How to read your prescription
To start, below you can find a few abbreviations used by your ophthalmologist :
- OD : This is the abbreviation for "Oculus Dexter", latin for Right eye
- OS : This is the abbreviation for "Oculus Sinister", latin for Left eye
- OU : Right and left eye
- ADD : Addition
- SPH : Sphere
- CYL : Cylinder
- DV : Distance vision
- NV : Near vision
- VA : Visual acuity
- IV : Intermediate vision
What do those values mean?
The values of the correction you need are expressed in quarters of diopters.
The values that are not between brackets, preceded by a + refer to hyperopia, those preceded by a - refer to myopia.
The values between brackets refer to an astigmatism, and the value that follows is expressed in degrees and corresponds to the axis of the astigmatism.
This is presbyopia, with the correction to apply.
The term "ADD" means "addition" for presbyopics. This is your reading addition and relates to the amount of additional correction needed to focus at close distance. This value is always positive.
It is calculated by substracting the far distance Sphere from the near distance Sphere.
Main defect of the eye
In ophthalmology, hyperopia, myopia, astigmatism and presbyopia are the main defects of the eyes that can be corrected with glasses or lenses.
Example of a prescription for a hypermetropic :
- OD: +2,50 OS: +3,00
It often occurs that each eye needs an individual correction.
Exemple of a prescription for a myopic :
- OD: -3,75 OS: -3,25
Astigmatism can accompany hyperopia and myopia.
Examples of prescriptions for a hypermetropic, astigmatic person :
- OD: +2,50 (+1,25) 90° OS: +3,00 (+0,75) 85°
- or OD: (90°+1,25) +2,50 OS: (85°+0,75) +3,00
The values between brackets indicate the value of the astigmatism. The last value, in degrees, indicates the axis of the astigmatism. It is indicated with a + or a - symbol between brackets. The description below can also be written as follows :
- OD: +3,75 (-1,25) 180° OS: +3,75 (-0,75) 175°
- or OD: (180° -1,25) +3,75 OS: (175° -0,75) +3,75
Exemples of prescriptions for a myopic and astigmatic person :
- OD: -4,50 (+2,00) 35° OS: -3,75 (+1,25) 65°
- or OD: (35° +2,00) -4,50 OS: (65° +1,25°) -3,75
Can also be written like this :
- OD: -2,50 ( -2,00) 125° OS: -2,50 (-1,25) 155°
- or OD: (125° -2,00) -4,50 OS: (155° -1,25) -2,50
The crystalline lens is unable to provide the power to adapt to a clear near vision. We have to assist the lens by adding a magnifying power for near vision, applied to the bottom part of multifocal lenses to correct presbyopia. The number appearing in this section of the prescription is always a "plus" power, even if it is not preceded by a plus sign. It is calculated as the difference between the power needed for the eye to have a clear far sight and the value needed to have a clear near vision. Generally, it will range from 0.50 to 3.50.
Example of a prescription for a presbiopic and myopic person:
On the prescription
- OD: -4,00 ADD: 2,00 OS: -3,50 ADD: 2,00
Example of a prescription for a hyperopic and presbiopic person:
On the prescription
- OD: +2,50 (+0,75) 15° ADD: 1,75 OS: +2,25 (+0,50) 75° ADD: 1,75