Click to view larger.
When a patient selects their glasses at Vista Eye Care, our opticians will help them select an appropriate lens material. It is important to consider what the glasses will be used for when selecting a material because their use may dictate which material would be most appropriate. Other factors to consider in lens material selection include the age and occupation of the patient, design of the frame, and the patient’s eyeglass prescription.
Polycarbonate is a shatter-resistant material with reasonable thickness and weight. Our opticians highly recommend polycarbonate for patients under 18 because of it’s shatter-resistance. Most safety glasses need to be made from polycarbonate. Polycarbonate inherently blocks ultraviolet light (UV) which makes it an ideal material for children. Some patients also like to have Transitions® in their lenses to allow their lenses to darken outdoors to address light sensitivity, but as far as UV getting through polycarbonate, you’re covered from the start. If you have a lot of astigmatism, trivex offers superior optical quality without the distortion seen in polycarbonate. If your prescription doesn’t include too much astigmatism, polycarbonate is a fantastic option. Polycarbonate is lightweight, thin, and blocks UV –a nice package deal of a material!
Selecting trivex as your lens material will result in a lightweight lens, superior optics, inherent UV-blockage, and shatter-resistance. This is a great material for adults who need to be in shatter-resistant lenses. Some frame styles dictate which lens material would work best. A standard, full-rimmed frame can use any type of lens, while a 3-piece, or semi-rimless frame should be made of trivex to prevent chipping or cracking of the edge of the lens. In a semi-rimless frame, a thin groove must be carved along the outside of the lens, and standard plastic doesn’t hold up well over time. Skimping on trivex in a 3-piece frame will likely mean a mid-year repair job which may require complete replacement of the lens.
For smaller adult prescriptions, regular plastic (also known as CR-39) works great if it is coupled with a good UV coating or Transitions®. CR-39 is half the weight of glass and was developed in the 1940’s as an lens material to replace crown glass. It is not considered shatter-resistant, but does have great optical qualities. In higher prescriptions, it tends to be a rather thick.
If your prescription is high, either because of high nearsightedness, farsightedness, or astigmatism, you should use a high index lens. Index refers to how thick a lens material is, and thus how thick your glasses lenses will be. The higher the index, the thinner the lens. If your goal is to minimize the thickness of your glasses, a high-index material, digitally-designed lenses, and a high-quality antireflective coating is how to achieve it.
Lens material selection can be tricky, and many glasses prescriptions fall between these recommendations. Be sure to ask our optometrists and opticians about what materials they recommend to protect your eyes and get you seeing comfortably! No appointment is needed to come in and discuss your eyewear.