How often should color vision testing be assessed if the ability to see colors is important in ones occupation?
Most color vision deficiencies are acquired and do not change through our lifetime. For those cases, once is enough to diagnose the presence or absence of a color vision deficiency. If you are interested in color discrimination ability (e.g. some of the information given by the Farnsworth-Munsell 100-Hue Test), then that can change with both age and motivation. I would suggest that doing that exam once every two years or so would be more than adequate. (As a note, I have done the test for more than 20 years and my results have not significantly changed when I am motivated to do the exam carefully.
