Search for tag: "cornea"

Dr. Miller: Treatments for a damaged cornea. We're going to talk about that next on Scope Radio.

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Dr. Miller: Hi, I'm here with Dr. Mark Mifflin. He's a Professor of Ophthalmology here at the University of Utah. I'd like to talk a little bit about what patients might expect if they go in for corneal transplantation or mention of some of the newer technologies related to corneal repair. I know you're an expert in that area so you might just tell us a little bit about that.

Dr. Mifflin: Traditionally, corneal transplantation involves basically replacing the front of the eye, the windshield, if you will, which is the curved clear dome of our eye is the cornea. And so in the traditional technique that is actually cut with a special instrument and replaced with a clear cornea from a human donor cadaver eye. The cadaver tissue is processed through an eye bank and it's very safe. It's much safer than obtaining, for example, a unit of blood from a transfusion.

The tissue is carefully screened and selected and amazingly does not need to be tissue-matched, unlike a kidney or a heart or something like that because the cornea does not have blood vessels and the eye has what we call immune privilege, meaning it's designed or evolved or whatever one believes to not scar and to not create an excessive immune response to injury or surgery.

In terms of some of the newer procedures, within the last ten or so years we have made really amazing advances in just transplanting the part of the eye that is actually diseased. So for example, in a condition called keratoconus where basically the structural part of the cornea is weak and distorted, we can replace the anterior part of the cornea, leaving all of the posterior structure intact. This speeds recovery, decreases the rate of rejection and generally results in better vision.

Dr. Miller: How does one choose between the best surgery or technique?

Dr. Mifflin: Well, typically the surgeon has to kind of choose for the patient, and some of the more advanced techniques are not always possible. There are other diseases where only the very inner layer of the cornea is damaged or diseased, and certainly replacing the inner layer only allows for a very quick recovery. For example, comparing traditional cornea transplantation which might take six months for visual recovery, transplantation of the inner layer or the endothelial keratoplasty that we do now may result in good vision in as little as two weeks.

Dr. Miller: That's a huge difference. How many patients do you think would qualify for the partial thickness corneal transplant?

Dr. Mifflin: It's pretty much become the standard of care. It's not that the traditional technique is wrong, but certainly, for example, in our center here at the University of Utah we always try to do the most advanced technique if we believe that it's going to result in the best outcome for the patient. Not all surgeons are necessarily trained in the most advanced techniques, but certainly these things are literally becoming the standard of care for most patients.

Dr. Miller: Dr. Mifflin, could you talk a little about the durability of the corneal transplantation or the partial corneal transplantation?

Dr. Mifflin: Durability in terms of survival rates and longevity of the graft is actually very good. Graft rejection or failure is quite low, in the range of perhaps as low as 1% for some groups or maybe up to 30%. The most difficult transplant patients that we deal with in terms of making the graft work long-term are children. Unfortunately, children do sometimes need corneal transplantation and the success rate is lower, although sometimes there's no option and corneal transplantation is required to prevent irreversible amblyopia or loss of vision due to basically what in layman's terms is known as lazy eye.

Dr. Miller: So either transplantation technique should result in equivalent duration, longevity of the transplant?

Dr. Mifflin: Yeah, and typically transplants will last anywhere from . . . there have been documented successful transplantations lasting more than 60 years. I've only been practicing for 20 years, but most of my transplants from 20 years ago are still doing fine.

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Dr. Miller: Do you know the difference between the cornea and the lens of your eyes? We're going to talk about that next on Scope Radio.

Announcer: Access to our experts with in-depth information about the biggest health issues facing you today. The Specialists, with Dr. Tom Miller, is on The Scope.

Dr. Miller: Hi, I'm Dr. Tom Miller and I'm here with Bala Ambati, and he is a Professor of Ophthalmology here at the University of Utah. Bala, tell us a little bit about the difference between the lens of the eye and the cornea of the eye for those who maybe don't know much about that.

Dr. Ambati: No one in the listening audience probably remembers a film camera, but the camera has many parts to it. Just like a camera, the eye has a focusing part in the front of the eye, and the film of the camera, in the case of the eye, is the retina.

Dr. Miller: The back of the eye.

Dr. Ambati: The back of the eye, exactly. So if you look just at the front part of the eye, there are two main structures that focus light: the cornea, which is the front clear window of the eye. And that's the part that sparkles when you're sitting across somebody that you care about in a romantic restaurant.

Dr. Miller: That hasn't happened for a while, but I like the idea of it.

Dr. Ambati: And then behind that . . .

Dr. Miller: Not true, not true. For my wife, if she's listening.

Dr. Ambati: Behind the cornea is the colored part of the eye, the iris, and behind that is the lens. And the cornea actually provides protection for the eye. It's the clear window of the eye. It provides two-thirds of the focusing power of the eye.

Dr. Miller: The cornea does?

Dr. Ambati: It does, more so than the lens. The lens provides the last third, but the lens provides what's adjustable. The lens is what helps you focus from distance to up close and then back out again. And so the lens provides the swing, in terms of accommodation and in terms of changing focus, and the cornea is providing structural protection and most of the focusing power.

Dr. Miller: So it sounds like the cornea is the anterior-most portion of the eye . . .

Dr. Ambati: Indeed.

Dr. Miller: Or the portion that is exposed to the environment . . .

Dr. Ambati: Absolutely.

Dr. Miller: So this is the part that can become dry or irritated. There can be problems with allergies. It's the front-facing piece, is that correct?

Dr. Ambati: Absolutely. The cornea is the window of the eye and it has to protect the rest of the eye from anything that hits it, whether it's speeding steel or allergy or infections.

Dr. Miller: So also, the cornea is exposed to tears and tears, I guess, lubricate the cornea and the eyelids. Is that . . .

Dr. Ambati: Indeed. The eye works because you have all of these intricate structures working together. The eyelids provide a windshield wiper as well as producing tears, which lubricate the cornea and keep it smooth.

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