I have been asked to give an overview of professional tint prescribing.
It is an extremely complex subject even if to the uneducated it appears simple.
To prescribe a tint accurately it is essential that you first ascertain the envelope within colour space within which the patients visual system responds optimally. To achieve this we use instrumentation which (as far as possible) separates cone cell pathways. Tolerance levels can be ascertained and from this we determine the absolute optimal luminosity, hue and saturation. However, this is not sufficient to determine the best filter. Ambient lighting has to be factored in and added to the equation (convolving for metamerism). In addition we may wish to add specialist needs in prescribing, such as blue free etc. McAdams Ellipses may also be taken into account to further determine tolerances. From this the optimum filter can be prescribed for particular situations as well as "average" best.

Now this would be unimportant if the visual stimulus has no effect. The evidence is becoming overwhelming that not only do tinted lenses have a potential for great positive effects, they also have potential for great negative effects! Therefore it is essential that any optical professional understands tint prescribing, does not rely on their own experience as it will invariably be inadequate, understand that suck it and see is frankly poor, and as for trying to use overlays etc!

Tinted lenses are extremely powerful weapons in the hands of a professional. They affect virtually every element of optometry and many in medicine in measurable ways. Research in the UK is still mainly unpublished as it the techniques are so new, but some papers have been published, and others are in the pipeline. But unless you are able to prescribe them accurately and understand the potential effects then it is impossible to understand the importance of accurate prescribing.

Stimulus modification is both an exciting area, a tremendous opportunity or threat. Ignorance is not an option for a professional.