Zero power Check the lens of the sunglasses for its quality and make sure it is zero-powered. “When you look through it, the image that you see on the other side of the lens should not move or change like a blur when you move the glasses up and down or sideways,” says Dr Mahipal Sachdev, Opthalmologist, Centre for Sight, Delhi. Glass or plastic? “There is no difference between glass or plastic lenses, both work fine,” says Dr Sachdev. For children, it is advisable to wear plastic glasses