Your Prescription, PD and Frame Size
Most problems with glasses bought online come from three numbers: the prescription itself, your pupillary distance (PD) and the frame size. In the US, your eye doctor must give you a copy of your glasses prescription after an exam, at no extra charge – but most states don’t require PD on it, so you may need to ask for it or measure it.
These guides walk through each step in plain English. They are general information, not medical advice; for anything unusual, such as a strong prescription or prism, ask your eye doctor or an optician.
Before you order
- How to Read Your Glasses Prescription (SPH, CYL, Axis, Add, PD)
What every number on an eyeglass prescription means, how to get your PD, and what to check before ordering glasses online.
- How to Get Your Pupillary Distance (PD) for Glasses Online
What PD is, why it's often missing from your prescription, the most accurate ways to get it, and when an exact number matters most.
- Glasses Frame Size Guide (2026): How to Read the Numbers on Your Frames and Pick a Size Online
What the three numbers inside your glasses arm mean (lens width, bridge, temple), how small/medium/large differ between Zenni, EyeBuyDirect and GlassesUSA, and how to choose a size online.
- Best Glasses for Your Face Shape (2026): What Retailers Recommend, Compared
What frame shape suits a round, oval, square, heart, oblong or diamond face? We compared the face-shape guides from GlassesUSA, FramesDirect and EyeBuyDirect, and show where they agree and differ.
- Best Glasses Frame Brands (2026): Budget, Mid-Range, Designer and Premium
Warby Parker, FramesDirect, Silhouette, Lindberg, Vint & York and budget online stores compared on starting prices, what's included, materials, warranty and returns, from each brand's own site.
- Can You Buy Glasses Online With Astigmatism? Prescription Limits and Tips (2026)
Yes – most online stores fill astigmatism prescriptions. What CYL and Axis mean, the cylinder limits stores publish, when buying in person is safer, and how to order correctly.
- Glasses vs Contacts (2026): Cost, Care and Who Each Suits
Eyeglasses vs contacts compared on cost, prescription, care and risks – using published store prices and the National Eye Institute's contact lens guidance, with a worked annual cost example.
Common questions
- Can You Buy Glasses Online With an Expired Prescription? (2026)
What the FTC Eyeglass Rule says about your prescription, why expiration depends on your state, what GlassesUSA, EyeBuyDirect and Zenni say about expired prescriptions, and your practical options.
- How Long Does It Take to Get Glasses Online? Delivery Times by Store (2026)
Real processing and shipping times at 8 online glasses stores, the fastest options (2-day prescription glasses), and what slows an order down.