Apple

The lenses are sapphire coated and pretty difficult to scratch. I wipe mine with a the tail of my cotton T-Short all of the time and it's fine. You're not going to scratch it so I wouldn't worry about it. That being said it doesn't hurt to get an inexpensive micro fiber cloth or even some inexpensive lense wipes for occasional cleaning. The front screen is softer glass and will pick up small scratches so use a screen protector or at least lenses cleaning wipes or microfiber.