SIST EN ISO 11979-2:2014

Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods (ISO 11979-2:2014)

EN ISO 11979-2 specifies requirements and test methods for certain optical properties of intraocular lenses (IOLs) with spherical, aspheric, toric, multifocal, and accommodative optics. The generic descriptor ‘IOL’ used throughout this document also includes phakic intraocular lenses (PIOL).

Ophthalmische Implantate - Intraokularlinsen - Teil 2: Optische Eigenschaften und Prüfverfahren (ISO 11979-2:2014)

Dieser Teil von ISO 11979 legt Anforderungen und Prüfverfahren für bestimmte optische Eigenschaften von sphärischen, asphärischen, torischen, multifokalen und akkommodierenden Intraokularlinsen (IOLs) fest. Die Bezeichnung „IOL“, die in diesem Dokument verwendet wird, schließt auch phake Intraokularlinsen (PIOL) ein.

Implants ophtalmiques - Lentilles intraoculaires - Partie 2: Propriétés optiques et méthodes d'essai (ISO 11979-2:2014)

L'ISO 11979-2:2014 définit les exigences et les méthodes d'essai relatives à certaines propriétés optiques des lentilles intraoculaires (LIO) sphériques, asphériques, monofocales, toriques, multifocales et/ou progressives. Le terme générique «LIO» utilisé dans l'ISO 11979-2:2014 inclut également les lentilles intraoculaires phaques (LIOP).

Očesni vsadki (implantati) - Intraokularne leče - 2. del: Optične lastnosti in preskusne metode (ISO 11979-2:2014)

Standard EN ISO 11979-2 določa zahteve in preskusne metode za nekatere optične lastnosti intraokularnih leč (IOL) s sferično, asferično, torusno, večgoriščno in prilagodljivo optiko. Splošni izraz »intraokularne leče« ali »IOL«, ki se uporablja v tem dokumentu, zajema tudi fakične intraokularne leče (PIOL).

General Information

• Status: Published
• Public Enquiry End Date: 14-Oct-2012
• Publication Date: 13-Oct-2014
• ICS: 11.040.70 - Ophthalmic equipment
• Technical Committee: VAZ - Healthcare
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 05-Sep-2014
• Due Date: 10-Nov-2014
• Completion Date: 14-Oct-2014
• Ref Project: EN ISO 11979-2:2014 - Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods (ISO 11979-2:2014)

Relations

• Replaces: SIST EN ISO 11979-2:2000 - Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods (ISO 11979-2:1999)
• Effective Date: 01-Nov-2014
• Replaces: SIST EN ISO 11979-2:2000/AC:2005 - Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods (ISO 11979-2:1999)
• Effective Date: 01-Nov-2014
• Replaces: SIST EN ISO 11979-2:2000 - Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods (ISO 11979-2:1999)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 11979-2:2014
01-november-2014
1DGRPHãþD
SIST EN ISO 11979-2:2000
SIST EN ISO 11979-2:2000/AC:2005
2þHVQLYVDGNLLPSODQWDWL,QWUDRNXODUQHOHþHGHO2SWLþQHODVWQRVWLLQ
SUHVNXVQHPHWRGH,62
Ophthalmic implants - Intraocular lenses - Part 2: Optical properties and test methods
(ISO 11979-2:2014)
Ophthalmische Implantate - Intraokularlinsen - Teil 2: Optische Eigenschaften und
Prüfverfahren (ISO 11979-2:2014)
Implants ophtalmiques - Lentilles intraoculaires - Partie 2: Propriétés optiques et
méthodes d'essai (ISO 11979-2:2014)
Ta slovenski standard je istoveten z: EN ISO 11979-2:2014
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
SIST EN ISO 11979-2:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 11979-2:2014

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SIST EN ISO 11979-2:2014

EUROPEAN STANDARD
EN ISO 11979-2

NORME EUROPÉENNE

EUROPÄISCHE NORM
August 2014
ICS 11.040.70 Supersedes EN ISO 11979-2:1999
English Version
Ophthalmic implants - Intraocular lenses - Part 2: Optical
properties and test methods (ISO 11979-2:2014)
Implants ophtalmiques - Lentilles intraoculaires - Partie 2: Ophthalmische Implantate - Intraokularlinsen - Teil 2:
Propriétés optiques et méthodes d'essai (ISO 11979- Optische Eigenschaften und Prüfverfahren (ISO 11979-
2:2014) 2:2014)
This European Standard was approved by CEN on 25 July 2014.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11979-2:2014 E
worldwide for CEN national Members.

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SIST EN ISO 11979-2:2014
EN ISO 11979-2:2014 (E)
Contents Page
Foreword .3
2

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SIST EN ISO 11979-2:2014
EN ISO 11979-2:2014 (E)
Foreword
This document (EN ISO 11979-2:2014) has been prepared by Technical Committee ISO/TC 172 "Optics and
photonics" 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 February 2015, and conflicting national standards shall be withdrawn
at the latest by February 2015.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 11979-2:1999.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 11979-2:2014 has been approved by CEN as EN ISO 11979-2:2014 without any modification.

3

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SIST EN ISO 11979-2:2014

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SIST EN ISO 11979-2:2014
INTERNATIONAL ISO
STANDARD 11979-2
Second edition
2014-08-15
Ophthalmic implants — Intraocular
lenses —
Part 2:
Optical properties and test methods
Implants ophtalmiques — Lentilles intraoculaires —
Partie 2: Propriétés optiques et méthodes d’essai
Reference number
ISO 11979-2:2014(E)
©
ISO 2014

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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested 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 [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved

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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 1
4.1 General . 1
4.2 Dioptric power . 2
4.3 Determination of imaging quality . 3
4.4 Spectral transmittance . 5
Annex A (normative) Measurement of dioptric power . 6
Annex B (normative) Measurement of resolution efficiency .14
Annex C (normative) Measurement of MTF .17
Bibliography .22
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(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 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 11979-2 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee
SC 7, Ophthalmic optics and instruments.
This second edition cancels and replaces the first edition (ISO 11979-2:1999), which has been technically
revised. It also incorporates the Technical Corrigendum ISO 11979-2:1999/Cor.1:2003.
ISO 11979 consists of the following parts, under the general title Ophthalmic implants — Intraocular
lenses:
— Part 1: Vocabulary
— Part 2: Optical properties and test methods
— Part 3: Mechanical properties and test methods
— Part 4: Labelling and information
— Part 5: Biocompatibility
— Part 6: Shelf-life and transport stability testing
— Part 7: Clinical investigations
— Part 8: Fundamental requirements
— Part 9: Multifocal intraocular lenses
— Part 10: Phakic intraocular lenses
iv © ISO 2014 – All rights reserved

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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

Introduction
This part of ISO 11979 initially addressed monofocal IOLs and now has been revised to include the
requirements and test methods for spherical monofocal, aspheric monofocal, toric, multifocal, and
accommodative IOLs. This part of ISO 11979 contains several test methods for which associated
requirements are given and one test method for which no requirement is formulated. The former
are directly connected to the optical functions of intraocular lenses. The latter, the test for spectral
transmittance, has been provided for information about UV transmission and in specific situations, e.g.
when using laser light sources for diagnosis and treatment.
For the original spherical monofocal IOLs, extensive interlaboratory testing was carried out before
setting the limits specified. During this testing some basic problems were encountered as described in
Reference [1]. The accuracy in the determination of dioptric power has an error that is not negligible
in relation to the half dioptre steps in which intraocular lenses are commonly labelled. The dioptric
power tolerances take this fact into account. Hence the limits set may lead to some overlap into the next
labelled power, especially for high dioptre lenses. Reference [1] gives further discussion on this subject.
The majority of lenses hitherto implanted were qualified using the method described in Annex B or
Annex C (model eye 1). The method in Annex B is limited in its applicability, however. The limits for the
more general method in Annex C have been set in terms of MTF in a model eye, following two approaches.
The first is by correlation to the method and limit in Annex B. Further discussion can be found in

Reference [2]. The second is set as a percentage of what is calculated as theoretical maximum for the
design, with the rationale that a minimum level of manufacturing accuracy be guaranteed. For common
PMMA lenses, these two limits correspond well with each other. For lenses made of materials with lower
refractive index, or with certain shape factors, or for extreme power lenses in general, the latter limit
is lower than the former. However, such lenses are already in use, indicating clinical acceptance. The
question of which is the absolute lowest limit that is compatible with good vision arises. No definite
answer can be found, but following clinical data presented to the working group, an absolute lower limit
has been set for the calculation method.
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SIST EN ISO 11979-2:2014

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SIST EN ISO 11979-2:2014
INTERNATIONAL STANDARD ISO 11979-2:2014(E)
Ophthalmic implants — Intraocular lenses —
Part 2:
Optical properties and test methods
1 Scope
This part of ISO 11979 specifies requirements and test methods for certain optical properties
of intraocular lenses (IOLs) with any of spherical, aspheric, monofocal, toric, multifocal, and/or
accommodative optics. The generic descriptor ‘IOL’ used throughout this document also includes phakic
intraocular lenses (PIOL).
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 6328:2000, Photography — Photographic materials — Determination of ISO resolving power
ISO 9334, Optics and photonics — Optical transfer function — Definitions and mathematical relationships
ISO 9335, Optics and photonics — Optical transfer function — Principles and procedures of measurement
ISO 11979-1, Ophthalmic implants — Intraocular lenses — Part 1: Vocabulary
ISO 11979-3, Ophthalmic implants — Intraocular lenses — Part 3: Mechanical properties and test methods
ISO 11979-4, Ophthalmic implants — Intraocular lenses — Part 4: Labelling and information
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11979-1 and ISO 9334 apply.
4 Requirements
4.1 General
The manufacturer shall demonstrate that the entire range of available powers meets the specifications
herein. All optical properties apply at in situ conditions, either by being measured at simulated in situ
conditions, or being measured at other conditions and then corrected to in situ conditions.
For IOLs where the optic is intended to be deformed during implantation, it shall be demonstrated that
dioptric power and imaging quality are retained at in situ conditions or equivalent following surgical
manipulation and recovery. See ISO 11979-3 for more detail.
The test methods described in this standard are reference methods. Alternative methods that produce
equivalent results to those obtained with the reference methods can be used if the manufacturer can
demonstrate that the IOLs meet the minimum dioptric power and imaging quality requirements.
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

4.2 Dioptric power
4.2.1 General
The dioptric power of spherical or aspheric lenses as stated by the manufacturer in the IOL labelling shall
be within the tolerance limits specified in Table 1. For rotationally symmetric lenses, these tolerances
apply in all meridians.
Table 1 — Tolerance limits on spherical dioptric power, S
Nominal spherical dioptric power Tolerance limits on spherical
a
range dioptric power
D D
0 ≤ S ≤ 15 ±0,3
15 < S ≤ 25 ±0,4
25 < S ≤ 30 ±0,5
30 < S ±1,0
a
The ranges apply to positive as well as negative dioptric powers.
4.2.2 Dioptric power for toric IOL (TIOL)
When determined by any of the methods in Annex A, the dioptric power in the meridians of highest
and lowest dioptric power and the spherical equivalent (SE) power shall be within the tolerance limits
for dioptric power specified in Table 1. Additionally, the cylindrical power calculated as the absolute
difference between the powers of the meridian of highest dioptric power and the meridian of lowest
dioptric power shall be within the cylindrical power tolerance limits specified in Table 2.
Table 2 — Tolerance limits on cylindrical dioptric power, C
Tolerance limits on cylindrical Tolerance limits on cylindrical
Nominal cylindrical dioptric
dioptric power dioptric power
power range
D D
D
SE < 25 D SE ≥ 25 D
0 < C ≤ 2,5 ±0,3 ±0,4
2,5 < C ≤ 4,5 ±0,4 ±0,4
4,5 < C ±0,5 ±0,5
The TIOL shall have a physical axis indicator such as a mark, engraving, or label that aligns with the
meridian of lowest dioptric power, and is visible to the surgeon during implantation. The angle difference
between the physical axis indicator and the meridian with the lowest dioptric power shall be less than
or equal to 5,0°.
4.2.3 Dioptric power for multifocal IOL (MIOL)
Methods A.2 to A.4 can be applied to MIOL for determining the far power and any distinct near powers.
When using A.2, dioptric power must be justified as a calculation based only on spherical surfaces. The
dioptric power of the far power shall be within the tolerance limits specified in Table 1 and the dioptric
power of the addition power(s) shall be within the tolerances in Table 3.
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

Table 3 — Tolerance limits on addition dioptric power, A
Tolerance limits on addition Tolerance limits on addition
Nominal addition dioptric power
dioptric power dioptric power
range
D D
D
far power < 25 D far power ≥ 25 D
0 < A ≤ 2,5 ±0,3 ±0,4
2,5 < A ≤ 4,5 ±0,4 ±0,4
4,5 < A ±0,5 ±0,5
4.2.4 Dioptric power for accommodating IOL (AIOL)
The power associated with the far power configuration of an AIOL shall be determined by one of the
methods in Annex A. When determined by one of these methods, the dioptric power tolerances specified
in Table 1 shall apply to the power associated with the far power configuration of the AIOL. The dioptric
change of the lens or system in the eye resulting from the accommodative action shall be determined in
a theoretical or laboratory eye model.
4.3 Determination of imaging quality
4.3.1 General
Imaging quality is dependent upon compatibility between the optical design and conditions that are
used to evaluate optical performance. Imaging quality can be specified either as resolution efficiency or
as the modulation transfer function (MTF) value at a specified spatial frequency. Resolution efficiency
is determined according to the method described in Annex B. MTF is measured according to the method
in Annex C.
MTF determined with the method described in Annex C is dependent on the compatibility between the
optical design and model eye that is used to evaluate optical performance. For the method described
in Annex C, example model eye specifications are given. Alternatively, the manufacturer can specify an
equivalent method or model eye with optical properties for the intended use and design. In this case
the model eye and the method shall be fully described and a justification for the use be provided. The
imaging quality specifications apply to all available powers, unless stated otherwise.
NOTE 1 Optical resolution is expressed in spatial frequency. In Annex B, by tradition, resolution is in line-pairs
−1
per millimetre (lp/mm) and in Annex C in cycles per millimetre (c/mm or mm ). In the ophthalmic literature,
cycles per degree is often used. For the eye, assuming a nodal point distance of 17 mm in image space, the
conversion between the two is:
c/degree=0,*297 c/mm

NOTE 2 The test apertures given in the subclauses of 4.3 and in Annexes A, B, and C represent the exposed
central area of the IOL under test, which can differ from the aperture stop of the test system.
4.3.2 Monofocal lenses
4.3.2.1 General
Imaging quality for monofocal IOLs shall fulfil one of the requirements in 4.3.2.2, 4.3.2.3 or 4.3.2.4.
4.3.2.2 Resolution efficiency
If determined in accordance with Annex B, the resolution efficiency of the IOL shall be no less than 60 %
of the diffraction limited cut-off spatial frequency for a 3 mm aperture. In addition, the image shall be
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

virtually free of detectable aberrations except due to spherical aberration normally expected for the
lens design.
4.3.2.3 MTF using model eye 1
If determined in accordance with Annex C using model eye 1 (C.3.1), the MTF value of the model eye with
−1
IOL configuration shall at 100 mm meet either of the two requirements given below:
a) be greater than or equal to 0,43;
b) be greater than or equal to 70 % of the maximum theoretically attainable modulation for the specific
IOL design, but in any case be greater than or equal to 0,28.
NOTE The acceptance levels given in 4.3.2.2 and 4.3.2.3 a) correspond well with each other for PMMA lenses
[2]
in the range of 10 D to 30 D .
4.3.2.4 MTF using model eye 2
If determined in accordance with Annex C using model eye 2 (C.3.2), the MTF value of the configuration
−1
of model eye with IOL shall at 100 mm be greater than or equal to 70 % of the maximum theoretical
attainable MTF for a 3 mm aperture, but in any case greater than or equal to 0,28.
4.3.3 Toric IOL (TIOL)
4.3.3.1 General
Imaging quality for toric IOLs shall fulfil one of the requirements in 4.3.3.2 or 4.3.3.3.
4.3.3.2 Resolution efficiency
When the null lens method described in Annex B is used, the general resolution efficiency requirements
in 4.3.2.2 shall apply to the combined system of toric IOL and null lens.
4.3.3.3 MTF
The MTF requirements described in 4.3.2.3 or 4.3.2.4 shall apply to the meridians of highest and lowest
dioptric power.
4.3.4 Multifocal IOL (MIOL)
4.3.4.1 MTF
The imaging quality specifications apply in all meridians, unless the MIOL also comprises a cylinder
component, in which case the considerations of 4.3.6 apply. The imaging quality of a MIOL shall be
evaluated by modulation transfer function (MTF) testing in one of the model eyes described in Annex C
with the following additions:
The method in Annex C is modified such that best focus for the dioptric power under evaluation is
−1
obtained by maximizing the MTF at 50 mm with a 3,0 mm ± 0,1 mm aperture. Using that focus, record
the MTF values at the following conditions:
−1 −1
a) small aperture (2 mm to 3 mm), 25 mm and 50 mm , for the far dioptric power;
−1 −1
b) large aperture (4 mm to 5 mm), 25 mm and 50 mm , for the far dioptric power;
−1 −1
c) small aperture (2 mm to 3 mm), 25 mm and 50 mm , for the near dioptric power(s) or power
range.
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

In order to best control the MTF performance of the MIOL, the small and large apertures used for testing
shall be chosen and defined for the lens model over the range of apertures provided above with a tolerance
of ± 0,1 mm. The manufacturer shall have the option of setting the minimum MTF specification based on
the area under the curve between the two spatial frequencies or on the MTF value for each individual
spatial frequency. The MTF shall be greater than or equal to 70 % of the maximum theoretically
attainable modulation for the specific IOL design. Alternatively, the minimum MTF specification shall
be set such that it results in an acceptable visual outcome, verifiable, or to be verified, by clinical data.
4.3.5 Accommodating IOL (AIOL)
The requirements given in 4.3.2 shall apply at the far power configuration and configurations associated
with the designed range of accommodation. Measurements shall be obtained in 0,5 D or smaller
increments over this range if applicable.
4.3.6 Combination of optical principles
For toric multifocal and toric accommodating lenses, the general imaging requirements for all principles
in 4.3.3 apply along with the special test requirements in 4.3.4 and 4.3.5, respectively.
For multifocal accommodating lenses the imaging requirements of 4.3.4 and 4.3.5 apply.
4.3.7 Exceptions
If the criteria specified in 4.3.2 through 4.3.6, for reasons of theoretical limitation, cannot be applied
to negative and low power lenses in conjunction with the model eye described, the manufacturer shall
justify any alternate spatial frequencies and criteria applied.
4.4 Spectral transmittance
4.4.1 Measurement of spectral transmittance
The spectral transmittance in the range 300 nm to 1 100 nm shall be recorded by a UV/Visible
spectrophotometer with a 3 mm aperture in aqueous, or be corrected for specular reflection if measured
in air. The measurement should be accurate to ± 2 % transmittance and the resolution should not be less
than 5 nm. The test specimen shall be either an actual IOL or a flat facsimile of the IOL optic material,
having a thickness equal to the centre thickness of a 20 D IOL and having undergone the same production
treatment as the finished IOL including sterilization.
4.4.2 Cut-off wavelength
Designate UV cut-off as UV(XXX) where XXX is the wavelength in nanometres at which the spectral
transmission is below 10 % when measured according to 4.4.1.
[3]
NOTE Guidance for the measurement of spectral transmittance can be found in ISO 18369-3:2006 .
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

Annex A
(normative)

Measurement of dioptric power
A.1 General
Multiple methods of determining IOL dioptric power are given below. The specific methods and
requirements for spherical and aspheric monofocal, toric, or multifocal IOL measurement are described
in this annex where applicable.
For all IOLs, the value of dioptric power is defined at in situ conditions (see ISO 11979-1) for a light source
that has a peak wavelength within ± 10 nm of 546 nm having a full width at half maximum of 20 nm or
less. For the methods in A.3 and A.4, an aperture of 3,0 ± 0,1 mm in diameter is used.
NOTE 1 For more details about optical measurement and calculations, see Reference [4] or similar textbooks
on optics.
NOTE 2 A modified bench (e.g. additional converging lens, a microscope objective of appropriate numerical
aperture, etc.) may be needed to quantify the focal length of negative and low dioptric power IOLs.
A.2 Determination of dioptric power by calculation from measured dimensions
A.2.1 Procedure
Measure the surface radii over a region of approximately 3 mm diameter using a radius meter,
[5]
interferometer, or optical coherence tomograph (OCT) . Measure the lens thickness with a micrometer
or equivalent device. Calculate the dioptric power, using the Equation:
DD=+Dt− /nD D (A.1)
()
fb cIOL fb
under in situ conditions, where
D is the dioptric power of the IOL;
D is the dioptric power of the front surface of the IOL;
f
D is the dioptric power of the back surface of the IOL;
b
t is the central thickness, in metres, of the IOL;
c
n is the refractive index of the IOL optic material at in situ conditions.
IOL
NOTE 1 Formula (A.1) is often referred to as the “thick lens equation”.
NOTE 2 In general, the value of n is influenced by temperature and water uptake by the IOL optic material.
IOL
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SIST EN ISO 11979-2:2014
ISO 11979-2:2014(E)

Calculate D from the Equation:
f
Dn=−()nr/ (A.2)
fIOL medf
where
n is the refractive index of the surrounding medium;
med
r is the radius, in metres, of the front surface of the IOL.
f
Calculate D from the Equation:
b
Dn=−nr/ (A.3)
()
bmed IOLb
where
r is the radius, in metres, of the back surface of the IOL.
b
NOTE 3 With respect to the incidence of light, a convex radius is positive and a concave radius is negative.
NOTE 4 These equations assume that there is exact alignment of front and back surfaces along the optical axis.
[6]
NOTE 5 ISO 18369-4:2006 describes a method that may be used to determine n , which should be known
IOL
to the third decimal place.
NOTE 6 If the lens material is flexible, appropriate care must be taken when measuring the two lens surfaces
to ensure that the two surface measurements are consistent with each other. Any flexing of the lens between the
measurements of the two surfaces will affect the results.
Use n = 1,336, and the dimensions
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