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Add power is the extra magnifying power added to the bottom part of a multifocal lens, like a bifocal or progressive. Its job is to help you see clearly for reading and other close-up tasks. This power is specifically for correcting presbyopia, the normal age-related change that makes it hard to focus on nearby objects.
read more about add power in multifocal lenses ...On an eyeglass prescription, the add power is usually labeled "ADD" and is written as a positive number with a plus sign, like +1.75. This number is the power that is added to your main distance prescription to create the reading power in your lenses. The add power is almost always the same for both eyes.
As people get older, usually after age 40, the natural lens inside the eye becomes less flexible. This makes it difficult for the eye's muscles to focus on close objects, a condition known as presbyopia. You might notice you have to hold books or your phone farther away to see them clearly. The add power in your glasses does the focusing work that your eye can no longer do on its own.
Different types of lenses use add power. In bifocals, the add power is in a distinct segment at the bottom of the lens, separated by a visible line. In progressive lenses, there is a smooth, invisible transition from your distance power at the top to the full add power for reading at the bottom. Multifocal contact lenses also use this principle to provide clear vision at multiple distances.
It is important to know that a higher add power means a shorter "working distance." This is the distance from your eyes where the focus is sharpest. For example, a +1.00 add power might focus best at arm's length, while a strong +2.50 add power will require you to hold a book much closer, perhaps 14 to 16 inches away. This is why your doctor tries to find the lowest effective number to keep your reading distance comfortable and natural.
During an eye exam, your doctor will have you look at a reading chart and will test different lens powers. They find the lowest power that allows you to read comfortably without straining your eyes. The add power you need increases as you age.
Yes. If you have perfect distance vision, you may still need reading glasses as you get older. The power of these over-the-counter reading glasses is simply your Add power (for example, +2.00).
The add power in a bifocal is set for a close reading distance, usually about 16 inches. Your computer screen is farther away, in an "intermediate" zone. Progressive lenses have a specific corridor of power for this intermediate distance, which often makes them better for computer work.
You should talk to your eye doctor if you start to experience the signs of presbyopia. These include blurry vision up close, needing to hold things farther away to see them, or getting headaches and eye strain from reading. An eye exam can determine if you need Add power and exactly what strength is right for you.
Presbyopia. American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-presbyopia. Accessed March 31, 2026.
Presbyopia. American Optometric Association. https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/presbyopia. Accessed March 31, 2026.
Presbyopia - Diagnosis and Treatment. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/presbyopia/diagnosis-treatment/drc-20363329. Accessed March 31, 2026.
How to Prescribe Spectacles for Presbyopia. Community Eye Health Journal via PubMed Central. https://pmc.ncbi.nlm.nih.gov/articles/PMC1705655/. Accessed March 31, 2026.
Lens-Based Strategies to Address Reading Issues Due to Mild Disease-Related Vision Loss. American Optometric Association. https://www.aoa.org/news/clinical-eye-care/diseases-and-conditions/lens-based-strategies-to-address-reading-issues-due-to-mild-disease-related-vision-loss. Accessed March 31, 2026.