Contact lens prescription is necessary to ensure that you get the right, safe and comfortable lens for your eyes to give excellent vision.
Your contact lens prescription is full of technical jargons and short forms, which you cannot understand at first. You can ask your doctor any details regarding your eye prescription. In case if you have forgotten to ask your eye doctor, and now googling hours for details. This guide will help you in understanding your contact lens prescription.
In the United States, it is your right to have your prescription handed over to you. Even if you do not ask for it, by law; your eye practitioner is obliged to give you, your contact lens prescription after extensive lens exam and fitting.
Listed and described in details below are the terms included in the prescription. It is not necessary that all items should be there, but as prescribed by Federal Trade Commission (FTC) the following items shall be included:
- Patient’s name – It is necessary so that no one else could use that prescription.
- Prescribed by – Name, address and any other details of your eye specialist.
- Issue date (Examination date) – At which patient receives prescription after fitting of the contact lens.
- Expiration date – Determined by your eye practitioner, based on his or her belief that your lens inspection is due. Usually, contact lens prescription is valid for one year or two.
- OD, OS, and OU – OD represents for “oculus,” is the Latin word which refers to the eye on the right. OS represents for “oculus sin,” is the Latin word which refers to the eye on left. The prescription has these two columns showing the measurements of both the eyes separately. If the same measurement applies to both of your eyes, then your prescription will have OU. OU stands for oculus uterque which means each eye. Usually, OD is in the left column, and OS is in the right column which is simply how your eye specialist sees you when he stands in front of you.
- Refractive power – The amount (measured in diopters – a unit of optical power of a lens), of lens correction required to sharpen the vision to a satisfactory level. A (-) minus sign shows that prescription is for nearsightedness (myopia). The (+) sign is for farsightedness (hyperopia). Higher number away from zero means that more correction is required.
You may have prescription written right and left and have columns in each stating “Sph” which means sphere, it is the same measurement of eyes explained above. In such a case, OD, OS, and OU will not be provided.
- Base Curve (BC) – The curvature of the inner surface of a lens is called a base curve. The back curvature of a lens should match with the curvature of the cornea for best fit. A lower number (measured in millimeters), means that the curvature of the cornea is steep.
- Diameter (DIA) – The distance from one point of a lens to another through the center of the lens, measured in millimeters. It is the most important measurement of the lens because it decides where the edges of the lens are going to rest.
- Cylinder (CYL) – A cylindrical value, measured in diopter, is the difference between the highest point (steepest) and lowest point (shallowest curves) of your cornea. The value simply tells you the shape of the cornea. A Higher number indicates that your cornea is more oval than round. The value does not show the amount of astigmatism.
- Axis – It is a value, measured in degrees, necessary to correct astigmatism. It indicates the adjustment of cylindrical power in a lens, to compensate for the non-spherical shape of the cornea when you have astigmatism.
- Add – It usually has value for people of age 45 plus. It is the extra magnifying power added in some part of your bifocal lenses for closely reading and viewing.
- Color – If your contact lens changes or enrich your eye color or a specific design will be suggested.
- Brand – A specific brand or equivalent substitution brand must be prescribed by your eye practitioner, under the state law. Sometimes, it also includes a replacement schedule e.g. (Optha lens one week)
It is important to note here that contact lens prescription and eyeglass prescription are different and you can search for more information here. Even if you have spectacles prescription, you will require a separate prescription for a contact lens before purchasing.