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An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist or ophthalmologist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient. If an examination indicates that corrective lenses are appropriate, the prescriber generally provides the patient with an eyewear prescription at the conclusion of the exam. In the United States, the FTC (Federal Trade Commission) requires eyewear prescribers to give each patient a copy of their prescription, immediately following an exam, even if the patient doesn't ask for a copy.〔(The Contact Lens Rule (16 C.F.R. Part 315) and the Eyeglass Rule (16 C.F.R. Part 456) ). Ftc.gov (2011-06-24). Retrieved on 2013-07-21.〕 The parameters specified on spectacle prescriptions vary, but typically include the power to which each lens should be made in order to correct blurred vision due to refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. It is typically determined using a phoropter and asking the patient which of two lenses is better, or by computer automated refractor, or through the technique of retinoscopy. A dispensing optician will take a prescription written by an optometrist or ophthalmologist and order and/or assemble the frames and lenses to then be dispensed and sold to the patient. ==Abbreviations and terms== Similar to medical prescriptions, eyeglass prescriptions are written on paper pads that frequently contain a number of different abbreviations and terms: *''DV'' is an abbreviation for ''distance vision''. This specifies the part of the prescription designed primarily to improve far vision. In a bifocal lens, this generally indicates what is to be placed in the top segment. *''NV'' is an abbreviation for ''near vision''. This may represent a single-vision lens prescription to improve near work, or the reading portion of a bifocal lens. Some prescription forms use ''ADD'' in place of ''NV'' with a single box to indicate the additional refractive power to be added to the spherical power of each eye. *''OD'' is an abbreviation for ''oculus dexter'', Latin for ''right eye'' from the patient's point of view. ''Oculus'' means ''eye''. In some countries, such as the United Kingdom ''RE'' (right eye), ''LE'' (left eye), and ''BE'' (both eyes) are used. Sometimes, just ''right'' and ''left'' are used. *''OS'' is an abbreviation for ''oculus sinister'', Latin for ''left eye'' from the patient's point of view. *''OU'' is an abbreviation for ''oculi uterque'', Latin for ''both eyes''. *''SPH'' is an abbreviation for ''spherical correction''. This corrects refractive error of the eye with a single convergent or divergent refractive power in all meridians. *''CYL'' is an abbreviation for ''cylindrical correction''. This corrects astigmatic refractive error of the eye by adding or subtracting power cylindrically in a meridian specified by the prescribed axis. *''AXIS'' is present only if there is a value for ''CYL''. This indicates the angle in degrees of one of two major meridians the prescribed cylindrical power is in. Which major meridian is referenced is indicated by the cylindrical correction being in plus or minus notation. The axis is measured on an imaginary semicircle with a horizontal baseline that starts with zero degrees in the 3 o'clock direction (as viewed by the person making the measurement), and increases to 180 degrees in a counter-clockwise direction. *''ADD'' is an abbreviation for ''Near Addition''. This is the additional correction required for reading. Most eyeglass prescriptions will contain values here. The ''spherical'' and ''cylindrical'' columns contain lens powers in ''diopters'' (see below). *''Prism'' and ''Base'' are usually left empty, as they are not seen in most prescriptions. Prism refers to a displacement of the image through the lens, and is used to treat eye muscle imbalances or other conditions (see vergence dysfunction) that cause errors in eye orientation or fixation. Prism correction is measured in ''prism diopters'', and ''Base'' refers to the direction of displacement. *''Pupillary Distance'' (''PD'') is the distance between pupil centers, usually expressed in millimeters. It is sometimes known as the ''interpupillary Distance'' (IPD). It is written as two values if the prescription is for bifocals or progressive lenses - these are the pupillary distances for the distance and near fixation (essentially, the upper and lower part of the lenses). They differ due to pupillary convergence when looking at near objects. Additionally, an eyeglasses prescription may include a ''monocular pupillary distance'' ("monocular PD"). These measurements indicate, in millimeters, the distances from the center of each pupil to the center of the nose where the center of the frame bridge rests. PD measurements are essential for all spectacle dispensings, monocular PDs being essential in progressive lenses and for those with high prescription. PDs can be measured using a pupilometer or by using a ruler. In some countries, such as the United Kingdom, PD measurement is not a legal requirement as part of the prescription and is often not included. *''Back vertex distance'' (''BVD'') is the distance between the back of the spectacle lens and the front of the cornea (the front surface of the eye). This is essential in higher prescriptions (usually above ±4.00D) as slight changes in the distance between the spectacles and the eyes above this level can cause the patient to perceive a different power, leading to blur and/or other symptoms. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「eyeglass prescription」の詳細全文を読む スポンサード リンク
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