Selasa, 11 Agustus 2009

[] Guide To Purchasing Glasses Online

has posted a new item, 'Guide To Purchasing Glasses Online'

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 FITSFrame 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 glassesHOWEVER, 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 SUITSThere 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:-Oval FacesMore
frames look good with this face shape than any other, as long as the size of the
frames is in proportion to the face.Oblong FacesLong 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.Round FacesTo
play down the roundness, select frames with straight or angular lines. Deep
colours such as black or tortoise also minimizes fullness.Square FacesCompliment
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.Triangular FacesThis 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.COMMON ABBREVIATIONSPlano, 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 LENSLenses 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 plasticGlass
(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.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
glasses.VarifocalsFirstly 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.BifocalsBifocals 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"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.Lens CoatingsTintsTints 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.PhotochromicPhotochromcs 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.PolarizedLight 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.Anti
ReflectiveUsually 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:-? Reduced glare when driving at night? People can see your eyes and not
a patch of light? Filters out radiation from computer screens? 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.? Provides UV protection? Anti static aiding lens cleaningSpex4less
provides MAR coated glasses for characters in Coronation Street to reduce
reflections from studio lights and reflections of camera men in the characters
glasses.SUMMARYThe 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.Mark Bowden B.Sc.(HONS) MCOptom specializes in supplying high quality
prescription glasses online visit http://www.spex4less.com for more details.

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