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446
Magnitude (uV)
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VA = ~0.18 LogMAR (11.88 CPD)
RE Response Magnitude vs Log(Spatial Frequency)
4.5
4
3.5
3
2.5
2
1. 5
1
0.5
O. R. Marmoy
-0.5
0.20.4 0.60.8 11.2 1.4
Log (SF)
Fig. 32.9 A teenage patient presented with only light perception in the right eye (RE) following an assault on the
right side of the face. The clinical impression was that the
patient was functional, but this could not be objectively
determined. Typical electrophysiological data (PERG,
prVEP, ash VEP) were within the reference range, indi-
32.6 Summary
The VEP is an incredibly valuable tool in assessing the visual pathway. It is easily performed and
provides complementary information not only in
neuro- ophthalmic and neurological diseases but
also in primary diseases of the eye itself. The
VEP is a robust method for assessing visual pathway integrity, but as described in this chapter, its
cating normal macular, retinal ganglion cell, and pathway
function in the affected eye. A sweep VEP showed a spatial
threshold of 11.88 CPD (~0.18 LogMAR), suggesting that
the objective visual acuity estimate was far better than the
patient’s reported visual acuity, consistent with the clinical
impression of functional visual loss
uses are often complementary to other structural
or functional techniques. One must remain aware
of the potential caveats to an abnormal VEP
response or the limitations of a normal VEP,
including the prompts for further investigation of
function.
Funding None.
Disclosure None.
32 The Visual Evoked Potential
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447
References
1. Walsh P, Kane N, Butler S.The clinical role of evoked
potentials. J Neurol Neurosurg Psychiatry. 2005;76:
Suppl 2(Suppl 2):ii16-22. https://doi.org/10.1136/
jnnp.2005.068130.
2. Robson AG, Nilsson J, Li S, etal. ISCEV guide to
visual electrodiagnostic procedures. Doc Ophthalmol.
2018;136(1):1–26. https://doi.org/10.1007/
s10633- 017- 9621- y.
3. Odom JV, Bach M, Brigell M, etal. ISCEV standard
for clinical visual evoked potentials: (2016 update).
Doc Ophthalmol. 2016;133(1):1–9. https://doi.
org/10.1007/s10633- 016- 9553- y.
4. Marmoy OR, Horvat-Gitsels LA, Cortina-Borja M,
Thompson DA.Pattern visual evoked potentials show
an inferior-superior topographic shift through maturation in childhood. J Physiol. 2023;601(10):1869–80.
https://doi.org/10.1113/jp283408.
5. Ghodrati M, Morris AP, Price NS.The (un)suitability
of modern liquid crystal displays (LCDs) for vision
research. Front Psychol. 2015;6:303. https://doi.
org/10.3389/fpsyg.2015.00303.
6. Matsumoto CS, Shinoda K, Matsumoto H, etal. Liquid
crystal display screens as stimulators for visually
evoked potentials: ash effect due to delay in luminance changes. Doc Ophthalmol. 2013;127(2):103–
12. https://doi.org/10.1007/s10633- 013- 9387- 9.
7. Marmoy OR, Thompson DA. Assessment of digital light processing (DLP) projector stimulators
for visual electrophysiology. Doc Ophthalmol.
2023;146(2):151–63. https://doi.org/10.1007/
s10633- 022- 09917- 4.
8. Matsumoto CS, Shinoda K, Matsumoto H,
et al. Pattern visual evoked potentials elicited by organic electroluminescence screen.
Biomed Res Int. 2014;2014:606951. https://doi.
org/10.1155/2014/606951.
9. Hamilton R, Bach M, Heinrich SP, etal. VEP estimation of visual acuity: a systematic review. Documenta
Ophthalmologica. 2021;142(1):25–74. https://doi.
org/10.1007/s10633- 020- 09770- 3.
10. Thompson DA, Kriss A, Taylor D, et al. Early
VEP and ERG evidence of visual dysfunction in autosomal recessive osteopetrosis.
Neuropediatrics. 1998;29(3):137–44. https://doi.
org/10.1055/s- 2007- 973550.
11. Thompson DA, Fritsch DM, Hardy SE.The changing shape of the ISCEV standard pattern onset
VEP. Doc Ophthalmol. 2017;135(1):69–76. https://
doi.org/10.1007/s10633- 017- 9596- 8.
12. Marmoy OR, Viswanathan S.Clinical electrophysiology of the optic nerve and retinal ganglion cells.
Eye. 2021;35(9):2386–405. https://doi.org/10.1038/
s41433- 021- 01614- x.
13. Rufai SR, Marmoy OR, Thompson DA, et al.
Electrophysiological and fundoscopic detection
of intracranial hypertension in craniosynostosis.
Eye. 2023;37(1):139–45. https://doi.org/10.1038/
s41433- 021- 01839- w.
14. Thompson DA, Marmoy OR, Prise KL, et al.
Giant pattern VEPs in children. Eur J Paediatr
Neurol. 2021;34:33–42. https://doi.org/10.1016/j.
ejpn.2021.07.008.
15. Thompson DA, Handley SE, Henderson RH, et al.
An ERG and OCT study of neuronal ceroid lipofuscinosis CLN2 battens retinopathy. Eye (Lond).
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s41433- 021- 01594- y.
16. Slotnick SD, Klein SA, Carney T, Sutter
EE.Electrophysiological estimate of human cortical
magnication. Clin Neurophysiol. 2001;112(7):1349–
56. https://doi.org/10.1016/s1388- 2457(01)00561- 2.
17. Thompson DA, Liasis A, Hardy S, et al. Prevalence
of abnormal pattern reversal visual evoked potentials in craniosynostosis. Plast Reconstr Surg.
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prs.0000220873.72953.3e.
18. Barrett G, Blumhardt L, Halliday AM, et al. A
paradox in the lateralisation of the visual evoked
response. Nature. 1976;261(5557):253–5. https://doi.
org/10.1038/261253a0.
19. Marmoy OR, Handley SE, Thompson DA. Patternonset and OFFset visual evoked potentials in the diagnosis of hemianopic eld defects. Doc Ophthalmol.
2021;142(2):165–76. https://doi.org/10.1007/
s10633- 020- 09785- w.
20. van Genderen MM, Riemslag FC, Schuil J, et al.
Chiasmal misrouting and foveal hypoplasia without
albinism. Br J Ophthalmol. 2006;90(9):1098–102.
https://doi.org/10.1136/bjo.2006.091702.
The Clinical Electro-Oculogram
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33
PaulA.Constable
33.1 Introduction
The clinical electro-oculogram (EOG) measures
the electrical activity of the retina and retinal pigment epithelium (RPE) in response to light stimulation. The test is especially useful in conditions
affecting the structural integrity of the rods and
the RPE. At rest, there is a positive “standing
potential” of the eye that is maintained by differences in the ionic conductance of the apical and
basal membranes of the RPE. Changes in the
ow of ions across these membranes alter the
standing potential of the eye; these can be
recorded from horizontal saccadic eye movements under dark - and light-adapted intervals.
Clinically, the standing potential falls during the
dark adaptation phase and increases during the
light-adapting phase. The ratio of the recorded
saccadic amplitudes during these phases is used
as a clinical index for the functional integrity of
the rods and the RPE.The EOG may be abnormal
in conditions affecting bestrophin, a calcium and
chloride regulator localized in the RPE.Mutations
in the gene encoding bestrophin (BEST1) result
in conditions such as Best’s vitelliform macular
dystrophy.
P. A. Constable (*)
Flinders University, College of Nursing
and Health Sciences, Caring Futures Institute,
Adelaide, SA, Australia
e-mail: paul.constable@inders.edu.au
33.2 History
The clinical utility of the EOG was rst described
by Geoffrey Arden, who recorded changes in the
standing potential of the eye as a measure of retinal function in response to light [1]. Arden found
that the standing potential was reduced in conditions where the retina was not in contact with the
RPE, such as retinal detachment, retinal hypoxia
following retinal artery occlusion, and in inherited retinal dystrophies such as retinitis pigmentosa [2, 3]. These clinical observations suggested
that the EOG largely depends on normal RPE and
rod function and when the RPE and the retina
remain in contact. Using micro-electrode recordings in retina-RPE whole mounts of geckos, Griff
and Steinberg later demonstrated that the standing potential originated in the RPE [4]. The
standing potential of the eye was later shown to
be due to the difference in the basal and apical
membrane potentials of the RPE (termed the
transepithelial potential) and depended upon the
integrity of the tight junctions; these junctions
maintain the difference in the electrical potentials
between the basolateral and apical membranes
[5]. An increase in basolateral chloride conductance produced a basolateral membrane depolarization that increased the transepithelial potential
that could be recorded as changes in the standing
potential of the eye [6, 7]. Further studies have
identied a large potassium conductance in the
apical membrane with voltage-gated potassium
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024
T. Das, P. Satgunam (eds.), Ophthalmic Diagnostics, https://doi.org/10.1007/978-981-97-0138-4_33
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P. A. Constable
channels and active and passive co-transporters
regulating potassium and pH within the subretinal space and RPE, respectively [8, 9]. One does
not know how light could change the basolateral
chloride conductance of the RPE, several hypotheses have been proposed.
Based on the slow time course and spectral
properties of the light-rise [3], Arden proposed
that a “light-rise” substance is released from the
rods; this substance then binds to an apical RPE
receptor that initiates an intracellular secondary
messenger cascade to open basolateral chloride
channels. Based on this model, several molecules
were proposed as candidates for the elusive
“light-rise” substance, including cyclic nucleotides [10], dopamine [4], epinephrine [11], and
adenosine triphosphate [12]; but to date, no
denitive human studies have identied the
“light-rise” substance. One suggestion was that
light might act directly on the apical phospholipid bilayer of the RPE, resulting in direct biosynthesis of the intracellular secondary messenger
molecule, inositol 1,4,5-trisphosphate (IP3); however, this model is also unconrmed in human
[13]. The photosensitive protein, melanopsin is
also a possible candidate, given its expression in
the RPE, but it has been reported that knock-out
−/−
opn4
mice exhibit a normal light-rise suggesting that this protein is not involved in the generation of the light-rise [14]. Despite this evidence,
IP3 is still implicated in the process due to its role
in the release of calcium from the endoplasmic
reticulum and the involvement of calcium in the
generation of the changes in basolateral chloride
conductance [11, 15]. In addition, studies on
humans have shown that individuals with cystic
brosis have a normal light-rise [16], but a
decrease in the light-rise following pharmacological blockade of L-type Ca2+ channels with
nifedipine supports the hypothesis that calcium
signaling is involved in the light-rise [17].
Even though the identity of the trigger for the
light-rise has not yet been conrmed, a greater
understanding of the mechanism for the basolateral depolarization has been developed. The
reduced light-rise in patients with Best’s disease
[18] led to the identication of the gene BEST1 or
VMD2 that encodes bestrophin. Mutations in this
gene cause Best’s vitelliform macular dystrophy
[19]. Although bestrophin is known to be involved
in the generation of the light-rise, it is also known
to play a central role in the pathogenesis of Best’s
vitelliform macular dystrophy, the precise function and location of this protein within the RPE
remains unclear [20]. Early studies suggested
that bestrophin could either be a calcium-gated
chloride channel or a regulator of intracellular
calcium stores [21–23].
Strauss and co-workers resolved these conicts by demonstrating that bestrophin was localized in the endoplasmic reticulum and not the
basolateral membrane of the RPE, as previously
thought [24]. At this location, bestrophin could
regulate intracellular calcium through direct
interactions with the basolateral L-type calcium
channel [15, 25] and thereby help regulate intracellular calcium stores. The transmembrane
calcium- gated (Transmembrane 16 A,
TMEM16A; also known as anoctamin1) chloride
channel [26–28] was then shown to be the ion
channel responsible for changes in the basolateral membrane potential and, ultimately, the generation of the light-rise. Thus, mutations affecting
bestrophin result in a reduced light-rise and
abnormal EOG [29]. Fig.33.1 is a schematic outline of the mechanism of the light-rise of the
EOG secondary to basolateral membrane
depolarization.
33 The Clinical Electro-Oculogram
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451
Fig. 33.1 The complete mechanism of the light-rise of
the EOG (EOG). The main pathways involved in the generation of the intracellular secondary messenger molecule, inositol 1,4,5-trisphosphate (IP3). The rod
photoreceptors may be a likely source of the “light-rise”
substance that triggers IP3 synthesis and release from the
phospholipid bilayer. IP3 releases calcium from intracellular stores that open the transmembrane (TMEM16A)
chloride channel to depolarize the basolateral membrane
33.3 Technology, Physics,
andMechanics
ofElectro-Oculogram
The clinical EOG has two main components that
reect changes in the standing potential of the
eye during dark adaptation (dark phase) and light
adaptation (light phase). In the dark phase, the
recorded standing potential of the eye falls to a
minimum value after 10–15min and is known as
the dark trough (DT). In the light phase, the
standing potential peaks at approximately
7–12 min after light onset and is known as the
light peak (LP) before falling again and continuing in a slow-damped oscillation. The ratio of the
LP:DT is a measure of the integrity of the
and increase the transepithelial potential of the retinal pigment epithelium (RPE). These changes are recorded from
horizontal saccadic eye movements in the dark and light
as changes in the standing potential of the eye. Bestrophin,
localized in the endoplasmic reticulum, regulates intracellular calcium stores and concentrations through direct
interactions with the voltage-gated L-type calcium channels that contribute to the slow oscillations of the standing
potential. (Schematic, not to scale)
photoreceptor/rod-RPE complex and is known as
the LP:DT ratio as dened by the current standards of the International Society for Clinical
Electrophysiology of Vision (ISCEV) [30]. The
slow-damped oscillations under dark or light
conditions will continue for 120min [2]. But the
dark and light slow oscillations may have different origins, with an unknown mechanism for the
dark oscillations; however, it is suspected that
these oscillations may be caused due to volume
changes in the RPE [31]. The slow oscillations
represent the slow changes in intracellular calcium concentrations driven by the L-type voltagegated calcium channel. Figure 33.2 shows the
slow dark and light-damped oscillations of the
standing potential.
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Fig. 33.2 The standing potential of the eye recorded
under prolonged light—and dark-adapted periods exhibits
a slow-damped oscillation. In the dark, the oscillations
form the rst negative trough, known as the dark trough.
The rst of the light oscillations form the light peak.
Although the mechanism underlying the dark oscillations
is unclear, the slow light oscillations are known to reect
changes in intracellular calcium concentrations that drive
an increase in chloride conductance across the basolateral
membrane, resulting in changes in the standing potential
of the eye. The squares represent the slow light oscillations, and the black circles represent the dark oscillations;
the dark oscillations are smaller than the light oscillations.
The plots represent the averages of values obtained from
11 normal human subjects
The fast oscillations of the EOG are not generally clinically recorded. They represent changes
in the apical membrane potential in response to
potassium currents during brief 1-min alternating
intervals of light and dark, which are reduced in
early diabetes [32, 33]. However, these fast oscillations are preserved in Best’s vitelliform macular dystrophy, which supports the hypothesis that
the fast oscillations of the EOG are caused by
mechanisms different from those responsible for
the slower changes in the potential that characterize the EOG [18]. The fast oscillations affect the
standing potential in a manner opposite to that of
the slower changes, with a fall during the light
phase and a rise in the dark phase [30]. The readers are encouraged to review section on “fast
oscillations” in “The electro-oculogram” by
Arden and Constable (2006) [34].
Incidentally, non-photic substances may also
change the standing potential, with ethanol mimicking the light-EOG that presumably triggers
the same intracellular pathways as light [35]. The
P. A. Constable
Fig. 33.3 The EOG with measurements made at 1-min
intervals during the dark phase (20 min) and the light
phase (20–50 min). The dark trough occurs at approximately 10–15 min of dark adaption, and the light-rise
commences at the light onset with a gradual increase in
the recorded potential; it reaches a peak at approximately
7–12min following light onset before falling again in a
slow-damped oscillation. The ratio of the amplitude at the
light peak (LP) to the amplitude at the dark trough (DT) or
the LP:DT ratio is a measure of the photoreceptor/rodRPE integrity
ethanol-induced EOG may help identify RPE
stress in early age-related macular degeneration
[36]. Other non-photic stimuli such as hypoxia,
hypercapnia, and hyperosmolarity have also been
evaluated as potential clinical tests for detecting
RPE stress, but these do not demonstrate any
potential as clinical tests despite their ability to
change the standing potential of the eye [37, 38].
Fig.33.3 shows a typical raw clinical recording
of the EOG from a normal subject.
33.4 Technique
ISCEV has developed guidelines on the methods
used for recording clinical EOGs and fast oscillations, which are updated as required [30].
Recordings are performed in people with dilated
pupils to ensure standard retinal illumination
with a ganzfeld stimulator to obtain responses
from the entire retina. The patient must avoid
bright lights before recording. The patient should
be allowed to practice eye movements beforehand and avoid talking during the recording
phases to minimize muscle artifacts. The patient
must be informed of the test procedure, and they
will be asked to look left and right (horizontal
33 The Clinical Electro-Oculogram
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Fig. 33.4 An illustration of the positioning of the electrodes with a central forehead earth electrode (green) and
recording electrodes (red and black) at the inner and outer
canthi, respectively. As the eyes move to the left and right,
the red and black electrodes measure the amplitude of the
standing potential as the positively charged cornea moves
from the positive to the negative electrode
saccades) for 10s at 1-s interval or on an auditory/verbal cue at 1-min intervals with 15min in
the dark and 15min in the light. White light is
used as the stimulus with a luminance of 100cd.
m−2± 10%. The patient should be in a dimly lit
room, and their skin should be cleaned to reduce
impedance to <5 kΩ. The electrodes (usually
gold cups) include two surface electrodes placed
on the skin—one on the outer canthus (the bony
part of the eye at the corner closest to the ear) and
one on the nose near the inner canthus. A third
reference electrode can be placed on the center of
the forehead or earlobe. Care should be taken to
avoid any contact between the nasal electrodes.
In cases where the patient cannot execute a horizontal saccade, such as in strabismus, then the
EOG cannot be recorded from that eye.
Figure 33.4 shows the typical electrode placement for recording an EOG.
The EOG signals are amplied using a biological amplier with a high input impedance
and are ltered between 0.1 and 30 Hz with a
sampling rate of >1kHz to record the saccades.
The horizontal saccades have a 30° amplitude;
dim red light-emitting diodes (LEDs) mounted in
the ganzfeld dome are typically used to aid with
xation. Averages of the saccadic amplitudes are
taken as the standing potential of the eye during
the dark and light phases. Fig.33.5 shows a typical averaged series of saccades with a cursor
mark indicating the measured amplitude.
453
Modications to the ISCEV standard protocol
have been proposed to improve patient comfort
by not dilating their eyes and reducing the periods of dark and light adaptation [30]. Türksever
etal. [39] proposed using a higher luminance of
450cd.m−2 if dilation is not possible; this gives a
quantitatively similar LP:DT ratio to that obtained
from a subject exposed to a luminance of 100cd.
m−2 with dilated eyes. In addition, the authors
proposed a shortened protocol with 10min of the
dark phase followed by 14min of the light phase.
Any variations from the ISCEV standard protocol should be noted in any reporting of the EOG
ndings and should include the LP:DT ratio, the
time to peak of the light-rise (taken from the time
of the light phase onset to the light peak), and the
dark trough amplitude [30]. The dark trough can
be variable between subjects, and hence, care
should be taken to ensure that the patient is comfortable during the recordings. In the initial minute of the light phase, the patient may be
uncomfortable owing to the large change in luminance and pupil dilatation. It is important to
inform them that the initial phase could be
uncomfortable, but that they must keep their eyes
open, as the light entering the eye is required to
initiate the light-rise. During recordings, it is
important to monitor the subject’s eye position to
ensure that they remain correctly centered and
have their eyes open during the recordings.
Typically, an infrared camera is mounted within
the ganzfeld dome in a recording instrument to
enable this.
Once the recordings are complete, a plot of the
saccadic amplitudes and time is made, as shown
in Fig. 33.3. The “raw” values characterize the
physiological shape of the changes in the standing potential and identify the dark trough from
the light peak. Although several smoothing or
averaging strategies of the recorded saccadic
amplitudes are possible, the ISCEV standard
does not have a preferred method [30]. The physiological response may be identied by simply
tting a curve using the line of best t or using a
moving average to smoothen the curve rst, or by
averaging values around the light peak and dark
trough. Smoothing using a moving average can
be applied using Eq.33.1, where the amplitude
454
10
12
13
14
15
16
17
28
19
20
21
22
23
24
25
26
27
28
29
30
31
Latencies
Amplitude
VV V
+
()
+
()
+−
2
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P. A. Constable
Fig. 33.5 A series of
averaged saccades
during a 10-s recording
epoch for one eye,
recorded at 1-min
intervals. Note the
smaller amplitudes in
the initial 15min of the
dark phase and with the
dark trough minimal
amplitude (321μV)
occurring at t=13min
and the maximal
amplitude at t=26min
(11min after light onset
with a saccadic
amplitude of 706μV)
for each standing potential voltage (Vt) at time (t)
can be weighted by 0.5 times the value of the preceding and subsequent standing potential
voltage.
=
t
1
2
3
4
5
6
7
8
9
11
05 05
.. ..
tt t
(33.1)
ms
440.000
400.000
350.000
430.000
700.000
480.000
600.000
520.000
640.000
390.000
630.000
560.000
430.000
580.000
580.000
490.000
640.000
650.000
750.000
820.000
730.000
740.000
880.000
670.000
700.000
880.000
820.000
540.000
590.000
660.000
920.000
D mV
300.781
281.250
334.717
340.820
331.543
343.018
331.543
318.115
359.863
350.342
342.773
344.971
321.045
348.633
354.980
363.770
368.164
310.059
364.746
457.275
542.480
632.324
670.410
694.824
700.684
706.055
695.557
596.436
637.939
586.182
549.561
This method results in a slight change to the
time axis as the rst and last recordings are lost
because of the averaging. Figure 33.6 shows a
raw and smoothed EOG using a moving average
of the recorded time interval values as described
initially by Arden and Wolf for the amplitude of
the measured saccades [35, 36]. In addition, the
33 The Clinical Electro-Oculogram
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455
Fig. 33.6 The raw and smoothed values of the saccadic
amplitudes (using Eq.33.1) recorded during the 20-min
dark and 30-min light phase. The main objective in the
interpretation of the plots is to dene the physiological
response, and so a line of best t or averages of the points
y-axis may be plotted as a normalized voltage to
the light peak maximum, or sometimes as μV/
degree with the recorded voltage divided by the
saccadic amplitude of typically 30°so that a
potential of 300μV would be recorded as 10μV/
degree.
Typical measures for the EOG clinical parameters are summarized in a meta-analysis of clinical values in subjects with a mean age of
34.1±12.9years [40]. The reported mean (95%
condence interval, CI) from the meta-analysis
of studies were as follows: for dilated pupil,
LP:DT ratio = 2.35 (2.28–2.42); dark trough
amplitude=358μV (292–424μV), and time to
peak of the light-rise was 8.2min (7.7–8.7min)
with amplitude = 835 μV (631–1039 μV); for
non-dilated pupil, LP:DT ratio = 2.37 (2.28–
2.45), and the fast oscillation peak to trough ratio
was 1.13 (1.11–1.16).
Thavikulwat etal. [41] performed one of the
largest clinical studies to study the impact of age
and gender on the EOG parameters in 121 sub-
at the peak and trough may be used to dene the light peak
and dark trough to calculate the LP:DT ratio. Since there
is no dened or preferred method, clinicians are advised
to report the method (if any) of smoothing or averaging
jects aged 7–72years. The study found that the
LP:DT ratio decreased at a rate of 0.13 per
decade, and the lower fth centile of the LP:DT
ratio decreased from 2.0 to 1.7 between the ages
of 10 and 60years. In addition, the time to peak
of the light-rise was 2 min slower in subjects
aged 55years or older, and that female subjects
had a higher absolute amplitude for the light
peak.
Artifacts can be caused by blinks or under or
overshoots of the target LED.One should carefully observe these in the saccadic recordings so
that the true saccade amplitude is noted when
placing the cursors. Automatic cursor placement
by in-built algorithms may misplace the cursors.
Figure33.7 shows a representation of an undershoot, then a corrective saccade to the target, and
a distinctive blink artifact in the saccadic recording. Generally, some practice runs are recommended to ensure that the patient knows what to
do. They should always be requested to refrain
from blinking during the 10-s recording interval.
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P. A. Constable
macular degeneration [19, 44]. The macula is
selectively affected owing to the low expression
of bestrophin in this area of the retina [45].
Fig. 33.8 shows the fundus, optical coherence
tomography (OCT) images, and EOG in a patient
with Best’s vitelliform macular dystrophy. In
cases where EOG cannot be performed (e.g., in a
child suspected of having Best’s macular dystrophy), testing the parents may show a reduced
EOG owing to the autosomal dominant inheritance pattern of this condition.
In autosomal recessive bestrophinopathies,
[46] the EOG is typically abnormal, with a normal electroretinogram in the early stages of the
disease. The typical age of onset ranges from 4 to
35years (mean=18.6years); the common ocular
ndings are hyperopia and narrow anterior chamber angles with increased risk of angle closure
glaucoma. The fundus appearance may vary, but
consists of vitelliform lesions in the retina, subretinal deposits with central serous retinopathy,
or a macular hole [47, 48]. Fig. 33.9 shows a
25-year-old male with autosomal recessive
Fig. 33.7 Illustrative artifacts in the saccades. In the
recording at t=1min, there is an undershoot and correction to the LED (lled arrow). In the recordings at
t=3–7min, there are blink artifacts during the recordings
(unlled arrows). Care should be taken to ensure that measurements of the saccadic amplitudes are not taken from
blinks or under/overshoots
bestrophinopathy with a homozygous splice variant in exon 4 of the BEST1 gene. In this case, the
subject had reported reductions in vision over
5years with nyctalopia and had a normal anterior
segment and color vision; the visual acuities of
the right and left eyes were 6/12 and 6/6, respectively. Light—and dark-adapted full-eld elec-
33.4.1 Clinical Applications
troretinograms were reduced with an absent
light-rise in the EOG.The fundus had a central
The main clinical application of the EOG is to
diagnose and monitor conditions where mutations occur in the BEST1/VMD2 gene that
encodes bestrophin (the calcium and chloride
regulator of the RPE). Collectively these conditions are referred to as bestrophinopathies (for
reviews on these, see Johnson etal. [42] and Toto
et al. [43]). The most common of these conditions is the autosomal dominant condition, Best’s
vitelliform macular dystrophy, where the lightrise is reduced or absent, but the fast oscillations
of the EOG are preserved [18]. This condition
may present in any decade of life, but is characterized by a central vitelliform lesion on the macula, that degenerates over time, leading to
macular edema (right>left) with a mid-peripheral
band of hyper-uorescence corresponding to
increased pigmentation in the RPE.
In autosomal dominant vitreoretinochoroidopathy [49] linked to mutations in BEST1 [50], the
EOG is also abnormal with an initially normal
electroretinogram; however, central cone dysfunction can develop [51]. Typically, the ocular
ndings include short axial length with hyperopia and small angles, and a typically hyperpigmented band at the equator with some white dots
and a cystoid macular edema [42]. In diseases
affecting the integrity of the RPE tight junctions,
such as Danon’s disease (where there is a loss of
regulation of lysozyme function), the dark trough
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