I don't know which sun rays your doctor meant. Mine wants me to keep out ultraviolet light she considers damaging like "sunburning" the back of your eyes. Poly-carbonate plastic from which prescription eye glass lenses are typically made is always UV-blocking, clear nor not. I think sunglasses are a personal preference thing. If worn, they should always for eye safety be made of some UV-blocking material because the dark lens opens up the eye to get more light, which would otherwise mean more ultraviolet radiation than wearing no glasses at all. Even cheap dollar store pairs labelled UVA/UVB blocking might do the job.