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Worldwide prevalence of red-green color deficiency
Jennifer Birch
Henry Wellcome Research Laboratories, Department of Optometry and Visual Science,
City University, Northampton Square, London EC1V OHB, UK
(J.Birch@City.ac.uk)
Received September 6, 2011; revised November 8, 2011; accepted November 10, 2011;
posted November 21, 2011 (Doc. ID 154174); published February 16, 2012
Literature that describes the prevalence of inherited red-green color deficiency in different populations is re-
viewed. Large random population surveys show that the prevalence of deficiency in European Caucasians is about
8% in men and about 0.4% in women and between 4% and 6.5% in men of Chinese and Japanese ethnicity.
However, the male: female prevalence ratio is markedly different in Europeans and Asians. Recent surveys suggest
that the prevalence is rising in men of African ethnicity and in geographic areas that have been settled by incoming
migrants. It is proposed that founder events and genetic drift, rather than natural selection, are the cause of these
differences. © 2012 Optical Society of America
OCIS codes: 330.1720, 330.0330, 170.1610, 170.4470.
1. INTRODUCTION
Congenital red-green color vision deficiency is the most com-
mon X-linked inherited abnormality in human populations.
There are two types, protan and deutan, and differences in
severity. Dichromats (protanopes and deuteranopes) have se-
vere deficiency and are able to match all spectral hues using
two color matching variables. Anomalous trichromats (prota-
nomalous and deuteranomalous) form two heterogenic
groups that require three variables but make color matches
that are unacceptable to normal trichromats. Anomalous tri-
chromats may have slight, moderate, or severe deficiency. All
color deficient people see fewer colors in the environment
and some colors that are easily distinguished by people with
normal color vision look the same if there is no perceived lu-
minance contrast. Color confusions are mainly between red,
yellow, and green hues and between blue-greens, greys, and
purples. Dichromats and severe anomalous trichromats con-
fuse fully saturated hues but slight/moderate anomalous tri-
chromats, who form the majority of color deficient people,
only confuse pale or desaturated colors.
A large number of surveys have been made to establish the
prevalence of deficiency in different populations. Published
summaries of all data available prior to 1960 showed that
the male frequency is about 8% in European Caucasians,
5% in Asians, 4% in Africans and less than 2% in indigenous
Americans, Australians, and Polynesians [1,2,3,4,5,6,7] How-
ever individual surveys vary in precision, depending on the
number of people examined and in accuracy due to the effi-
ciency of the screening method. The characteristics of the po-
pulation are not usually taken into consideration. In large
randomly mating populations the prevalence of nonfatal in-
herited abnormalities, such as red-green deficiency, remains
constant from one generation to another (The Hardy–
Weinberg Law). A different prevalence may be found in small
populations that are isolated geographically or by religious
faith because the gene pool is restricted and marriage is be-
tween individuals who share a common ancestor. The gene
pool is also reduced if marriage is limited to near neighbors
with a similar frequency of color deficiency. These popula-
tions are not in Hardy–Weinberg equilibrium and surveys pro-
vide a “snap shot”of the situation at a particular time. A higher
prevalence will be found in later years if migrants, with a high-
er prevalence of deficiency, become fully integrated with the
original population.
A large number of people must be examined to obtain a
precise prevalence figure within narrow confidence limits. If
the estimated prevalence is greater than 5% this can be deter-
mined using standard deviations The standard deviation (sd)
is given by the square root of p×q∕nwhere pis the percen-
tage of affected people found, qis the percentage of people
testing normal, and nis the total number examined. The
95% confidence limit is within 2sd of the figure obtained
(Table 1). These figures show that more than 5000 men must
be examined to obtain a precise estimate of the frequency of
red-green deficiency. The prevalence in women is too small to
be assessed using standard deviations and is compared with
that found for the corresponding male population. It is neces-
sary to know the ratio of different types of red-green defi-
ciency in the male population to do this effectively since
the expression of deficiency in women depends on paired
Xchromosomes that program the same type of deficiency
(protan or deutan).
A large random population is needed to avoid bias. Exam-
ination of all school leavers entering employment or military
service is ideal [8,9]. Data obtained in a single school are not
ideal because a large number of siblings and cousins may be
included. A representative group of color deficient subjects,
that includes protans and deutans with different severities
of deficiency, must be included in the survey in order to obtain
accurate results. A low prevalence will be found if volunteers
are recruited because symptomatic people with severe defi-
ciency will come forward whereas asymptomatic people with
slight deficiency may not. Conversely symptomatic people
with severe deficiency may not volunteer for examination
in Japan because abnormal color vision is considered to be
a social stigma. People with severe deficiency are also likely
to be under represented if data is collected from applicants for
J. Birch Vol. 29, No. 3 / March 2012 / J. Opt. Soc. Am. A 313
1084-7529/12/030313-08$15.00/0 © 2012 Optical Society of America
