According to research from the Vision Council, a nonprofit trade association, over 79% of American adults utilize some form of vision correction. Furthermore, statistics from vision insurance provider VSP reveal that the average cost of a pair of prescription glasses is 315.

If you purchase eyeglasses online cheap, you can reduce your expenses by up to half of the in-store price (or even more). However, please note that with optional upgrades or specialty lens requirements, your online costs can quickly accumulate - sometimes even matching or exceeding the prices you might encounter in-person with an optician.

If you struggle to find frames that suit your face shape or personal style, shopping online for glasses can offer a broader range of options. Online glasses retailers offer a far greater variety of frames, including different widths, depths, and styles, such as frames suitable for people with lower nose bridges, higher cheekbones, or weight restrictions. Many online glasses stores provide in-home frame trials and virtual try-on tools to help you find the perfect-fitting pair of glasses for your face. Additionally, they often offer generous return policies with no questions asked. To make it easier to find suitable frames, check the measurements inside the arms of your current glasses. You can then search for the same dimensions in a new set of frames. Many websites also have style-searching tools, allowing you to quickly find glasses that fit and appeal to you. However, if you're not quite sure what you're looking for, visiting an optician in person can be the most efficient way to try on a wide range of styles and sizes.

Buying prescription glasses online may not be suitable for everyone. Based on the collective opinion of eight eye-care professionals we consulted, purchasing online is generally acceptable if you have a mild or straightforward prescription. However, individuals with significantly high prescriptions or additional complications, such as the need for prism correction or progressive lenses, may prefer to obtain glasses from a physical storefront to ensure accurate prescription. 

To buy glasses online, you need two things: a valid prescription and your PD, or pupillary distance.

The American Optometric Association (AOA) advises that all adults under the age of 65 should have an in-person eye exam at least once every two years (although most prescriptions won't officially expire until closer to five years). The AOA strongly recommends against using online-only services for renewing eyeglasses prescriptions or do-it-yourself prescription checkers. "Patients should be cautious of any company that claims its [service or] device can replace the care provided by a doctor," the AOA stated in an emailed comment. Optometrist Dr. Camille Cohen pointed out that only in-person eye exams can detect early signs of glaucoma, diabetes, and high blood pressure.

In addition to a valid prescription, you will also require a measurement known as pupillary distance (PD), which is not typically included in the prescription. PD refers to the distance between your pupils (for a single PD measurement) or from your pupils to the center of your nose bridge (for dual PD). This value indicates where the company dispensing your prescription should position the horizontal center of vision in the lenses, ensuring clear vision. According to Dr. Neil Pence of Indiana University, the stronger your prescription (referring to the larger spherical numbers, positive or negative), the more crucial it is to have the lenses correctly aligned in front of your eyes.