What is an intra-ocular lens (IOL)?

An intra-ocular lens (IOL) is a tiny, artificial lens placed in the eye after the natural lens is surgically removed, most often due to cataracts.

Joel Hunter, MD
Joel Hunter, MD
Refractive Surgeon, Hunter Vision Updated 10/31/18 12:11 PM

Dr. Ridley was an ophthalmologist in Great Britain during WWII and in the years after it. He saw something a lot of eye doctors saw in war—shrapnel and debris that had penetrated the eye. Regular doctors saw that too. And people who weren’t doctors. War is awful. But in this case, Dr. Ridley saw something in the horrors that others missed. In one pilot he was treating, a piece of the windshield from his plane had ended up inside the eye. Interestingly, as it stayed there over the weeks, it didn’t cause inflammation. It just sat there, a tiny piece of windshield minding its own business. Somehow, the eye’s often overzealous security (immune) system didn’t pick up on it.

A Medical Innovation

The windshield was made of poly methyl methacrylate (PMMA), and Dr. Ridley got an idea. He’d take advantage of this weird ability of PMMA to sit quietly in the eye to craft it into an intra-ocular lens (IOL).

Up until this time, when people had their natural lens removed, usually because of cataracts, they just got giant glasses after the surgery. The natural lens in our eye is a hugely plus powered lens, so those glasses—called aphakic spectacles—were usually in the range of +15 diopters and gave people terrific magnified cartoon eyes afterward. It was like having magnifying glasses on your face. That’s not even an analogy, those lenses are magnifying glass levels of power. It wasn’t a great situation.

“Ridley me this… What if we put the lens inside the eye?” is something I’d imagine he said or should’ve. And with that, he made a tiny lens out of PMMA and placed it in an eye after cataract surgery. The results were terrible! But they were a lot better than aphakic spectacles. Plus, the PMMA did exactly as expected and laid low with eye security none the wiser. No inflammation and no damage inside the eye. From there, it was off to the races. Big, new ideas are somewhat rare in medicine; big, rapid improvements to those ideas are almost a certainty.

Evolution of IOLs

The IOLs were able to be crafted more accurately over time. More influential in accuracy was the improvement in the calculations for what IOL power should be required for each eye. Improvements to the acrylic material—acrylic is still used today—made it increasingly flexible. It also made it possible to craft the IOL into specific shapes capable of self-stabilizing in the eye with no extra anchoring pieces required. These improvements led incrementally to the IOLs we have today.

The answer to “what is an intra-ocular lens” involves a summation of all the evolution of IOLs since Dr. Ridley first bravely ventured ahead with his plan, despite widespread criticism at the time.

“I’m Ridley’d with doubts,” he probably said, but he went ahead and changed history anyway. And because of that, we have an IOL that’s optically perfect with zero optical aberrations, able to be placed into an incision less than 2 millimeters wide, and naturally fixate where the now-removed lens once sat. It has a 0% rejection rate and never needs to be replaced. An IOL is as close to perfect as medicine has to offer. It is a beauty born out of a place least expected.

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