It's been a while since I did a tech tip, so her's one for ya.
Did you know that if you get a scratch in a plastic lense, even if deep that it can usually be wet sanded out and then buffed back to a shine?.
Plastic buffs like butter. That means that it is really easy to buff out.
If you have a scratched lense, sand it out. Don't sand any area you won't be able to access with the buffer, or you'll have permanent sanding marks there.
Start with a coarse paper, and work your way down to a really fine grit. Then simply buff it up to a nice shine. a fine grit, to polish compound is all you need. If you have no rubbing compound, and don't want to buy any, toothpaste with baking soda will work in a pinch because plastic is so soft, that is all it will take! Oh yeah, and if you don't have rubbing compound, I'm gonna take a stab in the dark and assume you have no buffer either. Elbo grease will work here just fine.
This works, I promise. Over the years back in the body shop days, and even currently, I've saved thousands of dollars doing this on really expensive plastic headlamp lenses etc.
If you have a scratched lense, don't be afraid to try this.
You have nothing to loose!