b/ Differentiate between protan and deutan
Two tests are needed; one test identifies redgreen deficiency and classifies protan and deutan
deficiency, while the second test is used to estimate the severity and identify significant tritan deficiency.
03% efficiency trichromat Varies individually: slight, moderate or severe deficiency Deutan
Deuteranopia Severe 1% 0.
d Diagnostic plates can distinguish between protan defects and deutan
The test identifies protan, deutan
and tritan defects (the last of which cannot be detected by the Ishihara test), and has the added advantage of allowing the parent to understand what colour confusions the child experiences.
It is well established that retinal conditions, such as in diabetes and various macular conditions, may cause confusions between blue and other stimuli as well as protan and deutan
b) It can detect protan, deutan
and tritan colour vision defects
When a full colour discrimination ellipse is not required, thresholds along the protan, deutan
and tritan confusion lines will be of interest.
The design of these plates relies on selecting colours of the background and the figure from the protan and deutan
confusion zones (Figure 2).
Terms protan, deutan
and tritan refer to a colour vision deficiency in which the L-, M- and S-cone pigments, respectively, are affected.
Protans who obtained R/G CAD thresholds less than 12 SN (standard normal) units and deutans
that obtained thresholds less than 6 SN units were able to perform the PAPI test as normal and could safely begin pilot training (see Figure 3).
More protans than deutans
tended to report the difficulties.