Keeping your bag clean will help maintain their appearance and also technical performance. However, luxury accessories and especially their lenses require careful treatment. Improper care can damage leather, resulting in scratches or haziness, which in turn may cause eyestrain.
Always be sure to keep your sunglasses in a case to prevent damage. The best way to clean your sunglasses is by gently rubbing them with the lens cleaning cloth provided with your frames and a liquid cleaner specifically designed for eyewear lenses, or with a pre-moistened lens towelette. To avoid damage, never clean your bag with paper towels or clothing, which can grind dust and fibers into lenses and leave scratches. Also avoid using household detergents. House hold Glass cleaners especially are highly corrosive and can damage your lenses quickly.
While none of these products will cause immediate damage to your lenses, over time and with repetition, the damage will become visible.