The glasses mentioned in passing here really do seem to be effective for some people so they're well worth investigating if the price is manageable.

To quote an acquaintance who started using them a year or two back: "... it's like seeing an electric sign turned off (colorblind) VS turned on (with my glasses)" and from recent posts on Facebook he's clearly getting a huge amount of value from them.

My understanding of the mechanism is that they suppress the wavelengths that the other receptors are strong in so that the weaker receptors have more of an influence. Presumably they therefore can't help true dichromats.

Doubtless others here know and can explain more.