We get asked this question an awful lot over the past few years, especially since online glasses are getting more and more popular due to the prices often being lower. But lower prices can be a little deceptive. However, even with all of this popularity, there are some people that should not get their glasses from these sites.
So let’s start with people who are wearing multifocal glasses – either progressive, bifocal, trifocal, or any other type of multifocal lens. The reason this group of eyeglass wearers should never get online glasses is because these lenses are custom designed for your prescription and have to be accurately measured with a frame on your face. If these lenses are not accurately measured by a properly trained individual, there is a high chance that they won’t provide adequate vision; and at worst, may even cause a serious fall and/or injury. This is due to multifocal lenses having distinct zones within the lens that can distort how the world appears. So things that are normally close may appear farther; things that are one shape may appear misshapen, and so forth. When the measurements are “guessed at”, the apparent distance and/or shape of objects may be drastically off.
The other group of lenses are single vision lenses. These lenses also have interesting properties that also require accurate measurements to be taken to minimize eyestrain and maximize comfortable vision. Most online websites claim that having a “PD” measurement is sufficient enough to make a correct pair of glasses. This claim holds true for about 50% of the patients out there, but not for the other 50%. This is because in that group of patients there also needs to be a vertical measurement to ensure that a “prism” effect is not induced. Prism is a fancy term for light bending. When this vertical measurement is not taken (which changes with every different frame being chosen), patients will often have some degree of eye strain. The degree is which will vary depending on what the prescription is. Our office takes both horizontal and vertical measurements to help ensure that the viewing angle and centration is perfectly aligned in the glasses.
In conclusion, buying glasses online is perfectly OK if you’re willing to accept something less than 100% accuracy, clarity, and comfort. The low prices that they offer can often be offset by patients experiencing more eye discomfort than expected. All this, and I didn’t even begin to mention the problems found when the glasses are not adjusted properly on the patients’ faces – which, you guessed, can cause a great deal of eye strain too.