Know Your Pupillary Distance
In millimeters, pupillary distance (PD) is the distance between the centers of the pupils of both eyes. It’s a critical measurement whether you’re buying glasses in a store or online, as your lenses must be centered on your pupils. If they aren’t, the glasses will likely create eyestrain.
Your PD may be written on your prescription. If not, you can usually contact your prescriber and ask. Alternatively, you can go to an optician’s office and get a measurement there.
You can also find lots of online tutorials and do it yourself. Retailers that sell prescription glasses online may provide their own ways of finding your PD.
These Extras Make Cheap Glasses Expensive
Premium Lenses for Prescription Glasses
Regardless if you purchase prescription glasses offline or online, someone will possibly try to upsell you on coatings and lenses. Anything beyond a basic, single-strength lens will increase the overall cost, but some may be worth it. Here are the types of lens you’re probably will most likely see:
Polycarbonate and Trivex lenses
These lightweight plastic lenses provide solid durability. They’re the perfect choice for kids or for general wear when doing outdoor activities or playing sports.
High-index plastic lenses
As the name implies, these lenses have a higher index of refraction. In simple terms, this means they’re the thinnest lenses you can get and they remain thin while offering a clear vision for people who need stronger prescriptions.
Progressive lenses (cosmetic enhancement lens)
Made for folks who wear bifocals (glasses that have two strengths for seeing far and near) or trifocals (which have three strengths), progressive lenses are line-free where one strength lens links the next. This is certainly a cosmetic enhancement but can also make things simpler to see since there isn’t a line in the center of your lens.