However, prescribing and dispensing of glasses are closely linked, so it is best to have your glasses dispensed where you have your eyes examined. Your prescription can be dispensed wherever you choose. It does not contain certain information that is crucial to a contact lens prescription and that can be obtained only during a contact lens consultation and fitting.Ī prescription is usually valid for two years, but your optometrist may recommend that you have your eyes examined more frequently, depending on your particular circumstances. A spectacle prescription is for the purchase of glasses only. Spectacle and contact lens prescriptions aren’t the same.
Only a small percentage of eyeglass prescriptions include prism. Prism – This is the amount of prismatic power prescribed to compensate for eye alignment problems. If a reading addition is stated, this means you need different glasses prescriptions for reading and for distance. It is usually only needed for patients over 40-45 as focusing ability declines as we get older (presbyopia). Generally, it will range from +0.75 to +3.00 D and will be the same power for both eyes. The number appearing in this section of the prescription is always a “plus” power. N5 is the smallest sized type that you will normally find and N8 is approximately the size of normal newsprint.Īddition – This is the added magnifying power for reading. Near VA represents the smallest sized print that can be read. If you have 20/20 vision, you can see clearly at 20 feet (6m) what should normally be seen at that distance. 20/20 or 6/6 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet (6m). The larger the denominator, the worse the eye sees, so a VA of 6/12 is half as good as 6/6.
In the US, VA is measured at 20 feet (e.g. In the U.K visual acuity is conventionally measured at six metres, so the numerator is 6 (e.g. V.A stands for Visual Acuity which is the best attainable vision achieved with your spectacle lenses. If a prescription includes cylinder power, it also must include an axis value, which follows the Cyl power. The term “cylinder” means that this lens power added to correct astigmatism is not spherical, but instead is shaped so one meridian has no added curvature, and the meridian perpendicular to this “no added power” meridian contains the maximum power and lens curvature to correct astigmatism.Īxis represents the orientation of the cylinder (from 0-180 degrees) and is the angle at which the lens is set into the frame. This causes the vision to be distorted for both distance and near objects. Astigmatism is caused when the eye is not completely spherical, like a football, but is shaped more like a rugby ball. Most people have some degree of astigmatism.
If nothing appears here or the letters ‘DS’ after the Sphere it means that there is no astigmatism. The term “sphere” means that the correction for nearsightedness or farsightedness is “spherical,” or equal in all meridians of the eye.Ĭylinder (Cyl) indicates the amount of astigmatism, this is usually a negative number. If the number is positive (+) you are longsighted ( hypermetropic), if it is negative (-) you are shortsighted ( myopic). Sphere (Sph) represents the amount of dioptric power required to correct your long or short sightedness. When your eye examination is complete you’ll be given a prescription.
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