I have developed strabisbus, my eyes do not point in quite the same directions...one points down relative to the other. Double vision is the result. This is correctible in glasses with a "prism" correction, basically a wedge that bends the light in one direction. This is usually done by taking the measured amount of correction needed (in my case 6 diopters) and putting half in one lens (3) and half (of the opposite sign) in the other eye...so two corrective lenses are needed. This can be done with ground lenses, or stick-on Fresnel lenses. Has anyone used a prism correction in their dive mask, either ground or with stick-on Fresnel lenses?