add - Add in this case means any extra refractive power that needs to be added to your eyes.

a/r coating - The initials in a/r coating means "anti-reflective," a special kind of coating that is used on your lenses to mitigate reflection.

axis - Imagine a line sketched through the center of your eye to the back of it. This is the axis, which aligns your eye when it focuses on the center of something.

bifocals - Did you know that Benjamin Franklin was one of the first people to wear bifocal glasses? Bifocals are lenses with two different optical powers, a part for viewing closer and a part for viewing farther.

cyl - "Cyl" stands for cylindrical power, and depending on what kind of specialist you use, the doctor may use a "plus-cyl" form or a "minus-cyl" form, both of which denote the same thing on your prescription. Ophtalmologists often use the "plus-cyl" and optometrists often opt to use the "minus-cyl" form.

high index - High index lenses aren't your ordinary run-of-the-mill lenses. They tend to be pricier for people with a heavier prescription due to the time and effort it takes to cut down the lenses' thickness and weight.

multifocals - Unlike their cousins, the bifocals, multifocal lenses are comprised of multiple parts in addition to its main lens in order to accommodate different reading positions.

pd - "Pd" refers to pupillary distance, an extremely important measurement used for prescription glasses. Pupillary distance calculates the distance between the center of your left and right eyes.

photochromic - Photochromic lenses are perfect for people who venture out into the sun regularly. These lenses darken when exposed to UV radiation, but automatically revert to their original, un-darkened state once the wearer is no longer exposed to UV rays.

polarized - You may have heard of polarized lenses for sunglasses, but do you know why they are in such high demand? Natural light causes reflection in all directions, something that may be hazardous for people where vision is a crucial dependency. Polarized lenses basically mitigate the glare one would see from surfaces that reflect light, be it snow, the street, or the surface of water.

progressive lenses - These particular lenses go by many different names, including "progressive addition lenses" and "varifocal lenses," and they allow the wearer to see from a whole range of distances. These are corrective lenses with a gradient that increases in power to accommodate the wearer, starting off at no extra power at the bottom to the maximum corrective lens power at the top of a given lens.

rx - You've probably seen these initials before, they stem from the latin word "receive," and is typically placed on top of prescriptions from your doctor.

sph - These initials denote the strength of your lenses. The plus sign is used to adjust long-sightedness. Inversely, the minus sign is used to adjust the wearer's short-sightedness.

tinted - Tinted lenses come in various colors and hues. What most people don't know is that the specific color one chooses for their eyewear allots specifically qualities other than just the color itself. For example, yellow tinted lenses can enhance contrast and mitigate glare. Many have opted for this color for driving at night.

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