The above comment is a load of  ??*!

Colour vision defects, a term much prefered to colour blindness, are well
understood. In the retina
there are three types of cone receptors which respond respectively to red
light, green light and blue light.
The work identifying the visual pigments was done in the 1930's by Arnold
Soresby ( I think). Colour vision problems
are related to the lack of these pigments.

Colour vision is classified as Protanopia (red), deutranopia (green),
tritanopia (blue); there are two
other classifications tetratanopia ( which has a disputed existance) and
true monochromatism ( no colour perception), the
latter being very rare see the book by Sachs (?) about the Trioband
islanders for a fuller explanation.

The underlying cause for the lack of visual pigment is either genetic (
typically 10% of all males have a color vision defect),
or acquired due to disease or drug toxicity. Examples of the former may be
diabetes and the latter alcohol or quinine.

The problems of colour vision following on from a cataract operation may be
due to the spectral transmission characteristics of the
implant, also as you get older the media of the eye change their spectral
transmission. If one eye has an implant and the other does not
I have had reported to me differences in the colour response between the two
eyes.

As to whether one eye only can be colour deficient it is assumed to be
bilateral in genetic cases, though I would not be surprised that uniocular
may occur as, if I remember correctly Dalton who first described protanopia
only had it in one eye. And in acquired cases monocular deficiency
could certainly be present.

The only mental strain will be gatti getting his head around such concepts!

Regards

Ian Hodgson - Isle of Man