Fine scratches in your acrylic dome port can be removed using some NOVUS plastic polish, a lens cleaning cloth, and a light hand. Polish contains grit to smooth the surface of the material, so it requires a bit of technique to avoid damaging dome even more. John Brigham shows you exactly how to make things better instead of worse!
Additional Reading
When to Use a Compact 8" Dome Port Underwater
The Right Lens for Every Situation Underwater
A Deeper Look at the Dry Lock (DL) Lens Port System