The correction values for your glasses can be found on the glasses pass or on the prescription from the ophthalmologist.
The optician gives his customer a prescription for new prescription glasses or sunglasses with prescription lenses . At first, most people have little use for what is written on it. We translate the abbreviations on the glasses passport and explain their meaning.
The document has the format of a credit card, but no uniform, standardized design. But what is written on the different versions is basically the same. These are the most important individual values according to which the optician adjusted the lenses. These values are always preceded by a thorough eye test including eye measurement by the optician or ophthalmologist. The latter transmits the results of his examination by prescription for glasses, so that the optician makes the glasses on this basis.
On the one hand, the glasses pass is used to provide the glasses wearer with their own information. On the other hand, every optician and ophthalmologist can read from it when and how the glasses were made in detail. The date serves as an important indication of when the eye test and eye measurement were carried out. If this was already a few years ago, a new test should be carried out before the glasses are made. Poor eyesight is not a permanent condition, it also changes. Then the existing glasses can sometimes no longer optimally correct the visual deficit. That is why people who wear glasses should have their eyesight checked regularly – preferably every two years.
Thirdly, the glasses pass is a practical helper when you are out and about. Keywords: loss of glasses or damage to glasses. Anyone affected by this on vacation or while traveling takes their glasses pass to the nearest optician. He can then quickly and easily produce replacement glasses based on the glasses passport data (glasses values).
In addition to the name of the person who wears the glasses, the company name of the optician, the date the glasses were made, the lens material and sometimes the details of the glasses frame, a whole lot of other data appears on the glasses passport. These are whole words, abbreviations and numbers. A variety of information - and the abbreviations are different depending on the version of the glasses. There, for example, one and the same indication "R", "Re", "RA" or "L", "Li", "LA" or "P", "Pr." "Pr", "pr", " Prism.", "Prism.". Or the designation of a value is written out in full, but only as an abbreviation in another version of the prescription, such as "Base" and "B". What do terms, letters and numbers tell us?
The indications associated with these abbreviations refer to the right eye.
The information on these abbreviations relates to the left eye.
There are variants of glasses that contain these letters. They describe the type of glasses. Anyone who is short-sighted or far-sighted or has astigmatism gets distance glasses (F). Persons aged 45 and over need near-reading glasses (N) to read. Many of these presbyopia, whose ametropia has to be corrected for both near and far, wear varifocal glasses (G) or some other type of multifocal glasses. If this information is missing, it doesn't matter. TheThe optician or the ophthalmologist decides what type of lenses are involved.
The value of the refractive error for each eye is given under sphere in dioptres (dpt), the unit of measurement for the refractive power of a lens. In front of the number is a minus (–) for nearsightedness (myopia ), and a plus (+) for farsightedness (hyperopia). The degree of ametropia is graded in 0.25 increments, i.e. 0.25, 0.50, 0.75, 1.00 and so on. The higher the value, the more pronounced the visual impairment. These values describe the necessary correction through the glasses. For this purpose, the spectacle lens is given the necessary refractive power by means of a special finish to correct the ametropiaof the eye and make sharp, effortless vision possible again.
Not every prescription for glasses has a number next to the abbreviation for cylinder. If so, it is given in increments of 0.25 in dioptres. Depending on the type of calculation, there is either a plus (+) or a minus (–) in front of it. These prescription values indicate astigmatism (astigmatism). In those affected, the cornea of the eye is not smooth but uneven, which deflects light rays entering the eye and causes blurred vision. This ametropia is corrected according to the determined values with a special lens cut, the so-called cylinder. The Top Hat-Value of the right eye may differ from that of the left eye.
As with the cylinder, a value only appears in the glasses pass for the axis if astigmatism has been determined. This information is important for the correction of this ametropia in that it describes the direction of the astigmatism and thus specifies the direction for the correcting cylinder. This value is an angular measure and ranges from 0 to 180 degrees in 1 degree increments. Since very few people have the same eyes, the axial position of astigmatism can also be different in the right eye than in the left. That means: different axis values for both eyes.
Addition comes into play, for example, with varifocal glasses , bifocal glasses, VDU glasses or reading glasses. Varifocal glasses correct both distance and near vision problems. Presbyopic people in particular benefit from this, since their eye lenses, which are no longer so elastic, are becoming increasingly difficult to adjust to different distances.
The addition value is given in dioptres (dpt) in increments of 0.25 and is always a plus value. Behind this is the addition in the near vision range of the multifocal lens, which is added to the distance vision in order to achieve better close-up vision.
The addition value results from the difference between the sphere value for the distance and the sphere value for the near. The near value is always greater than the far value. Example: A distance value of -1.00 dpt and a near value of +1.50 dpt were determined for an eye. In this case, the difference between the two is 2.50 dpt, which is referred to as addition or near addition. Another example: distance value +1.50 dpt, near value +3.25 dpt, addition equals 1.75 dpt.
Usually there is only one sphere value on the glasses pass or on the glasses prescription, namely that for the distance, but also the value of the addition. For the required near value, the sum is formed from both values, i.e. sphere and addition. Examples: Sphere value +1.50 dpt plus addition 2.25 dpt equals near value +3.75 dpt; Sphere value –1.50 dpt plus addition 2.50 dpt equals near value +1.00 dpt.
In most cases, the addition is the same in both eyes. It increases with age as presbyopia progresses. Up to 3.00 dioptres are normal.
Pupillary distance is the distance between the center of the pupil and the middle of the bridge of the nose. The optician or ophthalmologist measures the PD in millimeters for each eye individually, whereby the gaze must be directed straight ahead. The distance is only the same for a few people - this is why the glasses passport usually contains different values for the right eye and for the left eye. Sometimes there is only a number in the glasses pass: This is the distance between the two centers of the pupils. This total PD averages about 62 millimeters in women and about 65 millimeters in men.
The lenses can only be precisely centered if the pupillary distance is carefully determined. And only then is the right point of vision through the finished lenses exactly in front of the pupil, and the spectacles wearer can look forward to an optimal viewing experience. Improper centering can cause blurred vision or headaches. In the case of varifocals in particular, even minor errors in the centering of the lenses have a significant impact on the quality of vision. Therefore, have the pupillary distance measured professionally - the optician uses high-precision technology for this.
The prism entry is necessary if the lenses are to correct a latent strabismus (heterophoria, corneal ametropia). The strength of the primate is usually given in centimeters per meter (cm/m). A prismatic lens deflects the light beam so that it hits the defective eye at the right angle. Such a lens is thicker on one side than on the other.
The optician needs the specification of the base position in order to incorporate the correct position of the prism in the spectacle lens. The base value in the glasses pass is given either as a whole number in degrees between 0o and 360o or as a directional indication "outside/a", "inside/i", "top/o" or "bottom/u".
In addition to the abbreviations mentioned, some versions of the glasses pass also contain additional information, such as: