In glasses prescription, ADD stands for "Addition", or "Near Addition", which means "Near Addition". This value is used to indicate the additional correction power of glasses, mainly used to correct presbyopia.
What ADD Does
The ADD value is a positive number that is added to the primary spherical power to create a bifocal or progressive lens to help improve near vision. This allows a pair of glasses to correct both farsightedness and presbyopia, allowing people to easily perform a variety of tasks when using glasses, whether looking at distant objects or close objects.
Example
A typical eyeglass prescription might look like this:
Right Eye (OD): -1.00 +0.50 x 90
Left Eye (OS): -1.25 +0.75 x 100
ADD: +2.00
In this example, the primary power for the right eye is -1.00 and the left eye is -1.25. The ADD value of +2.00 is added to these primary powers to provide additional magnification for near vision.
The specific value of the ADD is determined during an eye examination by an optometrist or ophthalmologist based on the individual's near vision requirements. It ensures that individuals with presbyopia can have clear vision at all distances with a single pair of glasses.
