What Is Addition Power (ADD)?
When people get their prescription and see a column labeled ADD, followed by a number like +2.00, they’re often puzzled. ADD stands for Addition Power, and in plain terms, it means:
The extra plus power (convex lens power) added on top of your regular distance prescription, specifically to help you see clearly up close.
It’s measured in diopters (D), usually with a ”+” in front. It isn’t an independent, standalone power — it’s a layer added on top of your distance prescription. That’s exactly where the name “addition” comes from.
Why Does Near Vision Need “Added” Power? First, Understand Presbyopia
To understand ADD, you first need to understand presbyopia — a physiological phenomenon.
When you’re young, your eyes focus at near distance by having the ciliary muscle contract, thickening the lens to increase its focusing power — this auto-focus ability is called accommodation. As you age, the lens gradually hardens and accommodation naturally declines, making near vision more effortful. This is a normal physiological process everyone goes through — it isn’t a disease.
Once your eye’s own accommodation can no longer make up the difference, a lens has to help compensate for the shortfall. That extra plus power the lens adds is addition power, or ADD. The less accommodation you have left, the more ADD you need to make up for it — which is why ADD tends to increase with age.
How to Read Your Presbyopia Prescription: Calculating Your Near-Vision Power
Your prescription usually lists distance power and ADD separately, but the power you actually use for near vision is the sum of the two:
Near-vision power = Distance sphere power (Sph) + Addition power (ADD)
A few examples (for illustrating the calculation only — always go by your actual refraction results):
| Distance Power (Sph) | Addition Power (ADD) | Calculated Near-Vision Power |
|---|---|---|
| 0.00 (distance already clear) | +2.00 | +2.00 |
| −2.00 (existing myopia) | +2.00 | 0.00 |
| −4.00 (higher myopia) | +2.50 | −1.50 |
| +1.50 (existing hyperopia) | +2.00 | +3.50 |
There’s an interesting detail hidden in this table: for someone who already has myopia, adding plus power for near vision pulls their near-vision power back toward “0” — or even into positive territory. This explains why some people with myopia find that taking their glasses off actually makes near vision clearer as they get older.
A Few Common Characteristics of ADD
| Question | General Pattern |
|---|---|
| Is ADD the same in both eyes? | Usually yes |
| Does ADD change with age? | Generally increases with age, as accommodation continues to decline |
| Is there an upper limit to ADD? | It generally stabilizes after a certain age, once accommodation has largely bottomed out |
| Is a higher ADD always better? | No — too high pushes your clear near point uncomfortably close |
One note: everything above describes general trends and calculation logic. In practice, the ADD that’s right for you depends on your working distance, visual habits, and binocular coordination — it has to be measured by a licensed optometrist. This article is only meant to explain the terminology and the math.
That Said: The Same ADD Can Turn Into Very Different Glasses
Everything above is about where that number comes from and how it’s calculated. What we see day to day is that getting ADD right is only half the job.
The same +2.00 addition can become a fixed reading pair, a progressive lens, or an office lens built mainly around arm’s-length distance — and those are three genuinely different experiences to wear. What you feel depends not only on the number but on the height it sits at in the lens, the angle at which you drop your gaze, and where the frame rests on your nose. Hand the same prescription to different people and the results differ, usually for these reasons.
One more thing worth saying early: higher ADD is not better. The more the lens adds, the closer it pulls your sharpest working distance. Someone gets a pair that reads a newspaper beautifully and then finds the computer screen has gone soft — that isn’t a mistake, it’s a pair built for a nearer distance. How much ADD you need depends on where you spend your day looking, not on an age chart.
So reading your prescription is step one. Step two is telling your optometrist what distances you actually work at. That sentence matters more than 0.25 either way on the ADD.
Common Misunderstandings / FAQ
Q1: Is ADD different between the two eyes?
Generally, the addition power is the same in both eyes, because ADD reflects the degree of age-related decline in accommodation, and both eyes age at the same rate, so the near-vision compensation needed is usually the same. Distance power, on the other hand, is often different between the two eyes — that’s a separate matter.
Q2: Is a higher ADD always better?
No. The higher the ADD, the more plus power the lens is adding, and the closer your clearest “near point” gets pushed in. Too high an ADD makes a comfortable reading distance feel unnatural. The right ADD is “just enough to cover your near-vision needs” — not as high as possible — and it depends on your actual working distance.
Q3: Why does ADD increase with age?
Because ADD compensates for the exact shortfall in “insufficient accommodation.” The older you get, the harder and less flexible the lens becomes, so your eyes can supply less accommodation on their own, and the lens has to make up more of the difference — which is why ADD naturally climbs with age. Past a certain age, accommodation is largely used up, and ADD tends to level off as well.
Q4: How do I convert the ADD on my prescription into a near-vision power?
The formula is: Near-vision power = Distance sphere power + ADD. For example, if your distance power is −2.00 and your ADD is +2.00, your near-vision power is 0.00; if your distance power is 0.00 and your ADD is +2.50, your near-vision power is +2.50. Astigmatism (Cyl) and axis usually carry over unchanged from your distance prescription — they don’t change with ADD.
In Short
Addition power (ADD) is the extra plus power added on top of your distance prescription specifically for near vision, compensating for the accommodation you’ve lost to presbyopia. Your near-vision power is simply “distance power + ADD.” Once you understand this term, the string of numbers on your prescription stops looking like a foreign language.
If you’d like to understand more about how presbyopia and near-vision lens designs work, take a look at the guide to progressive multifocal lenses put together by Beyond Visual Optometry (Xinzhuang and Banqiao stores).