Eye prescriptions can often appear as a series of numbers and abbreviations, which might seem confusing. Understanding each component helps clarify your vision needs. This article explains the “ADD” value, a specific part of an eye prescription that addresses a common age-related vision change.
Understanding the ADD Value
The “ADD” value on an eye prescription stands for “Addition,” representing the magnifying power needed for near vision tasks. This value is always a positive number, typically ranging from +0.75 to +3.00 diopters (D). Eye care professionals apply this power to the lower portion of a multifocal lens. This supplements your distance prescription, allowing for clear focus on close-up objects.
Why ADD is Necessary
The “ADD” value is necessary due to presbyopia, a natural, age-related condition. Presbyopia typically begins around age 40, causing a gradual loss of the eye’s ability to focus on nearby objects. This occurs because the crystalline lens inside the eye, flexible in youth, becomes more rigid with age, hindering its capacity to increase its power for clear near vision.
Common symptoms include difficulty reading fine print, especially in low light, and needing to hold reading material farther away. Individuals may also experience eyestrain or headaches after prolonged near work. This condition affects most people by their mid-50s.
How ADD is Applied in Lenses
The “ADD” power is incorporated into various types of multifocal lenses to provide clear vision at different distances.
Bifocal lenses contain two distinct powers: an upper section for distance vision and a lower segment with the “ADD” power for near vision. These lenses often have a visible line separating the two corrective areas.
Trifocal lenses expand upon bifocals by including three focal points: distance, intermediate, and near. The intermediate segment, typically located above the near vision portion, helps with tasks at arm’s length, such as computer work. Like bifocals, trifocals also feature visible lines.
Progressive lenses provide a gradual transition of power from distance at the top to intermediate in the middle, and near vision at the bottom. Unlike bifocals and trifocals, progressive lenses have no visible lines, offering a natural appearance and visual experience. This design allows for continuous clear vision across various distances.
What to Expect with Your ADD Prescription
The “ADD” value on your prescription typically increases over time as presbyopia progresses. Your eye care professional determines the appropriate “ADD” power based on your specific needs and the extent of your presbyopia. A higher “ADD” number indicates a greater need for magnifying power to see close objects clearly.
Adapting to new multifocal lenses, especially progressive ones, may require an adjustment period, typically a few days to a couple of weeks. During this time, some individuals might experience minor distortions, blurriness, or changes in depth perception. Wearing your new lenses consistently helps your eyes and brain adjust. If difficulties persist beyond a few weeks, consult your eye doctor to ensure the fit and prescription are optimal.