Keratoconus: the cornea that changes shape

Keratoconus is a fairly common corneal disease characterized by corneal ectasia – an abnormal bulging of the transparent window of our eyes. To understand it, the image of a water balloon is helpful: where the wall is thinner and more yielding, internal pressure pushes it outward, forming a bulge. In the same way, in keratoconus the cornea progressively thins and curves into a cone shape, losing its optical regularity.

Roughly speaking, keratoconus affects about one person in two thousand, but the latest diagnostic technologies are revealing an increasing number of mild forms. It typically begins in adolescence or early adulthood and tends to progress until around age thirty, after which it stabilizes: it is precisely this youthful window that makes early diagnosis so crucial.

Cross-linking creates new bonds between corneal fibers, stiffening and stabilizing the cornea.

Warning signs

The first sign is almost always astigmatism that changes quickly. The patient notices increasingly distorted, doubled vision, changes glasses often without ever seeing well, and perceives halos around lights at night. As the cornea becomes progressively more irregular, glasses eventually fail to provide satisfactory correction. High astigmatism that is rapidly increasing in a young person is a warning sign that should not be ignored.

Diagnosis

Today, keratoconus can be diagnosed well in advance thanks to corneal topography and tomography, examinations that create a three-dimensional map of the curvature and thickness of the cornea, revealing thinning and bulging even at the earliest stages, before the defect becomes symptomatic. It is no coincidence that this is the same examination performed before any refractive surgery procedure, precisely to rule out hidden keratoconus.

Intracorneal ring segments regularize the corneal profile in intermediate forms.

Halting progression: cross-linking

The real breakthrough in treatment is corneal cross-linking. The procedure saturates the cornea with riboflavin, a specific substance (vitamin B2), and exposes it to controlled ultraviolet light: this creates new bonds between the fibers of the tissue, increasing its rigidity and strength. It does not improve vision, but its valuable goal is to halt the progression of keratoconus, and it is all the more effective the earlier it is performed.

Seeing well again

To restore visual quality when glasses are no longer sufficient, rigid or semi-rigid contact lenses are used, which recreate a regular optical surface by “bridging over” the irregular cornea; they are custom-made by contact lens specialists, eye by eye, exactly like a tailored garment. In intermediate cases, intracorneal ring segments can be implanted to regularize the corneal profile, while in more advanced forms – now increasingly rare thanks to early diagnosis – corneal transplantation remains an option.

In conclusion

Keratoconus has changed face: once a disease that often progressed all the way to transplantation, it has become a condition that, when caught in time, can almost always be stabilized with cross-linking and managed with excellent visual results. The key, as is often the case in ophthalmology, is to catch it early – which is why rapidly worsening astigmatism in a young person always deserves an exam with corneal topography.