Optical lenses for the Moray dive mask may be use for near-sighted (-diopters) and far-sighted (+diopters) for diving or snorkeling. Lenses are available from -1.0 to -7.0 and from +1.0 to +4.0 in 0.5 increments. They are not your exact eye prescription, but are very close and will work very well for most people. Consult your eye physician for an estimate on the lenses that would be best suited for you.