Sphere (Sph) means the strength of lens required to correct your focus - a positive sphere value is used to correct long-sightedness (hyperopic - difficulty focusing on close objects) and a negative value is used to correct short-sightedness (myopia - difficulty focusing on distant objects).
The sphere is measured in dioptres. Your prescription may have the word Plano (or Pl), or an infinity sign, which means that you are not long- or short-sighted but zero power for the sphere. You may still have astigmatism – represented as CYL and AXIS on your prescription. Most values range from 0.00 to +/- 20.00, in steps of 0.25.
The CYL and AXIS are used for astigmatism. So what is astigmatism? Astigmatism is when the eyeball is shaped slightly like a rugby ball (often referred to as ‘toric’, not a perfect sphere like a football, but rather a rugby ball), resulting in difficulty focusing at certain angles.
The box for cylinder may be left empty, or have a plus or a minus value in it. It is measured in dioptres. Most values range from +/- 0.25 to +/- 4.00, in steps of 0.25.
The AXIS is present only if there is a value in the CYL box. This figure tells us where the astigmatism is located on your eye. The measurement is in degrees. The values range between 0 and 180, in steps of 1, 5 or 10 degrees.
The Add, short for Reading Addition, is the additional correction required for reading. This value is used for reading glasses, bifocal glasses, or progressive/multifocal glasses.
This figure is an indication of how much extra power is required in addition to the distance prescription for near or intermediate glasses. The ADD (Addition) will almost ALWAYS be the same for both eyes although only one figure is mentioned. Measured in dioptres, the values typically range from +0.50 to +3.50, in steps of 0.25.
ADD is mostly only used for reading glasses or a vision that requires looking at in a near sight. If your glasses are for distance only, the ADD will not be used. Sometimes, opticians may use the word 'add' or 'near'.
As mentioned above, they may only write it once, but it normally applies to both eyes and is almost always the same value for both eyes (e.g. 'Add' +2.50 - should be entered for both eyes).
is used to correct ‘lazy eye’ and may indicate a more delicate condition. This is to correct some special conditions or some eye disorders that require the focused image to move its position. The measurement is in prism dioptres. The value may be as high as 10 and are measured in steps of ½ or 1 prism dioptre.
Prism will always be accompanied by a direction, which is a base direction such as IN, OUT, UP and DOWN. (e.g. “Prism 2.00 Base IN”) Some people may have prism in two directions for one eye. (e.g. “Prism 2.00 Base IN & 1.00 Base UP”)
For most times, we have stocks of up to 3.00 prism dioptres readily available for online orders. If you require more than 3.00 prism dioptres or different directions for both eyes, please contact us.
Pupillary distance is an essential measurement in optics. It is the distance between the centre of one pupil and the centre of the other pupil measured in mm (ranges from 50 to 70mm). Each spectacle lens will have an ‘optical centre’, a point on the lens where it performs the best and has the least distortion. The optical centre of each lens should be placed directly in front of the centre of each of your pupils. That way, your eyes are looking through the best point on each lens. Some prescriptions may have a PD/Pupillary Distance for each eye. (e.g. RE: 32 LE: 32, in which case you enter 64mm).
An incorrect PD/Pupillary Distance figure may force you to squint, which may lead to discomforts such as headaches, eyestrain, visual distortion and, in severe cases, double vision.
While PD/Pupillary Distance is normally tested and measured in most eye exams, it may not always be shown on your prescription. Ask your optician to include this information.
Dist. refers to distance. This is required to correct distance vision. This correction is often used for driving, television, and general everyday wear (just walking around). These glasses are often worn full time.
Inter. ADD is used for vision for objects at an intermediate distance (e.g. when you look at your computer). If your prescription has it, please include this value.
Near ADD is used to correct near vision that involves activities like reading, sewing or any other near-vision tasks.
Your prescription has important information needed to correct your vision. Opticians and doctors across the globe share very similar or identical procedures and forms of prescription.
Let's look at a sample prescription below.
You will notice there is no CYL or AXIS for the left eye, this means there is no astigmatism present. Your optician may or may not write DS (Diopters Sphere) in the CYL box. DS (Diopters Sphere) means you only have a Sphere power. DS simply means no power is present in the CYL box so leave this as NONE or DS.
If your prescription only shows the SPH box with a value, leave the CYL and AXIS blank.
The BVD stands for Back Vertex Distance, this is a measurement that is included on any prescription where the sphere or cylinder powers are higher than + or - 5.00D and to a lesser extent some prescriptions where it is less than this power.
This measurement is important as it explains at what distance your lenses should sit from your eyes. Usually your lenses will be positioned around 10-12mm from your eyes, however this will vary from person to person. If your prescription includes a BVD, it is important that the lenses sit at the correct distance to ensure comfortable vision.
If you have difficulty deciding what type of lenses you should get, or deciphering your prescription full of jargon, just enter your prescription as you see it. Hover your mouse over the question mark next to the lens type to see more detailed information about the product.
We recommend you attach, email, or fax a copy of your prescription separately just to make sure everything is correct.