The many options for lens types and coatings can leave you feeling overwhelmed when it is time to purchase new vision correction. Choosing the right lenses is important in many respects: final appearance, functionality, safety, durability, adaptability and comfort. This guide will help you understand some of the options when it comes to determining the best way to have your lenses customized.
Optical Lens Material
As the first material to be used in eyeglass lenses, glass lenses provided an extremely clear and color distortion-free experience. However, they’re quite heavy, more of an injury risk and cannot be made for rimless or semi-rimless eyewear. For safety alone, glass lenses now make up only a small percentage of lenses, mostly in non-prescription sunglasses.
Due to its lightweight, ease-of-shaping and great optical performance, plastic lenses are the most popular lens material used today. (See refractive index for more details).
Originally created for Air Force helmet visors, polycarbonate is lighter and more impact-resistant than plastic lenses. This makes it perfect for children, safety glasses and sporting eyewear. They have a natural ability to block UV light, but on the other hand distort natural color perception due to their higher chromatic aberration. Another positive feature, conversely, is that they have a moderate index and low density, allowing them to be thinner and lighter than many other lens materials.
This material has an index of refraction of 1.53 and offers both low color distortion and impact resistance.It is an excellent choice for children, safety and sports lenses.
Lens Refractive Index
Hi-index plastic lenses are thinner and lighter than glass and polycarbonate counterparts, because of their ability to naturally bend light. The more a lens material can bend light, the higher refractive index it assumes.
A higher index results in thinner, flatter lenses. Flatter lenses are more aesthetically pleasing and distort vision less than more round or curved lens surfaces.
Index of refraction depends on the speed at which light travels through the material. Lenses typically come in the following variations: 1.5 (CR-39), 1.53 (Trivex),1.56, , 1.586 (polycarbonate), 1.6, 1.67 and 1.74 index.
Lens Coatings and Lens Treatments
Plastic and high-index lenses are much softer than glass and are more prone to scratches and abrasions. As polycarbonate is fairly impact resistant, it doesn’t require the coating as plastic lenses do. An anti-scratch coating can make a lens also as scratch resistant as glass.
An anti-reflective treatment (AR) coating applied to lenses stops reflections from appearing in the lenses, which in turn reduces contrast and clarity. The coating also makes your lenses nearly invisible, preventing others from getting distracted in the reflections dancing across your lenses. This is important if you choose a high-index lens, as they naturally reflect more light.
As prolonged exposure to U.V.. rays can be extremely harmful, this is an important coating to get for any pair of glasses. Polycarbonate and some high-index lenses have U.V. protection built in the material, but if you choose a plastic lens, this may be a required additional treatment.
As prolonged exposure to LED screens becomes the norm, protection from the blue end of the visible spectrum becomes even more important. Blue light can adversely affect the circadian rhythm of our body. It can be phototoxic to the cells that make up our retina over time, and it is a major source of glare that is both discomforting and disabling (i.e. a source of eye strain and poorer visual performance).
This feature allows lenses to darken automatically when they contact U.V. rays. They reverse back to their original clear state within minutes once you go indoors. They naturally block U.V. rays from entering the eye, offer major convenience, and are offered in several colors. The most popular transitions colors are grey, brown and then green.
Top Rated Eye Care
At Dr. Sciberras’ Eye Care Clinic, your vision matters to us. It is our goal to help you achieve the best in vision and eyewear. Let us help you make the best frame and lens choice, so that you both see and look your best.
Located in Mississauga, Ontario since 2007, we offer comprehensive eye care and quality eye care products. Our services include: primary and emergency eye care, contact lenses, frame fittings, low vision assessments, laser eye surgery and cataract surgery consultations. No eye emergency will be turned away. We treat chronic eye conditions and eye diseases, as well as pink eye, traumatic eye injury, dry eye, iritis, glaucoma, macular degeneration, keratoconus, presbyopia and myopia treatment, etc.
Dr. Jeff Sciberras and his team are proud to have earned the distinction of Top Rated Pediatric Optometrist and Top Rated Optometrist for 2019 in Mississauga by ThreeBestRated.ca and the Top Choice Optometry Clinic in Mississauga for 2019.
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