Reading Your Prescription
If you have good eyesight, that's fine. But if happened that you have been written a prescription for glasses, how to understand what those numbers mean, icons, incomprehensible terms and strange acronyms?
OD и OS and others abbreviations
OD and OS – are short for the Latin terms «oculus dexter» and «oculus sinister», translated as the right and left eyes, respectively. Sometimes there is only OU abbreviation ( «oculus uterque»), which means "both eyes."
These designations are traditionally used by ophthalmologists and optometrists when prescribing glasses, contact lenses or eye drops.
In ophthalmology in general and in eyeglass prescription in particular the information about the right eye, and then on the left always contains the first. It is easier to avoid confusion and errors.
You can meet other abbreviations in your eyeglass prescription:
Sph (sphere) - «sphere»-Indicates the optical power of the lens expressed in diopters, necessary to correct your nearsightedness, farsightedness or presbyopia. If the numerical value is before the "-" sign, it means that you have myopia, scientifically, myopia, is known to be compensated for minus, scattering, lenses. Most of the minus sign is written in Latin «concave». If it is "+" sign, and you have written out glasses for distance, then you farsightedness, or hyperopia, the need to plus-collecting lenses, designated «convex».
Cyl (Cylinder) - «cylinder" - indicates the optical power of the lens used for the correction of astigmatism. Astigmatism is said in the case when the surface of the cornea is irregular, nonspherical wherein one of the meridians refraction occurs more than in others.
This anomaly is corrected by cylindrical lenses. This must indicate the position of the cylinder axis (Axis, abbreviated Ax) in degrees from 0 to 180. This is due to the refraction of light passing through the cylindrical lens. Refracted rays coming perpendicular to the axis of the cylinder. But running parallel to the axis do not change their direction. These properties allow you to "fix" the refraction of light in the required specific meridian.
Such frame is used to determine visual acuity and selection of points
The value of the cylinder is a minus - for the correction of myopic (nearsighted), astigmatism, or positive - for the correction of hyperopic (farsighted) astigmatism.
Meridians are defined by the superposition of a special scale on the front surface of the eye. Typically, such a scale built into the rim of the test used to determine visual acuity and selection of points, called a scale or system TABO.
Add - add power - so-called "gain near vision" - the difference between the zones in diopters for distance vision and to work in close proximity in the manufacture of bifocal and progressive glasses to correct presbyopia. It means that if for distance vision Need lenses of +1.0 diopters, and in the vicinity of +2.5 diopters, the addition power of +1.5 diopters amount. The maximum addition power does not exceed +3.0 diopters.
Prism - this is the power of the prismatic lens, measured in prism diopters. (pd or the triangle sign, if the prescription is written by hand). Prismatic lens are used to correct strabismus. In appointing the prismatic lenses depending on the type of strabismus is indicated in which direction the prism base - the base upwards, downwards, inwards (towards the nose) outwards (to his head).
Optical power of spherical and cylindrical lenses, as well as the addition power is indicated in diopters with a maximum specification up to 0.25 diopters. (e.g, 0.75 D, 1.25 diopters, etc.) prismatic diopters are rounded to half the value of -0.5 pd
Dp (distancia pupilorum) - the distance between the center of the pupil in millimeters. To give it 2 mm larger than the vicinity.
An example of a prescription for glasses
OD sph-1.5 cyl -1.0 ax 90 (sph-1.5 - 1.0 x 90)
OS sph -2.0
This recipe means that the right eye needs spherical lens correction of myopia -1.5 diopters, has astigmatism, which compensated for the negative cylindrical lens 1.0 diopters, the axis of the cylinder; inactive meridian axis is 90 degrees. For the left eye -assigned spherical correction of the negative lens of 2.0 diopters.
OU sph +1.0 +1.5 add
In this case both eyes written bifocal lens area gave +1.0 diopters, and the addition of +1.5 diopters for near vision.
Prescription contact lenses
Why we cannot use the eyeglass prescription to purchase contact lenses? Prescriptions for eyeglasses and contact lenses are slightly different from each other. A contact lens, unlike glasses dressing directly on the cornea, is embedded in the optical system of the eye.
Firstly, in the prescription of the contact lenses must be indicated base curve and lens diameter. Secondly, contact lenses worn directly on the cornea, to form a single optical system with the eye, as opposed to points which are spaced from the cornea at a certain distance (on average 12 mm). Therefore, the short-sightedness necessary to significantly reduce the power of contact lenses, and for farsightedness - increase.
If you were selected the glasses or contact lenses, you should be given a prescription. Save it. When you will check vision next time, you be able to compare the results. In addition, regardless of where the survey, having the recipe, you can order glasses or contact lenses in our store.