Your practice does a lot of different things with specialty lenses, and while there are various areas that come up, I wanted to focus on dystrophies today to help clarify this condition. Dr. Charrier has come to share information about corneal dystrophies and how his practice helps treat these conditions.
Could you describe what is a corneal dystrophy?
There are essentially two categories of corneal decompensations or corneal diseases: dystrophies and degeneration.
A dystrophy is something that tends to be more genetic. they're usually autosomal dominant, and most of them occur early in life. Degenerations are different - they're not always genetic - in fact very few of them are.
What is an example of a degeneration?
That’s when the cornea degenerates to an abnormal state. For example, that would be pellucid marginal degeneration. Keratoconus is considered a degeneration because you're going from a normal state, which is the cornea you're born with, to when the cornea gets progressively thinner and goes to an abnormal state, usually in the mid to late teens. However, dystrophies tend to be more genetic as compared to those types of degeneration problems. However, both of them cause significant complications to vision in the way of blur, distortion, higher-order Aberrations - like the way lights will skew or halos that you'll see around lights. It pertains more to the quality of vision. It can be severely affected anytime the cornea is compromised.
What makes the difference between the lenses you give versus standard ones?
The difference between a soft contact lens and a rigid contact lens is night and day when it comes to corneal pathology. The problem with a soft contact lens is that if the cornea is irregular in shape the soft contact lens is going to just take the same shape as the cornea. It's going to drape over it the same way a tablecloth would drape over a table.
If the problem with the vision is due to that irregular shape of the cornea then the soft lens isn't going to correct that at all. So you might be able to give someone power to see with a soft lens but you're not correcting the problem which is the irregular cornea. With a rigid lens we can actually use the back surface of the lens to reshape the tiers over the cornea. Those tiers bend light the same way the cornea bends light so if we can reshape those tiers into a more optically perfect surface then we can essentially or optically change the cornea into a more optically perfect surface so we can address the problem.
To clarify, the eye normally has a round sphere shape and the problem with an unhealthy cornea is that it's misshaped?
The normal cornea is what we call aspheric, so it's not perfectly round but with these diseases, it causes a distortion of that normal aspheric shape. The eye is very complicated in the sense that all the tissues of the eye work together to give you good vision. For example, the aspheric shape of the cornea that actually causes spherical aberration but that spherical aberration caused by the shape of the normal cornea, that's canceled out by the lens inside the eye. We take all of that into consideration, even pupil size. For example, some of the videos that I put up were patients that had damaged pupils. One was from a hand-grenade injury that affects vision as well. The pupil is essentially a hole but if that hole is not the right size and the right shape, vision is affected and these are all things we can address with these lenses.
I wanted to point of some of these dystrophies just by name. Let me know if you’ve seen any of these cases. Fuchs dystrophy?
Yes, that’s one we commonly see.
Why is that common? I've heard it’s a rare disease.
It's common that we see, but it's not a common disease. We have many patients here that are referred in from their cornea specialists. The problem with Fuchs dystrophy is that Fuchs is a disease that affects the back layer of the cornea and that layer is responsible for pumping water out of the cornea to prevent it from swelling. From Fuchs dystrophy, the cornea will swell and cloud the vision or make vision blurry. If you wear contact lenses, the cornea will swell much more easily because it's not getting the oxygen that it needs.
Do Fuch’s Dystrophy patients typically need contact lenses?
For Fuchs patients, typically what we’ll do is put them in a contact lens that supplies about as much oxygen to the cornea as not wearing a contact lens at all. Also, Fuchs patients often end up with cornea transplants. When it gets to a certain level the only thing you can do is a transplant. But a corneal transplant is a very irregular optical surface once it's sutured in. We need those rigid contact lenses to reshape the tear film in front of the cornea to correct that irregular shape.
Do patients with Fuchs Dystrophy need contact lenses in general?
No, typically Fuchs patients can wear eyeglasses. The only Fuchs patients we see for contact lenses are the ones who've had transplants. Or, if they were previous contact lens wearers, and they can't wear their lenses anymore because the cornea keeps swelling. Patients can come to our practice to find contact lenses that won't lead to swelling.
Do you often recommend that Fuchs patients in Houston wear contact lenses even before the transplant?
Not necessarily - I wouldn’t recommend contact lenses for them any more than with an average person.
Let’s move on to the next one - Map Dot Fingerprint Dystrophy.
That’s a dystrophy that affects the anterior limiting lamina. Basically, this dystorphy affects the membrane that's just below the epithelial cells on the cornea. Or, the membranes that are right below the skin of the cornea. In this particular dystrophy, the anterior limiting lamina will start to produce excess material, in a very irregular pattern. When it does that, the excess material pushes those epithelial cells that are on top of it up and creates a very irregular cornea. In addition to that, that dystrophy is often painful because the skin of the cornea is weakened. Often, they get ripped off by the eyelid when you're blinking, and that can be pretty painful.
What we do with epithelial basement membrane dystrophy is we typically will insert a specialty contact lens that covers the entire cornea and bathe the cornea in fluid all day long. The most common type is a scleral lens. A scleral lens eliminates the friction between the eyelid and it also corrects irregular astigmatism caused by all that elevated epithelium.
That one's tough. Reis Buckley dystrophy also ends up in a cornea transplant a good percentage of the time. The dystrophy’s main problem is when the cornea becomes cloudy right in front of the pupil so vision becomes poor. The cornea also develops an irregular shape because of the cloudiness and distortion occurring in the cornea.
This type of irregular cornea creates irregular astigmatism as well as a cloudy cornea. We're able to use contact lenses on those patients when the cloudiness isn't right in the center of the cornea. This will correct any irregular astigmatism with any rigid contact lens. If the cloudiness were in the center of the cornea, the contact lens still wouldn't make them see any better.
Is this one also you've seen in the past?
It is a rare dystrophy, but we have seen quite a few of those patients here, too. Most of our patients are referred in, so we tend to see all the rare stuff with some frequency.