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Better Vision is More than Just a Good Prescription




Aberrations are distortions that occur as light travels through the eye.


Acetate or more specifically cellulose acetate is a plant-based plastic that is hypoallergenic. Cellulose acetate is widely used today to make frames because it has the widest range for transparency, rich colors, and finishes. Acetate is hypoallergenic, made from a renewable resource, lightweight, and very strong. This material was first used for eye wear in the late 1940’s because previously used plastics were brittle. Today’s acetates are known for being strong, lightweight, and flexible.


Accommodation is the ability for the eye to increase optical power in order to maintain a clear image (focus) the longer a person looks at an image.  

Add Power

Depending on your vision, this is a piece of your prescription that refers to the added magnification power you need to see clearly up close. Not everyone needs an add power, only people who have trouble seeing things close-up. If you need an add power and want to use one pair of glasses to see near and far, your glasses would be considered either progressives (Progressive Add Lens) or bifocals.


Amblyopia is the medical term used when the vision in one eye is reduced because the eye and the brain are not working together properly. It usually arises during childhood, the eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.

Anti-reflective Coating

All KEAGAN eyewear lenses are coated with the highest quality hydrophobic (water resistant) and oleophobic (oil resistant) coating that reduce glare. This treatment is especially important for those who work with computers. The added bonus is that it will also keep your glasses looking so clean and new!


The arm is the part of your glasses that runs alongside your head and holds them in place. It is also known as the temple.


Astigmatism is a common optical condition which results in blurry vision. While most eyes are more basketball in shape, some are more football in shape. This irregular shape prevents light from focusing properly on the back of the eye. This prevents you from seeing perfectly clear. Thank goodness for glasses! With the right prescription, glasses can correct your vision.


This is a machine that is often used to determine baseline prescription of your glasses. An autorefractor calculates your baseline prescription by shining light into your eye and measuring how the light changes.


If you have an astigmatism, the axis is the number on your prescription that determines the angle of your astigmatism correction (ranging from 0 to 180 degrees). The axis and cylinder are always together. You can say that they go together like peanut butter and jelly. You can't have one without the other!

Base Curve

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


BCVA or Best Corrected Visual Acuity is the best possible vision a person can achieve with corrective lenses. It is measured in terms of a Snellen chart, 20/20, 20/16, etc.


Bifocals are lenses containing two focal lengths. They are usually are arranged with the focus for distance on the top and the near focus on the bottom of the lens. They are different from PALs in that they have a distinct line (visible) between the two focal lengths.

Blink Reflex

The blink reflex, also known as the corneal reflex, is an involuntary blinking of the eyelids prompted by stimulation of the cornea. Such as touching or the introduction of a foreign body. It’s our body’s way of protecting the eye from any kind of threat, keeping them clean.

Cat Eye Glasses

Cat eye glasses is defined by having an up sweep at the outer edges where the temples or arms join the frame front, mimicking the shape of a cat’s eyes.

American artist, Altina Schinasi, is credited with designing cat eye shaped glasses. Schinasi’s glasses were so highly publicized by magazines like Vogue and Life that she decided to establish her own company to distribute them. In 1939, she received an American Design Award from Lord & Taylor for the flared-frame Harlequin glasses.

Color Blindness

Individuals with color blindness recognize colors differently from the way most of us do. Color blindness is very common, and the severity can range from mild to severe. People who are color blind are born with it. Typically, it is a genetic condition and is carried on the X chromosome, affecting more men than women. It is estimated that about 1 in 12 men and 1 in 200 women worldwide have some form of color blindness.


If you have astigmatism, this is 1 of 3 pieces of information that appears on your prescription. It refers to the lens power needed to correct for an astigmatism. If you have a cylinder, then you have an axis -- you can’t have one without the other!


Eye care professionals will sometimes dilate your pupils during an exam to get a better look at your retina. Simply put, this means that your pupils will be expanded (or dilated), using special dilating eyedrops. If you’ve ever had your eyes dilated, you know that it can make your vision blurry and your eyes especially sensitive to light for a few hours. If you have to have your eyes dilated, make sure you bring a designated driver! Driving isn’t recommended for several hours.


A diopter is a unit of measurement, like a centimeter or an inch. Instead of measuring distance, it measures the refractive or optical power of a lens. It is denoted as a “D” in your prescription. 

Expiration Date

Most things have an expiration date. This includes your glasses prescription. As we get older, our eyes change. This means your glasses prescription can sometimes change over time. Make sure you keep your prescription up-to-date because we can’t start making your glasses without it.

Eye Drops

Eye drops are any liquids that you apply to your eyeballs for any reason. There are several reasons why you may need eye drops, itchy eyes, dry eyes, etc. Some drops are medicated to treat glaucoma, eye infections, and other conditions.


Eyes are the round/globe shaped organs that provide organisms with vision or the ability to receive and process visual details. If they are not perfectly round, they cause your vision to become blurry and give you the perfect excuse to wear some super fashionable glasses!


Eyestrain is when your eyes become tired from too much activity, for example, reading or looking at a computer screen for too long or driving long distances.


Farsightedness or hyperopia, is a common vision condition in which one can see objects in the distance clearly, but objects nearby may appear blurry.


How to tell if your frames fit right:

  • The frame should rest with equal weight on your ears and nose, gripping your temples (or sides of your head) lightly.

  • The width of frame should be equal to width of face from ear to ear.

  • There should be little or no gap between top of nose and bridge of frame.

  • Your frames should not slide down your nose

  • Smiling (or your cheeks) should not push your frames up


If you aren’t sure or if you think they don’t fit properly bring them into one of our locations or you can go to any optical store or optometrist office.


The things that go on your face and give you better vision (if we’ve done our job right!). Typically, a frame with lenses set in them. They can be functional or functional AND fashionable. A little glimpse into the wearers personality.

High-index Lens

High-index lenses are a type of advanced thinner plastic lens that allows people with higher prescriptions that would normally have to wear “coke-bottle” lenses wear a lighter weight and thinner lens.


Hydrophobic refers to something that repels water.  All of our lenses are made with superhydrophobic coatings, which repel moisture to help reduce smudging.


See farsightedness.


The iris is the colorful part of your eye. The iris is like a shutter on a camera, regulating the amount of light that enters through the pupil.


Yellow coloring in the skin and eyes caused by a variety of conditions involving the liver, gallbladder and bile ducts, including hepatitis and cirrhosis.

Keyhole Bridge

A bridge is the piece of the frame that goes over your nose and connects the lenses. A keyhole bridge looks like an old-fashioned keyhole. Its slightly curved cutout gives a frame a little extra personality and vintage look. 

Low Bridge Fit

Low Bridge Fit frames are designed for those with low nose bridges. They are ideal for wide face or people with high cheekbones. The bridge of the frames tend to sit in-line with your pupils or lower than traditional frames.


A monocle is a type of corrective lens used to correct the vision in only one eye. It is a circular lens, surrounded by a wire ring around it. It is usually attached to a string or wire that attaches to the wearers clothes. Antiquarian Philipp von Stosch wore a monocle in Rome in the 1720s, in order to examine engravings more closely.


See nearsightedness.


People that are nearsighted have trouble seeing distant objects. Another word for it is myopia. It is probably the main reason you came to us for glasses.

Nose Bridge

Nose bridge refers to the part of the frame that connects the two lenses and sits just above the bridge of your nose.

Nose Pad

The pads that rest on the sides of your nose and ensure they fit comfortably.


You may see this on your prescription. It is an abbreviation that stands for oculus dexter, which means right eye in Latin.


An optician is an eye care professional who is trained to interpret, fit, and dispense prescription eyewear. They don’t provide you with the prescription itself. Think of them as the pharmacist of the eye care world.


Optometrists are eye care professionals who provide primary vision care ranging from sight testing and correction to the diagnosis, treatment, and management of vision changes.


An ophthalmologist is a medical doctor in eye care that diagnoses and treats all eye diseases, performs eye surgery and prescribes and fits eyeglasses and contact lenses to correct vision problems. Some ophthalmologists are also involved in scientific research trying to discover the causes and cures for eye diseases and vision disorders.


You may see this on your prescription. It is an abbreviation that stands for oculus sinister, which means left eye in Latin.


A phoropter is the instrument that looks like a butterfly mask. Your doctor will use for refraction during an eye examination to obtain your prescription. They most likely will ask you, “Which is better? 1 or 2”?


Pince-nez means pinch-nose in French. This old-fashioned style of glasses is easily recognizable because the frames stay put on your face by pinching the nose. It does not have temples that go over your ears.


Plano means level or flat. In glasses it refers to a lens that does not need a prescription.

Polarized Lenses

Polarized lenses deliver superior glare protection. These lenses contain a special filter that blocks intense light that is reflected, reducing glare. People with extreme light sensitivity can really benefit from a polarized lens.


Polycarbonate eyeglass lenses are 10 times more impact-resistant than glass or regular plastic lenses. All of KEAGAN eyewear’s standard lenses come with polycarbonate. Did you know that the polycarbonate material used for eyeglass lenses was developed by the aerospace industry for use in helmet visors worn by astronauts? If it’s good enough for the astronauts it’s good enough for us!


Presbyopia is a fancy word for farsightedness that is caused by a loss of elasticity of the eye’s lens, typically occurs in middle to old aged patients. Apparently it happens to the best of us as we age. Don’t worry, you’ll just need reading glasses, bifocals or progressives to correct it. Just another excuse to buy a cute pair of glasses if you ask us!


Some eyeglass prescriptions will contain only one number (the sphere) or they contain three numbers (sphere, cylinder, and axis). If you have three numbers, it means that you have astigmatism. The sphere indicates the strength of the lens you need. While the Cylinder indicates the lens power needed to correct your astigmatism. The axis indicates the angle to place the lens correction for astigmatism


Some people may require having prism added to their prescription. You’ll know you have prism if you see a little triangle symbol next to it, like this: ∆. Prism is usually prescribed in lenses to help you use your eyes together.


Some people's eyes have a tendency to try and pull apart while some go up and down. These are called muscle imbalances, or fixation disparities. Prism can help ease the symptoms of these imbalances by making the brain think the eyes are working together.

Progressive Lenses

Progressive lenses allow the wearer to see multiple focal corrections all in the same lens (the top provides distance correction, intermediate in the middle, and reading correction on bottom). Progressives lenses let you wear one pair of glasses instead of two! Kind of like a BOGO (buy one, get one) deal.

Pupillary Distance

Pupillary distance is the distance between your pupils (obviously)! This super important measurement helps make sure that your prescription is placed in the right place in your lenses to fit the frames you choose.

In some states the pupillary distance or PD isn’t considered part of your prescription. If you don’t have one on your prescription don’t worry, we can help you! Come into one of our locations get your PD measurement!

Quizzing Glass

The quizzing glass was popular with both men and women from the eighteenth century onward. Quizzing glass lenses are monocular and can be round, oval or oblong. The rims are often faceted, or pinchbeck, or mounted with diamonds, turquoise or imitation stones and they were typically hung from a chain worn around the neck. Not to be confused with a monocle, quizzing glass were meant to be held by a handle and not held within the eye socket.


Readers (or reading glasses) are glasses with non-custom prescription lenses that make it easier to read (or do anything really that would require seeing something close up). They can be found in various preset magnification strengths, which users choose themselves to match their needs. These are great in a pinch but it’s important to remember that readers are customized specifically to the wearer and may not be exactly the right strength in both eyes.


Scientifically speaking, refraction is the ability of the eye bending light so that an image can be focused on the retina. So it probably doesn’t surprise you that refraction in eye care is the process of determining your refractive error or in other words, your glasses prescription.


The retina is a layer at the back of the eyeball containing cells that are sensitive to light. These cells trigger nerve impulses that pass through the optic nerve to the brain -- Forming a visual image.

Segment Height

Segment Height, also known as seg height also known as SH, is the vertical measurement (in millimeters) from the bottom of the lens in your frames, to the beginning of the add power in progressive lens, or the top line of a lined bifocal lens. Which is a lot of big words that means that a measurement that helps to make sure that your prescription is put in the correct place in your progressive or bifocal glasses.

Single Vision Lenses

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

Snellen Eye Chart

You know that eye chart that has the big “E” at the top? Well in eye care, it’s called a Snellen Eye Chart. This is your classic eye chart. It was invented in 1862 by a professor of ophthalmology in the Netherlands named Dr. Herman Snellen.


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


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


Titanium is a silver-gray metal that is lightweight, durable, strong and corrosion-resistant. But don’t worry, just because it’s a gray metal doesn’t mean it only comes in gray. Titanium eyewear can be produced in a variety of colors for a clean, modern look with a hint of color. Bonus: it's hypoallergenic! 

Tortoise Shell

Tortoise shell frames mimic the real turtle shells and have a speckled look. The distinctive pattern has mottled yellow, honey and brown shell spots. While early tortoise shell glasses were made from actual tortoise shell, please note that NO turtles were harmed in the making of ANY of our tortoise shell frames!


Ultraviolet light is an electromagnetic radiation with a wavelength that is in the sweet spot between visible light and X-rays. The most common source of UV light is the sun. We all know how UV light can damage the skin, but did you know that it can also harm your eyes? Extended exposure to the sun's UV rays (without proper eyewear) has been linked to eye damage, including cataracts, macular degeneration, other eye diseases.

Visual Acuity

Visual acuity is another way of saying how well you see. Think of it as a grade scale. 20/20 vision is considered normal vision. What is means is that you can see at 20 feet what a normal person would be able to see at 20 feet. If you have better than 20/20 vision, (for example, 20/16), it means that you can see at 20 feet what normal people would be able to see at 15 feet. Come find out what DigiVision can do for you. #getbetterthan2020

Visual Field

Think of your visual field as your field of vision. It is the area that you are able to see when your eyes are in one fixated on one position.


What you're going to say when you see the clarity provided by your new KEAGAN glasses.




Your first reaction after seeing yourself in you new KEAGAN glasses

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