Looking over your eye test results; you may have seen the term ‘ADD’.
If this a new feature on your prescription that wasn’t there before (gulp) or you’re wondering what this abbreviation means, this guide will explain everything you need to know about ADD.
Let’s dive in.
What does ADD mean on an eye prescription?
‘ADD’ stands for Addition power. It’s the value that optometrists use to indicate the extra strength needed for close or intermediate visual focus. Essentially, it’s the extra magnifying power needed if you have presbyopia, a condition that affects near vision as you age.
On your prescription, the ADD value is specifically for multifocal lenses, which include bifocals or varifocals (progressives). Multifocal lenses are designed to provide clear vision at multiple distances, from far away to up close, all in one pair of glasses.
But, there are actually two types of ADD which you may see on your prescription;
Intermediate ADD aids visual tasks within arm’s length such as using a computer screen.
Near ADD aids visual tasks within 30cm such as reading or using your phone.
Anything beyond arm’s length is considered as distance vision for tasks such as watching TV or driving. ADD doesn’t aid this vision zone and is instead catered for by your SPH.
This is where things get interesting. If you have an ADD power listed on your eye test report, you can choose to have multifocal or single vision lenses. Single vision lenses can only cater for just one of these three vision zones, whilst varifocals (progressives) can cater for all three vision zones.
This is why varifocal lenses can be incredibly versatile as they save you from having to have multiple glasses frames for different purposes. The choice is yours.
Who needs an ADD value?
Most often, an ADD value is seen on the prescriptions of people over the age of 40. This is because presbyopia, the gradual loss of your eye’s ability to focus on nearby objects, becomes more common as you get older.
If you’ve found that reading small print or focusing on nearby tasks has become more difficult, your optometrist may prescribe lenses with an ADD value.
People who wear bifocal or varifocal lenses, which correct both distance and near vision, will have an ADD value on their prescription which calls for multifocal lenses. These lenses allow for smooth transitions between different vision zones, helping you see clearly whether you’re reading a book or looking across the room.
How is ADD measured?
Your ADD value is measured in dioptres as a positive value and generally falls between +1.00 and +3.50, depending on how much extra power you need for close-up tasks.
This number represents the additional lens power that will help you see more clearly when focusing on near objects, especially if you already wear glasses for distance vision. It is important to note that ADD values are usually always the same for both eyes.
Why is ADD important for multifocal lenses?
If you need multifocal lenses, the ADD value plays a key role in how well your glasses perform. It helps you see clearly at a range of distances, allowing for seamless transitions between reading, using digital devices, and looking at objects farther away.
Without the correct ADD value, you might find it difficult to read small print or focus on close-up tasks, which can be frustrating for everyday activities. That’s why it’s crucial to have regular eye tests to ensure your prescription is up to date and that your ADD value is accurate for your needs.
How to calculate ADD for glasses?
Strangely, on certain prescription papers, your ADD value may not be specifically stated despite your requirement for addition power.
In this case, your eye test results will instead state three versions of your single vision prescription. Using these, you can calculate your near ADD and your Inter ADD by using the following calculations;
- Near ADD = Distance SPH – Near SPH
- Inter ADD = Inter SPH – Near SPH
In the example below, the near ADD power is +1.75. The Inter ADD power is +1.00. You’ll notice that the CYL and AXIS values don’t change.
|
Distance |
SPH |
CYL |
AXIS |
|
OD (R) |
+1.00 |
+1.00 |
160 |
|
OS (L) |
+2.00 |
+0.25 |
005 |
|
|
|
|
|
|
Intermediate |
|
|
|
|
OD (R) |
+2.00 |
+1.00 |
160 |
|
OS (L) |
+3.00 |
+0.25 |
005 |
|
|
|
|
|
|
Near |
|
|
|
|
OD (R) |
+2.75 |
+1.00 |
160 |
|
OS (L) |
+3.75 |
+0.25 |
005 |
Beware that minus SPH powers makes the math a little trickier. In the example below, the near ADD power is +2.00 for each eye. The Inter ADD power is +1.50
|
Distance |
SPH |
CYL |
AXIS |
|
OD (R) |
-0.75 |
-1.00 |
155 |
|
OS (L) |
-1.75 |
-1.00 |
030 |
|
|
|
|
|
|
Intermediate |
|
|
|
|
OD (R) |
+0.75 |
-1.00 |
155 |
|
OS (L) |
-0.25 |
-1.00 |
030 |
|
|
|
|
|
|
Near |
|
|
|
|
OD (R) |
+1.25 |
-1.00 |
155 |
|
OS (L) |
+0.25 |
-1.00 |
030 |
Is ADD the same as reading glasses?
Not exactly. ADD refers to the additional strength needed for near vision, which is built into multifocal lenses such as bifocals or varifocals (progressives). Reading glasses, on the other hand, are single-vision lenses designed specifically for close-vision tasks within 30cm.
If you’re looking to just buy single vision reading glasses, you’ll need to add your near SPH power to your near ADD power. Using the example below, the right eye would be +2.50 and the left eye would be +3.50.
|
|
SPH |
CYL |
AXIS |
Near ADD |
|
OD (R) |
+1.00 |
+1.00 |
160 |
+1.50 |
|
OS (L) |
+2.00 |
+0.25 |
005 |
+1.50 |
It’s worth noting that prescription reading glasses can cater for astigmatism whilst ‘ready readers’ or ‘over the counter’ reading glasses cannot. If you have a strong CYL value (over +/-2.00) then it’s recommended you get prescription reading glasses.
Can your ADD value change over time?
Yes, your ADD value can change as your eyes age. Presbyopia tends to progress with time, which means your near vision may require a higher ADD value as you get older. Frequent eye tests will help track these changes and ensure that your glasses continue to meet your vision needs.
It’s a good idea to have your eyes tested at least every two years, or more frequently if you notice changes in your vision. This way, your optometrist can assess and adjust your prescription, including your ADD value, to ensure you maintain clear vision at all distances.
FAQs about ADD
What happens if you don’t have ADD on your eye prescription?
Not everyone needs an ADD value on their prescription as it’s typically only used for multifocal lenses or reading glasses. If you’re under the age of 40 and/or don’t have presbyopia, your prescription won’t usually include an ADD power. Yet…
However, certain eye test reports may (sneakily) include your ADD without actually stating it. This occasionally happens where your eye test report has three single vision prescriptions; one for your distance, intermediate and near vision and no ADD value. In this instance, you’ll have to use this calculation to know your near or intermediate ADD power.
What does ADD 2.50 mean on an eye prescription?
An ADD value of +2.50 means that an extra 2.50 dioptres of magnifying power is needed to help you see clearly at close range. This is fairly common for people with presbyopia.
Does ADD mean bifocal?
ADD values are found in bifocal, trifocal, and varifocal (progressive) lenses. If you’re unsure about the difference between these lenses, see the description below;
Bifocals have two distinct areas of vision correction (distance and near). The distance segment of the lens is in the upper half of the lens, accompanied by a discernible near-vision ‘segment’ in the lower half of the lens. The ADD value is what helps correct your near vision within those lenses.
Trifocals have three distinct segments for all three vision zones (distance, intermediate and near). The distance segment of the lens is in the upper third of the lens, an intermediate segment in the middle and near-vision segment in the lower half of the lens. Trifocals are still available, however are being outdated by the increasing quality and technology of varifocals.
Varifocals cater for all three vision zones but without any discernible segments. Instead, these lenses seamlessly progress from distance correction in the upper part of the lens, intermediate in the middle and near in the lowermost part. As these lenses have no lines between the ‘vision zones’ they have better aesthetic appeal.
Conclusion
In summary, the near ADD value on your eye prescription aids your near vision tasks within 30cm, especially if you have presbyopia. Inter ADD aids your intermediate vision within arm’s length.
Either type of ADD is a crucial part of any prescription for multifocal lenses and ensures that your glasses provide clear vision at all distances. Regular eye tests will help keep your prescription accurate as your eyes change over time.
If you want more information about your prescription or lenses, please check out our other eyecare blog posts.
Thanks for stopping by.