Buying Glasses Online

Glasses are a racket.  Luxottica owns a lot of the market and does anticompetitive things (CBS, Snopes).  Most glasses seem to be priced with the assumption that people have vision insurance, so prices are artificially inflated like a fashion accessory rather than being tread more or less like the commodity that they should be.  There is an information asymmetry (your optometrist knows your prescription better than you) that can make it hard to shop for glasses in the free market.  

I wanted to demystify the experience to make it easier for you to buy glasses online without having to do a ton of research.

Lens Measurements

First, when you get your eye exam, ask your doctor for your prescription.  Then, when you get home, write it down somewhere you'll remember (eg, Google Docs) so that you have a historical record of it over time.  OS means left eye and OD means right eye.  For each eye, you should have a number for Sphere, Cylinder, and Axis.  There will potentially be more numbers if your eyes are complicated.  You may notice that your left and right eyes have different prescriptions -- that's normal.  To give some context on what those numbers look like, for my OD, I have a -4.75 sphere, -0.25 cylinder, and 48 axis.  Make sure to write down the negatives where appropriate!  That covers the lens.

One concern you might have: will having a stronger prescription make your eyes worse?  Should you, then, choose a weaker prescription?  I looked into the research and wasn't able to find any data supporting those claims, though there are plenty of optometrists who will get behind them.  I did see at least some research indicating that if a kid gets a weaker prescription than they need (by following that advice), they actually end up with worse eyesight later in life.  That said, there isn't a whole lot of evidence either way, particularly for adults.

Lens Material

The main glasses materials are: glass, CR-39 (cheap plastic), polycarbonate (durable plastic), high index (plastic that bends light better so that you can get thinner glasses), and photochrome (glasess that darken in sunlight).

Some people worry about UV light giving them cataracts.  You don't need to get sunglasses if you already wear glasses!  CR-39 blocks most 88% of UV light.  Polycarbonate lenses, high index plastic lenses, and photochrome lenses block 100% of UV light.  I couldn't find a number for glass glasses, but those aren't used much anymore since they're heavy and breakable.  

I have tried photochrome in the past, and I wasn't a fan.  They did darken in the sunlight, but they took annoyingly long to clear up after going inside, they made taking pictures outside annoying (since it would look like I was wearing sunglasses in the pictures), and even in their darkened state, I usually would still need to squint or shield my eyes if the sun was bright enough, so they weren't worth it.

Since I want something with 100% UV blocking without needing an extra coating and I like durable things in general, I go with polycarbonate lenses.

Lens Coatings

There are a few popular lens coatings.  

Anti-reflective coatings do a reasonable job of reducing glare.  When I was a kid, anti-reflective coatings weren't popular yet, so I remember thinking it was cool that I could see little halos around light sources and that I could use my glasses to look behind me without turning my head by looking at the reflection in them.  Then, a pair of glasses didn't have those same properties, and I discovered that it was because of an anti reflective coating that I didn't even realize I got.  Some people like the coating because it helps the glasses get out of the way of pictures or because it makes night driving better.  I have continued to get this coating, but I don't have strong feelings about it.  If you want to tell if your current glasses have an anti-reflective coating, take them off and angle them so that you can see a light source reflected in them (no, it's not perfect anti-reflection).  If the reflection looks normal, then you don't have a coating.  If the reflection is a weird color (eg, the reflection of a white light source looks blue or green), then you have a coating.

There's also a new blue light reduction coating that supposedly reduces eye strain.  I couldn't find any information about it aside from the publicity by the creator of that coating, but my insurance covered it, so I decided to try it out.  I haven't noticed any difference (eg, blues don't look any less blue), so it might be snake oil, or it might actually help.

Anti-UV coatings are unnecessary if you have polycarbonate, high index plastic, or photochrome lenses.  Most people get one of these types of lenses, so you probably don't need an anti-UV coating.

I have never tried scratch resistant coatings, but I also don't tend to get any scratches on my glasses.

In general, I think that my glasses that didn't have any coatings were easier to clean than my glasses with coatings, which is annoying.

There are also some fancy propriety coatings.  For instance, this coating looks like it makes cleaning glasses much easier (in addition to doing all of the things described above), but it's not covered by my insurance.

Frame Measurements

For the frames, there are three numbers to keep in mind: temple, lens width, and bridge width.  The temple is the number of millimeters from the glasses back to where it rests on your ear.  Those are usually 135, 140, or 145.  I have used 145 for a while, but 140 fits me just fine too.  The lens width is how wide each lens is.  This number should be around 50.  The bridge width is between the two lenses.  That number should be somewhere around 18.  

If you have a pair of glasses that fits well, you can probably just use those numbers (which should be listed on the insides of the glasses -- check the temple and the bridge).  However, you should also go to a glasses store to try on some pairs with different numbers to get a better idea of what fits so that you won't be limited.  For instance, my last pair was 145-19-50, but the glasses that I liked weren't available in that size, so I tried on a 140-17-52, found that it fit well, and got my new frames in that size.

You also might be able to get your glasses adjusted at a glasses store even if you bought the glasses online.

Frame Materials

This is probably more of a style question than anything else, so you probably don't need any advice in choosing frame materials.

I prefer unassuming glasses, and metal frames generally seem to provide the lowest profile.  If you want your glasses to make a statement, though, there are a lot more options with plastic frames.

Some metal frames have a full rim (there is metal all the way around the lens), some have a half rim (there is metal halfway around the lens), and some are rimless (there is metal attaching the lens to the temple, but it doesn't go around the lens).

Even if you have metal frame, the temple might still be plastic, so be careful.  One nice thing about metal temples is that they are thin enough that you can't see them, whereas my current plastic temples are constantly in my peripheral vision.

Insurance

A few things to check in your insurance:

• What is their copay on an eye exam ("wellvision exam")?  After the copay, do they pay the full amount?
• What is their copay on glasses?  After the copay, how much do they cover for the frames?
• What coatings do they cover fully?  What coatings require a copay?
• What lens materials do they cover fully?  What coatings require a copay?
• How do those numbers differ depending on whether you buy your glasses in network versus out of network?

I have VSP as my insurance.  They have an online glasses website, eyeconic.com, that counts as in-network, so I got my glasses there.  I paid $20 for my exam, $20 for a copay on my glasses, $20 for polycarbonate lenses, and $20 in taxes.  So, even though I picked the cheapest options available and had insurance, my new pair of glasess cost $80.