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The Nagel anomaloscope: Its calibration and recommendations for diagnosis and research


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The Nagel anomaloscope Model I is the definitive clinical instrument for classifying phenotypic variations in X-linked color-vision disorders. Its system of classification is based on the Rayleigh equation: the relative amounts of red and green primary lights required to match a yellow primary. Our aim was to characterize how changes in mains voltage and ambient temperature influence the wavelength and intensity of each primary and alter the Rayleigh matches of normal and anomalous trichromats. A Nagel Model I anomaloscope was calibrated in wavelength and intensity while varying the temperature of its prism housing and the mains voltage. Three normal, three protanomalous and three deuteranomalous trichromats made Rayleigh matches at various temperatures and voltages. The intensities of the green and red primaries show an exponential growth with mains voltage. Additionally, the wavelengths and intensities of all three primaries change with prism housing temperature. As a result, the R-G match midpoints of normal and anomalous trichromats shift with increasing mains voltage, and more markedly with increasing prism housing temperature, to higher R-G settings. Rayleigh matches obtained with the Nagel I anomaloscope are sensitive to changes in voltage supply and prism housing temperature, arising largely from thermal effects of the internal light sources. However, the instrument may still be safely used for diagnostic and research purposes provided that: (1) a stable voltage supply is used; (2) it is kept at a constant temperature; and (3) the match midpoint of the reference population has been established under identical conditions.
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Graefe’s Arch Clin Exp Ophthalmol
(2005) 243:26–32
Herbert Jgle
Markus Pirzer
Lindsay T. Sharpe
The Nagel anomaloscope:
its calibration and recommendations
for diagnosis and research
Received: 18 December 2003
Revised: 3 February 2004
Accepted: 11 February 2004
Published online: 31 July 2004
Springer-Verlag 2004
H. Jgle (
) · M. Pirzer
Department of Pathophysiology
of Vision & Neuro-Ophthalmology,
University Eye Hospital,
Schleichstrasse 12–16, 72076 Tbingen,
Tel.: +49-7071-2980744
Fax: +49-7071-294678
L. T. Sharpe
Department of Psychology,
University of Newcastle upon Tyne,
Newcastle upon Tyne, UK
Abstract Background: The Nagel
anomaloscope Model I is the defini-
tive clinical instrument for classify-
ing phenotypic variations in X-linked
color-vision disorders. Its system of
classification is based on the Ray-
leigh equation: the relative amounts
of red and green primary lights re-
quired to match a yellow primary.
Our aim was to characterize how
changes in mains voltage and ambi-
ent temperature influence the wave-
length and intensity of each primary
and alter the Rayleigh matches of
normal and anomalous trichromats.
Methods: A Nagel Model I anoma-
loscope was calibrated in wavelength
and intensity while varying the tem-
perature of its prism housing and the
mains voltage. Three normal, three
protanomalous and three deutera-
nomalous trichromats made Rayleigh
matches at various temperatures and
voltages. Results: The intensities of
the green and red primaries show an
exponential growth with mains volt-
age. Additionally, the wavelengths
and intensities of all three primaries
change with prism housing tempera-
ture. As a result, the R-G match
midpoints of normal and anomalous
trichromats shift with increasing
mains voltage, and more markedly
with increasing prism housing tem-
perature, to higher R-G settings.
Conclusions: Rayleigh matches ob-
tained with the Nagel I anomaloscope
are sensitive to changes in voltage
supply and prism housing tempera-
ture, arising largely from thermal ef-
fects of the internal light sources.
However, the instrument may still be
safely used for diagnostic and re-
search purposes provided that: (1) a
stable voltage supply is used; (2) it is
kept at a constant temperature; and
(3) the match midpoint of the refer-
ence population has been established
under identical conditions.
The Nagel anomaloscope Model I, manufactured by
Schmidt & Haensch to a standard design until 1983, is
still the definitive clinical instrument for classifying the
phenotypic variation in X-chromosome linked color vi-
sion disorders [12]. Optically similar to an instrument first
described by Nagel [9], it is used to determine the Ray-
leigh equation; specifically, the match of a spectral yellow
light or primary to a mixture of spectral red and green
lights (the R-G match). It consists of a light source, a
separate internal adaptation light, an ocular, a compound
direct-vision prism and three entrance slits (see Fig. 1).
The entrance slits are carefully calibrated to define the
red, green and yellow primaries in terms of wavelength
and intensity, according to a norm (DIN 6160) of the
German Institute for Standardization [4]. However, the
accuracy of its calibrated settings is influenced by several
environmental factors, including temperature changes and
fluctuations in mains voltage, which have never been
fully investigated.
DOI 10.1007/s00417-004-0893-z
Mains voltage
It has long been known that the stability and reliability of
Nagel anomalocope matches are influenced by the mains
voltage [11]. Cavonius [2] found an increase of the R-G
match midpoints of normal trichromats with the mains
voltage of ca. 0.05 (Nagel) units per volt and concluded
that it is unlikely that these variations lead to clinical
misdiagnosis. However, although the nominal mains volt-
age was raised in 1983 from 220 V to 230 V in Germany,
no adjustment was made in the design or operation of the
instrument, which was constructed to run at 220 V. Fur-
ther, for reasons of harmonization within the European
Union, the permitted voltage range will be further ex-
tended to 195.5–253 V in 2004 [5, 6]. These changes
could potentially influence the Rayleigh matches and di-
agnosis of anomalous trichromats.
Richter [10] was the first to report a seasonal variation in
the amount of red and green required to match the yellow
primary on the Nagel anomaloscope. Jordan & Mollon [8]
replicated his results on three anomaloscopes, including
two different Model I instruments (Schmidt & Haensch)
and an antique Model II instrument (manufactured by
Spindler & Hoyer). Expressing the matches in terms of
the anomalous quotient, a normalizing technique intro-
duced by Trendelenburg [13] to compensate for minor
changes in line voltage and bulb aging and to allow
comparisons between different instruments, they con-
cluded that the variation was almost certainly owing to an
instrumental sensitivity to ambient temperature—in par-
ticular, thermal changes in the prism—rather than to a
seasonal change in human physiology [8]. They estimated
the magnitude of the increase of the Rayleigh match
midpoint per degree Celsius of ambient room temperature
to be 0.175 Nagel units. However, they did not explore
the relevant sources of instrument temperature variation
in detail. These include not only thermal fluctuations in
external air temperature, but also changes in the heat
being emitted by the internal incandescent source (see
Fig. 1), located near the prism in the same housing and
used to provide a neutral adaptation light. The contribu-
tion of both of these temperature effects to the R-G
matches of normal and anomalous trichromats is yet un-
Anomalous trichromacy
The classification of anomalous trichromacy is based on
the observation that protanomalous and deuteranomalous
observers require more of the red (protanomaly) or more
of the green (deuteranomaly) primary in the red–green
mixture to match the yellow primary than do normal
observers. The amount of red or green shift is a measure
of the severity of the anomaly. Given that the relative
amounts of red and green required in the match depend
upon the wavelength and intensity of each primary, and
that these, in turn, critically depend upon the lamp voltage
and the temperature of the instrument’s prism housing, it
is possible that voltage and temperature changes may
have a significant effect upon phenotype–genotype cor-
relations of anomalous red–green color vision. Therefore,
the principal aim of this study was to characterize the
wavelength and intensity changes of the Nagel Model I
anomaloscope primaries, arising from mains voltage and
temperature changes, and to estimate their effects on R-G
matches in normals and anomalous trichromats.
Fig. 1 Schematic diagram of
the Nagel Model I anomalo-
scope used in this study. The
diagram has been modified
from the original, which ap-
pears in the manufacturer’s
Nine subjects were selected from a population of normal and
anomalous trichromats who were previously diagnosed by their
anomaloscope matches on the Rayleigh Model I instrument and on
the Oculus anomaloscope. They were classified as normal (MB, JA,
TG), deuteranomalous (RS, AS, SJ) or protanomalous trichromats
(TT, TZ, MP). The study was conducted in accordance with the
tenets of the Declaration of Helsinki and with the approval of the
ethics committee on human experimentation of the University of
Apparatus and calibration
The Rayleigh equation settings were made with a Schmidt &
Haensch Nagel anomaloscope Model I constructed in 1979. All
physical (calibration) data were confirmed with a second instru-
ment constructed in 1980. Both instruments are equipped with a
220-V, 100-W cine-projection lamp for producing the red, green
and yellow primaries and a 220-V, 60-W incandescent bulb for
providing neutral adaptation. The instruments were connected to
the mains power supply through a variable transformer so that their
voltages could be adjusted between 100 and 250 V or kept constant
at 230 V. All voltages were controlled by a digital meter and
manually readjusted, resulting in residual fluctuations of less than
€0.5 V.
The emission spectra of the red, green and yellow primaries
were measured with a compact array spectroradiometer (CAS 140,
Instrument Systems, Munich, Germany). The half-field intensi-
ties—one half-field produces the yellow primary light, the other,
the mixture of the red and green primary lights—were measured
over the full range of R/G settings with a Pin-10 diode (United
Detector Technology, Santa Monica, CA) and a calibrated radi-
ometer (Model 80X Optometer, United Detector Technology).
To control the effect of the temperature on the R/G settings a
thermal sensor was mounted directly inside the prism housing, and
a second sensor was positioned 1 m away from the instrument on
the measuring table to monitor the ambient room temperature. To
reduce the instrument temperature below room temperature, the
prism housing was slowly cooled down to 15C by the appropriate
placing of Coolpacks (3 M “Nexcare” Coldhot Pack, 3 M Health
Care, D-41453 Neuss, Germany). Lower temperatures were avoid-
ed to prevent damage from water condensation within the prism
Anomaloscope matches were determined in the preferred eye of
each subject. To avoid learning effects, all subjects were trained in
performing Rayleigh matches prior to the first day of experimen-
tation. In the mains voltage experiments, only normal trichromat
matches were made. They were averages of at least five settings at
each of 14 voltages from 120 V to 250 V. The order of voltages was
randomly chosen by the investigator. During the experiments, the
neutral adaptation light was turned on and the prism housing
temperature was maintained between 34C and 36.6C, with lower
temperatures corresponding to lower mains voltage.
In the temperature variation experiments, all matches were
performed at a constant mains voltage of 230 V. All experiments
were conducted with the internal neutral adaptation light switched
on. To determine the full range of acceptable matches the investi-
gator presented a series of R/G settings starting with the lowest
temperature. The subject was then allowed to adjust the brightness
of the yellow half-field, until an acceptable match was found or not
found with the R/G half-field. In the event that the half-fields were
seen as identical in color and intensity, the R/G setting and the
actual prism housing temperature were recorded. This procedure
was repeated at higher prism housing temperatures, ranging from
16C to 39C.
Physical data
The physical calibration data, obtained at a prism housing
temperature of approximately 36C (see Methods), reveal
that the wavelengths of the green, red and yellow pri-
maries do not change with mains voltage. Further, at any
given temperature, the Nagel anomaloscope conforms to
the German DIN 6160, insofar as the calibrated primary
wavelengths and luminances fall within the standard,
accepted range of values. Nevertheless, the primary
wavelengths as well as the luminances vary systemati-
cally with mains voltage and prism housing temperature
so as to cause definable shifts in the Rayleigh matches of
both normal and anomalous trichromats.
Voltage data
The intensities (calculated for a 2-deg visual field) of
the green and red primaries (Fig. 2) grow approximate-
ly exponentially with the mains voltage. The significant-
ly higher increase in green primary intensity reflects
the color temperature change of the light source from
1821.5 K, at the lowest calibrated mains voltage of 100 V,
to 2292.2 K and 2512.9 K, at mains voltages of 196 V and
253 V, respectively (corresponding to the range permitted
in DIN EN 50160).
Fig. 2 The exponential growth of the red and green primary in-
tensities, in retinal illuminance (calculated for a two degree visual
field) with increasing mains voltage
Temperature data
The wavelengths of all three primaries change with prism
housing temperature. Two operational modes have to be
distinguished. When the internal neutral adaptation light
is switched off, the temperature stays approximately
constant at 24.5C for 15 min, then increases slowly until
it reaches its final temperature of 29C (Fig. 3A). Alter-
natively, when the internal neutral adaptation light is
switched on, after an initial 10-min period of nearly
constant temperature, the prism housing temperature in-
creases by about 12C, reaching its final temperature of
approximately 36.4C after about 90 min (Fig. 3B). Be-
cause the maximum temperature also depends on the
ambient room temperature, it may reach even higher
values. These data clearly show that the major source of
prism temperature variation is thermal variation (warm-up
effects) of the neutral adaptation light.
The temperature-dependent changes have two poten-
tial consequences for Rayleigh matches. First, the position
and width of the entrance slits defining the red and green
primaries (see Fig. 1) may be altered. Thus, the wave-
lengths of the primaries and the relative proportions of the
green and red primaries in the Rayleigh match may
change. Second, the refractive index of the prism and thus
the wavelengths of the green and red primaries may be
altered. As expected, our data (Fig. 4) show a shift of the
peak wavelength with increasing temperature from
549.7 nm and 667.0 nm, for the green and red primaries,
respectively, at 25.3C to 550.6 nm and 668.6 nm at
39.3C. These spectral shifts of 0.9 nm for the green and
1.6 nm for the red primary are clearly visible to both
normals and anomalous trichromats.
Rayleigh matches
Voltage data
As a result of the changes in the retinal illuminances of
the three primaries, the R-G match midpoints of all three
normal trichromats show a shift with increasing mains
voltage to higher R-G settings (i.e. requiring less green
and more of the red primary, see Fig. 5). Cavonius [2]
showed similar results obtained from two normal tri-
chromats and assumed a nearly linear dependency at
higher main voltage. We find, however, an approximately
exponential rise within the range from 190 V to 250 V.
From our data, we estimate the match midpoint of normal
trichromats to vary between 45 and 48 with a change of
the mains voltage from 190 V to 250 V. At the given
temperature of 36C, all values for the match midpoints
within this mains voltage range are higher than those
permitted by the DIN 6160 (36.5–43.8 units).
Temperature data
Figure 6 reveals, for two normal trichromats, three deu-
teranomalous and three protanomalous observers, how
R-G mixture settings on a Nagel Model I anomaloscope
vary with prism housing temperature. For each subject, a
series of matches were obtained within temperature ran-
ges centered at approximately 18C, 25C and 36C. Only
Fig. 3 Time-course of the change in room and prism housing
temperature, with the internal neutral adaptation light turned off (A)
or on (B)
Fig. 4 Dependency of the centroid wavelengths of the red and
green primaries upon the prism housing temperature. The wave-
length of the green primary shifts ca. 0.6 nm to longer wavelengths
per 10C temperature difference; that of the red primary, ca. 1.0 nm
the Rayleigh match determinations made at the two lower
temperatures by normal observers fall within the accepted
DIN 6160 ranges.
In the case of the anomalous trichromats, the width of
the matching range could be roughly estimated (see Ta-
ble 1). For all six, only a small range variation, between
ca. 1.5 and 3.0 Nagel units, was found, which did not
significantly change between low (18C) and high (36C)
temperature. (For the deuteranomalous subjects at 25C,
no range could be estimated because only a few matches
were obtained.) The anomalous quotients (AQ) have been
calculated using the average match midpoint of the nor-
mal trichromats obtained at the center of the given tem-
perature ranges. Based on these instrument- and temper-
ature-specific match midpoints, only small changes of the
AQ are observed for the three temperature ranges. How-
ever, usually the AQ is calculated using a fixed normal
match midpoint of 40 Nagel units, as suggested by
Zrenner [14]. If this is done, a significantly larger shift of
the anomalous quotient (AQ40) is found. For deutera-
nomalous observers, the AQ worsens (i.e., shifts away
from the normal value) with lower temperature; whereas
for the protanomalous observers, it improves (i.e., shifts
towards the normal value).
Fig. 5 The variation in R-G match midpoints for three normal
trichromats with increasing mains voltage. The solid lines represent
the best-fitting function (exponential rise to maximum) to the in-
dividual data
Fig. 6 Rayleigh-matches of two normal, three deuteranomalous
and three protanomalous observers on a Nagel anomaloscope as a
function of prism housing temperature. The continuous and dashed
curves represent the best-fitting linear regressions. The anomalous
quotient shown is based upon a normal match midpoint of 44
corresponding to a temperature of approximately 25C
Table 1 Rayleigh-matches of normal and anomalous trichromats
made at prism housing temperatures of the Nagel Model I anom-
aloscope within one of three ranges centered at 18C, 25C and
36C. Listed are the match midpoints (MMPs), ranges and anom-
alous quotients (AQs) calculated for each subject based on a normal
MMP estimated from the average normal matches at each tem-
perature. For comparison, the anomalous quotient for the highest
temperature range (36C), calculated for a normal MMP of 40, is
given as AQ40
Subject Eye Nagel 18C Nagel 25C Nagel 36C
MMP Range AQ MMP Range AQ MMP Range AQ AQ40
MB OD 41.20 0.5 0.99 44.40 0.5 1.02 46.43 1.0 1.04 0.69
JA OS 40.83 0.5 1.01 45.21 1.0 0.98 47.60 0.8 0.97 0.65
TT OD 63.25 1.5 0.16 63.75 1.5 0.20 67.00 2.0 0.13 0.09
TZ OS 62.75 2.5 0.16 64.75 1.5 0.17 67.25 2.5 0.10 0.07
MP OD 58.50 2.0 0.28 63.00 2.0 0.22 65.00 2.0 0.19 0.13
RS OD 24.00 3.0 2.79 27.50 2.71 29.75 2.5 2.91 1.95
AS OD 22.75 2.5 2.97 26.50 2.87 30.50 3.0 2.75 1.84
SJ OS 23.75 2.5 2.79 27.75 2.71 33.00 3.0 2.32 1.55
We find a significant shift in Rayleigh match midpoints in
normal and anomalous trichromats with mains voltage as
well as with prism housing temperature, which should
be taken into account when establishing normal match
midpoints and determining anomalous quotients for red-
green color blind observers.
Main sources of voltage fluctuations in modern envi-
ronments are elevators and generators connected to the
same circuit. In regions with heavy industry or far from
the energy source, the average voltage may be smaller
than in our laboratory, in which a mains voltage range of
221 to 237 Volt was measured. However, even the small
voltage changes measured in our laboratory result in in-
tensity changes in the Nagel primaries that are clearly
visible to a sensitive observer and correspond to a shift of
ca. 0.5 Nagel units. These shortcomings could easily be
avoided by using a stabilized power supply.
Furthermore our results show a correlation between the
R–G mixture required to match the yellow primary and
the prism housing temperature. The shift is towards the
red primary (i.e., higher values) with increasing temper-
ature and is estimated as ca. 0.5 Nagel units per degree
Celsius. The total shift may be up to 10 Nagel units with
significant seasonal variations in room and instrumental
temperature. In terms of Nagel units, compared with a
normal match midpoint of 40, deuteranomalous observers
improve (i.e., shift towards the normal value) with higher
temperature; whereas protanomalous observers worsen
(i.e., shift away from the normal value).
Our data also indicate that the original recommenda-
tion of Trendelenburg [13] to use a anomalous quotient to
reduce variability between instruments is still satisfactory
from a clinical point of view. However, the unavoidable
temperature-dependent shifts make it impossible to have
normative data of the match midpoint available for all the
temperatures within the possible range of prism housing
temperature. Additionally, the temperature reached after
ca. 90 min (steady state) will also vary significantly with
ambient room temperature from the lowest value in
winter (ca. 18–20C) to the highest value in summer (ca.
36–40C), in rooms that are not climate controlled. The
prism housing temperature will be far less variable if the
built-in neutral adaptation light is switched off and a
separate light source is used for neutral adaptation.
Although changes in wavelength and intensity of the
primaries are mainly responsible for the shift of the match
midpoints, other physiological factors may contribute as
well. A reduction of the retinal illumination of the stim-
ulus, in addition to direct voltage and prism temperature
related changes, may affect the optical density of the cone
pigments and the R–G mixture required to match the
yellow primary. The size of such effects may vary among
subjects and may be genetically influenced [12].
Given the dependency of the Rayleigh match upon
prism temperature and mains voltage, it will have to be
determined in further studies whether the strict limits for
anomalous quotients set by regulatory authorities are fair,
consistent and reliable when using the Nagel Model I and
other mechano-optical anomaloscopes.
The severity of congenital red-green color-vision defects
is routinely determined using Rayleigh matches on tradi-
tional mechano-optical anomaloscopes. The most widely
used instrument is the Nagel Model I anomaloscope. The
matches obtained with this instrument are sensitive to
changes in voltage supply and prism housing temperature,
arising largely from thermal effects produced by the in-
ternal light sources. Additionally, these instruments were
originally designed for a voltage of 220 V and have not
been modified, even though the standard voltage in Ger-
many and Europe has been 230 V since 1983. While this
small voltage change results in a shift of the match mid-
point of normal subjects by ca. 1 Nagel unit, a difference
in prism housing temperature of 20C—as occurs under
the usual conditions of clinical investigations—results in a
shift of the match midpoint by ca. 10 Nagel units in the
direction of the red primary. Modern electronic anoma-
loscopes, which are not yet as widely used as the Nagel
Model I anomaloscope, overcome these problems by using
stabilized power supplies and color LEDs as sources for
the three primaries.
Its shortcomings notwithstanding, the Nagel Model I
anomaloscope may still be safely used for diagnostic and
research purposes, especially those involving the deter-
mination of the AQ in anomalous trichromats, provided
that: (1) a stable voltage supply is used (a modern UPS for
a single personal computer may be sufficient); (2) the
instrument is kept at a constant temperature (e.g., the
power is turned on at least 60 min prior to an investiga-
tion); and (3) the match midpoint of the reference popu-
lation has been established under identical conditions.
However, it will not fail to diagnose inherited red-green
color-vision defects when operated at any of the tem-
peratures or mains voltages within the ranges investigated
in this study. Nevertheless, special care has to be taken if
an expert opinion about the eligibility of a patient’s color
vision for certain occupations (including driver’s and pi-
lot’s licenses) is based on Rayleigh matches obtained with
such anomaloscopes.
Acknowledgements This work was supported by a grant from the
Deutsche Forschungsgemeinschaft SFB 430/A6 awarded to Herbert
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... The Nagel Model I has some temperature-dependent wavelength characteristics [7,[40][41][42], and this 4 • C range would result in a change of 0.26 nm in the green and 0.46 nm in the red (calculated from [42] in which wavelength data are not reported for the yellow). It has been suggested [42] that temperature issues are overcome in the instruments using stabilized supplies and LEDs. ...
... The Nagel Model I has some temperature-dependent wavelength characteristics [7,[40][41][42], and this 4 • C range would result in a change of 0.26 nm in the green and 0.46 nm in the red (calculated from [42] in which wavelength data are not reported for the yellow). It has been suggested [42] that temperature issues are overcome in the instruments using stabilized supplies and LEDs. ...
... The Nagel Model I has some temperature-dependent wavelength characteristics [7,[40][41][42], and this 4 • C range would result in a change of 0.26 nm in the green and 0.46 nm in the red (calculated from [42] in which wavelength data are not reported for the yellow). It has been suggested [42] that temperature issues are overcome in the instruments using stabilized supplies and LEDs. However, the peak wavelengths of LEDs are certainly temperature-dependent [24,25], but this is a function of junction temperature, which is current-dependent rather than directly ambient temperature. ...
DIN 6160:2019 is a technical standard that sets requirements for Rayleigh equation anomaloscopes. Table 1 of the standard contains the limits for centroid wavelengths and spectral half power bandwidths (SHBW). The centroid limits are more restrictive than dominant wavelength recommendations. The SHBW limits have no known evidence base and are inconsistent between colors. The spectral characteristics of three commercial anomaloscopes brands were measured using a telespectroradiometer. Only the oculus instruments complied with DIN 6160 Table 1, but all the anomaloscopes complied with published recommendations. All complied with the DIN 6160 bandwidth requirements. This highlights the need to provide an evidence base for such requirements.
... The tests available nowadays can be divided into screening (including Ishihara [1], HRR Pseudo Isochromatic Plates [2]) and diagnostic methods (such as Farnsworth 100 HueColor Vision Test or the anomaloscope [3,4]). The general idea of the Anomaloscope is a comparison (matching) of two illuminated fields based on hue, saturation, and brightness [5]. ...
... This, in turn, could suggest a decrease in sensitivity to red color. The above observations were later confirmed by Jordan & Mollon [9] and Jagle et al. [5] who proved that voltage fluctuations in the power grid could significantly affect the intensity of the light emitted by the lamp and, as a consequence, affect the test results. In order to eliminate the measurement errors resulting from anomaloscope's inaccuracy, Kintz designed a device with HP diodes used as light sources [8]. ...
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Aim: To validate the reference ranges proposed by the manufacturer of the Oculus HMC Anomaloscope MR for Rayleigh and Moreland tests in healthy young adults. Method: The manual Rayleigh (red-green) and the Moreland (blue-green) anomaloscope tests were performed on 90 healthy subjects (54 female, 36 male, 178 eyes) residing in Poland, aged between 18-45 years, and without color vision disorders (assessed with HRR test). The analyzed parameters for both the Rayleigh and the Moreland tests were as follows: the lower (R1/M1) and the upper (R2/M2) limits; the center (RC/MC) and the width (RW/MW) of the matching ranges. Results: The results of the Rayleigh test were similar to the values proposed in the anomaloscope user's manual, however, with a small shift of RC and R2 towards the red color. The double-peak distribution of R2 with a small second peak (approximately at R2 = 52) was mainly due to the measurements in male subjects (nmale = 8, nfemale = 2), which suggests that this group might be diagnosed with subtle protanomaly. The results of the Moreland test showed a high MW which did not correspond to the reference range described in the anomaloscope user's manual. The observed significant correlations between R1 and M1 suggest that the M1 parameter seems to be the best indicator of blue vision quality. Conclusions: Oculus HMC Anomaloscope MR is a sensitive tool for detection of prot-deuteranomalies but the reference ranges for young adults require a certain adjustment towards the red color. The parameters obtained for the Moreland test varied significantly between the subjects and therefore the test should not be used as is to diagnose color vision deficits in the green-blue area (tritanomaly).
... 4 It has been regarded as the gold standard, and widely used as the standard of comparison to other colour vision tests. [60][61][62] One study, which used the Nagel anomaloscope, demonstrated 100% sensitivity and specificity. 63 However, the device is not readily available in all ASEAN countries, 11 and is expensive and technically difficult to operate. ...
... Amongst the wide range of color vision tests, there lacks existing evidence to support which test is the most accurate and practical. Despite the anomaloscope's high sensitivity and specificity [4], often regarded as the gold standard [20,28,41], it is expensive and technically challenging to use hence limiting its feasibility for routine use. On the other hand, commonly used tests like the Ishihara pseudoisochromatic test have been reported to have poor correlation with the type and severity of color vision deficiency [3,33]. ...
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Color vision deficiency impairs one’s ability to perceive and discriminate colors. Color-deficient individuals may face discrimination in various occupations, particularly in medical school admissions. This discussion seeks to compare the existing color vision requirements for entry to medical school in Southeast Asian countries as compared to countries across the world. Following this, we explore the published evidence in this field, to provide recommendations for future guidelines that will maximize the occupational opportunities for color-deficient individuals.
... Αυτά τα τεστ, όμως, δεν είναι ικανά να διαχωρίσουν τα άτομα με δυσχρωματοψία από τα πάσχοντα από αχρωματοψία. Ένα φασματικό ανωμαλοσκόπιο, όπως το "Nagel Anomaloscope", είναι το «χρυσό» στάνταρ της εξέτασης εντοπισμού της αχρωματοψίας κόκκινου/πράσινου (Jägle et al., 2005). Κατ' αυτόν τον τρόπο θα πρέπει να συγκρίνονται τα αποτελέσματα των άλλων δοκιμασιών με αυτά του ανωμαλοσκοπίου (Εικόνα 3.19). ...
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Optometry is an autonomous profession in the field of health, which requires special training and is governed by specific rules. The science of Optometry includes a number of special techniques for diagnosing and investigating optometric problems. Visual acuity is the measurement of the ability to distinguish two stimuli, which are separated in space, in high contrast compared to the background. Visual acuity is a measure of a person's ability to analyze minimal details. The recording of visual acuity is used to evaluate the adequacy of corrective glasses but also as a general indicator of eye health and good vision. Visual acuity is also used to assess whether or not a person is capable of driving a vehicle or hired for certain professions. Sensitivity of light contrast is a psychophysical examination of the quality of vision. It is based on the change of the spatial frequency of the fixed targets, either by the projection of stimuli of gradual damping of its intensity, or by the formation of a periodic increase and decrease of it (as in gratings), which usually differ only in spatial frequency Emmetropia is the ideal refractive effect in which the distal point of clear vision is at infinity, of the eye to form a clear image at different distances. This is achieved by the "mechanism" of adjustment. As a normal part of the aging process, the lens becomes less elastic with age, due to the hardening of the lens fibers and capsular changes. The provision of eye health services requires excellent record keeping and data collection. This is because comprehensive record keeping ensures the continuity of eye care, meets medical and legal requirements and highlights professionalism.
... Rather, it is more convenient to use different tests. Moreover, Davidoff et al. conclude that genetic tests correlate well with the anomaloscope test [26], and Jagle et al. estate that the anomaloscope is suitable for distinguishing protan from deutan and dichromats from trichromats [27]. In our case, we performed these three tests, which agreed in the resulting diagnosis for all observers. ...
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There is a belief that observers with color vision deficiencies (CVD) perform better in detecting camouflaged objects than normal observers. Some studies have concluded contradictory findings when studying the performance of normal and CVD observers in the camouflage detection tasks in different conditions. This work presents a literature review on this topic, dividing it into three different and contradictory types of results: better performance for CVD, for normal observers, or same performance. Besides, two psychophysical experiments have been designed and carried out in a calibrated computer monitor on both normal and CVD human observers to measure the searching times of the different types of observers needed to find camouflaged stimuli in two different types of stimuli. Results show the trend that, in our experimental conditions, normal observers need shorter searching times than CVD observers in finding camouflaged stimuli both in images of natural scenes and in images with synthetic stimuli.
Difference scaling experiment was conducted to investigate the mental color representation of congenital color-deficient observers and observers with normal color vision. Two decks of cards, high and medium chroma, each containing 10 Munsell chips, were prepared. A total of 45 pairs of hues were prepared for each of the decks. Ten protans, 10 deutans, and 10 people with normal color vision participated as observers, with each asked to rate the perceptual distance between two colors on a given color card. The results were analyzed using the multidimensional scaling method. All observers with normal color vision showed a circular shape close to the Munsell hue circle, while the majority of color-deficient observers showed a concave shape bending at Y and PB. To indicate the degree of distortion from a circle, the distortion index was proposed to quantitatively evaluate intergroup and individual differences. To investigate the underlying mechanism of intergroup differences as well as individual differences in color representations of observers with normal color vision and color-deficient observers, we proposed a model that considers various levels of human color vision mechanism from the cone pigment absorption, the luminance and opponent-color coding level, and nonlinear transformation to difference-scaling judgment. The circular shape for observers with normal color vision and some color-deficient observers, as well as concave shapes for most color-deficient observers were estimated. The correlation coefficient between the estimation and experiment-based difference ranged from r = 0.64 to r = 0.94 with the grand average of r = 0.82, with p-values less than 0.001 for all observers, suggesting that the concept of proposed model is appropriate.
The main purpose of this study was to produce reliable, color assessment outcomes to examine the extent to which single and multi‐test protocols in use meet current clinical and occupational needs. The latter include the detection of small changes in chromatic sensitivity as the earliest signs of retinal and/or systemic disease, and the need to assess the class of color vision in congenital deficiency and to quantify severity of loss. Color vision was assessed using Ishihara (IH), Farnsworth Munsell D‐15, City University (CU, 2nd ed.) and Holmes‐Wright type A (HW‐A) lantern tests. All subjects also carried out Colour Assessment and Diagnosis and Nagel anomaloscope tests. The sample included 350 normal trichromats, 1012 deutans and 465 protans (age 31.1 ± 12.4, range 10‐65 years). The results reveal the trade‐off between sensitivity and specificity, depending on the number of errors accepted as a pass on the IH test. The D‐15 and CU tests pass all normals and almost 50% of subjects with color vision deficiency. The HW‐A lantern passes all normals, 22% of deutans and 1% of protans. The multi‐test protocols designed to identify protans and to pass only subjects with mild color loss, pass over 50% of protans and deutans. Many of the subjects who fail exhibit less severe loss of color vision than others who pass. When high sensitivity for detection of congenital deficiency is achieved, single‐test protocols fail many normal trichromats. Multi‐test protocols produce large variability and fail to achieve desired aims.
The Farnsworth D‐15 test (D‐15) is commonly used to screen for moderate to severe congenital color vision deficiency. The aim of this study was to establish reliable D‐15 statistics for normal, deutan and protan subjects, and to investigate the different visual signals one can use to carry out the test, even in dichromats and rod monochromats. Six hundred and seventy‐four subjects were examined using the D‐15, the Colour Assessment and Diagnosis test and the Nagel anomaloscope. A rod monochromat and five dichromats were tested using the standard D‐15 protocol before the caps were separated into two groups and subjects were asked to repeat the task. D‐15 spectral radiance data, measured under D65 illumination, were used to estimate differences in photoreceptor excitations for each of the caps. When no crossings and up to two adjacent transpositions on the D‐15 results diagram are accepted as a pass, 100% of normal trichromats, 54% of deutans and 43% of protans pass the D‐15. A rod monochromat and two protanopes and deuteranopes were able to complete the D‐15 when the caps were separated into two groups, despite severe loss or even complete absence of color vision. When up to two adjacent transpositions are accepted 50% of color deficient subjects, some with severe red/green loss, pass the D‐15. While the D‐15 is normally used to screen for moderate to severe color deficiency, subjects with severe loss can still use combined, residual red/green, yellow/blue and luminance signals to pass.
Purpose to evaluate the validity, reproducibility and feasibility of the “COLOUR VISION EVALUATION TEST” (CVET) for the diagnosis of congenital dyschromatopsia. Design prospective, monocentric, sensitivity and specificity analysis study comparing the CVET to the Farnsworth 15 Hue standard test (15 Hue STF). Methods 155 children from the Paediatric University Hospital of Nice were screened (both eyes) using the Ishihara’s pseudoisochromatic cards, which allowed dividing them into a dyschromatic group and a control group. All children underwent twice the 15 Hue STF and the CVET with at least seven days between both series of tests. Results patient’s mean age was 7.56 ± 3.51 years in the dyschromatic group, and 8.92 ± 2.9 years in the control group. At the first evaluation, the sensitivity and specificity were 95.7% and 96.4%, respectively for the CVET and 75% and 58.9%, respectively for the 15 Hue STF (p <0.001). The reproducibility of the CVET was 100% while that of the 15 Hue STF was 88.4% (p=0.01). The mean test explanation duration was 18.8 seconds for the CVET and 17.7 seconds for the 15 Hue STF (p=0.3). In the dyschromatic group, the mean duration of the CVET was always significantly longer than that of the 15 Hue STF (p <0.001). The children subjectively preferred to undergo the CVET rather than the 15 Hue STF in 84.6% of cases (p <0.001). Conclusions the CVET is a rapid, reliable and reproducible test for the diagnosis of congenital dyschromatopsia. It is accessible to young children.
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In 1948 the German physicist, Manfred Richter, reported that colour vision has a seasonal variation. For four colour-normal subjects, he found a sinusoidal variation in the proportion of red and green required to match a monochromatic yellow, the equation known as the 'Rayleigh match'. In summer, subjects required more red in their mixture. The measurements were made with the Nagel anomaloscope, an instrument introduced in 1907 and which today, essentially unchanged, remains the definitive clinical instrument for classifying the many phenotypic variations in colour vision. The variation that Richter recorded in the red-green ratio was large (three Nagel units), and it now takes on fresh interest because it is comparable in size to the difference in Nagel settings later reported between normal observers of different genetic types. We have been able to replicate Richter's result, but report here that it is almost certainly instrumental: the Nagel anomaloscope proves to be very sensitive to ambient temperature.
While it has long been known that Nagel anomaloscope matches are influenced by the mains voltage (e.g. Schmidt, 1955) there seem to be no reports of the magnitude of this effect. Because of a recent increase in the nominal mains voltage in Germany from 220 to 230 volts, with a permitted range of 207 to 253 volts in the future, it seemed prudent to see whether this could influence routine tests of color vision. Between 190 and 250 volts a normal trichromat’s R-G settings increase by approximately 0.05 Nagel units/volt, in a highly linear manner (r2 = 0.98). Thus, a 10-volt increase will raise the R-G setting by ≈ 0.5; and a change from 207 to 253 volts corresponds to just over two R-G units. The accompanying change in the brightness setting (-0.0056 units/volt) is trivial. While it is unlikely that these variations would lead to a clinical misdiagnosis, they could result in an artifactual bimodality in Nagel settings when comparing populations, especially if different populations are tested at different sites.
The colour matches obtained with the Nagel Anomaloscope by 127 consecutive, unrelated, male anomalous trichromats are reviewed. One hundred subjects were deuteranomalous trichromats, twenty were protanomalous trichromats and seven were extreme anomalous trichromats having combined protan and deutan characteristics. Although some subjects have identical matching ranges in each of these three categories, the data show a continuous range of severity rather than discrete subgroups. The matching ranges of deuteranomalous observers are more clearly separated from the normal matching range than those of protanomalous observers. The Nagel anomaloscope is the standard reference test for red-green colour deficiency and new colour vision theories derived from molecular genetics must be able to explain the individual variations demonstrated by the test.
It has been accepted that defective colour vision is an occupational handicap since Wilson observed the high prevalence of defective colour vision among his students and wrote, in 1855, about the dangers ‘attending the present system of railway and marine coloured signals’. Standards for colour vision were introduced for the maritime and railroad transport in the 1870s and for aviation in 1919. Colour vision standards for drivers of motor vehicles have not been widely adopted and never effectively, and there is no accepted system of standards for that wide gamut of occupations that involve colour recognition, colour discrimination or aesthetic judgment of colour. The recent emergence of the concept of equal employment opportunity to prevent unjustified exclusion of the handicapped from employment and the advocacy of an articulate group of people with defective colour vision who do not wish to be excluded from their choice of occupation has weakened some existing standards. Yet there is an impressive body of evidence to show that colour figures importantly in many occupations and that some of those with defective colour vision will perform less effectively in those occupations because of their defect. There is also evidence that those with defective colour vision have a range of difficulties in everyday life, although this has been studied surprisingly little in the last 125 years. There are accident data to suggest that defective colour vision is a risk factor, but accident data are always uncertain and in weighing up the extent to which defective colour vision is a risk factor more credence has been given to the uncertainty of the data than to the indications of risk. There is a need for better definition of colour vision standards and of test protocols and for international advocacy and acceptance of the standards. A schema of colour vision standards and test procedures is proposed.
By testing individuals as well as a group seasonal oscillations of the Anomaloscope's mixing screw regulation could be observed. For that reason further standardization of research methods is requested.
The report concerns a discussion of some methodological and statistical problems in testing color vision with the Nagel anomaloscope and an evaluation of records compiled during a period of four and a half years’ research work at the U. S. Air Force School of Aviation Medicine, Randolph Field, Texas. Following topics are dealt with: elimination of training effects and determination of the total number of readings required to detect specified minimum practical differences between individuals; application and frequency distribution of the anomalous quotient; determination of the normal matching range of mixtures and of comparison yellow; and test-retest reliability of the Nagel anomaloscope.
Vom gegenw�rtigen Stand der Farbenlehre
  • M Richter
  • Richter
Richter M (1948) Vom gegenwärtigen Stand der Farbenlehre. Z Wiss Photogr 43:209-237