Keratoconus and corneal cross linking: stopping the problem instead of chasing it
3 min readRand Eye Institute
Keratoconus is usually caught late, and it is usually caught late for the same reason every time. The vision keeps changing, so everyone assumes the prescription is just unstable, and a new pair of glasses gets made instead of a diagnosis.
What keratoconus is
The cornea is meant to be a smooth, round dome. In keratoconus the collagen fibers that hold that shape weaken, and the pressure of the eye pushes the cornea outward into a cone. A cone does not focus light evenly, which is why the astigmatism it creates is called irregular. Glasses correct regular astigmatism well. They struggle with this.
It typically shows up in the late teens and twenties and can keep progressing for years, often at different rates in each eye. There is frequently a family history, and chronic hard eye rubbing is associated with it, which is one reason we ask about allergies.
The signs that get missed
- A prescription that changes noticeably more than once a year
- Ghosting or doubling of images in one eye, especially at night
- Glare and streaking around headlights that keeps getting worse
- Contact lenses that will not sit comfortably or keep popping out
- Vision that glasses simply cannot sharpen past a certain point
How it is diagnosed
Corneal topography is the test that settles it. It maps the curvature of the cornea point by point and shows the steepening that an eye chart cannot. We also measure corneal thickness, because thinning tends to accompany the change in shape.
Topography is also how we catch it in people who came in for something else entirely. More than a few patients have arrived asking about LASIK and left with a keratoconus diagnosis instead, which is a far better outcome than having a laser applied to a cornea that was already weakening.
What cross linking does
Corneal collagen cross linking is the procedure that addresses the underlying problem. Riboflavin, which is vitamin B2, is applied to the cornea and then activated with a controlled ultraviolet light. That reaction creates new bonds between the collagen fibers, stiffening the tissue that had been giving way.
The goal is to halt progression. That is the honest framing and it is worth being clear about it. Cross linking is not a procedure that hands you sharp vision on its own, and some patients see modest flattening afterward while others simply stay where they are. What it does is stop the cone from getting worse, which protects the vision you still have and can keep you away from a corneal transplant later.
There are different approaches, including epithelium off techniques and epithelium on techniques such as Epioxa that leave the surface layer of the cornea in place. Which one fits depends on your cornea, and we go through that at the consultation.
You will probably still need correction
After cross linking most patients continue in glasses or specialty contact lenses, and for irregular corneas a scleral or other specialty lens often gives far better vision than glasses can. Cross linking and vision correction are two different jobs. One stabilizes the cornea, the other sharpens what you see through it.
Timing is the whole point
Cross linking protects the cornea you have today. It cannot restore a shape that has already been lost. That is the entire argument for getting an irregular, shifting prescription properly mapped rather than corrected again and hoped about.
If your prescription keeps moving, or someone in your family has keratoconus, ask for corneal topography. If you are already diagnosed, we can tell you whether your cornea is progressing and whether cross linking is the right step.
This article is general information about eye conditions and the procedures we perform. It is not medical advice, and it cannot tell you what is happening in your eyes. Only an examination can do that.