Uncertainty Visualization and Color Vision Deficiency - Scientific Visualization: Uncertainty, Multifield, Biomedical, and Scalable Visualization - page 28

Reference (2 nm) (8 nm) (14 nm) Protanope

Fig. 2.1 Simulation of the color perception of individuals with CVD. A reference image ( left )
is followed by the simulation of the perceptions of anomalous trichromats (protanomalous) with
various degrees of severity (spectral shifts of 2, 8, and 14 nm). The perception of a protanope is
shown on the right . All images were simulated using the model described in [ 4 ]

(a) (b) (c)

Fig. 2.2 Example image recoloring: a reference image. b Simulated perception of a deuteranope,
using [ 4 ]. c Recolored version of the reference image for deuteranopes, using [ 5 ]. Note the significant
enhancement of color contrast with respect to b . Since the color gamut of deuteranopes is a subset
of the RGB color space, this image is perceived the same way both by deuteranopes and by normal
trichromats. The case of recoloring for other dichromats is similar

2.1.1 Color Vision Deficiency

Human normal color vision requires three kinds of retinal photoreceptors. These
are called L , M , and S cone cells, and have higher sensitivity to the long, medium,
and short wavelengths of the visible spectrum, respectively. The specific type of
photopigment contained in each kind of cone cell determines its spectral response.
Some natural variations in the composition of these photopigments can shift their
spectral sensitivities to different bands of the visible spectrum [ 11 ]. In this case, the
affected individuals are called anomalous trichromats , and can be further classified
as protanomalous , deuteranomalous ,or tritanomalous , if the affected photopigment
is associated with the L, M, or S cones, respectively. The bigger the shift, the more the
individual's color perception will vary with respect to the perception of an individual
with normal color vision ( normal trichromat ). In case one type of photopigment
is missing, the individual is called a dichromat . Likewise, (s)he can be classified as
protanope , deuteranope ,or tritanope , according to the type of missing photopigment
(L, M, or S, respectively). Much rarer conditions include the cases of individuals with
a single kind of photopigment ( cone monochromats ) or no functional cone cells at
all ( rod monochromats ).