The costa del mar sunglasses are usually expensive. You'd better protect it well. The easy way to clean it is using the clean cloth and the water. Just use the water to wash the sunglasses lenses and then use the clean cloth to dry it. After cleaning it, you'd better put it in the sunglasses case to avoid the dust.
you needn't so careful to your costa del mar sunglasses. In fact, It is the same way as you clean other sunglasses or regular eyeglasses. First, you need to wet the sunglasses and then use your sunglasses cloth to wipe the lenses. If you need some detergent, you can also take some mild soap to help you clean the sunglasses. It won't cause scratches as long as you don't touch it with hard objects.