What Is Keratoconus?

Many patients are young and frustrated that their glasses never seem to work well: their prescription keeps changing, vision is blurry or doubled even with correction, and lights streak and glare, especially at night. Some are told during an eye exam that their cornea has an unusual shape. They want to understand what keratoconus is, why it is happening to them, and whether their sight can be protected.

The cornea does most of the eye's focusing, and it works best when it is a smooth, regular dome. In keratoconus the cornea weakens and thins, so the normal eye pressure pushes it outward into a cone. That cone-shaped surface bends light unevenly, producing irregular astigmatism, which glasses cannot fully correct because they only fix regular shapes.

As a result, vision becomes blurred and distorted, straight lines may look wavy, and lights develop halos and streaks that make night driving hard. In the early stages, stronger or frequently changing glasses may keep up, but as the cone steepens, glasses stop working and rigid or specialty contact lenses are needed to create a smooth optical surface. In advanced cases the cornea can scar, which further blurs vision and can make contact lenses uncomfortable to wear.

Keratoconus develops when the structural fibers of the cornea weaken, allowing the front of the eye to thin and bulge. It usually appears in adolescence or early adulthood and often progresses over years before stabilizing, though the rate varies widely from person to person. A family history raises the risk, and it is associated with chronic eye rubbing, allergic eye disease, and certain conditions such as Down syndrome and connective tissue disorders. Vigorous eye rubbing, in particular, is thought to mechanically weaken the cornea and speed progression.

The typical course begins with increasing nearsightedness and astigmatism that prompts frequent prescription changes. As the cone steepens, glasses no longer give clear vision and specialty contact lenses become the mainstay of correction. Progression tends to be faster in younger patients. In a minority of cases the cornea scars or, rarely, swells suddenly (a condition called hydrops), causing an abrupt drop in vision. Because damage from steepening and scarring is not reversible, the goal of modern care is to detect the condition early and stop it from advancing.

Keratoconus is not an emergency in the usual sense, but certain changes deserve prompt attention:

• A sudden, marked drop in vision with eye pain, redness, and light sensitivity can signal corneal hydrops (sudden corneal swelling) and should be evaluated quickly.
• Rapidly worsening vision or frequently changing prescriptions, especially in a young patient, suggests active progression that may benefit from cross-linking.
• Contact lenses that become painful or impossible to wear may mean the cornea is scarring.

Most importantly, progressive keratoconus that is not treated can lead to permanent vision loss, so worsening vision should not simply be watched.

The key test is corneal topography (and tomography), which maps the shape and steepness of the cornea and can reveal keratoconus even in early stages before it is obvious. These maps also measure corneal thickness and detect thinning. At the slit lamp, the doctor looks for the classic signs of a steepened, thinned cornea and any scarring, and measures how much vision can be corrected with glasses versus specialty lenses. Repeat topography over time shows whether the condition is stable or progressing, which directly guides whether cross-linking is recommended. Because it often affects both eyes to different degrees, both are examined and monitored.

Treatment is matched to severity. Mild to moderate keratoconus can often be corrected with eyeglasses or contact lenses. As the cornea steepens, rigid gas-permeable or scleral contact lenses create a smooth front surface and restore clearer vision when glasses no longer can.

To stop progression, the cornea can be strengthened with corneal collagen cross-linking, which uses riboflavin (vitamin B2) drops activated by ultraviolet light to reinforce the bonds within the cornea. Cross-linking does not reverse the cone, but it halts further steepening in most patients, so it is most valuable when the disease is caught early. Intacs, small crescent-shaped corneal implants, can be inserted to support the cornea's shape and improve vision, and are sometimes combined with cross-linking. If the cornea becomes badly scarred or too irregular for comfortable lens wear, a corneal transplant is an option; recovery can take up to a year, and rigid contact lenses may still be needed afterward for the sharpest vision.

• Do not rub your eyes; vigorous rubbing is linked to worsening keratoconus.
• Do not ignore steadily worsening vision or a rapidly changing prescription, since progression that is caught early can be halted.
• Do not assume glasses alone are the answer once vision is distorted; specialty contact lenses often do far better.
• Do not leave allergies or itchy eyes untreated, because the urge to rub can drive the disease.
• Do not skip follow-up visits, as monitoring the corneal shape is how progression is detected in time to treat it.

Call for an evaluation if you are a young adult with blurry, distorted vision that glasses do not fully correct, or if your astigmatism keeps changing, so the corneal shape can be mapped. Patients in the Hanover area can be assessed and, if appropriate, offered cross-linking to protect their vision. Seek prompt care for a sudden drop in vision with a painful, red, light-sensitive eye.

Keratoconus is a progressive thinning and coning of the cornea that distorts vision and usually starts in the teens or twenties, but early detection and cross-linking can halt it before it damages sight. If your vision is blurry and glasses are not enough, have your corneas evaluated at May Eye Care Center.