Keratoconus is a rare eye condition that affects the shape and clarity of the cornea, the transparent front part of the eye. A person with keratoconus has a thin, bulging cornea that resembles a cone rather than a dome. It causes blurry vision, sensitivity to light, and other vision problems. It can affect either eye, but one eye may be worse than the other. It can occur at any age, but it tends to begin during adolescence or young adulthood.
The exact cause of keratoconus is unknown, but it may involve a combination of genetic, environmental, and hormonal factors. Some possible risk factors for keratoconus are:
Family history: About 7% of people with keratoconus have a relative with the condition1.
Eye rubbing: Rubbing the eyes vigorously or frequently may damage the cornea and contribute to its weakening.
Allergies: People with allergies, especially those that affect the eyes, may be more prone to eye rubbing and inflammation.
Hormonal changes: Keratoconus often begins or worsens during puberty, pregnancy, or menopause, suggesting that hormones may play a role.
The symptoms of keratoconus vary depending on the stage and severity of the condition. Some common symptoms are:
Blurred or distorted vision: The irregular shape of the cornea makes it difficult to focus light properly, resulting in blurry or distorted vision. People with keratoconus may have trouble seeing fine details, reading, or driving.
Frequent changes in prescription: As the cornea changes shape over time, people with keratoconus may need to change their glasses or contact lenses more often to correct their vision.
Sensitivity to light and glare: The thin and protruding cornea may make the eyes more sensitive to bright light and glare, causing discomfort or headaches.
Double vision or ghost images: People with keratoconus may see double or multiple images of the same object, especially in one eye. This can affect the depth perception and coordination of the eyes.
Reduced or absent sense of smell: In some cases, keratoconus may be associated with a condition called Kallmann syndrome, which affects the development of the reproductive system and the sense of smell.
Keratoconus is diagnosed by an eye doctor (ophthalmologist or optometrist) who will perform a comprehensive eye exam. The eye exam may include:
Medical history: The eye doctor will ask about the personal and family history of vision problems, allergies, eye rubbing, and other medical conditions.
Visual acuity test: The eye doctor will measure how well the person can see at different distances, using an eye chart or a device called a phoropter.
Refraction test: The eye doctor will use a device called a retinoscope or an automated instrument to determine the prescription needed to correct the vision.
Slit-lamp exam: The eye doctor will use a microscope with a bright light to examine the front and back parts of the eye, looking for signs of thinning, bulging, scarring, or irregularities of the cornea.
Keratometry: The eye doctor will use a device called a keratometer to measure the curvature of the cornea and detect any changes in its shape.
Corneal topography: The eye doctor will use a device called a corneal topographer to create a detailed map of the surface of the cornea, showing its contours, elevation, and power. This can help diagnose and monitor the progression of keratoconus.
Corneal pachymetry: The eye doctor will use a device called a pachymeter to measure the thickness of the cornea at different points. This can help assess the severity and risk of complications of keratoconus.
Treatment for keratoconus depends on the stage, severity, and rate of progression of the condition. Treatment options include:
In the early stages of keratoconus, eyeglasses or soft contact lenses may be sufficient to correct the vision and provide comfort. However, as the condition progresses, they may no longer be effective or appropriate.
The rigid gas permeable contact lens (RGP) is a hard contact lens that does not conform to the shape of the cornea, but rather creates a smooth and regular surface for light to focus on. For people with moderate to advanced keratoconus, they can improve vision and comfort better than eyeglasses or soft contact lenses. However, they require regular maintenance and cleaning and may take a while to adjust to.
Contact lenses with a rigid center and soft outer ring are hybrid contact lenses. A combination of RGP and soft contact lenses, they offer better vision and comfort than eyeglasses or soft contact lenses, as well as easier fitting and adaptation than RGP contact lenses. For people with mild to moderate keratoconus, they may be appropriate.
Contact lenses that cover the entire cornea and rest on the white part of the eye are called scleral contact lenses. By creating a tear-filled space between the lens and the cornea, they correct vision and protect the cornea. In addition to providing excellent vision and comfort, they can be used by those with advanced keratoconus or who are unable to tolerate other types of contact lenses. In contrast to other contact lenses, they are more expensive and require more care and maintenance.
A corneal collagen cross-linking (CXL) is a procedure that strengthens the cornea by establishing new bonds between its collagen fibers. By applying vitamin B2 (riboflavin) eye drops and ultraviolet light to the cornea, CXL can stop or slow down the progression of keratoconus and prevent further thinning and bulging of the cornea. While CXL does not improve vision, it may prevent the need for more invasive treatments, like corneal transplants. In order to enhance vision outcomes, CXL may be combined with other treatments, such as contact lenses or laser surgery.
A laser beam is used to reshape the cornea and correct vision in this procedure. Several types of laser surgery are available for people with keratoconus, including photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). For people with mild keratoconus who do not have significant scarring or thinning of their corneas, laser surgery may be an option. In order to optimize the results of CXL, laser surgery may be performed before or after the procedure.
Corneal transplant: The surgery involves replacing a damaged cornea with a healthy donor cornea. This restores the cornea's normal shape and clarity and improves vision. When people with severe keratoconus have tried all other treatments and their vision and quality of life are poor, cornea transplants are usually the last resort. There are some risks and complications associated with cornea transplants, including infection, rejection, or glaucoma. Regular follow-up visits and lifelong use of eye drops are also required.
In spite of the fact that keratoconus is a genetic condition that cannot be prevented, there are some steps people with the condition can take to reduce the complications and progression of the disease, such as:
Avoid rubbing the eyes, as this may damage the cornea and worsen the condition. If the eyes are itchy or irritated, use eye drops or cold compresses to soothe them.
Avoid allergens, such as dust, pollen, or pet dander, that may trigger eye rubbing or inflammation. If the allergies are severe, consult a doctor for medication or immunotherapy.
Wear sunglasses or a hat to protect the eyes from UV light, which may harm the cornea and increase the risk of CXL complications.
Follow the eye doctor’s instructions for the use and care of eyeglasses or contact lenses, and have regular eye exams to monitor the condition and adjust the treatment as needed.
Seek medical attention promptly if the vision changes suddenly or significantly, or if there are signs of infection, such as redness, pain, or discharge from the eyes.
