Eyeglasses Frequently Asked Questions
How do I read my eyeglass prescription?
While you don't need to completely understand how to read your eyeglass prescription to place an order on AC Lens, you'll need to know the basics in order to select and order the right lenses for your eyes. We've provided assistance with how to read and enter your prescription in the information below. If you don't have a copy of your prescription, or are not sure how to read it, rest assured that as long as you have your doctor's information we can contact your doctor directly in order to obtain your correct prescription.
I want to purchase eyeglasses through AC Lens, but this prescription stuff is confusing. Is there an easier way?
Absolutely! You can always leave the prescription fields blank when ordering, and then either send us a copy of your prescription, or give us your eye doctor's contact information and we will collect your prescription information directly; ensuring that your prescription is correct while you remain free of worry!
What's the difference between being nearsighted or farsighted, and how do I know which one I am?
For the most part, knowing whether you are nearsighted or farsighted won't affect how you order glasses on AC Lens. An explanation of what they mean is provided below:
Also called Myopia or shortsightedness, those with nearsighted vision are able to see things that are near or close-up clearly, but need vision correction in order to see things that are distant or far away. Nearsightedness is usually corrected with convex lens, which results in a prescription that has a negative (-) Sphere.
Also called Hyperopia or longsightedness or hypermetropia, those with farsighted vision are able to see things that are distant or far away clearly, but need vision correction in order to see things that are near or close-up. Farsightedness is usually corrected with a concave lens, which results in a prescription that has a positive (+) Sphere.
Also called Emmetropia, those that are neither nearsighted nor farsighted are able to see both far away and up close without vision correction. Though rare, some patients have one eye with 20/20 vision while the other eye requires vision correction.
Also called Presbyopia, those that require vision correction to see things both close-up and far away need a special correction that requires an ADD value in their prescription. These prescriptions can be written with either a positive (+) or negative (-) Sphere.
What is the difference between Bifocal and Progressive Bifocal?
Bifocal eyeglass prescriptions were originally only able to be corrected with lenses called lined bifocals; these types of glasses have a visible line at the point where the prescription changes from near to far vision. Progressive Bifocals are lenses that have no visible line and gradually change from near to far vision in a way that is easier for your eyes to adjust to. AC Lens currently only offers Progressive Bifocal lenses. Unless your prescription notes "Bifocal Only" or "No Progressives", then you can use your Bifocal prescription to place an order for Progressive Bifocal lenses.
What if my doctor says I need Bifocal correction in only one eye?
AC Lens is only able to process orders with one type of lens per frame. Since a prescription with bifocal correction in only one eye would require a progressive lens in one eye and a single vision lens in the other, we are unable to fulfill these types of orders. We apologize for the inconvenience.
My prescription is for Trifocal lenses. Can I purchase Trifocal lenses through AC Lens?
Unfortunately, AC Lens does not offer trifocal lenses at this time.
My prescription has expired or it doesn't have an expiration date, can I still order glasses?
We can only fill orders for unexpired prescriptions. If your prescription does not have an expiration date, then the expiration date is either 1 or 2 years from your exam date, depending on your doctor's preference. We will verify your prescription with your doctor and notify you if the prescription is expired. Some doctors offer prescription extensions if your current lenses have broken. We must verify these exceptions through your doctor though.
Will there be any extra fees for creating my prescription lenses?
Nope! As long as you selected the correct lens type (Single Vision vs. Progressive Bifocal), the cost you see at checkout will be the cost you pay. Not all lens requests are guaranteed though. If our lab is unable to create the requested prescription for the selected lens or frame, we will contact you immediately in order to select a lens/frame that works.
Ophthalmologists and a few older optometrists (different types of eye doctors), write astigmatism prescriptions with positive (+) cylinders. This is because many years ago the instruments used to measure and cut lenses were only able to do so in positive increments.
Nowadays the majority of labs, including ours, cut lenses in the negative (-), and require that any positive (+) cylinder prescriptions be converted into the negative (-) equivalent. Rest assured this conversion does not alter the type or quality of the vision correction that your doctor prescribed you. The conversion will affect (change) the SPH, CYL, and AX parameters in your prescription, but will result in the exact same vision correction you were fit for by your doctor.
We automatically perform this conversion if the prescription you enter is written with a positive (+) cylinder. You can also use our Positive Cylinder Conversion tool by going to our Positive Cylinder Conversion page.
What's the difference between my eyeglasses prescription and contact lens prescription?
An eyeglass prescription is not a contact lens prescription, and cannot be used to order contact lenses and vice versa. Each prescription contains information that is specific to the type of correction. Contact lenses sit directly on the eye whereas glasses are worn on the bridge of the nose. The distance between these two spaces dramatically changes the level of correction for each type. Also, not everyone who needs eyeglasses can wear contact lenses.
Does AC Lens accept Vision Insurance?
AC Lens does not accept vision insurance as payment for orders, but we do provide a receipt which can be submitted to your insurance company as an Out-of-Network purchase. Make sure you consult with your insurance provider before you place your order to determine whether they reimburse Out-of-Network purchases and/or whether they have reimbursement limits for Out-of-Network purchases.
Does AC Lens offer repairs services?
AC Lens does not offer repairs services at this time. Please consider visiting a local optical store for assistance with repair requests.
Does AC Lens sell replacement parts?
AC Lens does not sell replacement parts. You can check with your local eye doctor to see if they can assist you with replacement parts, or you can contact the manufacturer directly to find out where their replacement parts are sold.
Can AC Lens make lenses for my existing frames?
AC Lens does not currently offer lenses-only orders for frames that were not originally purchased through AC Lens. But, if you are looking to replace the lenses in a pair of eyeglasses that you purchased through AC Lens you can contact our Customer Service Department at 1-888-248-5367 to set up a Lens Remake order. Please note: this process will require you to mail-in your existing frames, though we will provide you with Free Return Postage.
What happens if my doctor changes my prescription after I receive my glasses?
If your doctor changes your prescription due to vision problems you are experiencing with your recent glasses purchase, we will replace your lenses one-time for free. You must return the frames to us within 30 days from the delivery date. The replacement lenses will be made with the same lens material and treatments that were previously selected, and will require you to mail-in your existing frames, though we will provide you with Free Return Postage.
What are the best lenses for my prescription?
For the most part, selecting a lens material has to do with preference, but some lens materials and treatments are better for certain lifestyles and prescriptions.
Lens Material: CR-39 Plastic
Lens Material: Polycarbonate
Lens Material: Hi-Index 1.67
Lens Treatment: Anti-Glare Coating
Does AC Lens offer prescription sunglasses or Transitions?
AC Lens does not offer prescription sunglasses or transition lenses at this time.
Do I get a case or cleaning cloth with my glasses?
Some manufacturers provide custom eyeglass cases and cloths with their frames. Any frames that do not come with custom cases or cloths will be shipped with a basic sleeve and cleaning cloth free of charge.
How do I know my prescription will be correct?
In order to make sure you receive your glasses with the correct prescription we will always contact your doctor directly to confirm your prescription. You can rest assured in the confidence that what you are prescribed will be what you receive. Our lab has over 50 years of experience with creating lenses, and all lenses are double checked by an optical specialist immediately prior to shipment.
How do Progressive Lenses work?
Progressive lenses provide bifocal vision correction, but with no visible lines! Lined Bifocals have a distinct line or etch in the lens which visibly indicates where the lens switches from reading to distance vision. Progressive lenses are able to complete the transition between the vision corrections smoothly; letting your eyes naturally move between reading and distance vision without the distracting line in your lenses.
How do I know that my Progressive Bifocal glasses will be correct?
Our lab has over 50 years of experiencing with creating progressive lenses. We use a very accurate progressive lens formula that is precisely calculated to the frames you order. Our formula is accurate is most cases.
If you feel that the segment height on your progressive bifocal lenses is not correct for your vision, then we will be happy to remake the lenses one-time at no cost to you. To do this you will have to provide us with the new segment height measurement by going to our How Do I Measure My Progressive Lens Segment Height Myself? page. Once you've measured your segment height on your recently purchased glasses, you can contact our Customer Service department at 1-888-248-5367 to request a Lens Remake order with the new segment height.
Other Notes and Tips
Eyeglasses Prescription Glossary / Abbreviations
OD - This is shorthand for oculus dextraous which means Right Eye.
OS - This is shorthand for oculus sinister which really means Left Eye.
OU - This is shorthand for oculus uterque which really means Both Eyes. If you see this, you'll want to enter the prescription the same on both eyes.
Sphere or Power - SPH or PWR - This is the main strength of your eyeglass prescription, and is written in 0.25 increments. If the field has 'SPH', 'PL', 'PLANO', or '00', this means your there is a 0.00 power as should be entered as so. AC Lens can create lenses for prescriptions with Sphere ranges between -20.00 and +20.00.
Plano - PL - This indicates there is no spherical correction in this eye. A plano lens would have no focusing power or correction to it.
Balance - This indicates there is no vision correction in this eye. It's a non-prescription lens and is used when only one of your eyes requires vision correction
Cylinder - CYL - This indicates the amount of astigmatism, and is written in 0.25 increments. Not all prescriptions have a cylinder correction, and some prescriptions have a cylinder correction in only one eye. If you don't have an astigmatism correction then your doctor may leave this field blank, or they may put 'SPH', 'DS', 'Plano', or '00' in this field. This means you do not have an astigmatism correction in one or both eyes. AC Lens can create lenses for prescriptions with Cylinder ranges between -5.00 and +5.00. Positive (+) Cylinder values will be converted into negative (-). See Why Does AC Lens convert positive (+) Cylinders values to negative (-) values? for an explanation of why.
Axis - AX or X - This is also part of the astigmatism correction, and is written in increments of 1 (one). If there is no cylinder, then there should be no axis. Since it's a degree/angle, it will be represented as a value between 1 and 180. If there is no cylinder, it's possible that the doctor might enter 0, but this would just indicate that there is no axis. AC Lens can create lenses for prescriptions with ADD ranges between +0.25 and +3.00.
ADD - This is a value that is commonly used for bifocal or progressive lenses, as well as reading glasses. It indicates how much power gets added to the distance Rx to create the reading-only Rx; or as it applies to the glasses you'll order from AC Lens, it determines the correction strength for the bottom half of your bifocals progressive lenses. It is written in increments of 0.25. AC Lens can create lenses for prescriptions with ADD ranges between +0.25 and +3.00.
Prism or Base or Base Curve - A prism is used when both eyes are not properly aligned and they need a prism to re-align them. The Base is the rotation of the prism. These fields are rarely used, and the correction type is not currently offered on AC Lens eyeglasses. There are two separate parts to a Prism correction. The first part is the diopter strength (e.g. 2.0) and the second is the direction (e.g. BU). There are four different directions. Base-Up (BU), Base-Down (BD), Base-In (BI), and Base-Out (BO).
Pupilary Distance - PD - This is the distance in millimeters between your right pupil and left pupil. A more detailed explanation of Pupillary Distance can be found in our What is Pupillary Distance (PD)? page.
Segment Height or Seg Height - SH - This is the vertical measurement in millimeters from the bottom of the lens to the beginning of the progressive addition on a progressive lens, or the top line of a lined bifocal. Segment height does not apply to Single Vision lenses. You will need the frame to be able to measure segment height because you can only measure it while the glasses are on your head.
Near Vision or Near Vision Only - NV or NVO - This is written when your doctor is recommending reading-only glasses. (This is also known as farsighted)
Distance Vision or Distance Vision Only - DV or DVO - This is written when your doctor is recommending distance-only glasses. (This is also known as nearsighted)
Amblyopia - The medical term for lazy eye, which is a loss or dimness of vision without any apparent disease of the eye.
Astigmatism - An optical condition that can cause blurry vision. This is corrected by a Cylinder and Axis correction on a prescription.
Barrel - The barrels attached to the endpiece, combined with the barrels attached to the temples, interlock and join together to hold both the frame and temple pieces together.
Bench Alignment - The standard adjustment of an eyeglass frame before it is custom fit to the customer.
Bend - The bend is where the temple curves behind the ear.
Binocular -v A term used to describe the simultaneous use of both eyes at the same time.
Bridge - BRG - The measurement in millimeters of the small connecting piece between the lenses of a frame.
Combination - These frames are made of both plastic and metal. They can have a metal front with plastic temples or other variations.
Compound Lens - A lens that contains both a sphere and cylinder
Cornea - The clear, transparent portion of the outer covering of the eyeball which covers the front part of the eye.
Crystalline Lens - Also known as just "lens", it is a transparent and colorless body located towards the front of the eyeball. Its function is to bring rays of light to a sharp focus on the retina.
Diopter - A unit of measurement of the refractive power of a lens equal to the reciprocal of the focal length measured in meters.
Diplopia - The medical term for when someone sees one object as two, it is also called double vision.
Distance Between Centers - DBC - This is the distance from the geometric center of one lens to the geometric center of the other lens, measured in millimeters.
Distance Between Lenses - DBL - This is the measurement in millimeters between the lenses of a frame.
Effective Diameter - ED - The largest diagonal measurement of the lens that passes through the center of the lens.
Emmetropia - The medical term for someone with 20/20 or better vision. This type of vision does not need correction.
End Piece - The part of the frame that connects the temples to the frame front.
Eyewire or Rim - The part of the frame which surrounds the lens and holds it in place.
Frame PD or Geometric Center Distance (GCD) - This is the distance from the geometric center of one lens to the geometric center of the other lens, measured in millimeters.
Full Frame - A one piece frame usually composed of just one type of metal.
Geometric Center - G - The center of each lens within the frame.
Half Eye - Designed for reading but can also be sold for other uses. The B measurement (vertical measurement of the eyewire) is half the size of a normal full frame.
Hinge - The hinge on a frame is made up of a screw and two pieces that have barrels.
Horizontal - A -The horizontal measurement of the lens for a specific frame, measured in millimeters.
Hyperopia - The medical term for someone with farsighted vision who is able see things that are distant or far away clearly, but need vision correction in order to see things that are near or close-up. Hyperopia is usually corrected with a prescription that has a positive (+) Sphere.
Keratitis Sicca - The medical term for dry eye.
Lensometer - An instrument which measures dioptric power, axis location, optical center and prism of a lens.
Macular Degeneration - A deterioration of the macula which results in a gradual loss of central vision (the center of your vision).
Monocular - Refers to only one eye.
Myopia - The medical term for someone with nearsighted vision who is able to see things that are near or close-up clearly, but need vision correction in order to see things that are distant or far away. Myopia is usually corrected with a prescription that has a negative (-) Sphere.
Ocular Height - OC - The measurement in millimeters from the center of the pupil to the bottom edge of the frame.
Oculus Dexter (OD) - Latin for right eye
Oculus Sinister (OS) - Latin for left eye
Oculus Uterque (OU) - Latin for both eyes
Opthalmologist - A medical doctor who has extensive education and training in surgery, diseases, functions, and refractive errors of the eye.
Optician - A person who prepares and dispenses optical devices to fill the needs of the patient's prescription. He or she also maintains these devices by making adjustments to them.
Optometrist - A person who is professionally trained and licensed to examine the eyes for visual defects, diagnose problems and impairments and prescribe corrective lenses or provide other types of treatment.
Pantoscopic Tilt - The tilting of a spectacle frame so that the top of the frame is farther away from the face than the bottom.
Presbyopia - The medical term for someone who needs vision correction in order to see things that are both close-up and far away. A Bifocal prescription is used for this type of vision correction.
Progressive Additive Lens - PAL - The ADD value specifically for progressive lenses.
Refraction - The change in direction of light as it passes obliquely from one medium to another; such as the refraction of light as it passes through the crystalline lens (eye).
Retina - The innermost membrane lining located at the back of the eye. It is comprised of nerve fibers and functions like the film in a camera. To see clearly, light must form a single focus point on the retina.
Retroscopic Tilt - The tilting of a spectacle frame so that the bottom of the frame is farther from the face than the top of the frame. Retroscopic tilt should be added to frames when they rest on the cheeks.
Rimless - Usually made of metal and made up of temples, end pieces, a bridge, and two lenses. The lenses are mounted to the bridge and end pieces, which creates the frame front.
Semi-Rimless - The eyewire on these frames does not go completely around the lens, instead it connects to both the end pieces and the bridge, and can be mounted in a variety of ways. The most common mounting uses a nylon cord to secure the lenses to the bridge and end pieces.
Shank - The longest portion of the temple.
Spatula - The temple spatula, also known as the temple tip, end, or earpiece, is the portion of the temple which extends from the bend to the end.
Strabismus - Also known as being cross-eyed, it is the failure of the two eyes to simultaneously look at the same object.
Temple - Temples are the component of the frame which rest over the ears to properly hold eyeglasses in place.
Vertex Distance - The distance from the back surface of a lens to the front of the cornea.
Vertical - A - The vertical measurement of the lens for a specific frame, measured in millimeters.
Still have questions? Call us at 1-888-248-5367 to speak to one of our trained Customer Service Representatives.