EN ISO 9913-1:1998

Optics and optical instruments - Contact lenses - Part 1: Determination of oxygen permeability and transmissibility by the FATT method (ISO 9913-1:1996)

Optik und optische Instrumente - Kontaktlinsen - Teil 1: Bestimmung der Sauerstoff-Permeabilität und - Transmissibilität nach dem Verfahren nach FATT (ISO 9913-1:1996)

Dieser Teil von ISO 9913 beschreibt ein polarographisches Verfahren zur Bestimmung der Sauerstoff-Permeabilität von Kontaktlinsenmaterialien sowie der Sauerstoff-Transmissibilität von Kontaktlinsen. Er legt die Verfahrensweisen für die durchzuführenden Messungen sowie die Bedingungen fest, unter denen die Messungen durchgeführt werden. Er gilt für die Bestimmung der Sauerstoff-Permeabilität Dk im Bereich 0 bis 75 x 10-11 (cm2/s) (ml O2/(ml.hPa)).

Optique et instruments d'optique - Lentilles de contact - Partie 1: Détermination de la perméabilité à l'oxygène et de la transmissibilité de l'oxygène avec la méthode FATT (ISO 9913:1996)

Optika in optični instrumenti - Kontaktne leče - 1. del: Ugotavljanje prepustnosti za kisik in prenosa kisika z metodo FATT (ISO 9913-1:1996)

General Information

• Status: Withdrawn
• Publication Date: 19-May-1998
• Withdrawal Date: 14-Aug-2006
• ICS: 11.040.70 - Ophthalmic equipment
• Technical Committee: CEN/TC 170 - Ophthalmic optics
• Drafting Committee: CEN/TC 170 - Ophthalmic optics
• Current Stage: 9960 - Withdrawal effective - Withdrawal
• Start Date: 15-Aug-2006
• Completion Date: 15-Aug-2006
• Ref Project: SIST EN ISO 9913-1:2000 - Optics and optical instruments - Contact lenses - Part 1: Determination of oxygen permeability and transmissibility by the FATT method (ISO 9913-1:1996)

Relations

• Replaced By: EN ISO 18369-4:2006 - Ophthalmic optics - Contact lenses - Part 4: Physicochemical properties of contact lens materials (ISO 18369-4:2006)
• Effective Date: 22-Dec-2008

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 9913-1:2000
01-januar-2000
2SWLNDLQRSWLþQLLQVWUXPHQWL.RQWDNWQHOHþHGHO8JRWDYOMDQMHSUHSXVWQRVWL]D
NLVLNLQSUHQRVDNLVLND]PHWRGR)$77,62
Optics and optical instruments - Contact lenses - Part 1: Determination of oxygen
permeability and transmissibility by the FATT method (ISO 9913-1:1996)
Optik und optische Instrumente - Kontaktlinsen - Teil 1: Bestimmung der Sauerstoff-
Permeabilität und - Transmissibilität nach dem Verfahren nach FATT (ISO 9913-1:1996)
Optique et instruments d'optique - Lentilles de contact - Partie 1: Détermination de la
perméabilité a l'oxygene et de la transmissibilité de l'oxygene avec la méthode FATT
(ISO 9913:1996)
Ta slovenski standard je istoveten z: EN ISO 9913-1:1998
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
SIST EN ISO 9913-1:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 9913-1:2000

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SIST EN ISO 9913-1:2000

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SIST EN ISO 9913-1:2000

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SIST EN ISO 9913-1:2000
INTERNATIONAL IS0
STANDARD 9913-1
First edition
1996-I l-01
Optics and optical instruments - Contact
lenses -
Part 1:
Determination of oxygen permeability and
transmissibility by the FATT method
Optique et instruments d’optique - Lentil/es de contact -
Partie 7: D&ermination de la permkabilit4 2 I’oxyg&ne et de la
transmissibilit6 de I’oxyg&ne avec la m&hode FATT
Reference number
IS0 9913-I :I 996(E)

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SIST EN ISO 9913-1:2000
IS0 99134:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 9913-1 was prepared by Technical Committee
ISOfTC 172, Optics and optical instruments, Subcommittee SC 7, Oph-
thalmic optics and instruments.
IS0 9913 consists of the following parts, under the general title Optics and
optical instruments - Con tact lenses:
- Part I: Determination of oxygen permeability and transmissibility by
the FA77 method
- Part 2: Determination of oxygen permeability and transmissibility by
the coulome tric method
Annex A forms an integral part of this part of IS0 9913. Annexes B and C
are for information only.
0 IS0 1996
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 the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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SIST EN ISO 9913-1:2000
IS0 99134:1996(E)
INTERNATIONAL STANDARD o Iso
Optics and optical instruments - Contact lenses -
Part 1:
Determination of oxygen permeability and transmissibility by the FATT
method
IS0 10344: 1996, Optics and optical instruments -
1 Scope
Contact lenses - Saline solution for contact lens
testing.
This part of IS0 9913 describes a polarographic method
for the determination of oxygen permeability of contact
lens materials and oxygen transmissibility of contact
lenses. It specifies the procedures for making the
3 Definitions
measurements and establishes the conditions under
which measurements are made.
For the purposes of this part of IS0 9913, the defi-
nitions given in IS0 8320 and the following definitions
It is applicable for determining permeability (Dk) in the
apply.
range 0 to 75 X IO-11 (cm*/s) [ml 02/(mLhPa)].
3.1 dark current (Id): Current passing through a cell
2 Normative references when an impermeable barrier is placed in between the
electrodes.
The following standards contain provisions which,
through reference in this text, constitute provisions of
3.2 oxygen permeability (Dk): Rate of oxygen flow
this part of IS0 9913. At the time of publication, the
under specified conditions through a unit area of con-
editions indicated were valid. All standards are subject
tact lens material of unit thickness when subjected to
to revision, and parties to agreements based on this
unit pressure difference.
part of IS0 9913 are encouraged to investigate the
possibility of applying the most recent editions of the
NOTES
standards indicated below. Members of IEC and IS0
maintain registers of currently valid International Stan-
1 Oxygen permeability is expressed in units of (cm*/s)
dards. [ml 02/(mI.hPa)]. An alternative expression for the units is
cm3 02(cm/cm2)/(shPa).
IS0 8320:1986, Optics and optical instruments -
2 Oxygen permeability is a physical property of the ma-
terial. It is not a function of the shape or thickness of the
Contact lenses - Vocabulary and symbols.
material sample.
IS0 10339:- 1), Optics and optical instruments -
3 To convert the units of Dk for use with mmHg instead of
Contact lenses - Determination of water content of
hectopascals (hPa), multiply the numerical value of Dk by
soft lenses.
1,333 22.
1) To be published.

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SIST EN ISO 9913-1:2000
@ IS0
IS0 9913=1:1996(E)
3.3 oxygen transmissibility (Dk/t): Value for oxygen spherical surface with a radius of curvature in the
range 7,70 mm to 8,30 mm.
permeability divided by the thickness (measured in
centimetres) of the measured sample under specified
conditions.
6.5 The electrode face to be used for measuring flat
samples and hydrogel lenses shall be plane.
NOTES
4 Oxygen transmissibility is not an absolute physical prop-
6.6 The apparatus shall include a device (see fig-
erty; it is dependent upon the sample thickness.
ure B.l) by which the test sample may be pressed
5 The reciprocal of oxygen transmissibility (ok/t) is called against the electrode. The device shall allow oxygen
electrical resistivity (l/ok).
to pass freely into the sample.
6.7 The apparatus shall be capable of maintaining
3.4 thickness (t): Either the thickness at a specified
the test sample at 35 “C + 0,5 OC in an atmosphere
point or the harmonic mean thickness of the specified
with a relative humidity of not less than 95 %.
area of the lens or sample.
6.8 If a bath of oxygen saturated water is needed as
the oxygen source, then a means of stirring or mixing
the water shall be incorporated in the apparatus. The
4 Principle
stirrer shall ensure that a minimal but constant stag-
nant boundary layer is maintained at the sample sur-
The polarographic method directly measures the
face.
number of oxygen molecules diffusing through a piece
of test material by electrochemically removing the
re monito ring device having good
6.9 A temperatu
molecules from solution as soon as they pass through
thermal contact with the test sample shall be
the material. For full details of the theoretical back-
mounted. This device shall be capable of measuring
ground, see annex C.
the temperature with an accuracy of 0,5 OC.
NOTE 6 For examples of apparatus, see annex B.
5 Reagents
6.10 An ammeter having a range from 0,O PA to
5.1 Oxygen, commercial grade, in a steel cylinder.
IO,0 PA.
5.2 Nitrogen, commercial grade, oxygen free, in a
steel cylinder.
7 Test samples
7.1 The test samples shall have parallel or near-
6 Apparatus
parallel (see note) anterior and posterior surfaces.
NOTE 7 The thickness of the sample used for measure-
The test cell shall have the following characteristics.
ment should be as uniform as possible. In the case of
manufactured lenses, the near-parallel condition would cor-
6.1 The cathode shall be made of 24 carat gold or
respond to dioptric powers within the range + 0,50 to
99,9 % (m/m) platinum (min.), shall be located centrally
- 0,50.
under the test sample, shall have a diameter of 4 mm
to 7,2 mm and shall have a polished surface.
7.2 The back optic zone radii of the test samples
shall be within the range 7,40 mm to 8,60 mm.
6.2 The anode shall be made of silver [99,9 % (m/m)
min.], shall be concentric to the cathode and shall
7.3 The surfaces of test samples shall be clean and
have an area greater than that of the cathode.
polished to the quality acceptable in normal lens pro-
duction for human use.
63 . The apparatus shall be capable of maintaining a
potential difference between the electrodes of
7.4 In the case of hydrogel material, the samples
(0,75 k 0,051 v.
shall be stored in saline test solution in accordance
with IS0 10344 for a minimum of 24 h prior to testing
6.4 The electrode face to be used for measuring and shall be equilibrated for at least 2 h at test tem-
samples of rigid lens material shall be a smooth perature.
2

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SIST EN ISO 9913-1:2000
0 IS0 IS0 9913=1:1996(E)
9 Expression of results
8 Test procedure
NOTE 13 For the theoretical background, see annex C.
8.1 Dark current/zero-point correction
Determine the dark current of the cell by placing a
barrier between anode and cathode consisting of two
9.1 Calculate the value of t/Dk (total) for each test
Polymethylmethacrylate (PMMA) lenses with an alu-
sample using the following equation:
minium foil disc between them and measuring the
current.
t/Dk = po,IF
NOTES
8 As this barrier will not transmit oxygen, the equilibrium
current is the dark current (Id) which is the reference for
- pH20) x 0,209;
PO, = k’bar
L
material of zero permeability.
9 Necessary characteristics of the barrier are that it should
F= (I - Id) x 5,804 x 1 O-*/A.
transmit no oxygen, that it should fit tightly against the an-
ode so that no oxygen can pass around its edge and under
where
it to the cathode and that it should be an electrical non-
conductor.
is t he partial pressure of oxygen above
PO2
10 If the oxygen-saturated water bath method is used, it
the cell in hectop ascals (hPa);
will be necessary to carry out the zero-point adjustment (or
F is the oxygen flux in hundreds of met res
“correction”) using oxygen-free nitrogen gas.
Per
cubic centimetre second
[m x 1 O*/(s x cm*)l;
is the barometric pressure in hectopascals
Pbar
NW;
is t he vapour pressure of water in the at-
PH20
mo Isphere in hectopascals (hPa);
8.2 Measurement of t/Dk
20,9 is the percentage oxygen in the atmos-
Bring the test equipment to 35 “C + 0,5 OC and allow
phere in air at 0 % humidity (if the per-
the temperature to stabilize. Remove the sample from
centage of oxygen is other than 20,9 %,
the saline solution, blot and place the lens on the test
that value is used);
cell. If the sample is made of material that does not
I is the measured electric current in am-
incorporate water in its molecular structure, place a
peres;
piece of saturated paper, e.g. cigarette paper, on the
surface of the cell and place the sample thereon. is the dark current of the cell, in amperes,
i.e. the current which flows in the ab-
Firmly clamp the sample to the surface of the elec-
sence of the 02 flux;
trode. If the source of oxygen is a water bath, fill the
electrode assembly with electrolyte (for example,
A
is the a rea of the central electrode
standard saline solution in accordance with
(cathode in square cent imetres.
I)
IS0 10344), establish the gas flow, activate the stir-
ring mechanism and ensure that an equilibrium condi-
The area of the cathode when using electrodes with
tion has been reached before proceeding.
spherical surfaces is given by the equation
Allow the current reading to stabilize and record the
measurement. Remove the sample from the test cell
A = 27tr(r- Jy2_D2/4)
and measure the centre thickness to an accuracy of
+ 0,005 mm.
where
Repeat the procedure for at least four samples with
thicknesses of approximately 0,lO mm, 0,17 mm,
D is the diameter of cathode, in millimetres;
0,24 mm and 0,30 mm.
is the radiu s of curvature of the surface, in
millim etres.
NOTES
11 Samples should be no thicker than 0,40 mm.
The area of a cathode with a flat surface is given by
the equation
12 Accuracy may be improved by making multiple inde-
pendent measurements on each sample. Independent
measurements are made by removing the sample from the
apparatus, re-equilibrating it and repeating the procedure.
A = n;(D/Z)*
3

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SIST EN ISO 9913-1:2000
@ IS0
IS0 9913=1:1996(E)
9.3 Calculate the value of Dk using the following re-
This procedure is carried out for at least four different
sample thicknesses and the resulting values of t/Dk gression equation:
are used to find the rate of change of t/Dk with
change of t. This value is equal to l/Dk.
9.2 Correct each t/Dk value for diffusion “edge ef-
fects” by using one of the following equations, as
4 r
applicable.
-$ Cti CctIDk)i
i
i
II
For hydrogels when using a cathode with a spherical
surface:
(t/Dk)i is the reciprocal of the transmissibility
(TkJcorrected = (kk)meas”red x (I+%)
(electrical resistivity) of the ith sample;
of the ith test
is the centre thickness
For hydrogels when using a flat cathode:
4
sa mple , in mill metres;
n is the number of test samples;
(&med = (&!as”red x (l+F)
is the summation over n different sam-
c
ples.
For non-hydrogels when using a cathode with a
spherical surface: 9.4 If the value of Dk is to be normalized (see note),
carry out the following procedure.
Measure samples of the standard material specified in
annex A. Normalize the calculated values of permeabil-
ity [Dk (talc)] as follows:
4[0,587 - 0,001 93(Dk)]t
Dk (normalized) = Dk (talc) x Dk (standardized
D
I
value of standard materiaI)/Dk (measured value of
standard material).
For non-hydrogels when using a flat cathode:
NOTE 15 This normalization procedure is necessary to
make results obtained with different apparatus directly
comparable. As the oxygen source concentration is more
difficult to verify when using the oxygen-saturated water
(&rected = (+k)meas”r.,
bath method, it is recommended that the normalization
procedure be used whenever this method is employed.
4[0,471- 0,001 93(Dk)lt
D
1
10 Test report
The test report shall include the following information:
D is the diameter of the cathode, in millimetres;
a) the type of apparatus used (i.e. water saturated
t is the thickness of the sample, in millimetres;
with oxygen or oxygen saturated with water);
b) the type of material tested;
Dk is the measured Dk.
...