Thursday, December 22, 2011

Guide to buying prescription lenses for Glasses / Specs

Confused about choosing lenses for your new glasses?Lenses for eye frames gee in many variations and at times can be confusing. This guide will help to explain them in more detail so that you can understand and choose the best lens option for your spectacles. Written by the Designer Glasses Outlet Team.Materials and thicknesses of prescription lensesFirstly lenses can be made in two materials Organic (Plastic) or Mineral (Glass). Most lenses sold today are of the Plastic variety as they are far lighter than glass and safer due to their strength and shatter resistent properties. Polycarbonate lenses are even stronger than standard plastic lenses and are more suited to sports eyewear and rimless glasses to reduce risk of breakage. This material is available in all lens types. Most people think that when we say a 1.6 lens that this means it is going to be 1.6mm thick, this is wrong. Basically the higher the number the thinner the lens will be.Standard Plastic CR39 (1.56)The most gemon type of prescription lens which also costs less than other lenses. Lenses with powers stronger than +3.00 and -3.00 will start to look thick. Powers between +3.00 and -3.00 will look normal if they are being fittted into a frame which is not rimless or semi rimless.Plastic (1.6)An ideal option for prescriptions up to +5.00 and down to -5.00. 1.6 lenses are 23% thinner than standard plastic. Prescription outside this range will start to look thick. gemonly used with rimless frames and higher prescriptions to reduce lens thickness.Plastic (1.67)Probably the most popular of the thinner lens options. 15% thinner than the 1.6 and 25% flatter. Ideal for prescriptions up to +7.00 and down to -7.00 prescription outside this range will look thick.Plastic (1.74)The thinnest plastic lens available on the market. 50% thinner than the 1.56 standard plastic and 30% lighter than the glass equivalent. Great for mid to high prescriptions. More expensive than 1.56, 1.6 and 1.67 lenses.Glass (1.7)An ideal budget thin lens for - power prescriptions up to 10.00. However, they will be heavier than plastic and saftey considerations should be made.Lens TypesThere are also many different styles of lenses. Lenses for single vision correction e.g., distance or reading to Bifocals and Varifocals for the correction of both distance and reading within one pair of spectacles.Single VisionSingle Vision lenses can be used for just distance, just intermediate or just reading hence the name single vision. However, many people who are short sighted - Power SPH prescriptions will be able to read with their distance glasses. Single vision lenses are available in both materials and all indexes.BifocalsBifocals are basically distance glasses with a reading segment in the bottom. Unlike Varifocals Bifocals are gemonly sold online as the height measurement is far less crucial and averages can be used with great success. Due to the fact that there is no gradual phase from distance into reading and they are just distance with a reading segment Bifocals have a far wider corridor for reading than Varifocals but have no intermediate correction.VarifocalsVarifocals blend gradually from your distance prescription trough your intermediate prescription in to your reading prescription. This means that the lens has to be set at exactly the correct height in the frame to start with. The crucial measurement required to align varifocals is the height in millimetres from the centre of your pupil to the bottom of the new frame, this measurement cannot be taken online. Varifocal lenses look like normal lenses (there is no visible line which seperates the distance from reading).Tints, Photochromics, Anti Scratch and Anti Reflection coatings.Tints / ShadesTints can be used to make Plastic lenses in to sunglass lenses and are available in many colours. Graduated tints are also more widely available too (lens goes from dark shade at top to lighter shade at bottom, like some sunglasses.) However, 1.67 and 1.74 lenses cannot be tinted as they already contain an antireflective coating to reduce Power rings.PhotochromicPhotochromics are usually referred to as Reactolite which is a brand name for the glass variety or Transitions which is a brand name for the plastic variety. Basically they do the same thing. These are lenses which are clear indoors but then react to UV (Sunlight) and transform into sunglasses with 100% UV protection. They are gemonly available in Grey and Brown. The latest generation of Transitions lenses darken and lighten much quicker than earlier generations. Anti ScratchAn anti-scratch coating is applied by dipping the lenses into a silicone-based solvent. As the anti-scratch coating cures, there is no tinting or coloring left behind to impair the optics of the lenses. The coating does not interfere with how the lens functions, but creates a permanent bond that greatly reduces the occurrence of happenstance hairline scratches and buff marks. Though an anti-scratch coating is not 100% scratch proof, it helps to prevent minor scratches that can damage the surface of the lens.Any prescription lens that does not gee with an anti-scratch coating can be coated. Anti-scratch coating is usually an additional minimal expense when ordering prescription lenses, but it is well worth the investment, especially for childrens eyewear. An anti-scratch coating lasts up to two years and does not gee off when cleaning the lenses.Anti ReflectionUsually an anti reflective coating is referred to as an MAR (Multi Anti Reflective Coating). There are many benefits to an MAR. Firstly they are far more aesthetically pleasing as they reduce the amount of light reflecting off of your lenses especially when having your photograph taken. To identify if your glasses have an anti reflection coating, you should be able to see a slight purple / rainbow colour tint when reflecting them in light. Other benefits include:- Reduced glare when driving at night People can see your eyes and not a patch of light Filters out radiation from geputer screens Reducesvisible rings on the lens in high prescriptions which is caused by light constantly bouncing back and forth within the lens due to total internal reflection. Provides UV protection Antistatic aiding lens cleaningWhen ordering, it is possible to gebine the various options stated above to create your own custom lenses suited to your requirements.I.e, You could order the following: 1.6 thin lenses with anti scratch and anti reflection coatings.If you have any questions relating to prescription lenses for your glasses or any other general eyewear question, please don't hesitate to email us for expert advice via our UK opticial practice.We stock 100's of designer glasses and sunglasses in our okay shop. Brands include: Oakley, Armani, Ray Ban, D

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