. from the target T [figure A.1 a)] is reflected down the
. . -, II -
HI# : .-* *
THT
I
T” is at the first principal
r
focus of the eyepiece TM = MT”
Semi-silvered
mirror, M
I
T’
c
1
,
b)
a)
Figure A.1 - Optical microspherometer showing the images of target T
3
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SIST EN ISO 10338:2000
@ ISO
ISO 10338:1996(E)
2 “Repeatability” means the closeness of agreement be-
the microscope tube by the semi-silvered mirror M
tween mutually independent test results obtained under
and passes through the microscope objective to form
repeatability conditions.
an image of the target at T’. If the focus coincides
with the lens surface, then light is reflected back
3 The gauge mechanism should incorporate some means
along the diametrically opposite path to form images
for eliminating backlash (retrace). If readings are taken in
both at T and T”. T” coincides with the first principal
one direction, this source of error need not be considered.
focus of the eyepiece when a Sharp image of the tar-
get is seen by the observer.
A.3.2 Test plates, concave and made of crown
glass, to be used for calibration. Three test plates shall
The distance between the microscope and the lens
be used having radii of curvature in the range
surface is increased by either raising the microscope
6,30 mm to 6,70 mm, 7,80 mm to 8,20 mm and
or lowering the stage until the image formed by the
9,30 mm to 9,70 mm. The test plates shall have radii
objective (T’) coincides with C, the centre of curvature
accurately known to rt 0,007 5 mm.
of the surface [see figure A.1 b)]. Light from target T
strikes the surface normally and is reflected back
along its own path to form images at T and T” as be-
fore. The distance through which the microscope of
A.4 Procedure
stage has been moved is equal to the radius (r) of cur-
vature of the surface.
A.4.1 Calibration
Using the test plates described in A.3.2, mount each
SO that the optical axis of the microscope is normal to
A.3 Apparatus
the test surface. Adjust the separation of microscope
and stage SO that the image of the target is focused
A.3.1 Optical microspherometer, comprising an
on the surface [figure A.1 a)] and a clear image of the
optical microscope fitted with a vertical illuminator and
target is seen in the microscope. Set the gauge to
a target, and having a fine focus adjustment. The ad-
read zero. Increase the separation between the micro-
justment control shall allow fine movement of the
scope and the stage until a second clear image of the
microscope or of its stage. The adjustment gauge
target is seen in the microscope. The microscope and
shall have a Iinear scale.
the surface now occupy the position shown in figure
A.1 b). Record the distance shown on the gauge as
A.3.1.1 The objective lens shall have a magnification
the radius of curvature. Take ten independent meas-
of not less than x 65 and a numerical aperture of not
urements from each test plate and calculate the arith-
less than 0,25.
metic mean for each set. Plot the results on a cali-
bration curve and use this to correct the results ob-
A.3.1.2 The total magnification of the microscope
tained in A.4.2.
shall be not less than x 65.
NOTE 4 The term “independent” means that the test
A.3.1.3 The real image of the target abject formed by
plate or lens is to be removed from the instrument and re-
the microscope shall be not greater than 1,2 mm in
mounted between each reading.
diameter.
A.4.2 Measurement
A.3.1.4 The scale interval for the gauge shall be not
more than 0,02 mm.
A.4.2.1 Carry out the measurements on the test lens
in air at 20 “C + 5 “C.
A.3.1.5 The accuracy of the gauge shall be
k 0,010 mm for readings of 2,00 mm or more at a
A.4.2.2 Mount the lens SO that the optical axis of the
temperature of 20 OC + 5 “C. The repeatability of the
microscope is normal to that part of the lens surface
gauge (see note 1) shall be + 0,003 mm.
of which the radius is to be measured. Three inde-
pendent readings shall be made as described in A.4.1.
NOTES
Correct the arithmetic mean of this set of measure-
1 The term “gauge” refers to both analogue and digital ments, using the calibration curve obtained in A.4.1,
instruments.
and record the result to the nearest 0,Ol mm.
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SIST EN ISO 10338:2000
ISO 10338:1996(E)
Annex B
(normative)
Determination of radius of curvature using the ophthalmometer
schematically a typical optical system in which light
B.l Scope
from two targets arranged at a known angle is
reflected by the central area of the surface being
This annex specifies a method for determining the
measured. The two images formed are observed
radius of curvature of rigid or hydrogel contact lenses,
through a short-focus telescope fitted with a doubling
using an ophthalmometer.
system. The amount of doubling required to super-
impose the two central images of the four observed in
B.2 Principle the telescope field is a measure of the angular size of
the reflected images.
In ophthalmometry, radius of curvature is derived in-
directly by measuring the angular size of the reflected
image formed by the surface being measured of an
abject of known angular size. Figure B.l shows
Doubling system
Image of target 1
image plane of the objective
Image of target 2
Object plane of the eyepiece
Figure B.1 - Measuring principle
5
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SIST EN ISO 10338:2000
@ ISO
ISO 10338:1996(E)
The radius of curvature shall be derived to a first ap- measurement is made. The cell shall be at least 5 mm
proximation, assuming the surface is spherical in the larger than the diameter of the lens [see figure B.3 a)].
area measured, from the following equation:
Alternatively, the lens shall be supported on a short
tube, having a diameter in the range 8,0 mm to
-Y’
r-J =-
10,O mm, with the back surface upwards. Hydraulic
sin E
pressure is equalized by a hole in the tube. The cell is
filled with saline and closed with an optically parallel
where
flat glass lid [see figure 8.3 b)].
is the radius of curvature;
rO B.3.3 Test plates, concave and made of crown
glass, to be used for calibration. Three test plates shall
is half the distance between the reflected im-
Y'
be used having radii of curvature in the range
ages;
6,30 mm to 6,70 mm, 7,80 mm to 8,20 mm and
& is the angle of incidence.
9,30 mm to 9,70 mm. The test plates shall have radii
accurately known to + 0,007 5 mm.
Figure B.2 shows an adaptation of the optical system
of figure B.l to measure rigid (hard) contact lenses in
8.3.4 Constant temperature bath, capable of con-
air.
trol at 20 “C + 1,O “C.
When the measurement is made in a wet cell, the ra-
dius of curvature is derived from:
B.4 Procedure
-y’n
ro =-
sin E
B.4.1 Calibration
Using the test plates (B.3.3) mounted in a lens holder
where
(B.3.2), carry out ten determinations of the curvature
of each plate, and calculate the arithmetic mean for
r. is the radius of curvature;
each. Plot the means on a calibration curve and use
y’ is half the distance between the reflected im-
this to correct the test measurements. Use saline sol-
ages;
ution conforming to ISO 10344 when calibrating the
instrument for the measurement of lenses in solution.
E is the angle of incidence;
n is the refractive index of the saline solution.
NOTE 5 The term “independent” means that the test
plate or lens is to be removed from the instrument and re-
mounted between each reading.
Figure B.3 shows an adaptation of the optical system
of figure B.l to measure contact lenses in solution.
B.4.2 Measurement
8.3 Apparatus B.4.2.1 Measurement in air
B.3.1 Ophthalmome
...
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