Comfort – Fit
A critical element when fitting sunglasses is the elimination or reduction of sunlight (ultraviolet A & B rays) entering the eye from the top of the sunglasses frame or from the sides. With everyone’s face configuration unique, finding a lens shape that provides thorough “eye” coverage is very important. A lens’s “base curve” is the amount of curvature of the front of the lens. You’ve noticed that to fit the curved lens into the sunglasses frame, the frame has far more aggressive curvature than do reading glasses. Higher base curves mean the lenses are more curved, wrapping around the face to provide coverage to the eyes. Reading glasses provide a base curve of zero, while a standard sunglasses provides an 8 based curve.
Sunglasses frames come in a variety of widths. A frame that is too wide will allow ambient light to enter from the side and top. Conversely, a frame too snug will be uncomfortable during extended wear. Most individuals prefer a lighter weight and feel when wearing sunglasses, typically weight is determined by the lens material, lens thickness and frame material