When ophthalmologists detect a visual deficiency, they write a prescription for glasses.
This prescription is given to the optician so that they can place the right lenses with the exact visual correction on the pair.
However, for non-professionals, such a prescription can be complex to understand, especially terms such as axis.
Written in medical jargon, a prescription for eyeglasses contains many complex words or abbreviations.
The first data are visual eye measurements given in dioptres.
OD and OS refer to the right and left eyes respectively.
The abbreviation OU refers to both eyes.
The higher the number following the abbreviation, the stronger the visual correction required.
These figures are preceded by a minus in the case of myopia and a plus in the case of hyperopia.
Many other abbreviations such as NV (near vision), DV (distance vision) or PD (pupillary distance) also appear on the prescription.
Among the terms appearing on a prescription for glasses is the word axis.
The information displayed under the name axis only concerns people with astigmatism.
As a matter of fact, the axis refers to the angle or specific orientation of your astigmatism.
This axis number is used by the optician to determine the position of any cylindrical power on the eyeglass lenses.
This data is measured in degrees and ranges from 1 to 180.
However, the height of the number does not determine the severity of your visual defect but only your astigmatism's position.
The closer the number is to 180 degrees, the more horizontal the position is.
A vertical one tends to match 90 degrees.
Do not hesitate to ask your optician for more information on the specific axis data noted on your prescription.
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