Keratoconus causes the cornea to become thin, weaken, and bulge. The word itself translates to “cone-shaped cornea.” Nearsightedness, astigmatism, glare, and light sensitivity are common early symptoms of the disorder. Over time the cornea can become very thin, steep, and irregular causing severe vision loss and making it impossible to wear contact lenses.
Symptoms normally start to appear when a person is in their late teens or early twenties, and then progress for ten to 20 years. Each eye may be affected differently. In some people the progression eventually slows down, and the condition may stabilize. Symptoms can include:
- Blurred vision
- Light sensitivity
- Frequently changing corrective lens prescription
- Eye rubbing
- Munson’s sign – only appears in advanced cases, lower lid is visibly distorted due to protrusion of the cornea
In advanced cases, a protective layer of tissue called Descemet’s membrane can rupture allowing fluid to flow into the cornea and causing sudden vision impairment. This phenomenon is called hydrops. A white spot appears on the cornea, and the entire eye may appear opaque. The effects diminish as the Descemet’s layer heals. In some patients hydrops causes corneal scarring which flattens the cornea and actually makes it easier to fit contact lenses.
The cause of keratoconus is uncertain, but heredity is thought to play a role. Recent research shows a link between a malfunction of enzymes in the eye and a chemical imbalance causing the cornea to thin. Some believe that it is a side effect of disease. What we do know is that exposure to sunlight, eye rubbing, chronic eye irritation, and wearing contact lenses which do not fit correctly can further the damage.
Treatments and vision correction vary depending on how advanced the condition has become. Over time keratoconus caused the cornea to become very steep, thin, and irregular, meaning that as the disorder progresses the measures necessary to correct vision advance as well.
- Glasses and soft contacts. Corrective lenses can improve vision during the very early stages of keratoconus, but eventually most people will need to wear rigid gas permeable contact lenses. They must be fitted correctly to prevent further damage.
- Intacs. Plastic inserts, placed inside of the eye, can help stabilize the cornea. They can correct some amount of nearsightedness, and by making the shape of the cornea more regular, can mean the ability to wear contact lenses.
- Corneal collagen cross-linking riboflavin. A new treatment using eye drops containing Vitamin B2 (riboflavin) and a special light, can strengthen collagen in the eye, and may stop the progression of the disorder.
- Corneal Transplant. About 20 percent of patients will require a cornea transplant. In most patients corneal transplant provides good vision for at least five years.
Keratoconus involves corneal thinning and, therefore, LASIK and any other type of refractive surgery that involves removing corneal tissue are unsafe for people with the disorder. Because there is strong evidence that the condition may be hereditary and delayed diagnoses of keratoconus is fairly common, if you have a family history of the disorder you should inform your ophthalmologist and be tested before undergoing refractive surgery.