Getting a prescription for glasses requires an eye exam performed by a licensed optometrist or ophthalmologist. The exam typically takes 20 to 30 minutes, costs between $50 and $300 depending on where you go, and ends with a written prescription you can use at any glasses retailer you choose. Here’s what the process looks like from start to finish.
Who Can Write Your Prescription
Two types of eye care professionals are licensed to examine your eyes and write a glasses prescription: optometrists and ophthalmologists. Optometrists perform eye exams, prescribe corrective lenses, and detect eye abnormalities. Ophthalmologists do all of that plus diagnose and treat eye diseases and perform surgery. For a straightforward glasses prescription, either one works.
Opticians, the staff who help you pick out frames and fit your glasses, cannot write prescriptions. They work from the prescription your doctor provides.
Where to Get the Exam
You have several options, and cost varies significantly by setting. Without insurance, a basic eye exam runs between $75 and $250 on average. Retail vision centers like Walmart, Costco Optical, and America’s Best often charge $60 to $100. Private optometry clinics range from $120 to $300, and ophthalmologist offices tend to be $200 to $350. In major metro areas like New York or Los Angeles, prices skew toward the higher end. Smaller towns and discount clinics can start as low as $50 to $70.
You don’t need a referral. Just call any optometrist or ophthalmologist office and schedule a comprehensive eye exam. Many retail locations accept walk-ins.
What Happens During the Exam
The core of a glasses prescription is a test called refraction. You sit behind a device called a phoropter (the machine with all the lenses) and look at a letter chart. The doctor flips between lens options and asks, “Which is clearer, one or two?” This isn’t a test you can fail. If both options look the same, that’s a perfectly valid answer, and the doctor will tell you so.
The process starts by finding the basic lens power you need, then fine-tunes for astigmatism (an uneven curve in the front of your eye), and finishes by dialing in the final power in small increments. The doctor works with the smallest line of letters you can read, gradually narrowing down the combination that gives you the sharpest vision.
Beyond refraction, the doctor will check your overall eye health. This often includes dilation, where drops widen your pupils so the doctor can see the retina and optic nerve at the back of your eye. Dilation is the gold standard for catching problems like glaucoma or retinal damage, and it’s especially important if you have diabetes, a family history of eye disease, or haven’t had an exam in years. Some offices offer digital retinal imaging as an alternative, though it’s not as thorough. Dilation temporarily blurs your near vision and makes you light-sensitive for a few hours, so bring sunglasses or arrange a ride if you’re concerned.
Reading Your Prescription
Your prescription will include a few abbreviations that look confusing but are straightforward once you know what they mean.
- OD and OS: OD is your right eye, OS is your left eye. These are Latin abbreviations.
- Sphere (SPH): The main lens power. A minus sign means you’re nearsighted (trouble seeing far away). A plus sign means you’re farsighted (trouble seeing up close).
- Cylinder (CYL): How much astigmatism correction you need, if any. Many people have at least a small amount.
- Axis: A number between 1 and 180 that indicates the angle of your astigmatism. It tells the lens maker which direction to orient the correction.
If you’re over 40, you may also see an “Add” power, which is extra magnification for reading.
Your Right to Your Prescription
Federal law requires your eye doctor to hand you a copy of your prescription immediately after the exam, whether you ask for it or not. The FTC’s Eyeglass Rule is explicit: the doctor must provide it automatically, before offering to sell you glasses. Simply asking if you want it doesn’t count as compliance. You’re entitled to it in hand (or delivered digitally) before any sales pitch.
This means you’re free to take your prescription anywhere: a different optical shop, a big-box retailer, or an online glasses store. The doctor cannot withhold it, charge extra for it, or require you to buy glasses from their office to receive it.
One Detail Often Missing: Pupillary Distance
Your pupillary distance (PD) is the measurement in millimeters between the centers of your pupils. Lens makers need it to align the optical center of each lens with your eyes. Without it, even a perfect prescription can cause eye strain or blurry vision.
PD is not always included on your prescription. You can ask your eye doctor to measure it and add it, and most will. If they don’t, you can measure it yourself using a millimeter ruler and a mirror, a smartphone app, or by asking a friend to measure while you look at a distant object. Many online glasses retailers also provide measurement tools on their websites.
Online Vision Tests
Several companies now offer online vision tests that can generate or update a glasses prescription remotely. These involve reading letters on a screen from a set distance and are reviewed by a licensed doctor who signs off on the prescription. They’re generally cheaper and faster than an in-person visit.
There are real limitations, though. Online tests can measure your lens power, but they can’t detect eye diseases that often have no symptoms in their early stages. The American Academy of Ophthalmology considers them appropriate only for adults aged 18 to 39 who have healthy eyes, a mild to moderate prescription, and no risk factors for eye disease. They work best as a follow-up tool to update an existing prescription when you’ve already had a recent comprehensive exam confirming your eyes are healthy.
Online tests are not recommended for anyone under 18, anyone 40 or older, or anyone with a strong prescription, diabetes, a family history of glaucoma, or symptoms like flashes, floaters, or vision changes. People with complex or high-power prescriptions may not even be eligible through these services.
Insurance and Payment
Health insurance and vision insurance are often separate. All Health Insurance Marketplace plans cover children’s vision care, but only some include adult vision coverage. If your health plan doesn’t cover eye exams for glasses, you can purchase a standalone vision plan to reduce costs. Many employer-sponsored benefits packages include vision coverage that pays for one exam per year and offers an allowance toward frames or lenses.
If you don’t have any vision coverage, the retail and discount clinic options mentioned earlier keep costs manageable. Some offices also offer payment plans or accept health savings account (HSA) and flexible spending account (FSA) funds, since eye exams and prescription eyewear are eligible expenses under both.
How Long Your Prescription Lasts
There is no federal expiration date for eyeglass prescriptions. Expiration is set by state law, and it varies. Most states require prescriptions to be valid for one to two years. After that, you’ll need a new exam to get an updated prescription. Even if your state allows a longer validity period, your vision can change, so getting an exam every one to two years ensures your glasses actually match what your eyes need. Adults 18 to 39 with no symptoms or risk factors should have a comprehensive eye exam at least every five to ten years, though more frequent exams are a good idea if you already wear corrective lenses.