Buying glasses online from a leading eyeglass supplier will give you the same options, frames and progressive, bifocal, multifocal, and transition lenses. Many online companies offer a virtual eyeglass fitting section where consumers are able to try on different frames by uploading their photo off the computer. Some sites even offer a virtual instructor that help with selecting frames.
Online eyeglass providers usually have a big selection of frames, but the really important issue is the lens. You have to decide what lens material and coatings you want...polycarbonate, high-index or regular plastic lenses....ultraviolet light filtering lens...anti-reflective coating...photochromic lenses.
If you're comfortable making these decisions yourself, there's no problem. However, you need to consider that glasses are custom-made because everybody's head and eyes are different which requires that an optician take various measurements for a proper fit.
The optical center of the lens is the part that gives you the truest vision and it should be directly in front of your pupils. This means that the optical center is customized for your eyes and the lab needs to know the distance between your pupils.
You really cannot accurately measure the distance between you pupils (pupillary distance or PD as it's called) yourself. Most online dealers offer several ways to do this yourself, but don't count on it being exact! If the PD is wrong, or out of tolerance, you won’t be able to focus your eyes properly. You can ask the eye doctor for the PD, but they are often reluctant to give it because it's a tip off that you are probably going to their competition, online retailers. See the 20/20 article The Power and Politics of the PD HERE.
Of course, fit is also important. Frames that are too large are uncomfortable and can slip. Too small they will be uncomfortable, pinch the sides of your head and leave red marks on your temples. They also can cause discomfort behind your ears or on your nose. Also, the prescription strength and weight of the lenses play into whether glasses will be comfortable and look good. Bifocals and progressive lenses present additional challenges because fitting multifocal lenses is a delicate process and extra measurements must be taken.
Many online sites don't offer bifocals and progressive lenses. Multifocal lenses also come in many different styles. Determining which one is right for you often requires an in-depth discussion with a knowledgeable dispenser or doctor. Even if you already wear bifocals, if you are limited to just certain lenses on a website, you might not be able to determine if you're getting the optimal lens for your visual needs
It's a good idea to pay careful attention to web-based optical sites return policies, too.
A study published by the medical journal Optometry: Journal of the American Optometric Association reported that almost half of prescription eyeglasses purchased online either failed safety standards or fell below prescription specifications. Some of their findings showed that over one in five pairs of glasses was incorrect upon delivery, 28.6 percent of online glasses had at least one lens that contained the wrong prescription, and 22.7 percent of one or both lenses failed the U.S. Food and Drug Administrations impact-resistance regulation.
A 2012 study out of the School of Optometry of the Université de Montréal examined 16 frames and 32 lenses that were purchased from online glasses retailers and they found that six of the lenses did not match the prescription and 13 of the 16 frames did not receive a passing grade in terms of fit.
Like most everything else lower cost can mean cheaper quality and high expectations can't be associated with a $39 price tag.