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May 28, 2014

Understanding Your Eyeglass Prescription

After getting an eye exam and learning that you’ll need glasses, the next step is picking out a pair that’s right for you. Perhaps you’ve also learned that you’re nearsighted, or farsighted, and maybe even have astigmatism.  On your prescription, it won’t be written so simply, and all the numbers and abbreviations are likely to confuse you. Knowing how to interpret your prescription will help you be more knowledgeable when talking with the optician and buying your eyeglasses and other eye care needs.

Some doctors abbreviate right eye and left eye as RE and LE, but a more traditional way of referring to them is OD and OS which in Latin means oculus dexter and oculus sinister. Oculus uterque means both eyes.

Your prescription might also have abbreviations or words like SPH, CYL, “axis,” “prism” or “add.” The first, SPH refers to sphere. The term sphere indicates that the correction for farsightedness or nearsightedness is spherical. There will be a number next to it, or below a heading. If the number has a minus sign in front of it, you are nearsighted, and if it has a plus, or no negative sign, you are farsighted. The numbers refer to the amount of lens power that is prescribed to correct your vision.

Some prescriptions will have a CYL which stands for cylinder. This indicates astigmatism and that the lens power to added to correct for astigmatism is not spherical. Cylinder power always follows sphere power in an eyeglass prescription.

The axis value or “x” describes the lens meridian. It is defined by numbers ranging from 1 to 180, 90 being the vertical meridian and 180 being the horizontal meridian. Eyeglass prescriptions that contain cylinder power must have an axis value following the cylinder power. The “add” value is the magnifying power that is added to the bottom part of a multifocal lens to correct presbyopia. It will always be a positive value even if it isn’t preceded by a “+” sign and should be the same value for both eyes.

Only a small amount of prescriptions have prismatic power, which refers to eye alignment problems. There are four abbreviations to describe the prescription, BU (base up), BD (base down), BI (base in), BO (base out).

Keep in mind that eyeglass prescriptions and contact lens prescriptions are not the same so if you want contact lenses you’ll have to get a separate consultation and fitting. It is also good to know that by law, you are entitled to keep your prescription and take it home with you. If you have any questions regarding eye glass prescriptions or would like to get a new exam, call us at 877-871-1684 or visit our website www.eastwesteye.com for more information.

 

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