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Buying glasses online can appear to be a bit of a minefield. Programmes that allow you to `try` the frames on don`t seem to work effectively. However by following a few guidelines choosing a perfect pair of glasses is easier that you would think!
Firstly though it is worth having a look at a pair of glasses and explaining what all those letters and number mean!
All measurements are given in millimetres, for conversion to inches please divide by 25.4.
Often both arms will have numbers printed on the insides:
In the first picture the GJ1 is the model code and the G57 a color code. Unless you know exactly the model you require these can be ignored. The 140 is important though, this is the arm length. There are three arm lengths that can be regarded as standard; 135mm, 140mm and 145mm. Usually the arm length corresponds to the frame size so a small frame is more likely to have 135mm arms and a large one 145mm.
The second photograph shows the arms length being repeated as well as the manufacturers name and country of origin.
While ensuring the arm length is acceptable it is not an issue should they be too long when you receive the glasses. Virtually all metal frames have end tips which can be removed and the arms cut back should the required adjustment be beyond the normal procedure of bending the the arms to fit. All opticians will have the facilities to carry out this simple task.
Next we come to the frame size. This can be found in a variety of places depending on the manufacturer. The two most common places are the arms and the inside of the nose bridge. On this particular frame it is found on the inside of the bridge. The numbers are normally separated by a small square.
The first number always refers to the lens width. This is measured across the lens in a line from the bridge:
The second number is the bridge width:
Some people will advise that adding the bridge width to twice the lens width will give the total width of the frame. This is not correct. As you can see from the following picture the arms of the frame protrude a small amount from the lenses so increasing the lens width.
This is where frame details from the information on the glasses is completed but there are additional measurements that prove invaluable. Firstly, a ruler is placed across the arms at the hinge:
One side of the ruler is zeroed on the frame then an accurate measurement can be taken to ascertain the total width of the glasses. I call this the `arm to arm` measurement:
With most pairs of glasses the arm to arm measurement is used for guidance only. It is always possible to adjust the arm position to allow for a slightly smaller or larger width. It is an invaluable measurement though and one that is often my first reference point when advising customers on the correct sized frames for their needs.
It is always useful to know the lens depth if you are considering having your optician fit bifocal or varifocal lenses:
All optical frames can be fitted with single vision lenses but bifocal and varifocal lenses need a deep enough frame to allow for correct fitting. If they are too shallow the reading area of the lenses could be greatly reduced or even cut out of the lens completely! As a general rule a multifocal lens will require a minimum frame depth of 28mm.
I find the additional measurements of arm to arm width and lens depth are the most important ones for online buyers as these are the ones that determine the suitability of the frames.
For any additional information please contact me on the following link
Glasses. Determining the correct size frame for you
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17 February 2007
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