Whether you are buying your first pair of prescription eyeglasses or getting a new pair, it is essential that you get a pair that sits comfortably on the bridge of your nose and is light but firm behind the ears. Getting the right frame size will ensure this comfort. It does not matter if you require the glasses only to read or when using the computer, it must be comfortable.
When purchasing them from a store, make sure you try out a number of frames to find the one that feels just right. Even though the optician is able to tweak and bend the frame to fit in well, do not depend on that when the frame is too tight or too loose. One good way of checking this out is by looking down your glasses to see if they slide down your nose or if there is undue pressure on the back of your ears.
Your current prescription will have 3 columns:
Sphere – this is abbreviated as SPH. and is further divided into 2 rows, left and right. This could also read OD (for right eye) and OS (for the left eye).
Cylindrical – the often used abbreviation for this is CYL. There will be 2 rows of left and right for this as well.
Axis – there isn’t any abbreviation for this and you can get the numbers off the 2 right and left rows for this too.
Any time you are filling your eyeglass prescription online, you will be required to fill in these numbers to determine how the lenses will be carved. Other than these, there is one more number that is essential to getting your eyeglass dimension right and that is the Pupillary Distance or the PD.
This is the distance between the centre of the pupils of both your eyes and is measured in millimetres. This will determine exactly where the lens goes in your eyeglass frames in order to ensure that your point of focus when using the glasses is through the optical centre. If you need a high lens power, the accuracy of this number is vital. Most adults have this number ranging between 54 to 68 millimetres.
There is one other dimension that isn’t critical but helps you choose a well-fitting pair. This is the temple length. This is a measurement that begins from the curve of the side bars to the end of the temple including the curve. You could measure it yourself with a measuring tape; if you do not have one in mm, simply measure it to the nearest whole inches and then multiply by 25.4. On an average, for men, it would range from 135 to 145 millimetres and for women, 130 to 140 millimetres. Sometimes you may even find a bridge size mentioned on your prescription.
Such is the design of glasses these days that a lot of the above is taken into account, even with fashion brands such as Ray Ban sunglasses, however, armed with all these dimensions you are bound to get a pair of eyeglasses that fits really well and make using them a delight every day!