Second we need to decide on a Lens Material:
Plastic or CR39
Outstanding optical quality and low cost. Lower index material, thicker and heavier than other materials and not shatter resistant. Recommended Rx range -2D to +2D.
Shatter resistant and impact resistant. Is suitable for sports with children and teens, and certain occupation such as firefighters, police officers, and patients with a weak or lazy eye. Thinner and lighter weight than plastic. Lower optical quality than CR-39, recommend anti glare coating to increase clarity. Recommended range -3D to +3D.
Shatter resistant, suitable for sports and children/lenses. Thinner and lighter weight than plastic. Superior optical quality to polycarbonate, similar to that of CR-39 lenses. Recommended Rx rage -4D to +4D.
The latest lens material that has a lens index of 1.55 and is lightweight, has UV protection, but is not as impact resistant as polycarbonate.
The lightest and thinnest material that is available. It minimizes edge thickness on prescriptions for nearsightedness and keeps magnification of the eye to a minimum with prescriptions for farsightedness.