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Dr. Miller: Your vision has been changing rapidly over time, could that be a problem with your cornea?
I'm here with Balamurali Ambati, and he's a professor of ophthalmology . And we're going to talk a bit about problems that arise with the cornea, which is the foremost part of the eye that faces the environment.
Early Signs and Symptoms of Keratoconus
Dr. Ambati: The cornea is the front window of the eye, and it has layers to it. Even though it's very thin, it's only about 0.5mm thick, it has five different layers. The two most common problems of the cornea are a condition called keratoconus, where the cornea changes from its normal spherical shape into more of a cone-like shape.
Dr. Miller: And it does this over time?
Dr. Ambati: And it does this over time. Usually, it does this in the late teenage years, 20s and 30s. So it's a condition primarily of young adults who may know or report that the eye has been unstable and changing. Most people, the eye stops growing by age 20 or 21, and the prescription...
Dr. Miller: Like the bones almost.
Dr. Ambati: Exactly, the prescription is stable. But if someone's astigmatism is changing... Astigmatism is when the cornea is shaped more like a football than a perfect sphere. That can be an early sign of keratoconus, and patients might report needing to go from soft lenses to soft toric lenses, or to hard contact lenses. They might report increasing near-sightedness and increasing astigmatism over the course of years. This is something that is often undiagnosed till late stages, and so if you do have an unstable refraction or fluctuating vision over time it would be wise to get a cornea scan with an ophthalmologist.
Fluctuating Vision vs Progressive Vision Loss
Dr. Miller: What's the difference between, as you mentioned, fluctuating eyesight and progressive worsening of vision? Can you give a definition of that? I know you mentioned that when we talked about keratoconus as a problem.
Dr. Ambati: In fluctuating vision, which can occur especially in Fuchs' Dystrophy, the vision is different between morning and afternoon. In progressive loss of vision over the course of years, people recognize that their vision was not as bad a year ago, or two years ago.
Dr. Miller: The end result of that would be at some point perhaps the contacts and lenses are no longer effective in changing the vision, would that be the end stage?
Treatment Options for Keratoconus
Dr. Ambati: That can occur. The end stage of keratoconus requires what is called a cornea transplant, to replace the cornea with a donated cornea from someone who's passed away and donated their eye. Fortunately now, in the last five years, we've really changed the management of keratoconus to where we can prevent advancement from mild or moderate keratoconus to advanced keratoconus.
With things like intacs, which are rings that are placed inside the cornea that provide structural support, they're essentially an under-wire for the cornea to change it from a cone to a sphere. As well as the emerging technology of cross-linking, where we use a laser to stiffen the cornea and prevent weakening of the cornea.
Dr. Miller: So there are different options in the treatment?
Dr. Ambati: Very much so.
Genetic Risk and Screening for Keratoconus
Dr. Miller: So is this a hereditary problem?
Dr. Ambati: It is a hereditary problem with what's called variable penetrance. So if you have a first-degree relative with it you're at a higher risk for it.
Dr. Miller: Somewhat like glaucoma.
Dr. Ambati: Indeed.
Dr. Miller: And so if someone has a family history of keratoconus should they seek out an ophthalmological examination and a cornea scan?
Dr. Ambati: I think that would be advisable if they have any significant near-sightedness or astigmatism. And certainly, it would be advisable if they are considering LASIK. One of the things that we do at Moran Eye Center is to carefully screen patients coming in for potential LASIK or laser vision correction to make sure they don't have keratoconus or other cornea problems.
Dr. Miller: So just to be sure, if one has keratoconus does it always require a transplant, or is there, as you said, variable stages of the development of the problem?
Dr. Ambati: It is definitely a spectrum of progression, and if we can catch it in the mild or moderate stage the goal would be to employ intacs, or cross-linking, or some of these other options to prevent the need for a cornea transplant.
Corneal Damage from UV Radiation and Pterygium
Dr. Miller: Are there any other problems with the cornea? I notice since the cornea is the forward-facing part to the environment, UV radiation, and sunlight. Does that affect the cornea more so than other parts of the eye such as the lens or retina?
Dr. Ambati: Certainly patients who are exposed to a lot of sunlight and UV light can develop pterygium, which is a growth on the surface of the cornea.
Dr. Miller: So that's a result of UV exposure sometimes?
Fuchs' Dystrophy and Cornea Transplant Procedures
Dr. Ambati: Indeed. The UV radiation can also damage the back layer of the cornea, which is the endothelium. And those cells are actually what's called post-mitotic, they can't replace themselves. And so that can contribute to a condition called Fuchs' Dystrophy, where the cells of the back of the cornea slowly die. And that does require a partial thickness cornea transplant, but not a full cornea transplant, just replacing the back layer of the cornea. And those two conditions, Fuchs' Dystrophy, and keratoconus, are probably the two most common causes of needing a cornea transplant procedure.
Preventive Ophthalmologic Exams for Family History of Corneal Conditions
Dr. Miller: So in summary, would it be advisable if one has a family history of either of these problems to probably seek an ophthalmologic examination sometime in their 20s, or perhaps if they are having changing vision or astigmatism?
Dr. Ambati: Yeah, if you have fluctuating vision it is advisable to see an ophthalmologist at any time of your life. If you have a family history of keratoconus, in your brothers, sisters, or parents, I think it would be advisable to see an ophthalmologist in the early or mid-20s. And if you have a family history of Fuchs' Dystrophy, that usually presents itself in the 40s or 50s, so that would be the best time to present.
Dr. Miller: Untreated what would be the end result of this if it continues untreated?
Dr. Ambati: Without therapy, you would eventually lose vision, and your eye would become cloudy and scarred. But generally, people come well before that.
Dr. Miller: Thank you very much.
Dr. Ambati: Thank you.
updated: October 1, 2024
originally published: August 18, 2015