Farnsworth D-15 dichotomous test is a colour blindness test, is a quick and convenient test for routine clinical use to differentiate between protan (Figure 4), deutan
(Figure 5) and tritan (Figure 6) colour vision deficiencies and calculate an approximate severity of colour blindness.
b/ Differentiate between protan and deutan
Protan and Deutan
defects were not revealed by any diabetic patient.
However, errors were frequent, and very specific, when the filter was used: No protan or deutan
errors were made in response to Ishihara and CUCVT.
TABLE 1: Color Vision Deficient Groups Extent Selection Criteria Deutan
Protan Mild anomalous Pass Farnsworth lantern, pass 5 5 trichromats Farnsworth-Munsell Panel D-15 Moderate anomalous Fail Farnsworth lantern, pass 5 5 trichromats Farnsworth-Munsell Panel D-15 Strong anomalous Fail Farnsworth-Munsell Panel 5 5 trichromats D-15 (but not dichromats or extreme anomalous trichromats (a)) Dichromats Match whole red-green range on 10 9 Nagel anomaloscope even after adaptation on Trendelenberg plate Note.
The diagnosis as deutan
, rather than protan ("red blind"), was confirmed with the Farnsworth D15 test and the Medmont C100 test.
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