What is keratoconus and corneal ectasia
Updated: May 30
I decided to write this blog because I have been having large uptake of corneal ectasia and keratoconus cases recently which makes me very thankful that I'm a specialist when it comes to fitting them in contact lenses. Let's start off with why contacts are so important to keratoconus cases, the simple answer is they can't see unless they are wearing these specialty contact lenses. I have had multiple cases of people with keratoconus that at best can see 20/200 or worse in glasses and then with specialty lenses like a scleral lens go down to seeing 20/20. It's one of the most rewarding parts of my job is helping people who can't see sometimes for years and allowing them to see again. The worst I saw was someone who waited 20 years plus and went to an eye doctor on a regular basis and didn't realize this was an option to help improve his vision! The worst part is they were wearing regular contact lenses for years beforehand so it wasn't even a question if they wanted to wear contacts. I'm just glad I was able to help them see 20/20 again and also be able to see out of both eyes again. I was kinda rambling there let go to what corneal ectasia is. The simple answer is the cornea isn't round it has more of a wavy shape. If you have been told your cornea is more shaped like a football that is most likely regular astigmatism and a very overly simplified explanation and isn't correct. If you want to see football-shaped eyes look below at Munson sign which is caused by severe keratoconus.
This basically causes light/image to focus weirdly. How weirdly you may ask let's put it this way they may see one image multiple times over. Their ghost image to everything they see and if it is bad enough it can just be a blur. It is not like a normal blur where you can maybe able to tell grossly what the shape is. If you have a normal bad vision you can see a person walking towards you can tell by the shape it is a person you may not know if it's a man or woman but you can tell that it is a person. Especially since the blur is consistent and doesn't change very much from day to day. With severe corneal ectasia, the image is so warped it could be a car, bird, or even a mountain lion because of how badly the vision is distorted that you can't even tell it is the person moving. The worst part is that distortion can change from day to day.
Corneal ectasia is a group of disorders that all cause some warping or waviness to the cornea. These can be caused by diseases like keratoconus or even shingles in the eyes. I have heard of some other viral/bacterial infections causing problems like cornea ectasia but they are rare. The other major one that can cause cornea ectasia is any type of surgery on the eye including things like LASIK, PRK, RK, and sometimes scleral buckles from retinal detachment surgery. These problems cause irregular astigmatism completely different then regular astigmatism that most people have. This is what causes them not to be able to see in glasses and regular contact lenses. This also causes all the ghosting of images, starbursts, and lines off of lights. A lot of people have some form of this problem which is called higher-order aberration that can cause the above problems but normally to a significantly less degree compared to keratoconus.
Let's move on to the most common disease-causing corneal ectasia. Let's start off with keratoconus. It normally starts off with inferior steeping or truncated (shorten) figure eight on the topography. These are normally the first early signs of keratoconus.
BCD are early keratoconus and EF truncated figure eight
Some of the signs of keratoconus not using a corneal topographer (which we use on every patient) are things like Volk striae and Fleischer ring. Volk striae are basically like stretch marks on the cornea and Fleischer ring is iron deposit on the cornea. In severe cases, you get Munson sign, the football-shaped cornea. Some of the causes of it are genetic which is only 10% of cases and the others are allergies, and most commonly eye rubbing! The most common reason why kids rub their eyes is due to allergies and so that is why I normally ask if the kid rubs their eyes when I do children's eye exam if I see any signs of allergies. Other disease that can cause keratoconus is sleep apnea (snoring), connective tissue disorder like Ehler Danlos syndrome, Down syndrome, and retinitis pigmontosa. Keratoconus is the most common disease that comes from cornea ectasia and is normally one of the more devastating to vision. Other examples are Pellucid marginal degeneration and Keratoglobus and imaged below.