Lasik Surgery — The Eyes Have It

Circa 2011

Mackin: Let’s talk about 3D Lasik surgery. What exactly is it?

Joel Hunter, MD: Lasik is an acronym that stands for “laser-assisted in situ keratomileusis.” That’s a longwinded way of saying doctors create a small flap in the cornea, which is a clear window of tissue on the front of the eye. Doctors lift that flap and use a laser to reshape the cornea, then they lay the flap back down. This takes the pain and recovery time out of the process.

It used to be that you’d laser the surface, which was painful, and required several days to recover. Then it took a couple of weeks to a couple of months for the patient’s vision to fully return. Eventually we found out, “Wow, we can just do this under this flap, and people heal and see well pretty quickly.” Everybody liked that, so there was a big boom in these surgeries in the late 1990’s and early 2000’s, and you started hearing a lot about them, because they became really popular.

Mackin: So what’s 3D about the operation?

Hunter: As with any field, the technology advances, and then you look back and realize things have changed so much that you need a new name for what you’re talking about. That’s what happened with 3D Lasik. The technology we use to capture the images of the eye, the optics inside the eye—from the cornea to the lens to the retina— seemed far off 10 years ago. Now it’s stuff we can do in a 90-minute appointment in the office. We can determine in that time frame if people are candidates for surgery.

These 3D images are so high-resolution that they show us what the optics are, as well as the health of the eye, which helps us figure out who will do well and who probably won’t. And if you look at the happiness rate for Lasik across tens of thousands of people, about 95 percent of people say, “Yeah, I’d be happy to do it again.” But that means five percent wouldn’t. And really, with how precise the technology’s gotten, that figure should be even lower. There should be pretty close to 100 percent comfort with the surgery. So we’re finding that a lot of people who responded negatively were people who should have been screened out by using more advanced technology.

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In respect to the actual laser itself, there was the advancement from using a blade to using a laser. That development has been implemented since around 2002, and was a step forward. But the newest lasers, specifically the WaveLight Allegretto, can capture the threedimensional curvature at the front of the eye. So if somebody has less curvature, we can program that in the laser. If somebody has more curvature, we can put that in the laser, too. The laser’s activity is based on specific readings of the eye. Your eye is not like anybody else’s; it’s like a fingerprint.

So the laser reshapes the cornea based on the curvature of your individual eye, and helps it keep its natural shape better than older lasers did. That helps the eye focus light better. It’s also part of the reason that glare at night—halos and other things we used to worry about—have decreased dramatically from previous laser generations.

Mackin: Would you say, then, that 3D has just as much to do with the diagnosis as with the actual procedure?

Hunter: Yes. The ocular coherence tomography (OCT) machine, for instance, gives us a three-dimensional scan of the retina, down to four-thousandths of a millimeter. Your retina is about 300 microns thick. The OCT lets us detect subtle changes that might be there before somebody ever notices a change in their vision. That’s really important when you’re talking about doing an elective surgical procedure, because even if it’s safe and effective, people still need the best advice they can get to make the best decision possible.

Mackin: Who chooses this surgery?

Hunter: People who don’t want to wear glasses or contacts because they’re near-sighted or far-sighted or have an astigmatism. A lot of people wear reading glasses and want to get out of wearing them. So they go through this whole exam process that helps us narrow down who we can and who we can’t.

Mackin: Why isn’t surgery effective for certain people?

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Hunter: They may have little membranes on their retina, tiny amounts of swelling in the retina, little congenital anomalies that a person was born with that may or may not change over time. If we see subtle changes in someone’s retina, we want to know about that before surgery, rather than after. The retina is kind of like film in a camera: No matter how sharply you get the image focused, if the film’s not good, then you won’t get a good picture. So if we detect subtle changes, we want people to know about them, as well as whether we think those changes may be progressive. We can say, “Here’s all this information,” so you’ll know where your eyes are headed 15 years down the road. Then you can decide if surgery is right for you.

We might tell some patients, “This probably isn’t the right choice for you, because we know that your retina doesn’t work well.” In those cases, we may dilate their pupils and take basically a cross-sectional picture— almost like a CAT scan.

There are two parts that play a role in letting your eyes focus light: the cornea, which we talked about, and the lens inside the eye. Everybody has a lens in their eyes. We can now get the objective density measurement of that lens, and the camera can tell us that the lens is scattering 20 percent of the light that hits it, or the lens is scattering 15 percent of the light that hits it. Those measurements help us, especially with elderly people who are starting to notice, “Boy, I just can’t read no matter how good my glasses are,” or “I have trouble reading subtitles on a screen no matter what glasses I have.”

Before that stage of life comes—when people start to realize they’re having changes that are consistent with cataracts—there’s a stage of density in a person’s lens that may be problematic, even if it is not necessarily noticeable. People don’t notice the little things so much, like needing more light to read the menu in a restaurant, but those things become really apparent when we do density measurements. We can even show the patient a picture: “Here’s your lens and how dense it is, and how much light it’s filtering, compared to this 30 year old’s lens.”

For some of these people, laser surgery works in the short term. Then, a couple of years later, they’re noticing the alteration is no longer helping them very much. That’s because the change inside the lens has started to filter and decrease the vision. So you’ve fixed the patient’s need for glasses, but his lens is still filtering things on the inside. That’s why it’s really helpful to have as much information as possible before going into surgery, so you can say to people, “Your best choice here is probably to do nothing and wait a year or two or three or longer, and then have lens surgery when the time comes. That will fix the problem at its root, rather than mask it temporarily.”

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Mackin: Is there surgery for the retina?

Hunter: Retina surgery is hard. It is its own specialty, just as refractive surgery is its own specialty in ophthalmology. Retina surgery, in general, is rarely ever elective. Retinal tissue is neurosensory tissue. It’s attached to your brain by your optic nerve. So it’s very delicate surgery, and you want to make sure you have a clear benefit-vsrisk ratio. Retina surgery doesn’t happen until people have pretty poor vision.

When we detect subclinical changes that don’t have signs or symptoms, the answer is not always going to be something surgical. Even if we find early macular degeneration, there are different therapies, nutritional therapies, and ongoing care that can be managed by a specialist in those different fields. Vision correction by way of retinal surgery generally only happens when people have pretty significant visual dysfunction that stems from retinal pathology or disease.

Mackin: During lens surgery, does the surgeon actually put a new lens inside the eye?

Hunter: Yes. Cataract surgery is lens surgery, and it’s probably one of the most common surgeries in the world. It’s done when the lens becomes so cloudy that the person can’t really see through it, no matter what glasses he has. Through a couple of tiny incisions, doctors can use ultrasound to remove the lens and then replace it with a new, clear lens that’s artificial. That lens is usually made of acrylic, and sometimes silicone. If we’ve noticed lens change in a patient, I have him hold off on Lasik surgery. I feel like he’s going to get a somewhat temporary gain out of 3D Lasik, however, because we’re on the cusp of a new generation of lens surgery. The surgery itself, the incisions and the breaking up of that lens inside the eye, will be done with a laser, which will make the process even more precise.

Even more exciting is the fact that the new lenses we are putting into people’s eyes are getting better and better every year. They allow people to see near and far, which is something that is not possible after a person reaches his mid-40’s and typically needs reading glasses. These new lenses allow people to see in a way they couldn’t before. With a lot of these patients I’ll say, “I’d hold off and see where you are at in a year, and where the technology’s is in a year.”

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As lens technology improves, the age at which someone would benefit from lens replacement is dropping and dropping and dropping. It used to be that the average age of these patients was somewhere in the mid70s. Now, in some clinics, that age is dropping to the mid-50s because lens technology is so much better. We’re finding that people get enough benefit out of the procedure that it’s worth doing lens surgery earlier in life. It prevents the need for cataract surgery later.

Mackin: How does the cornea get misshapen in the first place?

Hunter: It’s not that the cornea necessarily becomes misshapen over time, or that a person had a nice cornea and now it’s gotten weird—although, that may be true in cases involving genetic problems. In general, though, when somebody is near-sighted or far-sighted or has an astigmatism—because their eyeball is too long or too short, or their lens is a little too powerful, or their cornea is a too steep or flat—it’s been that way, usually, since they were in elementary or middle school, when they put on their first pair of glasses.

If somebody needs glasses, it’s because light isn’t focusing correctly on his retina. Instead the light is focusing a little in front of the retina, or a little behind. If he has an astigmatism, the light is skewed on his retina. The cornea—that front, clear window—supplies two-thirds of your eye’s focusing power, so subtle changes to it make a really big difference in how clearly the eye focuses.

When we’re dealing with laser vision correction, we can create a precise focusing pattern on the retina by removing a small amount of tissue. The same thing goes for people who wear reading glasses. We can give those people their reading vision back using 3D Lasik to reshape their corneas in a way that allows them to see their cell phones without putting on reading glasses. So whatever the problem is with the optics of the eye, much of the time you can treat it just by fixing the shape of the cornea, which is customized for each person. If somebody comes in and is near-sighted—say, a minus-3 cornea—that might be a completely different shape than the next person I see who’s also a minus-3.

Mackin: Interesting. So even if a person’s lens has lost flexibility, you can treat the cornea for that?

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Hunter: There are a lot of people who can see down the road with one eye, while the other eye is useless at a distance and is only good for reading. So we blend vision. Think of stereo music. When audio engineers pioneered stereo music, they had to figure out what came out of each speaker and blend those sounds together into the stereo music in your head. Experts have been working to do that for the eyes, as well, for people who have lost flexibility in their lenses. There is a sweet spot you can create. About 99 percent of people can actually learn to blend the vision of both eyes and can see better in the distance and up close. It’s a neat trick we’ve been able to make work for most people who come here wearing reading glasses.

Mackin: What’s the trick? Is there some kind of exercise they do?

Hunter: I compare it to going to live in Spain. For the first couple of weeks you have to concentrate and use your dictionary to try to figure out what people are saying, but if you live there for a couple of months, you’re going to pick up the language and start speaking it. Your brain has the ability, when it’s being saturated, to adapt. There’s plasticity over time, for everybody, and that’s how your brain learns new things. Every minute of every day your eyes are open, you’re learning, whether you intend to or not.

Blended vision takes a couple of months for most people. And even with their brain figuring it out, they can still see everything. They just have a temptation to close one eye to see what’s happening, and that temptation goes away over time, because the brain is learning to see better with both eyes open.

We have a program called RevitalVision. It’s a computer program that essentially trains your brain to see better. Studies showed the vision of people who used RevitalVision improved by two lines on the eye chart: They were going from 20/30 to 20/20 vision, or from 20/40 to 20/25, and their contrast sensitivity, which is kind of the real-world measure—brown letters on a yellow menu— improved 100 percent, on average.

We wondered if we gave this to people who were having trouble blending, or who wanted to do it faster, would it help them with that ability? A lot of what we do is about getting the brain to process information. If you think about it, you don’t really see with your eyes, you see with your brain. There’s no screen in the head. It’s all about how neurons talk to each other, and how they form new synapses to process information efficiently. That work has been really promising.

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In the RevitalVision program, which runs about twice a week for 10 weeks, you sit in front of a computer screen for about a half hour, and you hit a button as you watch patterns form on the screen. It’s pretty boring. So people who commit to it do really well.

Mackin: Without the computer, how can you learn to blend your vision?

Hunter: The same way that you learn anything: Present your brain with a new stimulus, and it neuro-adapts to it over time. The first time you drove a stick shift, the first time you swung a golf club or hit a tennis ball, your brain told your muscles what to do. But we’re finding that processing visual information is also a learned process. From the time you’re born until you’re two years old, your brain is learning to see. Your eyes send images back, while your brain learns to process those images more sharply and clearly over time.

Mackin: This is the same sort of new learning that occurs after surgery?

Hunter: Yes. What basically happens is somebody comes in and says, “Hey, I hate my reading glasses,” and I say, “I believe you, because everybody hates their reading glasses.” And then we do 3D Lasik on the person and, on day one, we check their vision and find they can read 20/20 on the eye chart, and can read really small print up close. I tell them, “You’re doing great. You can see us any time, but we’ll see you back here in a month, no matter what.”

So we see them in a month, and in a month they say, “I can read and I can see down the road, but I notice there’s a difference in the vision between my eyes.” And I say, “That means you’re right on track. You will notice it less over the next couple of months.” We see them again in two months—a total of three months out of surgery—and, by that time, most people have forgotten about vision change. They don’t really think about it any more, and there’s kind of a neutrality. The eyes don’t interfere with each other; they’ve learned to process the vision in a different way.

After that three-month period, the brain gets better and better and better at processing, so people reach a point where not only do the eyes not interfere with each other, they can actually see better both at a distance and up close. What’s so cool about this is that’s what the brain wants to do. It wants to process information coming in from both eyes. Naturally, your brain sees better with both eyes open than it can with either eye. That’s the eventual goal.

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Mackin: Are there situations in which you do surgery on only one eye?

Hunter: Sometimes a person happens to be born with what he needs in one eye, so we’ll only have to do surgery on the other one. But for most people, surgery is necessary in both eyes because you need a very, very precise difference in refractive error between the two eyes. You have to be dead on or they won’t blend. It’s not common that you’d find someone who would only need surgery in one eye. My father was one of those people: I only had to do surgery on one of his eyes.

Mackin: What about performing surgery on people who, say, have Cerebral Palsy?

Hunter: We can do that because lasers track the eye at 400 times per second, so you can still get precision when you’re hitting a moving target.

Mackin: What do you suggest for people you turn away from surgery?

Hunter: It’s as varied as the reasons we turn them away. Glaucoma, macular degeneration or crossed eyes would be better handled by a subspecialist. But there are also antioxidant dietary changes that someone with early macular degeneration might benefit from, as well as different vitamin therapies that a retina doctor might prescribe. If a person has glaucoma or progressive disease, then their treatment could be taking an eye drop each night, as prescribed by a glaucoma specialist. A big part of what we do with our 3D diagnosis is provide people with information that helps them determine the best approach.

by Molly Mackin

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