It’s a fact of life that not everyone has perfect vision and it’s perfectly natural, particularly in a world where we now use computers on a daily basis, to need a little visual assistance. If you find yourself straining to read the fine print, suffering from headaches midway through the workday, having trouble seeing while driving at night, or if you feel like you can’t focus upon what is in front of you, we recommend that you make an appointment to see an optometrist. Seeing an optometrist isn’t just about getting glasses; while most vision problems can be corrected simply with prescription glasses, your optometrist will also be on the lookout for eye diseases such as glaucoma or ocular hypertension as well as more serious issues such as indications of high blood pressure or diabetes.
Okay, so maybe I need glasses….
The need for glasses is the result of what is called a “refractive error”. Simply put, a refractive error is the inability on the part of the eye to properly transmit and refract light onto the retina clearly. Thus, blurry vision.
Myopia – Those who suffer from myopia are said to be nearsighted, meaning that objects in the distance appear blurry causing them to squint as they force their eyes to focus. This can result in eyestrain and headaches, not too mention wrinkles and crows-feet caused by squinting. People who are myopic tend to wear glasses a great portion of the time for activities such as television viewing or driving, unlike those who suffer from hyperopia who may only need glasses for close up seeing. And with that…
Hyperopia – Hyperopia is often referred to as farsightedness meaning that, while objects in the distance remain clear, reading, small detail work, and even reading a computer screen can be anywhere from difficult to impossible because of the eyes inability to focus on close objects. You will often see people suffering with hyperopia taking their glasses on and off (or looking over the top of the frames) as they go from reading to looking and speaking to someone.
Astigmia – Most commonly known as astigmatism, astigmia is a condition in which the cornea of the eye is aspherical, or to put in more easily understood terms; most eyes are spherical like a basketball, an aspherical eye is shaped more along the lines of a football, meaning that the curvature changes by degrees making it difficult for the eye to define fine details. Astigmia can be present in both farsighted as well as nearsighted people and, in fact, a minor degree of astigmatism is fairly common in all people. However, as the degree increases, a lens design known as a “cylinder lens” is used for corrective purposes in order to see properly.
What types of lenses are used to correct my vision?
In a nutshell there are four types of lenses used to correct vision: Single vision, bifocal, trifocal, and progressive lenses.
Single vision – As the name indicates, a single vision lens has the same focal power (or magnification) from top to bottom and can be used for nearsightedness, farsightedness, as well as for correcting astigmatism. Single vision lenses are the most common lenses used and, for most first time glass wearers, the first lenses prescribed. While you can purchase inexpensive ready-made single vision readers in most drugstores, they will not correct for astigmatism or in the case where your eyes have different corrective needs, i.e. one eye is a +1.50 and the other is a +2.00. Using readers, in this case, can cause a additional eyestrain problems.
Bifocal – A bifocal lens has two parts; the separate and very distinct lower portion designed for reading or close-up work, with the upper portion containing a prescription for distance or even with no correction at all. Using bifocals allows a person to leave their glasses on at all times while retaining the ability to see at varying distances.
Trifocal – Much like the bifocal, the trifocal contains three separate and distinct levels of prescription, correcting for close-up work, a middle distance for using, for example a computer, and the top portion for distance. Trifocals are fairly rare these days with the advent of…
Progressive lenses – Progressive lenses (like bifocals and trifocals) are used for people with multiple corrective needs such as close-up, distance, and middle distance. Unlike bifocals and trifocals, progressive lenses are true multi-focal lenses that allow a seamless progression through all of the lens powers that you need to see, with no lines or sudden jumps from one magnification to another. Thus your eye is allowed to adjust focus in a more natural and comfortable manner. Progressive lenses are particularly useful for people who need both a strong power for reading as well as lesser visual assistance for a computer monitor that is slightly beyond comfortable reading distance.
What kind of lens materials do I have to choose from?
While some companies, such as sunglass manufacturer Kaenon, use proprietary lens materials, the majority of prescription eyewear lenses are made with either CR39, polycarbonate, Trivex, or, on rare occasions, glass. With higher (or stronger) prescription glasses you may want to consider ‘high index’ lenses which, while more expensive, are lenses that are thinner, lighter and aesthetically more attractive by eliminating thick edges or making your eyes look unnaturally large.
Glass – Known for it’s optical clarity, glass is used rarely and, thus, is a very expensive alternative for use in prescription glasses. On the plus side, glass is more scratch-resistant than the various plastics and polymers available on the market. On the negative, besides the high cost, glass lenses can be heavy and are not available across the full range of optical needs.
CR39 – CR39 is a plastic polymer that has been in use for optical lenses since 1947. CR39 is lightweight and used more frequently in prescription sunglasses because it absorbs tint more easily than polycarbonate. While CR39 is the most popular lens material used, it chips more easily and is thicker than polycarbonate making it unsuitable for rimless or half-rim frames. Using CR39 lenses for a heavy prescription may lead to the thick “Coke bottle” look in many frames.
Polycarbonate - Polycarbonate lenses are thinner and lighter than traditional plastic eyeglass lenses. They also offer 100 percent ultraviolet (UV) protection (without any additional coatings) and are up to 10 times more impact-resistant than regular plastic lenses. Not only is polycarbonate lighter than CR39 and glass, unlike them, it will not shatter upon violent impact making it the safest choice for sports or children’s glasses. Additionally polycarbonate lenses are available as higher index lenses meaning even thinner lenses for patients with very high prescriptions.
Trivex – Similar to polycarbonate, Trivex is a urethane-based lens which is cast-molded like a plastic-based lens for outstanding optical clarity, while retaining the thinness and lightweight qualities (although marginally heavier) than polycarbonate. Trivex is an excellent choice for rimless (or drill-mounted) glasses since it resists the small “spider-cracks” at the drilling points. Trivex also provides 100 percent UV protection.
Coatings and Tints
Lens coatings can provide additional optical benefits as well as improving the appearance of your glasses. Among the coatings available are: Anti-Reflective, scratch coats, and UV (ultraviolet) coatings. Mirror coatings are also available.
Anti-Reflective coatings - Anti-Reflective coatings, also know as ‘AR’ or anti-glare coatings, are coatings generally applied to the front and backside surface of lenses for the purpose of diminishing glare or reflections. If you drive at night a good AR coating shrinks down glare or the star/halo effect from oncoming headlights while improving your night vision. Anti-Reflective coatings have also been proven beneficial when using a computer for extended periods of time by reducing glare off of the monitor, which, in turn, eases eyestrain. From a cosmetic standpoint, AR coatings reduce the shine and reflection off of high index lenses, which tend to be brighter due to their thinness.
Scratch coating – Even metal can be scratched, so what chance does glass or plastic have? While not protective against deep scratches or gouging, a scratch-proof coating can make your lenses more resistant to the fine scratches that come with day-to-day wear and even from cleaning them with something as seemingly soft as paper towels or napkins. Generally a scratchproof coat will come with an extended warranty on your lenses.
UV coating – In much the same way that ultraviolet rays can damage your skin, UV rays are believed to be a contributing cause to cataracts and retinal damage. As noted above, polycarbonate, Trivex, and high index lenses provide natural 100 % UV protection for your eyes. Plastic lenses provide minimal UV protection that can be increased to 100% protection with a clear UV-blocking dye.
Tints – Tinting lenses is an option but is limited to plastic lenses, Trivex, and some hi-index lenses.
What about prescription sunglasses?
There are many options when it comes to sun protection when wearing glasses including clip-on’s, magnetic clips, or “cheaters”: those oversized sunglasses that fit over your optical frames. But if you spend a great deal of time in the sun, you may want to consider the convenience of either prescription sunglasses or Transition lenses.
Prescription sunglasses – Sunglasses can be created in any prescription using the latest in stylish sunglass frames. Your only limitations are dictated by the curvature of ‘wraparound’ frames, which can cause distortion in your peripheral vision particularly in high prescriptions. Choose from Polarized, non-Polarized, or a custom tint.
Transition lenses - Transition lenses (also known as photochromic lenses) are lenses that change from clear to dark when exposed to UV rays. Indoors and at night, Transition lenses are as clear as regular clear lenses. Outdoors, when exposed to the sun's UV rays, they turn sunglass dark, enhancing the quality of vision by reducing glare, minimizing eyestrain and fatigue, and improving contrast in all light conditions. Transition lenses are compatible with all frames and, if your prescription is available in clear lenses, it’s probably available in transition.
Which lenses does Sunglass & Optical Warehouse offer
If a lens is made by a lab in the United States (and even most of the ones made outside the US), we can get it. Among others, we offer Varilux, Zeiss, Hoya, AO/Sola, Definity, Shamir, PixelOptics, Rodenstock, Optima, Seiko, Pentax, Signet Armorlite, Vision-Ease, Nikon, Kodak, and Essilor.
Sunglass & Optical Warehouse is also proud to carry complete frames and prescription lenses from Maui Jim, Nike, Kaenon, and Rudy Project.