Bi-focal sunglasses allow you see clearly both near and far without having to remove or change your sunglasses. There are two types of bi-focal sunglasses: sun readers and true bi-focal sunglasses (which have tinted bi-focal lenses).
Sun readers are simply reading glasses with dark-tinted lenses. The majority of the lens in a sun reader does not contain any corrective power. However, there is a small portion at the bottom of the lens, separated by a visible line, that contains a slight magnification power (usually +1.50 to +2.50) for reading.
Bi-focal sunglasses are just like bi-focal glasses, except that the lenses are tinted to shield your eyes from sunlight. The lenses in bi-focal sunglasses contain two different corrective powers, separated by a visible line. Nearly all of the prescription sunglasses you see on FramesDirect.com can be purchased with bi-focal lenses.
If you do not like the appearance of bi-focal sunglass lenses, consider trying progressive sunglass lenses, the no-line bi-focal option.