Understanding what your optometrist prescribes
OK, you have just had an eye test and your optometrist or ophthalmologist has given you an eyeglass prescription. He or she probably said that you’re nearsighted or farsighted, or maybe you have astigmatism. But what do all those numbers in your eyeglass prescription mean? Your eyeglass prescription also might have a column labeled OU; This is the abbreviation for the Latin term oculus uterque, meaning both eyes.
Though the use of these abbreviated Latin phrases is conventional for prescriptions written for glasses, contact lenses and eye medications, some physicians and clinics have chosen to update their prescriptions and utilize RE (right eye) and LE (left eye) instead of OD and OS. On your glasses prescription, the data for your right eye (OD) comes before the information for your left eye (OS). Your eyeglass prescription comprises other terms and abbreviations also.
If the number appearing under this heading includes a minus sign (–), then you’re nearsighted; if the amount has a plus sign (+) or isn’t preceded by a plus sign or a minus sign, you’re farsighted. The period sphere means the correction for nearsightedness or farsightedness is spherical or equivalent in all meridians of the eye.
If nothing appears in this column, either you don’t have any astigmatism, or your astigmatism is so slight it’s not actually necessary to fix it with your eyeglass lenses. The expression cylinder; means that this lens power inserted to correct astigmatism isn’t spherical, but rather is shaped so 1 meridian has no extra curvature, and the meridian perpendicular to this no extra power meridian comprises the most power and lens curvature to correct astigmatism. Cylinder power consistently follows sphere power in an eyeglass prescription.
This clarifies the lens meridian which comprises no cylinder ability to correct astigmatism. The axis is characterized by a number from 1 to 180. The number 90 corresponds to the vertical meridian of the eye, along with the amount 180 corresponds to the horizontal meridian.
The axis is the lens meridian that’s 90 degrees from the meridian which comprises the cylinder power. This is the additional magnifying power put on the bottom portion of multifocal lenses to correct presbyopia. The amount appearing in this section of this prescription is obviously a plus energy, even if it’s not preceded by a plus sign. Generally, it is going to vary from +0.75 to +3.00 D and are the identical power for the two eyes. Only a small proportion of eyeglass prescriptions include prism.
When present, the total amount of prism is indicated in either metric or fractional English units (0.5 for example), and the management of the prism is signaled by noting the relative position of its foundation or thickest edge. Four abbreviations are used for prism management: BU = foundation upwards; BD = base ; BI = foundation in (toward the wearer’s nose); BO = base out (toward the wearer’s ear).
Sphere power, cylinder power always appear in diopters. They are in decimal form and are composed in quarter-diopter (0.25 D) increments. Axis values are whole numbers from 1 to 180 and indicate just a meridional place, not a power. When prism diopters are indicated in decimal form, typically just 1 digit appears after the interval (e.g., 0.5).
An Eyeglass Prescription Isn’t A Contact Lens Prescription
Eyeglass and contact lens prescriptions are not the same. It doesn’t contain certain information that’s imperative to a contact lens prescription and that may be obtained only through a contact lens consultation and fitting. One reason that eyeglass and contact lens prescriptions aren’t the same: Eyeglass lenses are positioned at a distance in the eyes, while contacts rest directly on the eyes. That space affects the lens power needed for eyes to focus properly.
As well as the data in an eyeglass prescription, a contact lens prescription should specify the base (fundamental) curve of the rear surface of the contact lens, the lens diameter, and the particular manufacturer and brand name of this lens. Additionally, the power of an eyeglass prescription often is altered when deciding the best contact lens power. 1 reason is that eyeglass lenses are worn some space (typically about 12 millimeters) in the surface of the eye, whereas contact lenses rest directly on the eye’s cornea.
A true contact lens prescription can be written only after a contact lens fitting was performed and the prescribing physician has evaluated your eyes’ answer to the lenses and to contact lens wear generally.
Your Eyeglass Prescription: It Is Yours To Keep
Your eye doctor must provide you a copy of the prescription whether you request it. Eye doctors may not condition the release of your prescription on your arrangement to buy eyeglasses out of them, nor will they charge you an additional fee to release your prescription. They may also not disclaim liability for the accuracy of the prescription if you buy eyeglasses elsewhere.
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