Because contact lenses are medical devices, the correct prescription is key to providing comfort and maintaining eye health. A wrong fit or strength can cause irritation, abrasions and even possible damage to the eye.
That’s why potential contact lens wearers must be examined by an eye care professional to get a prescription, which will be valid for one year. During the exam, eye care professionals check vision and eye health and take eye measurements that help them determine the best fit and strength for the patient. Once a prescription has expired, patients will need another exam and prescription before they may buy more lenses.
But what exactly does a contact lens prescription tell the person who fills it? The abbreviations and numbers within the prescription give key information about the patient’s eye(s) to ensure proper fit and vision correction.
The information on a prescription might be divided under the headings OD and OS. OD is an abbreviation for the Latin “oculus dexter,” or right eye, while OS is short for “oculus sinister,” or left eye.
Patients who have the same prescription for both eyes will find their information under a single heading, OU, which is an abbreviation for the Latin “oculus uterque,” or each eye.
The information under these headings includes:
PWR – Refractive Power (sometimes listed as “sphere”)
This number tells how much refractive, or light-bending, power is necessary to correct the patient’s vision. A minus indicates the patient is nearsighted, while a plus indicates the person is farsighted. The farther the number is from zero, the greater amount of refraction needed. For patients who do not need vision correction but choose to wear colored lenses, this number will be zero or plano (or the abbreviated “pl”).
BC – Base Curve
This number indicates the curvature of a contact lens in millimeters. It will match or complement the patient’s cornea. A lower number indicates a deeper curve.
DIA – Diameter
This number reflects the width of the lens in millimeters.
Brand
In the U.S., a contact lens prescription specifies a brand, and the patient may buy only that brand. An exception may made for “private label” brands sold by the eye care professional; in this case, substitution of an equivalent may be permitted.
A contact lens prescription will give the following information for certain patients only:
CYL – Cylinder, and AXIS
Patients who have astigmatism, an abnormal curvature of the cornea or eye lens, will have cylinder and axis information. Cylinder tells how much astigmatism the patient has, while axis indicates the orientation of the cylinder.
ADD – Add power
Patients needing bifocal lenses will have an add power number, which indicates the amount of power needed for reading or viewing items close up. This number may be preceded by a plus sign, but it is usually understood.
Other information that may be on the prescription includes color, style or how often the patient should change the lenses.
Popularity: 1% [?]
Related Searches:
Free Contact Lenses Samples - This website explains how to go about getting in on the offers available for free contact lenses, sample lenses and 