In my family (parents and 5 siblings) I’m the only one that never needed glasses. But for some time (I’m 79) I do use over the counter reading glasses for close work. I use +1.75 for using the computer and I just went up to +4.0 for reading. However when doing research I go back and forth from the screen to reference books and have to switch glasses which gets real tedious. I was thinking of buying some bifocals online to try them out. So how do I spec the specs? +1.75 for the main lens and + 4.0 for the additive, or +1.75 and +2.25 for the additive?
Have you thought about getting checked by a professional and using an actual prescription?
I had bifocals and hated them. I now wear contact lenses and put on readers to read things up close. The other option was a bit harder to manage - I could not figure out a way to make my arms longer.
I use these. Mine graduate from 1.25 to 2.5, they go up to 1.75 to 3.5. There may be other brands with stronger option:
The problem with ordering custom is that any place I’ve checked wants a prescription less than one year old.
“You haven’t got a baboon in your pocket, have you?”
There are several kinds of bifocals now. The old traditional type with two separate lenses in one frame, progressive lenses without a line or distinction. This is one of those times you really should go to the eye doctor.
Now, I have a very old prescription that I use to order my glasses. The places on the internet do not care about the age of your or acuracy of your prescription, they will send you a pair. I have even tweeked the range, orbit, etc, and ordered glasses. There are places, where the glases are so cheap that it doesn’t matter.
New Bifocals if you haven’t had them before is one of those times you really need to see the professionals.
There are very few products that I have owned in this life that have given me as much satisfaction as my progressive lenses. Some people find them a challenge to adapt to, but I took to them immediately. I’ll say that you get what you pay for, IMO of course, and that the cheaper ones are a total pain in the ass. Narrow vision corridors, unpleasant distortion of straight lines, generally hard to use. I would have thought that lenses were lenses, but nope, not my experience.
Agree on all counts.
Cheaply made ill fitting glasses are nothing like optically perfect glasses matching your measurements despite having identical prescriptions.
Hey, it’s genetics. 
I’m in the camp of getting to an optometrist.
Those look perfect!
It’s 1.75 plus 2.25 for the additive.
But i agree that it’s worth going to a professional, especially for your first pair. You want to get the distance between your pupils right, and there are probably other things. Try an optometrist. Their specialty is during your with suitable glasses.
Likely your vision is not identical between eyes. One eye may need a stronger magnification than the other. In addition, you may also have astigmatism, which is an imperfection in the curvature of your lens. The benefit of an eye exam is that it will give you a prescription to correct these issues much better than readers will.
Some of the discount eye glass stores, like America’s Best, have deals where you get an exam and two pairs of single-vision glasses for $100 or so. For a bit extra, you can upgrade to bifocals. Before you go in for your exam, figure out the distance from your eyes to your computer screen so the doctor can create the prescription for that distance. Readers will be a standard distance, but depending on how far you sit from the monitor, the computer vision prescription will need to be based on your distance to the monitor.
Repeated for emphasis. My vision was fine until I hit about 45, and then slowly got worse. One eye needed more correction than the other, though that has switched (!) over the course of the last 6 years (normal aging brough one eyes distance correction closer to the norm, and the “better” eye just got the age related loss of close up).
Another advantage for bifocals from a dedicated store is you can within reason determine the height of the bifurcation - I still can drive and read without them, but it’s far less eye stress when I do, so my reader/close vision is a few degrees lower than the default. I still mostly use them for night time driving and the rare in-theater movie because it’s much harder to compensate when it’s dark. YMMV of course.
Though if cost or insurance (or lack thereof) is an issue, that is a very different set of choices for the OP.
puzzlegal answered. Just to chime in, I gather the underlying principal is that the “adds” are called that because they add onto the underlying prescription which applies everyplace.
Additionally, someplace it must be specified how high the transition line is placed. And, also, how far apart the pupils are (needed for any nontrivial glasses). I’m not sure these are part of the prescription; they may be side details. But they’re part of the specs spec.
I never needed glasses. That is, I didn’t think so. I could function. Then in my 30s I got an eye exam, they prescribed glasses, and all of a sudden things were clearer. Turns out I have astigmatism but was too stubborn to consider it. I don’t wear them for everything (pass my driver’s test without them) but they are great for driving or watching TV.
[/quote]I do use over the counter reading glasses for close work. I use +1.75 for using the computer and I just went up to +4.0 for reading.
[/quote]
I do something similar. I took my prescription and ordered a pair with +1.5 for the computer and +2.0 for reading, something like that. They are far better than just the OTC reading glasses.
Do yourself a favor and get an eye exam. They also check for things like glaucoma, or other medical issues that might not be obvious to you but could result in a referral to an ophthalmologist.
I’m reading this stuff and using my screen with a cheap pair of reading glasses (about $C40 or $US30) that I ordered online. They work great. I have aspherical eyes, the doctor described them as lenses shaped sort of like footballs (exaggeration…) When I got my most recent eye exam, I asked for reading/computer glasses prescription too. Comparing my last few prescriptions:
For one eye, the prescription was +0.75 and the ADD was +2.50 (CYL -1.00, 90°)
For the other , -.50 and ADD +2.50 (CYL -0.50 and 90°)
Yet reading glasses (Computer glasses, for reading about 2 feet from screen, the doctor said) was +2.75 and +1.50 respectively same CYLs. They work great for most closeup work. I even have my pupil distance info from a previous optometrist purchase, so I could provide that to the online store. I typed in the info, and the glasses are great. (some company called KITS). Plain retail +2.00 helps, but doesn’t work too well, probably because of my eye shape and different eyes. It works best for my one eye from a foot away with 2 instead of 2.75
My ADD has been consistently +2.50 for several years. I have several (progressive) bifocals from local optometrists over the years, no problem with the prescriptions provided.
However, this is what ADD means according to google which is nowhere close to what I should have have (this says it calculates to +3.25 and +2.00). Whether it’s because computer glasses are supposed to be further away than reading glasses, I don’t know. Mine work fine from about a foot to over 3 feet) Maybe you should get a specific prescription next opthamologist visit, especially if your prescription has aspherical numbers :
How ADD works: It’s combined with the distance prescription to create a lens that works for multiple distances. For example, a reading prescription would be the sum of your distance prescription and your ADD value
FWIW my optometrist measured a pair of the graduated readers I mentioned upthread and verified that they match the advertised values. He is perfectly fine with me using them for close work.
Helps that I don’t have astigmatism thanks to lens replacement and I only care about vision through one eye due to retinal detachment in the other.
That’s exactly what astigmatism is.
Ah. I’ve learned my one thing for the day…
I thought that astigmatism was irregularly shaped lenses.