There are tons of products on the market. The range is 660-670nm. It's promoted for all kinds of therapy. Basically the theory is that it boosts mitochondrial repair and power, reverses aging, etc.
Study participants over 40 saw dramatic (> 20%) improvement in color differentiation, and even bigger improvements in low light discrimination.
I'm keenly interested in this, need to figure out what intensity is safe for viewing, or else find a white wall to bounce a higher-powered light off of.