The lens and the sled are hidden under a metal cover held in place by a few screws and probably an adhesive grounding strip connected to the case. Once you remove the cover, the lens will be visible - approximately 1/4" in diameter mounted in the center of a spring-loaded mechanism that moves it from the center to the outer edge of the disc.
Very gently brush the lens with a clean cotton swab. You may consider using a bit of isopropyl alcohol to help clean the surface, but it probably isn’t necessary.
Examine the metal rails on which the laser sled travels. You may gently push the sled along the rails to facilitate cleaning. Remove any accumulated debris you find.
Take this opportunity to blow dust and and foreign matter out of the rest of the unit, too. Looking inside the player can be very educational.
If you’re uncomfortable doing this and don’t mind the unit being away for a week, send it to Oppo as jeffstarr suggested. They can also check the laser to ensure it isn’t failing. Ship insured for the replacement value of the unit and carefully document the exact kind of player you’re shipping.
Either way, I hope you get your 93 fixed. It’s a fine machine.