Medmont C-100

A device for the differential diagnosis of Protan and Deutan CVD. It should NOT be used for the diagnosis of CVD, but only used after CVD has already been diagnosed by Pseudoisochromatic Plates.

The C-100 comprises an aperture containing a flickering yellowish light (16 Hz) that is actually made up of alternating red and green LEDs. As the red and green flicker back and forth, the observer will notice a constant color, but a varying brightness. My turning the adjustment wheel, the subject changes the relative brightness of the two LEDs until the flicker is eliminated (or at a minimum), meaning the two lights have the same luminosity for that observer. Because of Protan’s Scoteythrous Vision (reds appear darker), the Protans will see the flicker eliminated when the red LED is brighter, thus identifying them as Protan instead of Deutan.

When the adjustment wheel is centered on red, the subject is protan, green for deutan and yellow for color normal. However, the tool is actually quite bad at separating the color deficient from the color normals. Again, it should only be used for differentiating Protans and Deutans, for which it is almost perfectly accurate (Cole 2007).

This devices succeeded the Medilog OSCAR in 2001, but was discontinued by their Australian makers in 2013. However, units are still consistently available through online marketplaces.

The device has also been useful in detecting Schmidt’s Sign and therefore being able to diagnose a female subject as being a Carrier for CVD.