SIST EN ISO 10939:2000

SLOVENSKI STANDARD
SIST EN ISO 10939:2000
01-januar-2000
2IWDOPLþQLLQVWUXPHQWLâSUDQMVNHVYHWLONH,62
Ophthalmic instruments - Slit-lamp microscopes (ISO 10939:1998)
Ophthalmische Instrumente - Spaltleuchten (ISO 10939:1998)
Instruments ophtalmiques - Microscopes avec lampe a fente (ISO 10939:1998)
Ta slovenski standard je istoveten z: EN ISO 10939:1998
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
SIST EN ISO 10939:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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INTERNATIONAL ISO
STANDARD 10939
First edition
1998-07-15
Ophthalmic instruments — Slit-lamp
microscopes
Instruments ophtalmiques — Microscopes avec lampe à fente
A
Reference number
ISO 10939:1998(E)

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ISO 10939:1998(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.
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 ISO 10939 was prepared by Techncial Committee
ISO/TC 172, Optics and optical instruments, Subcommittee SC 7,
Ophthalmic optics and instruments.
Annex A forms an integral part of this International Standard. Annexes B
and C are for information only.
©  ISO 1998
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 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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©
INTERNATIONAL STANDARD  ISO ISO 10939:1998(E)
Ophthalmic instruments — Slit-lamp microscopes
1  Scope
This International Standard, together with ISO 15004, specifies requirements and test methods for slit-lamp
microscopes to provide slit illumination and observation under magnification of the eye and its adnexa.
This International Standard is not applicable to microscope accessories, e.g. photographic equipment and lasers.
This International Standard takes precedence over ISO 15004, if differences exist.
2  Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreements based on this International Standard are encouraged to investigate the possibility of
applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of
currently valid International Standards.
ISO 7944:1998, Optics and optical instruments — Reference wavelengths.
ISO 15004:1997, Ophthalmic instruments — Fundamental requirements and test methods.
IEC 60601-1:1988, Medical electrical equipment — Part 1: General requirements for safety.
3  Definitions
For the purposes of this International Standard, the following definitions apply.
3.1
slit-lamp microscope
instrument consisting of a microscope and a swivelling illumination system providing a slit image
3.2
magnification
ratio of the viewing angle of an object when observed through a magnifying system with the image at infinity to that of
the object when observed by the naked eye at a reference viewing distance of 250 mm
NOTE 1 The magnification, G, can be calculated using the following equation:
tans'
G =
tans
where
s’ is the angle at which an object is seen through the microscope;
s is the angle at which the same object is seen without any instrument at a viewing distance of 250 mm.
NOTE 2 The magnification of the microscope comprises the magnifications of the complete system.
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ISO
ISO 10939:1998(E)
3.3
high eye point eyepiece
eyepiece in which the exit pupil is of sufficient clearance from the eyepiece to allow spectacles to be worn
4  Requirements
4.1  General
The slit-lamp microscope shall conform to the requirements specified in ISO 15004.
4.2  Optical requirements
The slit-lamp microscope shall conform to the requirements given in table 1. These requirements are verified as
described in 5.1.
Table 1 — Requirements for optical properties
No. Criterion Requirement
1 Permissible tolerance of microscope magnification (see 3.2) + 5 %
2 Difference in magnification between left and right observation systems < 3 %
Interpupillary distance between < 10’
60 mm and 66 mm
Difference in
axis betweeen Vertical Interpupillary distance between
3 left and right 55 mm and < 60 mm and between < 15’
1)
optical systems > 66 mm and 72 mm
2)
Horizontal Convergence < 45’
Divergence < 10’
4 Shift in the object plane by change in magnification < 0,4 mm
3)
5 Focus tolerance for illumination system with Axial Δa = + 0,5 mm
3) 3)
respect to the mechanical rotation axis Lateral (Δa) = + 0,35 mm
α
6 Tolerance for foci planes of left and right observation systems
4)
(ΔR, ΔL) including all magnifications with respect to the focus of illumination system (slit .
ΔR, ΔL < x d
5)
image) in any position
x = 2
4)
7 Focus difference between the left and right observation systems .
Δ(R, L) < x d
5)
x = 2
Calibration error of dioptre scale + 0,25 D at zero on
the dioptre scale
Range for interpupillary distance adjustment 55 mm to 72 mm
-5,00 D to +5,00 D
8 Eyepiece Adjustment range (minimum)
-4,00 D to +2,00 D
for high eye point
eyepieces
Difference in axial positions of the exit pupils < 1,5 mm
between left and right observation systems
Minimum width < 0,2 mm
Minimum length > 8,0 mm
9 Slit image Parallelism of the sides < 0,5°
(for a slit image 0,2 mm x 0,8 mm)
Maximum width Equal to slit length
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ISO
ISO 10939:1998(E)
Table 1 (concluded)
1) With the eyepiece for which the slit-lamp microscope is designed.
2) This requirement does not apply to those slit-lamp microscopes where, due to the design, the mechanical axes of the eyepieces are not
parallel to each other.
3) Explanation to criterion No. 5 (see also figure 1).
(Δa) = Δa sin for a rotational angle range up to = 45°
α α
α
OS is the observation system;
IS is the illumination system;
RC is the rotational centre of OS and IS;
Δa is the axial focus tolerance.
4) Depth of field, expressed in millimetres
l 1
−6
=⋅ +
d 10
2
7 N
2N G⋅
   where:
N is the numerical aperture;
G is the total magnification of the microscope (see 3.2);
λ is the reference wavelength according to ISO 7944, expressed in nanometres.
5) x is a weighting factor.
Figure 1 — Explanation to criterion No. 5
4.3  Construction and function
4.3.1  General
The following requirements shall apply:
a) the parallel slit edges shall be smooth and free from any imperfections when observed using the highest
magnification;

b) the slit image shall be evenly illuminated;

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ISO
ISO 10939:1998(E)
c) no contrast decrease in the slit image caused by reflections or scattered light shall be observed;

d) the brightness and colour transmission of the left and right optical systems shall be identical;

e) at the highest magnification, the resolving power in the centre of the field shall be at least 1800 ⋅ N line
pairs/mm.
Compliance with these requirements is checked by observation.
4.3.2  High eye point eyepiece
If the manufacturer states that the eyepiece is a high eye point eyepiece, the distance between the exit pupil of the
observation system and the nearest part of the eyepiece shall be not less than 17 mm.
4.4  Optical radiation hazard with slit-lamp microscopes
4.4.1  General
This clause replaces clauses 32, 33 and 34 of IEC 60601-1:1988.
The limit values given in items a) and b) of 4.4.2 shall apply to the radiation emerging from the slit-lamp microscope
used to illuminate and view the human eye with visible light (380 nm to 700 nm) and in which the full beam
homogeneously illuminates a circular pupil of 8 mm diameter (see notes 1 and 2 of 4.4.2).
NOTE The limit values given in 4.4.2 are considered acceptable with respect to the risks when weighted against the
performances intended.
4.4.2  Limit values
a) Short wavelength limit:
The amount of radiant power exiting the slit-lamp microscope in the portion of the spectrum from 305 nm to
2
400 nm shall have an irradiance no greater than 0,22 mW/cm as measured in the corneal plane when the slit-
1)
lamp microscope is operating at maximum intensity and, if the aperture can be varied, at maximum aperture.
b) Long wavelength limit:
The amount of energy exiting the slit-lamp microscope in the wavelength range 700 nm to 1100 nm shall not
2
exceed 100 mW/cm nor shall it exceed the amount of energy exiting the slit-lamp microscope in the range
between 380 nm and 700 nm. The energy shall be measured in the corneal plane when the slit-lamp microscope
is operating at maximum intensity and maximum aperture.
NOTE 1 If due to stops or other obstructions of the beam, a circular pupil of less than 8 mm diameter is illuminated, the
limit values may be increased by the ratio of the area of an 8 mm pupil divided by the true area illuminated.
NOTE 2 It is recommended that the energy in the range of the spectrum below 420 nm be attenuated as much as
possible.
NOTE 3 For slit-lamp microscopes with non-pulsed radiation, the assumptions used to set the limit value for radiation
shorter in wavelength than 400 nm are based on considerations of the typical spectral distribution of a 3000 K standard
black body source, an illuminating solid angle at the corneal plane of 0,031 sr, a maximum exposure time of 5 min and
the weighting factors for L (see annex A).
A
____________
1)  Maximum intensity is the highest brightness the slit-lamp microscope is capable of delivering, including the highest intensity achievable
if overvoltage is provided.
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ISO 10939:1998(E)
The limit is set to ensure that the fraction of the photochemical hazard dose due to radiation shorter in wavelength than
400 nm is no greater than 1/8 of the total photochemical hazard dose over all wavelengths when that total dose is at the
threshold limit for an 8 mm diameter pupil.
Using the American Conference of Governmental Industrial Hygienists (ACGIH) guidelines, that threshold limit is
2
14 J/(cm ⋅ sr). To convert from photochemical hazard weighted radiance to irradiance, over the designated spectral
range 305 nm to 400 nm, the conversion factor 0,276 is used. Thus the limit is then found by the formula
2 2
[14 J/(cm ⋅ sr)] x (0,031 sr) x [0,276/(300s ⋅ 8)] = 0,05 mW/cm
2
However, several of the assumptions used in determining the 0,05 mW/cm limit are not valid for slit-lamp microscopes:
i) the pupil of the eye, assumed to have a diameter of 8 mm, is no longer the limiting stop in the system;
ii) the assumed solid angle subtended by the source at the retina of 0,173 9, based on an 8 mm pupil and used to
create the ISO 15004 hazard weighting values, is no longer the effective solid angle experienced by the retina under
the direct view
...