Eyeglasses Prescription Glossary / Abbreviations
OD - This is shorthand for oculus dextrus which means Right Eye.
OS - This is shorthand for oculus sinister which really means Left Eye.
OU - This is shorthand for oculus uterque which really means Both Eyes. If you see this, you'll want to enter the prescription the same on both eyes.
Sphere or Power - SPH or PWR - This is the main strength of your eyeglass prescription, and is written in 0.25 increments. If the field has 'SPH', 'PL', 'PLANO', or '00', this means your there is a 0.00 power as should be entered as so. Military Contact Lenses can create lenses for prescriptions with Sphere ranges between -20.00 and +20.00.
Plano - PL - This indicates there is no spherical correction in this eye. A plano lens would have no focusing power or correction to it.
Balance - This indicates there is no vision correction in this eye. It's a non-prescription lens and is used when only one of your eyes requires vision correction
Cylinder - CYL - This indicates the amount of astigmatism, and is written in 0.25 increments. Not all prescriptions have a cylinder correction, and some prescriptions have a cylinder correction in only one eye. If you don't have an astigmatism correction then your doctor may leave this field blank, or they may put 'SPH', 'DS', 'Plano', or '00' in this field. This means you do not have an astigmatism correction in one or both eyes. Military Contact Lenses can create lenses for prescriptions with Cylinder ranges between -5.00 and +5.00. Positive (+) Cylinder values will be converted into negative (-). See Why Does Military Contact Lenses convert positive (+) Cylinders values to negative (-) values? for an explanation of why.
Axis - AX or X - This is also part of the astigmatism correction, and is written in increments of 1 (one). If there is no cylinder, then there should be no axis. Since it's a degree/angle, it will be represented as a value between 1 and 180. If there is no cylinder, it's possible that the doctor might enter 0, but this would just indicate that there is no axis. Military Contact Lenses can create lenses for prescriptions with ADD ranges between +0.25 and +3.00.
ADD - This is a value that is commonly used for bifocal or progressive lenses, as well as reading glasses. It indicates how much power gets added to the distance prescription to create the reading-only prescription; or as it applies to the glasses you'll order from Military Contact Lenses, it determines the correction strength for the bottom half of your bifocals progressive lenses. It is written in increments of 0.25. Military Contact Lenses can create lenses for prescriptions with ADD ranges between +0.25 and +3.00.
Prism or Base or Base Curve - A prism is used when both eyes are not properly aligned and they need a prism to re-align them. The Base is the rotation of the prism. These fields are rarely used, and the correction type is not currently offered on Military Contact Lenses eyeglasses. There are two separate parts to a Prism correction. The first part is the diopter strength (e.g. 2.0) and the second is the direction (e.g. BU). There are four different directions. Base-Up (BU), Base-Down (BD), Base-In (BI), and Base-Out (BO).
Pupilary Distance - PD - This is the distance in millimeters between your right pupil and left pupil. A more detailed explanation of Pupillary Distance can be found in our What is Pupillary Distance (PD)? page.
Segment Height or Seg Height - SH - This is the vertical measurement in millimeters from the bottom of the lens to the beginning of the progressive addition on a progressive lens, or the top line of a lined bifocal. Segment height does not apply to Single Vision lenses. You will need the frame to be able to measure segment height because you can only measure it while the glasses are on your head.
Near Vision or Near Vision Only - NV or NVO - This is written when your doctor is recommending reading-only glasses. (This is also known as farsighted)
Distance Vision or Distance Vision Only - DV or DVO - This is written when your doctor is recommending distance-only glasses. (This is also known as nearsighted)
Amblyopia - The medical term for lazy eye, which is a loss or dimness of vision without any apparent disease of the eye.
Antimetropia - The medical term for when one eye is Myopic and the other is Hyperopic.
Astigmatism - An optical condition that can cause blurry vision. This is corrected by a Cylinder and Axis correction on a prescription.
Barrel - The barrels attached to the endpiece, combined with the barrels attached to the temples, interlock and join together to hold both the frame and temple pieces together.
Bench Alignment - The standard adjustment of an eyeglass frame before it is custom fit to the customer.
Bend - The bend is where the temple curves behind the ear.
Binocular -v A term used to describe the simultaneous use of both eyes at the same time.
Bridge - BRG - The measurement in millimeters of the small connecting piece between the lenses of a frame.
Combination - These frames are made of both plastic and metal. They can have a metal front with plastic temples or other variations.
Compound Lens - A lens that contains both a sphere and cylinder
Cornea - The clear, transparent portion of the outer covering of the eyeball which covers the front part of the eye.
Crystalline Lens - Also known as just "lens", it is a transparent and colorless body located towards the front of the eyeball. Its function is to bring rays of light to a sharp focus on the retina.
Diopter - A unit of measurement of the refractive power of a lens equal to the reciprocal of the focal length measured in meters.
Diplopia - The medical term for when someone sees one object as two, it is also called double vision.
Distance Between Centers - DBC - This is the distance from the geometric center of one lens to the geometric center of the other lens, measured in millimeters.
Distance Between Lenses - DBL - This is the measurement in millimeters between the lenses of a frame.
Effective Diameter - ED - The largest diagonal measurement of the lens that passes through the center of the lens.
Emmetropia - The medical term for someone with 20/20 or better vision. This type of vision does not need correction.
End Piece - The part of the frame that connects the temples to the frame front.
Eyewire or Rim - The part of the frame which surrounds the lens and holds it in place.
Frame PD or Geometric Center Distance (GCD) - This is the distance from the geometric center of one lens to the geometric center of the other lens, measured in millimeters.
Full Frame - A one piece frame usually composed of just one type of metal.
Geometric Center - G - The center of each lens within the frame.
Half Eye - Designed for reading but can also be sold for other uses. The B measurement (vertical measurement of the eyewire) is half the size of a normal full frame.
Hinge - The hinge on a frame is made up of a screw and two pieces that have barrels.
Horizontal - A -The horizontal measurement of the lens for a specific frame, measured in millimeters.
Hyperopia - The medical term for someone with farsighted vision who is able see things that are distant or far away clearly, but need vision correction in order to see things that are near or close-up. Hyperopia is usually corrected with a prescription that has a positive (+) Sphere.
Keratitis Sicca - The medical term for dry eye.
Lensometer - An instrument which measures dioptric power, axis location, optical center and prism of a lens.
Macular Degeneration - A deterioration of the macula which results in a gradual loss of central vision (the center of your vision).
Monocular - Refers to only one eye.
Myopia - The medical term for someone with nearsighted vision who is able to see things that are near or close-up clearly, but need vision correction in order to see things that are distant or far away. Myopia is usually corrected with a prescription that has a negative (-) Sphere.
Ocular Height - OC - The measurement in millimeters from the center of the pupil to the bottom edge of the frame.
Oculus Dexter (OD) - Latin for right eye
Oculus Sinister (OS) - Latin for left eye
Oculus Uterque (OU) - Latin for both eyes
Opthalmologist - A medical doctor who has extensive education and training in surgery, diseases, functions, and refractive errors of the eye.
Optician - A person who prepares and dispenses optical devices to fill the needs of the patient's prescription. He or she also maintains these devices by making adjustments to them.
Optometrist - A person who is professionally trained and licensed to examine the eyes for visual defects, diagnose problems and impairments and prescribe corrective lenses or provide other types of treatment.
Pantoscopic Tilt - The tilting of a spectacle frame so that the top of the frame is farther away from the face than the bottom.
Presbyopia - The medical term for someone who needs vision correction in order to see things that are both close-up and far away. A Bifocal prescription is used for this type of vision correction.
Progressive Additive Lens - PAL - The ADD value specifically for progressive lenses.
Refraction - The change in direction of light as it passes obliquely from one medium to another; such as the refraction of light as it passes through the crystalline lens (eye).
Retina - The innermost membrane lining located at the back of the eye. It is comprised of nerve fibers and functions like the film in a camera. To see clearly, light must form a single focus point on the retina.
Retroscopic Tilt - The tilting of a spectacle frame so that the bottom of the frame is farther from the face than the top of the frame. Retroscopic tilt should be added to frames when they rest on the cheeks.
Rimless - Usually made of metal and made up of temples, end pieces, a bridge, and two lenses. The lenses are mounted to the bridge and end pieces, which creates the frame front.
Semi-Rimless - The eyewire on these frames does not go completely around the lens, instead it connects to both the end pieces and the bridge, and can be mounted in a variety of ways. The most common mounting uses a nylon cord to secure the lenses to the bridge and end pieces.
Shank - The longest portion of the temple.
Spatula - The temple spatula, also known as the temple tip, end, or earpiece, is the portion of the temple which extends from the bend to the end.
Strabismus - Also known as being cross-eyed, it is the failure of the two eyes to simultaneously look at the same object.
Temple - Temples are the component of the frame which rest over the ears to properly hold eyeglasses in place.
Vertex Distance - The distance from the back surface of a lens to the front of the cornea.
Vertical - A - The vertical measurement of the lens for a specific frame, measured in millimeters.