Vision Correction

Autorefractors: Rise of the Machines

While a computer does a better job processing huge data sets, it has a harder time evaluating personal preferences for people. That's a job for us humans.

Joel Hunter, MD
Joel Hunter, MD
Refractive Surgeon, Hunter Vision Updated 09/16/15 4:26 PM

If you've ever been to an eye doctor, put your face in a machine, and been asked to stare straight ahead, chances are it was either an auto refractor that quickly measures your prescription for glasses, or that it blew a puff of air in your eye and made you hate eye doctors forever. If it was the second one, I am sorry. That machine, called a non-contact tonometer, measure the pressure inside the eye and used to terrify me when I was a kid. What's worse, I found out decades later, it's not even super accurate! There are much more accurate, less terrifying ways to check eye pressure. The Hunter Vision mission statement is that we will love patients well, and never shoot a surprise jet stream of air at their eye. I think that's it, anyway. I don't have the exact wording here with me.

If it was the first machine, the auto refractor, then it was much easier because all you have to do is look at an image of a barn or a hot air balloon, while it measures the prescription using invisible infrared light. It's amazing technology. It's even more amazing to me that it's been around for several decades. And while it is more accurate now, a lot of the key principles of it are pretty much the same. The question is, will there ever be a time when an auto refractor is accurate enough that it can entirely replace the mind-numbing "better one, better two, orrrr….one? or two? orrrr one?…" test, which is called a phoropter.

The short answer is, I'd say no it will never replace it, but in general it is a bad idea to bet against technology. I would have been surprised if someone had told me in high school, "Joel, there will be a day about two decades from now when you will be sitting in a restaurant and actually get annoyed at a handheld device, that you personally own, because it took five seconds instead of two seconds to answer when you asked it, with your voice, 'How many grams of carbohydrates are there in an avocado?'" So it would be unwise for me to assume that my current perspective is a good indication of future technology in general.

With that caveat, the reason that it will be hard to replace a human-driven phoropter entirely with an auto refractor is that there are variabilities in getting a good prescription that require active, creative thinking on the part of the examiner. To name a few, there are variabilities in people's tear film (the glassy fluid layer on top of the cornea that actually focuses the light coming in), in people's focusing muscles (with young people typically over-focusing, even when their eye is relaxed), and variabilities in what some brains want vs. others (one example being hyperopic—farsighted—folks that will hate and never wear a glasses prescription that actually have their full correction). So while a computer does a better job processing huge data sets, it has a harder time evaluating personal preferences for people. That's a job for us humans.

The reason I do the final prescription check on laser day here isn't that I'm trying to figure out their prescription, because we already know it in five different ways at that point. It is because I'm measuring what machines can't; it is the prescription that a person will do best with based on who they are and what they need for their vision. The final check makes people nervous sometimes because they want to "get it right" but even that is part of the process here. Reading people and seeing what they hold most dear about their vision, which is different for a commercial pilot and an accountant, all becomes a part of calculating the best outcome possible. It isn't a coincidence that very close to 100% of our LASIK patients are really, really happy. As a rule, I won't bet against technology, but it is difficult to see today how our machines will get that part—the human connection—perfect.

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