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ZDNET's key takeaways

• My doctor wrote computer glasses for the wrong distance.
• ChatGPT, Claude, and Gemini agreed on the problem and the results.
• The AI-derived glasses worked where the first pair failed.

I recently visited my eye doctor for the usual eye exam and glasses prescription update. While the distance prescription was good, my doc completely failed when it came to my computer glasses.

Fortunately, with the help of ChatGPT, Claude, and Gemini, I was able to get computer glasses that actually do their job.

Most people go for their regular eye exams to an optometrist, a doctor who specializes in eye exams, glasses, contacts, and more routine eye conditions. But since my family has a history of cataracts and glaucoma, I visit an ophthalmologist, a medical doctor who can do all the routine eye care but who also specializes in eye disease, eye surgery, and medical eye treatment.

My ophthalmologist also has techs who work with him to help with the basic eye chart testing. He interprets those results and does the more in-depth eye health exams.

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I find the eye chart tests that determine glasses prescriptions to be very frustrating. Because the test rapidly swaps lenses in an effort to discover which makes the distant text clearer to read, the results are very subjective. Because the stakes are high, exam time is limited, and conditions aren't ideal, I almost always second-guess every swap.

Even so, I usually end up with a distance prescription that works well enough to help me see clearly.

I am nearsighted, also called myopic. I can easily read a book or a Kindle device near my eyes without needing glasses. I do need glasses to see at a farther distance.

That includes the middle distance where my main computer monitor is. The distance from my eyes to the center of my monitor is 23 inches. It's a 38-inch, slightly curved monitor, so when I sit at its center, the distance from my eye to the edge is about 29 inches. All hail the Pythagorean theorem.

For years, my then-current distance prescription worked pretty well with the monitor I use. But I noticed over the last year or so that my eyes had started to really strain to see the monitor clearly.

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Beyond the good health practice of getting an eye exam regularly, my primary reason for visiting the eye doctor this time around was to get a new computer glasses prescription.

That exercise failed miserably. I got completely yeah-yeah-yeahed by both the doctor and the exam tech.

Before I went to the exam, I carefully measured the distances I described above. I knew exactly how far my eyes needed to focus when working on the computer.

Given that I work on the computer far more than I do anything else, this prescription was even more important than the distance prescription. After all, my previous prescription still worked pretty well for distance.

I was very clear about my needs. I described that I generally look up to my monitor, not down like when you read a book. I gave them the measurements. I explained the size of the monitor. I explained the number of hours each day I spend writing, coding, researching, and communicating. I explained that I needed a pair of glasses for computer use, and a pair for distance. I do not want progressives or bifocals.

They gave me back a prescription for progressive or bifocal lenses, with the upper part of the glasses good for distance and the lower part of the glasses good for reading a book.

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When I received that piece of paper, I reiterated my needs. This time, they went off and consulted their screens, and wrote me two prescriptions, one for distance and one that they said was a computer glasses prescription. I know it was a computer glasses prescription because they had printed "computer glasses" right on it.

I took both of those prescriptions and uploaded them to Eyebuydirect, an online eyeglasses firm I've had success with in the past. A few weeks later, my glasses arrived.

My distance glasses were fine. I could see clearly. I even ordered sunglasses with that same prescription. It's been years since I've had prescription sunglasses, and that was a total win.

The computer glasses, which were created using the prescription labeled "computer glasses," unfortunately made it impossible for me to clearly see my computer screen.

I had been a little worried this might be the case because they hadn't tested my vision at a 23-inch distance. They had used a chart at the far end of the room. They'd apparently derived the so-called computer glasses prescription based on the distance prescription, either mathematically or by using some sort of lookup table.

This is where the AI comes in

According to ChatGPT, they derived that prescription wrong. The first thing I did was have ChatGPT look at the prescriptions given to me by my doctor.

My distance prescription had four columns: sphere, cyl, axis, and add, with values for both the left and right eyes. ChatGPT picked up on this right away. Apparently, the add column is the value indicating the extra magnifying power that needs to be added for reading.

This four-column prescription is normally used when prescribing for progressive or bifocal lenses. The idea is that you look down to read, so the lower part of the lens is used to magnify the words on the page. It's your distance prescription plus extra magnification for looking down at a piece of paper or book. When you look up, like when watching TV or driving, you look through the top of the lens, which has the strength you need for distance vision.

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But I don't need regular reading glasses. I need computer glasses. Unfortunately, my "computer glasses" prescription was written for a standalone pair of glasses, incorporating the add value that would normally be used at the proper distance for reading a book.

In other words, when I told the eye doctor that I looked up to read my computer screen, they didn't listen and still wrote the prescription assuming that I would be looking down. When I told the eye doctor my computer screen is 23 to 29 inches away, they didn't listen and still wrote the prescription for a focus distance of what ChatGPT said was 17 inches.

I also fed the prescriptions into Claude and Gemini, and both reached the same conclusion as ChatGPT. My doctor had completely ignored my use case and gave me one prescription for reading glasses and one prescription for progressives.

Why, I asked the AIs, didn't the doctor do an eye test at 23 inches? I was told by all three robot brains that that's not how eye exams are done. Most doctors determine your prescription based on an eye chart across the room, and then use math or a lookup table to determine your reading prescription.

By this point, I was annoyed. I had already called my eye doctor a few times and left messages wanting to explore getting a correct glasses prescription. Meanwhile, I was now almost a month into 12-hour days of seeing my screen more poorly than necessary.

Kids, don't try this at home

It's at this point that I need to provide a warning and a disclaimer. Don't do what I did. I mean, what I did worked out, but don't do it. You should always go see your doctor and always do what your doctor tells you. Doctors know more than you and me, and they certainly know more than AIs.

Got it? Good.

So, here's what I did. I fed the details of my screen and the distances of the edges and center from my eyes into ChatGPT, Claude, and Gemini. I also confirmed they were able to read my two scanned-in prescription forms.

Then -- now, remember, do not do this at home -- I asked them to produce a new computer glasses prescription corresponding to the actual focus distance of my actual screen, not some assumed distance where I might hold a book.

I asked all three AIs because I wanted to get a second and third opinion. I also wanted to avoid the non-deterministic hallucination possibilities that might result from getting calculated numbers back from just one AI.

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All three AIs agreed and gave me back the same numbers.

Hmm, thought I. OK, thought I. Perhaps, thought I, I should reach out to the glasses company and see what it would cost to redo my computer glasses prescription. If it wasn't too much, perhaps I'd have it make a pair so I could test the AI-generated prescription.

So I did. Much to my surprise, Eyebuydirect not only offered to remake the glasses for free and ship them to me for free, it refunded 15% of the original purchase price for absolutely no reason I could come up with. I accepted its kind offer, but that was an above-and-beyond, zero-risk opportunity to test out the AI versus the doctor's prescription.

By this point, I had a three-part plan. The first part was to just try the revised glasses using the AI's prescription numbers. The second part was, if that didn't work, go back to my doctor for a revised prescription. The third part was to go to a local glasses shop that offered an in-house exam to see if it came up with a better computer glasses prescription.

The moral of the story

But the revised prescription based on the numbers my AI buddies came up with works perfectly. I'm using those glasses now and have been for a few weeks.

I never did get a call back from my doctor.

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The moral of this story has to be that you should only get glasses prescriptions from your doctor. Anything else would be irresponsible for me to recommend.

But I rolled the dice and have been quite pleased with the AI-computed results. In two years, when it's time to go back to my ophthalmologist, I will once again try to explain my working environment. We'll see if they listen then.

Would you trust AI to double-check a glasses prescription if your new computer glasses made your monitor harder to see? Let us know in the comments below.

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