ISCEV Standard for Clinical Electro-oculography (EOG) 2006
Malcolm Brown
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Michael Marmor
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Vaegan
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Eberhard Zrenner
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Mitchell Brigell
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Michael Bach
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Vaegan University of New South Wales
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Sydney, Australia
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M. Marmor Stanford University
,
Stanford, CA, USA
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M. Brown (&) Dept. of Clinical Engineering, Royal Liverpool University Hospital
, Liverpool L7 8XP,
UK
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M. Bach Universita t-Augenklinik
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Freiburg, Germany
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M. Brigell Pfizer Global. R&D,
Ann Arbor, MI, USA
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E. Zrenner University Eye Hospital
, Tuebingen,
Germany
The Clinical Electro-oculogram (EOG) is an electrophysiological test of function of the outer retina and retinal pigment epithelium (RPE) in which the change in the electrical potential between the cornea and the ocular fundus is recorded during successive periods of dark and light adaptation. This document sets out a Standard Method for performance of the test, and also gives detailed guidance on technical and practical issues, and on reporting test results. The main object of the Standard is to promote consistent quality of testing and reporting within All authors represent for the International Society for Clinical Electrophysiology of Vision, www.iscev.org
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Purpose and use of this Standard
This Standard is one of a series of Standards and
Guidelines for electrophysiology of vision [18]
available for download from www.iscev.org, and
is a revision of the ISCEV Standard for Clinical
Electro-oculography (first issued 1993
reapproved 1998) [1, 2], which provides a Standard
Method for measurement of the
electro-oculogram (EOG). Also included is advice on possible
variations on the Standard Method, additional
tests, and comment on the procedures
recommended. The major change in this current
standard compared with the earlier EOG
standards is that it recommends one single standard
testing protocol and measurement strategy.
Clinical and research users of the clinical EOG
are encouraged to use the current Standard
Method where possible, to achieve consistency
of results within and between test centres.
Reports of EOG recordings performed to the
Standard Method given here should cite this 2006
Standard. Where a method is used which deviates
from the Standard Method, the deviations should
be stated, together with any normative or
reference data. Where the method used conforms to a
previous EOG Standard, this may be cited
instead.
The eye has a standing electrical potential
between front and back, sometimes called the
corneo-fundal potential. The potential is mainly
derived from the retinal pigment epithelium
(RPE), and it changes in response to retinal
illumination. The potential decreases for 8
10 min in darkness. Subsequent retinal
illumination causes an initial fall in the standing
potential over 6075 s (the fast oscillation
(FO)), followed by a slow rise for 714 min
(the light response). These phenomena arise
from ion permeability changes across the basal
RPE membrane. The clinical electro-oculogram
(EOG) makes an indirect measurement of the
minimum amplitude of the standing potential in
the dark and then again at its peak after the
light rise. This is usually expressed as a ratio of
light peak to dark trough and referred to as
the Arden ratio. The behaviour of the
corneofundal potential in the normal eye is predictable
in defined conditions, such as those described in
this Standard, but changing from dark to light
actually initiates a triggered response extending
for about 2 h in the form of a diminishing
sinusoidal oscillation.
The light response is affected in diffuse disorders
of the RPE and the photoreceptor layer of the
retina including some characterised by rod
dysfunction, or chorio-retinal atrophic and
inflammatory diseases. In most of these there is
correlation with the electroretinogram (ERG),
except notably in the case of Bests vitelliform
maculopathy, in which the clinical EOG is usually
highly abnormal in the presence of a normal
ERG.
Measurement of the clinical EOG
The potential across the RPE causes the front of
the eye to be electrically positive compared to the
back. As a result, potentials measured between
two electrodes placed on the skin at each side of
an eye will change as the eye turns from left to
right. The EOG method is used widely to record
eye movements, on the assumption of unchanging
corneo-fundal potentials. In the clinical EOG
described here, we use defined eye movements to
monitor the changes in corneo-fundal potential. If
the test subject looks alternately at targets a fixed
angle apart, the potential recorded from the skin
resembles a square wave whose amplitude will be
a fixed proportion of the corneo-fundal potential.
During a light/dark cycle, this indirectly measured
potential will change in the same way as the
source potentials, so that the Arden ratios (and
timing of peaks etc.) will be a close
approximation to the average changes occurring across the
RPE.
The Standard Method
This section outlines the Standard Clinical
EOG method, defi (...truncated)