Understanding Glasses Measurements - Blue Light Glasses

Understanding Glasses Measurements - Blue Light Glasses

Ever wonder what the numbers on the arms of your blue light glasses stand for? 

Understanding the frame measurements are an important part in choosing a pair of glasses that fits your face and suits your facial features. 

Next we'll go through each of the measurements from eye size to arm lengths. 


Typically on a pair of glasses you will find three numbers or measurements printed on the inside of the arm. These numbers are measured in millimeters.  



The first number is the eye size

The second number is the bridge width and 

The third number is the arm length. 

The eye size relates to the width of your glssses, the bigger the number the wider the glasses will be on your face. A measurement of 51mm is average so if you have a narrow face you will be looking for a figure less than 51mm or if you have a wide face or if you are looking for an "over-sized" frame you will be looking for a frame with a value greater than 51mm. 

The bridge width also relates to the total width of the frame as multiplying the eye size times 2 and adding the bridge width will give you the total overall frame width. 

The third figure the arm length relates to the distance from the frame to the tip of the arm. The typical arm length is 1350140mm. If you have a small head and typically find that the arm juts out past your ears and the frame needs to be bent down at the ear you will be looking for a smaller number than 140mm. if you have a large head and typically find that the bend in the arm comes before your ear you will be looking for a number greater than 140mm. 

Another important measurement and one that is not typically on frames is the vertical eye size i.e. the measurement from the top to the bottom of the frame. 

This size can vary quite a lot but typically is in the range of 20mm to 25mm. If you are wearing glasses for normal everyday use you can usually get away with a narrow frame from top to bottom but if you are using them for reading, your eyes will automatically drop when looking down to read and its nice to have a little extra depth to the frame to give yourself a wide field of view. A larger eyesize is also beneficial for reading glasses as we scan from left to right a lot more when reading as apposed to wearing distance glasses so again having a larger field of view helps make this more comfortable. 

The eye size also plays in a factor in determining how thick your lens will be. This only comes into play for prescription over +/- 3.00 DS. The bigger the eye size, especially the vertical size, the thicker the prescription lens will be.              Because of this it is often a balancing act to choose an eye size that is sufficiently small to give a reasonable thickness to the lens but not too small as to restrict your field of view.

If you are short sighted you will have a minus prescription power and the thickness of a lens will be more noticable at the edges. In these situations an acetate or plastic frame often works best as the frame tends to be thicker than a metal frame and can hide the thickness. If you are long sighted you will have a plus prescription and the thickness of the lens will be in the center of the lens. This can also have the effect of magnifying your eyes slightly for someone looking at your face. 

In situations where your prescription is greater than either +3.00 or -3,00 it is recommended to get your lenses thinner down to make them look better cosmetically and to make the glasses thinner and lighter on your face. 


The bridge size is another important measurement. This is the distance from the inside edge of one lens to the inside edge of the other. It is an important measurement as it will determine how the glasses sit on your nose, to tight a fit will cause the glasses to sit high up on your nose and result in your eyes looking out through a lower area of the lens. Too big a bridge distance will cause the glasses to fall down the face and your eyes to look through the top of the lens. This is not that big of an issue with metal frames as the nosepads can be adjusted to bring the frames up or down as appropriate but is more important to get right for acetate feames. 

If you have noticed that glasses tend to fall down your face slightly try choosing a bridge in the range of 14-16mm and if you notice that glasses tend to sit up high on your face choose a bridge size in the range of 20-23mm. 


Another important measurement is the pupillary distance or pd. Whilst this is not a frame measurement it is important to ensure you are looking out through the optical centre of the lens. Details on how to measure the pd can be found here. 

At Sapphire Eyewear you can find our frames measurements for our blue light glasses on the inside of the arm.  You can browse all our blue blocking glasses here safe in the knowledge that our acetate frames are made from the highest grade acetates and our metal glasses from the strongest available metals. 

Our blue light lenses are top of the range and filter out blue light from digital devises such as smartphones laptops and computers.