Getting a contact lens prescription requires a specific type of eye exam called a contact lens fitting, which is separate from a standard glasses exam. Even if you already have a glasses prescription, you’ll need additional measurements before you can buy contacts. The whole process typically takes one or two appointments and costs between $120 and $250.
Why a Glasses Prescription Won’t Work
A glasses prescription and a contact lens prescription are not interchangeable. Glasses sit about 12 millimeters from your eyes, while contacts rest directly on the surface. That difference in distance changes the lens power you need. A contact lens prescription also includes measurements that a glasses prescription doesn’t, like the curvature of your cornea and the physical diameter of the lens. Without those numbers, you can’t order contacts.
What Happens During the Exam
A contact lens exam starts the same way as a regular eye exam: your doctor checks your visual acuity, tests your overall eye health, and determines your corrective lens power. Then comes the contact-specific portion.
Your doctor will measure the curvature of your cornea, which determines the base curve of your lenses. A lens that’s too flat or too steep won’t sit properly on your eye. They’ll also examine your eye’s surface with a microscope called a slit lamp, checking for dryness, blood vessel growth into the cornea, or other issues that could affect lens wear. This surface check happens even if you have no complaints, because some contact lens complications develop without symptoms.
If you already wear contacts, your doctor will examine your eyes with the lenses in place to see how they’re sitting and whether the fit is still correct. They’ll also check them with the lenses removed to look for any signs of oxygen deprivation or irritation.
Trial Lenses and Follow-Up
After taking measurements, your doctor will give you trial lenses to wear. This is a test run to make sure the fit, comfort, and vision correction all work in your daily life. You’ll wear the trial lenses for a set period, then return for a follow-up visit where your doctor confirms everything looks good. If the fit needs adjusting, you may try a different brand or base curve before the prescription is finalized.
First-time wearers should expect this appointment to include basic training on how to insert, remove, and care for lenses. Don’t be surprised if it takes a few tries to get comfortable touching your eye.
What’s on the Prescription
Your final contact lens prescription will include several values:
- Power (PWR or Sphere): The strength of correction needed, just like a glasses prescription but adjusted for the lens sitting on your eye.
- Base Curve (BC): The curvature of the lens, matched to the shape of your cornea so the lens fits comfortably.
- Diameter (DIA): The overall size of the lens, ensuring it covers the right area of your eye.
- Brand name: Contact lens prescriptions are brand-specific because different manufacturers use different materials and designs, even at the same power.
If you have astigmatism, your prescription will also include a cylinder value and an axis, which correct for the uneven curvature of your cornea. These are called toric lenses. If you need reading correction on top of distance correction (presbyopia), you’ll be fitted for multifocal lenses, which require additional testing to determine your dominant eye and the right add power. Both of these specialty fits tend to cost more and may require extra follow-up visits to dial in.
How Much It Costs
A contact lens exam typically runs between $120 and $250. That range covers standard soft lenses. If you need specialty lenses for astigmatism, presbyopia, dry eye, or a condition like keratoconus, expect to pay more because of additional testing like corneal mapping or tear film analysis. Some offices bundle the fitting fee into the exam cost, while others charge them separately, so ask upfront.
Vision insurance plans often cover part of the exam but may not cover the fitting fee in full. It’s worth checking your specific plan before booking.
Your Right to the Prescription
Under the Fairness to Contact Lens Consumers Act, your eye doctor is required to give you a copy of your contact lens prescription once the fitting is complete. They cannot withhold it or require you to buy lenses from their office. This means you’re free to shop wherever you find the best price, whether that’s an online retailer, a warehouse club, or another optical shop.
Federal rules set a minimum expiration of one year from the date the prescription is issued. Many states set longer windows. If your state law specifies an expiration of one year or more, that state deadline applies. If your state tries to set a shorter window, the federal one-year minimum overrides it. Your doctor can set a shorter expiration only if there’s a documented medical reason.
Online Prescription Renewals
If you already wear contacts and just need to renew an expiring prescription, some online services offer remote vision tests. These are not full eye exams. A licensed eye doctor reviews your results remotely and can issue an updated prescription if everything looks stable.
To qualify, you typically need to be between 18 and 55 years old, have a previous prescription on file, and live in a participating state (currently around 34 states allow it). You’ll need your current contacts or glasses, a computer, a smartphone, and about 10 feet of space. These services are not available if you have conditions like diabetes or glaucoma that require in-person monitoring.
First-time contact lens wearers cannot use online services. You need an in-person fitting to determine your base curve, diameter, and lens brand. There’s no shortcut for that initial exam. Even for renewals, an online vision test doesn’t replace a comprehensive eye health screening, so you should still get a full in-person exam periodically to check for conditions that don’t affect your day-to-day vision.