My buddy brought over his HK VP9 with a rail mounted flashlight/laser complaining that he couldn't see the green dot laser. He changed batteries - no improvement. He has the same light/laser combo on his HK 45C--green laser is bright and focused.
Q tips came out, sprayed with some brake cleaner. Slight improvement--still pretty dim. Plastic dental pick, then repeat Q tip n brake cleaner with significant improvement.
I didn't believe how much carbon/gunk deposited in that laser.

I'd be careful with the brake cleaner....I'm not sure what the lens on those is made of, but brake cleaner can do nasty things to plastic, and could permanently fog the lens. Isopropyl alcohol is good. If there's junk down in the recesses, I'd probably try and carefully loosten it with your plastic pick or wooden toothpick then hit it with high pressure compressed air to blow out the chunks, then more alcohol....repeat until clean.

Crimson Trace states the lens is glass. Also recommends isopropyl alcohol.
Brake Cleaner = Degreaser but much cheaper.
I was surprised at how much gunk was there.

Ah cool, you're probably fine then. It's amazing how much crud can build up over years of carry.