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Over the last three years thousands of people have been turning to the internet looking for online suppliers of prescription glasses. The prices of prescription eye wear online is at an all time low and savings of up to 75% of the normal retail price is not unheard of.
This guide to help you avoid any pitfalls and decide upon a frame and lens that will suit, fit and work, so saving you valuable time and money!
HOW TO CHOOSE A FRAME THAT FITS
Frame sizes are usually in the format “50 – 20 – 140”. In this example this means that the lens diameter is 50mm the bridge distance is 20mm and the arm length is 140mm. This can usually be found on the inside arm or on the back of the bridge.
You can use this as a guideline by comparing them to your own glasses
HOWEVER, this is NOT the BEST way to obtain a good fitting frame. At spex4less there are two further measurements that are FAR easier to understand and ensure a much better result.
Each of the frames on the website includes the total frame width in millimeters and total frame depth in millimeters, compare these to your own frames for a good fitting frame.
HOW TO CHOOSE A FRAME THAT SUITS
There are certain face shapes that suit certain lens shapes and many guides to this are floating about the internet. The general guide is listed here:-
More frames look good with this face shape than any other, as long as the size of the frames is in proportion to the face.
Long narrow faces are similar to square faces in that the chin and cheek are of nearly the same width. Facial length, however, is far greater than the width. Frames should cover as much of the centre of the face as possible in order to minimize the length.
To play down the roundness, select frames with straight or angular lines. Deep colours such as black or tortoise also minimizes fullness.
Compliment a square face with frames that are slightly curved. The top of the frames should sit high enough on the face to downplay the jaw line.
This shape is defined by a broad forehead and narrow mouth and chin. Frames with a thin rim and vertical lines will help balance the bottom part of the face. Frames should not sit too high on the face. Avoid large frames, heavy nose bridges, bold colours and square shapes.
HOWEVER, as many people know there are always exceptions to any rule!
My advice is to use this guide if you have never worn glasses before. Many people who are already wearing glasses know which shapes suit them and which don’t.
Choose a pair of glasses similar to the ones you have at the moment, OR, if you are trying to find a new look why not go for a rimless or semi-rimless frame with the same lens shape as your current glasses, or vice versa.
YOUR PRESCRIPTION AND AVOIDING COMMON MISTAKES
“*Please pay particular attention here*”
Your prescription may seem a little confusing at first glance but it really is quite simple to understand.
Firstly, every prescription follows the same format wherever you are in the world. There may be a few variations and abbreviations, but I will explain them later.
Let’s describe what it all means first.
Each prescription will have a left and right value for the correction of your vision within the following boxes:
“SPH” (sphere). The correction for long or short sightedness.
“CYL” (cylindrical). The correction for an Astigmatism.
“AXIS” The axis that the correction for the Astigmatism needs to be set at.
Sometimes an Add or Addition, always “+” value is included for us to decipher your reading prescription, but only if you require glasses for both distance and for reading.
In some rarer cases Prism and Base is used for the correction of double vision.
On our website and most of the others out there you can select your prescription from drop down boxes so that you can simply copy the details you have on your written prescription.
*VERY IMPORTANT – Do not fall for the most common mistake!*
The single most common mistake when entering prescriptions online is selecting a ” +”value instead of a “-” value or vice versa.
Your prescription may consist of both “+” AND “-” Values. For example:-
SPH (Spherical) will consist of a + or – power (unless 0.00) in 0.25 steps. EG, -0.25, -0.50, -0.75, -1.00, -1.25 and so on..
CYL (cylindrical) may consist of a + or – power in 0.25 steps. EG, -0.25, -0.50, -0.75, -1.00, -1.25 and so on..
Axis will consist of a numerical value from 0 to 180, BUT, only when you have a CYL value.
Note: Usually opticians will write the “-” and “+” signs above the value.
ADD / Addition Will only consist of a + value as is it is what it says on the tin, an “addition”. We add this value to your distance prescription if you need reading glasses as well as distance or for bifocals.
Note: Some opticians will write out your complete near prescription underneath your complete distance prescription. In this case you will need to call us to tell you what the “add” is.
Plano, 0.00, Infinity – All mean the same thing nothing! Or No correction is needed.
DS – “Dioptre Spheres” Usually appears under the CYL box indicating that there is no astigmatism (No CYL value). However, this can sometime appear after a reading addition.
OD – Means your right eye.
OS – Means your left eye.
PD – “Pupillary Distance” is the distance between the centre of one pupil to the centre of the other in millimeters. I would like to take a moment to talk about your “PD” as this has caused much debate in dispensing glasses online.
Opticians generally will not give this to you as they will probably figure that you wish to buy your glasses online and not from them. In most cases, except for those with particularly high prescriptions, we can calculate this usually within a millimeter using experience and certain order criteria such as your gender and the size of frame you have chosen etc.
HOWEVER, it is very simple to measure your own “PD”. The best way is to have a friend help you. Look at a point in the distance whilst your friend takes the measurement in millimeters, if you wanted to be super accurate measure the left side of the left pupil to the left side of the right pupil.
Outside UK prescription format = EG: +1.25 (-1.00) x 180° Although it looks different it’s the same. The first value is the SPH, the second in brackets id the CYL, and the x180° is the Axis in this case 180.
HOW TO CHOOSE THE BEST LENS
Lenses come in many flavours and again, at first, things can become a little confusing. But don’t worry. I am here to explain them all in detail so that you can understand and choose the best lens option for you.
Firstly 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. In some rare occasions when extremely thin lenses are required for very high prescriptions glass can be the best option.
Each lens will also have what we call a “Refractive index” The way in which the refractive index is calculated is not important at this time. What is important is what it means to the thickness of the lens.
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. This is because materials that bend light more than others have a higher “Refractive index” and hence a shorter or longer focal length. This means that the same correction and focal length can be achieved from “less” lens (material) making them thinner.
Here is a key to choosing the best lens.
Standard Plastic CR39 (1.5) We use 1.56 on all standard lenses Ideal for most prescriptions (prescriptions with powers stronger than +3.00 and -3.00 will start to look thick, powers between the two will look fine).
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.
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 1.5 standard plastic and 30% lighter than the glass equivalent. Great for mid to high prescriptions.
Glass (1.7) An ideal budget thin lens for “-” power prescriptions up to – 10.00. However, they will be heavier than plastic
Glass (1.8) Rarely used but good for high power prescriptions. Expensive option.
Glass (1.9) Rarely used but excellent for high power prescriptions. Expensive option.
There 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 glasses.
Firstly I would like to talk about Varifocals as there is much debate about whether or not they should be supplied online. At Spex4less we do not feel that it is morally correct to supply these online just yet, UNLESS it is part of our Re Glaze Service and you have varifocal lens in your glasses already.
Varifocals blend gradually from your distance prescription through 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 millimeters from the centre of your pupil to the bottom of the new frame, this measurement cannot be taken online.
Although it is becoming common practice online to use averages and experience along with other factors such as order information to calculate some measurements such as the “PD” we spoke about earlier, it is not yet possible to do this with Varifocals. Some online companies will still provide varifocals for you and you may get lucky. HOWEVER I would not advise anyone to do this until technology allows us to take the accurate measurements needed.
We are currently working on a varifocal system that should allow us to supply Varifocals accurately. I will let you know when the results are in.
Bifocals are basically distance glasses with a reading segment in the bottom. Unlike Varifocals Bifocals are commonly 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.
There are also various types or “shapes” of the reading segment.
Typically the standard is the “D Seg” this one looks like the letter D on its side with the flat part it the top hence the name D Seg.
There is also a “round” segment in various sizes and executive or “E Type” bifocal where the whole bottom half of the lens is dedicated to reading (Great for people who do a lot of reading at work using plans etc).
Bifocals are only available in standard plastic, standard glass and 1.6 plastic.
“Single 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.
Tints can be used to make “Plastic” lenses in to sunglass lenses and are available in many colours. However, 1.67 and 1.74 lenses cannot be tinted as they already contain an antireflective coating to reduce “Power rings” which I will explain later.
Photochromcs 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.
NOTE: As photocromic lenses require UV to change, using them behind a car windscreen will not work as effectively as normal due to the windscreen filtering out some of the UV.
However, we have found that the glass reactolite works better than the plastic behind a car windscreen, but not as good as the plastic in normal conditions.
Light reflected from surfaces like a flat road or smooth water is generally horizontally polarized. This horizontally polarized light is blocked by the vertically oriented polarizers in the lenses filtering our glare and allowing you to see below the water line. Available in grey or brown polarized lenses are ideal for fisherman and also for drivers.
Usually 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 your lenses especially when having your photograph taken.
Other benefits include:-
o Reduced glare when driving at night
o People can see your eyes and not a patch of light
o Filters out radiation from computer screens
o Reduces “Power rings” visible 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.
o Provides UV protection
o Anti static aiding lens cleaning
Spex4less provides MAR coated glasses for characters in Coronation Street to reduce reflections from studio lights and reflections of camera men in the characters glasses.
The internet is reaching further and further in to our daily lives as more and more products become available online.
Buying your glasses online is surely going to be an exciting and hassle free experience now that you have taken time to read this guide and you could also save yourself a small fortune.[ad_2]
write by Emery