Inside of E92/335i headlight oxidized?

Just wondering how those of us with oxidizing on the inner portion of our headlights clean that? Is it recommended to just get new lenses? Mine have an "O" from the halo ring almost burned into them and you can kinda see it from certain angles.. Replacement lenses are like $149 so I'd like to see what others have done first before I fork over $149 bucks.. The reason I assume it's the inside portion of the headlight is because the outside is super smooth and doesn't really seem affected.. I'll put pics later..



Thanks!