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Acetate—or, more specifically, cellulose acetate—is the caviar of plastics. It’s durable, hypoallergenic, and capable of holding exceptionally rich colors, which makes it an ideal material for eyeglasses. It’s our signature material.

Add power

This is a piece of information that appears on your prescription. It refers to the added magnification power you need to see clearly close-up.


Amblyopia is an inability to see clearly through one eye. It arises during childhood, typically when the nerve pathway between the brain and eye doesn’t develop quite normally, and for this reason the eye doesn’t “learn” to see correctly. Amblyopia is sometimes referred to as “lazy eye”...but it’s not very nice to call anything “lazy,” including your eye. So we prefer the scientific term.

Base curve

The “base curve” is the amount of curvature on the front surface of a lens. It can also refer to a contact lens curvature.

Blink reflex

Your eyes are fragile little orbs. They must be protected! Thankfully, we have eyelids and a blink reflex which ensures that we close our eyes the instant a threat is perceived. Fun fact: We blink an average of once every 3–4 seconds. Blinking helps distribute tears over your eyeball in order to keep it nice ‘n moist (and to wash away bacteria and other foreign particles).

Cat-eye frames

Cat-eye frames are a shape of frame that swoop upwards, like…um…cats' eyes. (You saw that coming.)

A woman named Altina Schinasi Miranda is credited with inventing the first cat-eye-like shape in the 1930s. Miranda was a window display designer in Manhattan who thought most glasses were hideous and unsuitable for fashionable ladies. Inspired by harlequin masks she’d seen in Venice, Miranda got creative and designed a pair of glasses that mimicked the masks. (She snipped the first prototypes out of paper.) Fast-forward a few years and the new style of glasses is suddenly in vogue AND in Vogue. Marilyn Monroe wore them, Nina Simone wore them, Brigitte Bardot wore them…all the cool girls. Now we call them cat-eye frames. You can wear them even if you’re more of a dog person. It’s allowed.

Color blindness

Individuals with color blindness perceive colors differently from the way most of us do. It’s very common, and the degree of color blindness can range from mild to severe. (Those with very mild color blindness might not even know that they have it.) It’s usually a genetic condition, meaning that you are born with it. Because inherited color blindness is carried on the X chromosome, it affects more men than women. It is estimated that about 8% of all men and 0.5% of all women have some form of colorblindness.

Demo lenses

If you order a Home Try-On, you’ll receive glasses fitted with demo lenses. These lenses have no prescription—they’re for “demo purposes” only! (Like looking out of a window.) When you place an order, we’ll customize a fresh pair of glasses with your prescription.

Expiration date

As you age, so do your eyes. (Ugh, why.) Because we are responsible upstanding citizens, we can't start making your glasses without seeing your valid prescription with our own two eyes. That’s why it’s important to keep your prescription updated :-)


If you are farsighted, you have trouble seeing near objects, but you can see distant objects clearly. (We know, we know—the name is confusing.) The medical term for this is hyperopia.


This…this is what we sell. Glasses..!!

Googly eyes

Googly eyes are little plastic craft supplies that look like eyeballs. They have literally endless uses and are always funny. Googly eyes pair well with sock puppets.

High-index lenses

“High-index lens” is a fancy phrase for a type of thin plastic lens that comes in handy for some higher prescriptions. Remember the kid from The Sandlot? High-index lenses make it possible to not wear glasses like that. (Although high-index lenses are not recommended for children 16 and under.)

Home Try-On

Our Home Try-On program lets you try out five frames at home for five days—for free. When you find one you love, check out with your prescription and we’ll send you a fresh pair. (It's as easy as it sounds.)


We do 14 steps of inspections and quality checks just before shipping your eyeglasses just to make sure they are perfect. 

Jazz hands

This is what you’ll do when you put on your first pair of Twin sunglasses.

Keyhole bridge

A keyhole bridge looks like a very simplified keyhole. (You knew that was coming.) It’s lightly curved; it has a vintage look; it’s versatile. We likey.

Lacrimal caruncle

In addition to being a good name for a band (that’s a free idea, by the way), the lacrimal caruncle is the little pink spot at the inner corner of your eye. A fun thing to say to someone when they wake up in the morning is, “You have a crusty deposit in your lacrimal caruncle."

Low Bridge Fit

Low Bridge Fit frames are crafted for those with low nose bridges (if the bridge of your nose sits level with or below your pupils), wide faces, and/or high cheekbones. These are sometimes called “Asian fit” glasses.

What makes them fit well? Glad you asked—a few things. First, we outfit ours with nose pads designed to sit on the sides of the nose, ensuring that your frames rest with zero tension and zero slippage. Second, we adjust the tilt of the lens to provide more space between your cheekbones and frames. Third, we subtly arch the temples (frame arms) for a roomier fit that banishes pinching. (Toodle-oo, pinching!)


Thought to derive from the Latin monoculus ("one-eyed"), the monocle rose to popularity in the mid-19th century. Like a delicate ocular pet, the lens was attached to a wearer's clothing by means of a silk string or a chain. Early frames were made of luxury materials, such as bone or horn.

Mixed Material

Some mixed things are bad (like mixed messages). Some mixed things are good (like mixed nuts). Our Mixed Material frames definitely belong to the second category. These frames include densely-hued acetate and metal flourishes. Yum.


If you are nearsighted, you have trouble seeing distant objects. Another word for it is “myopia.” If you’re sitting in the back row of a movie theatre and the screen is blurry? Yep, that would be nearsightedness. It’s pretty common.

Nose bridge

“Nose bridge” refers to the slope of the nose in between your eyes. (Put your finger there. It’s a nice little area, isn’t it? Definitely an underrated body part.) A low nose bridge is where the bridge of your nose sits level with or below your pupils. People with low nose bridges often have wide faces and/or high cheekbones. (Tip: Low Bridge Fit frames minimize any pinching and prevent frames from sliding down your nose or resting on your cheeks. Which is fantastic, because no one on earth wants to be pinched by a pair of glasses.)


This abbreviation appears on your prescription. It stands for “oculus dexter,” which is “right eye” in Latin. Everything sounds cooler in Latin.


A phoropter is a big instrument that your doctor will use for refraction during an eye examination. It looks like a science-fiction mask. (VERY cool.)


This is an old-fashioned style of glasses you may recognize from old paintings or photographs of Theodore Roosevelt. “Pince-nez” means “pinch-nose” in French, which is appropriate because these frames stay put by pinching the nose. Sir Arthur Conan Doyle wrote a story called “The Adventure of the Golden Pince-Nez,” which we might consider the cultural apex of this style.


Quinoa is a delicious and healthy food. We didn’t have any eye-related words that start with the letter “Q” so we’re going with quinoa, because otherwise the “Q” section will be lonely. Bon appétit.


Readers (or reading glasses) are glasses with non-prescription lenses that make it easier to read (or do anything that requires really good eyesight at close range). They’re available in various preset magnification strengths, which users can choose from to match their needs.


In science terms, refraction is the bending of any wave (but for our purposes, a light wave) as it passes from one medium into another. In eyewear terms, refraction refers to the process of determining your refractive error.

Segment height

Segment height is one of the measurements used to create super-accurate progressive lenses. It's a vertical measurement (in millimeters) that tells the lab where to start your progression. Sometimes we refer to it as “seg height,” just to be cool. 😎

Single-vision lenses

Single vision lenses correct for one field of vision (usually for distance or reading).


This is one piece of information that appears on your prescription. It indicates how strong your lens needs to be.


Also known as the arm, this is the part of your glasses that runs alongside your head and holds them in place.

Ultraviolet light

Ultraviolet light is a form of electromagnetic radiation that surrounds us, but it’s not visible with the human eye. Our main source of UV light is the sun. (If you’re overexposed to UV light, you can get a sunburn. Be safe out there, guys.)

Visual acuity

Visual acuity is a schmancy way of saying “how well you can see.”

You may have heard the term “20/20 vision” tossed around. That term describes “normal” vision. If you have 20/20 vision, you can see at 20 feet what a person with normal vision would see at 20 feet. It’s possible to have better than average vision—some people, for example, have 20/15 vision, which means they can see at 20 feet what most people can only see at 15 feet! (#jealous).

Windshield wipers

We wish we had these for our glasses :/

X-ray glasses

These are not a thing.


This is what you will shout—possibly accompanied by a fist pump—when you put on your first pair of Twin glasses. Good times.


This is what happens when you close your eyes in bed at night.