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 eyewear 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 (See
example frame here). 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:-
Oval
Faces
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.
Oblong
Faces
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.
Round
Faces
To play down the roundness, select frames with straight or angular
lines. Deep colours such as black or tortoise also minimizes fullness.
Square
Faces
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.
Triangular
Faces
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.
COMMON ABBREVIATIONS
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.
Lens
Types
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.
Varifocals
Varifocal
glasses blend gradually from your distance vision through your
intermeadiate and in to your reading vision. This means that the
lenses have to be acuratley measured and alligned perfectly with
your pupils.
The only way
to correctly achive this online is for us to send you a frame
to try on and take a photograph of you wearing the frame.
This then
allows us to acratley scale the photo and take the required mesurments.
Note: We are
constantly being asked to provide a sytem where customers can
upload a photo and try on a virtual frame for the measurements.
This does not work as the crucial measurement to align varifocals
is the height from the pupil to the bottom of the frame.
Unfortunately
systems like this are in accurate as there is no way of knowing
exactly how high the frame will sit on your face in real life.
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
"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
Coatings
Tints
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.
Photochromic
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.
Polarized
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.
Anti
Reflective
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:-
•
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 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.
SUMMARY
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've taken time to read this guide and you could also
save yourself a small fortune.
Many
Thanks Mark Bowden
B.SC. (HONS) MCOptom
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About The Author: Mark Bowden B.Sc (HONS) MCOptom provides high
quality prescription glasses, designer glasses, specialist sports
glasses and safety glasses at a fraction of the normal retail
prices you can visit his web site here at www.spex4less.com
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