Myopia, or nearsightedness, is the most common refractive error of the eye. If you are nearsighted, you typically will have difficulty in seeing distant objects clearly but will be able to see well for close-up tasks such as reading and computer use. If there is a minus in your SPH, it means you have myopia (nearsightedness).
Hyperopia, or farsightedness, is a common vision problem, affecting about a fourth of the population. People with hyperopia need correction focusing on objects that are both up close and far, and often feel eyestrain. The condition is sometimes referred to as "hypermetropia" rather than hyperopia. If there is a plus in your SPH, it means you have hyperopia (farsightedness).
Presbyopia is when your eyes gradually lose the ability to see things clearly up close. It is a normal part of aging. In fact, the word "presbyopia" means "old eye" in Greek. You may start to notice presbyopia shortly after age 40. You will probably find that you hold reading materials farther away in order to see them clearly.
Astigmatism is a common vision problem caused by an error in the shape of the cornea. With astigmatism, the lens of the eye or the cornea, which is the front surface of the eye, has an irregular curve. This can change the way light passes, or refracts, to your retina. This causes blurry, fuzzy, or distorted vision.
5. ADD (Addition)
The Add, short for Reading Addition, is the additional correction required for reading. It can be used to make either reading glasses, bifocal glasses or multifocal glasses. If you choose the bifocal/progressive lens, the ADD number should be included in your prescription.
This figure is an indication of how much extra power is required "on top" of the distance prescription for near or intermediate glasses. This extra power will ALWAYS be the same for each eye and may only appear once on your prescription but it is understood to be meant for both eyes. The measurement is the Dioptre, and most values range from +0.50 to +3.50 and will go up in steps of 0.25.
The 'addition' is only required if the glasses are going to be used for reading or close work. If your glasses are for distance only, this will not be an issue. Please kindly note that if you have ADD and choose distance glasses, the glasses can only be used for seeing far, not available for reading. Sometimes opticians use the word 'Add' or 'Near' instead of 'addition'. 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).
Age Add Power
SPH (Sphere) indicates the amount of lens power, prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted. The larger the number following the +/-, the stronger the prescription.
7. CYL (Cylinder)
CYL (Cylinder) indicates the amount of lens power for astigmatism. This number also has "+" or "-" signs. If "DS" or"SPH" or "spherical" or "PL" is stated at the place of CYL, it means you have no astigmatism.
The axis indicates the orientation of astigmatism, measured in degrees from 1 to 180. If an eyeglass prescription includes cylinder power, it also must include an axis value, which follows the cylinder power.
9. OD. OS .OU
"OD" and OS" are abbreviations for oculus dexter and oculus sinister, which are Latin terms for the right eye and the left eye.
Your eyeglass prescription also may have a column labeled "OU." This is the abbreviation for the Latin term oculus uterque, which means "both eyes."
Some doctors and clinics have opted to modernize their prescriptions and use RE (right eye) and LE (left eye) instead of OD and OS.
On your eyeglasses prescription, the information for your right eye (OD) comes before the information for your left eye (OS).
Prism refers to the prismatic power used to correct vision displacement. It helps to correct some special conditions or some eye disorders (like squints) that require the focused image to move position. The measurement is Prism Dioptre. The value may be as high as 10 and may go up in steps of ½ or 1 Prism Dioptres.
Prism powers will always be accompanied by a direction that is usually seen as a base direction such as IN, OUT, UP, and DOWN; for example; Prism 2.00 Base IN. Some people may have a prism in two directions for one eye, for example; Prism 2.00 Base IN & 1.00 Base UP.
We can only make single-vision glasses for prism prescription. If you have a prism, please upload your original prescription picture when you order.
PD(or pupillary distance) is the distance between your pupils in millimeters. Your PD is very important for accurately fitting your lenses to achieve vision acuity. In general, this number will be provided on your prescription after the eye exam; if not, you can also get it measured at home. All you need is a friend or a mirror and a ruler.
1. The average PD is between 54mm and 78mm.
2. For those requiring progressive lenses, we strongly recommend you get this information from your optician to ensure the accuracy of your glasses.
3. Your PD may be written in three ways:
▪ PD (OU), written as "64", means the Binocular PD which is for both eyes.
▪ PD (OD), means the Monocular PD for the right eye, PD (OS), means the Monocular PD for the left eye. A Monocular OD is written as two numbers, for example, "32/30", and "32" represents the PD for the right eye and "30" for the left eye.
▪ Sometimes PD is written as "62/59" or they are labeled "Far" and "Near". Your PD is usually measured for distance vision, which is "Far PD", or "62" in this example. For reading glasses, doctors measure your "Near PD" or "59" in the example.
Always enter your "Far PD" for distance vision eyeglasses and enter your "Near PD" for your reading glasses only. For most people, the difference between Far PD and Near PD is about 2-3mm.
For more information about PD, please refer to this artical: How to Measure Your Pupillary Distance(PD)?