Should you buy prescription glasses online?

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It’s clear that online shopping has transformed the landscape of the retail environment. The immense growth of internet titan Amazon is proof of that. The main drivers of online shopping are cost savings and convenience. Despite these two important virtues, the key to the success of such ventures is that most internet retailers supply the exact same product that can be purchased in a “brick and mortar” setting.

The failure to deliver on this promise is the reason why purchasing online eyewear is so problematic. The product provided by many online eyewear retailers simply doesn’t match the quality and specifications of the product available from reputable eyewear dispensers.

The lack of online prescription specification largely comes from errors and omissions in measurements of prescription placement. Every spectacle lens has an optical center that represents the “sweetspot” of the lens. The optics of every prescription is purest at the optical center and degrades the farther you progress from the optical center. Therefore, precise placement of the optical center over the center of the eye is critical for clear and comfortable vision.

Most online eyewear retailers require entry of the interpupillary distance (PD) to fulfil the placement of the optical center. This measurement is usually achieved by an optician utilizing an optical instrument in a direct measurement on you that provides great accuracy in the alignment of the eyes. Due to the lack of an in-person fitting, many online retailers provide rudimentary instructions for you to perform this measurement on yourself. Performing this task on yourself has been likened to giving yourself a haircut. The virtual nature of this measurement can result in errors of optical placement.

Further, the PD only measures the horizontal displacement of the pupils and neglects the vertical dimension altogether. The vertical measurement, known as the major reference point (MRP), is a customized measurement specific to the physical fit of a frame on your face. During a professional eyewear fitting, an optician measures the MRP, in addition to the PD, to provide you with a customized placement of the prescription. Without this measurement, online retailers routinely place the vertical dimension in the geometric center of the lens. This often results in improper optical center placement and has you looking through impure optics. The combination of improper placement of the PD and MRP can result in blurred vision, distortion, eyestrain, double vision and headaches.

You might ask, how can a company supply these prescriptions that might have erroneous measurements? When these lenses are measured on a lensometer, they’re automatically measured through the optical center. Therefore, the glasses will often measure the proper amount of the nearsighted or farsighted prescription, but the misalignment of that prescription when you wear it will cause poor vision.

The quality of online optical materials is often lacking compared to those purchased through a reputable dispensary. Lower-quality polymers of plastic frames and lenses can result in frequent breakage, scratches and poor visual quality. Because of this, online eyewear retailers have a high rate of returns from dissatisfied customers unable to wear the prescriptions purchased online.

We see a high volume of patients in our Eyewear Gallery who return for a professional fitting after going through the hassle of returning faulty product purchased online. Based on the advice of our patients, beware of online eyewear purchases. The lack of quality and performance of the online products creates more of a burden than a convenience and outweighs any cost savings.

Gregory J. Nixon is associate dean for clinical services and professor of clinical optometry in The Ohio State University College of Optometry.