What is Keratoconus?
Keratoconus is a condition that causes the cornea (the clear surface at the front of the eye) to gradually thin and swell into a cone shape. The cone-shaped cornea can often cause myopia and astigmatism, causing blurry and distorted vision. It usually starts at a young age and can gradually get worse, although it is different for each individual.
WHAT IS KERATOCONUS?
Keratoconus is characterized by thinning of the cornea and irregularities on the corneal surface. The cornea is the transparent outer layer at the front of the eye. The middle layer is the thickest part of the cornea, consisting mostly of water and a protein called collagen. Collagen makes the cornea strong and flexible and helps it maintain its regular and round shape. With keratoconus, the cornea becomes thinner and swells into an irregular cone shape, which can lead to vision loss.
Keratoconus can also occur when there are not enough protective antioxidants in the cornea. If antioxidant levels are low, collagen weakens and the cornea swells. The cone-shaped cornea can cause sensitivity to light and glare, as well as causing blurred vision. Keratoconus usually affects both eyes, but often affects one eye more than the other. It usually begins to affect people between the ages of 10 and 25.
In the early stages of keratoconus, vision problems can be corrected with glasses or soft contact lenses. Later, different types of lenses may be needed, such as rigid, scleral lenses. In advanced stages, corneal transplantation may be needed.
A new treatment called corneal collagen cross-linking may slow or stop the progression of keratoconus. This could possibly prevent the need for a future corneal transplant.
WHO HAS KERATOCONUS?
The real cause of keratoconus is not fully known. It is not a common eye disease, but it is not a rare eye disease either. It is estimated to occur in 1 in every 2000 people in the general population. Keratoconus is usually first diagnosed in young people who are in their teens or late teens.
KERATOKONUS NEDEN OLUŞUR?
Important studies have been conducted on keratoconus in recent years. In line with these studies, some ideas about the causes of keratoconus have been put forward. Accordingly, keratoconus occurs due to the weakening of the corneal tissue and the imbalance of collagen in the cornea. An imbalance of enzymes in the cornea causes free radicals to make the cornea more susceptible to oxidative damage. Additionally, both environmental and genetic factors are thought to play a role in its development.
Family history: In some cases it appears to be genetic (runs in families). 1 in 10 people with keratoconus has a parent with keratoconus. Genetic reasons are also among the causes of corneal damage, weakening and enzyme imbalance.
Underlying disorders: Keratoconus sometimes occurs in the presence of several different underlying disorders, but a direct cause and effect has not been determined. These disorders include Down syndrome, eye allergies, sleep apnea, asthma, certain connective tissue disorders such as Marfan syndrome and fragile cornea syndrome, and Leber congenital amaurosis.
Environmental risk factors: Some environmental risk factors can contribute to the development of keratoconus, including excessive eye rubbing and contact wearing. Harmful ultraviolet rays from the sun also cause the structure of the cornea to deteriorate. Excessive eye rubbing, worn lenses and irritation that may occur in the eyes are also among the triggers of keratoconus.
WHAT ARE THE SYMPTOMS OF KERATOCONUS?
The most distinctive feature of keratoconus is thinning that disrupts the natural dome shape of the cornea. In the early stages of keratoconus, there are usually no symptoms. As the condition progresses, asymmetry of the cornea can cause blurred vision and mild to significant impairment of vision.
Keratoconus changes your vision in two ways:
When the cornea changes from a ball shape to a cone, the smooth surface becomes wavy. This is called irregular astigmatism. As the front widens, myopia may develop. This means objects can only be seen clearly when they are close. Everything that is very far away looks blurry. Additionally, the following symptoms may frequently occur in keratoconus:
•Double vision when looking with one eye
Both near and distant objects appear blurry
•Bright lights that appear to have halos around them
•Sensitivity to light
Blurred vision that makes driving difficult
•The desire to rub the eyes
•Frequent changes in eyeglass prescriptions
HOW IS KERATOCONUS DIAGNOSED?
In addition to a complete medical history and eye exam, your eye doctor may perform the following tests to diagnose keratoconus:
Corneal topography: It is the most accurate way to diagnose early keratoconus and follow its progression. A computerized image is taken that creates a map of the curve of the cornea.
Slit Lamp Examination: This examination of the cornea can help detect abnormalities in the outer and middle layers of the cornea.
Pachymetry: This test is used to measure the thinnest areas of the cornea.
Children of parents with keratoconus should have an eye examination every year starting from the age of 10.
HOW IS KERATOCONUS TREATED?
Keratoconus treatment focuses on restoring vision and varies depending on the stage of the disease.
EARLY STAGES
Treatment in the early stages of keratoconus includes the use of glasses to treat myopia and astigmatism. As keratoconus progresses and worsens, glasses can no longer provide clear vision and patients must wear a contact lens, usually a rigid contact lens.
INTERMEDIATE STAGES
Progressive keratoconus can be treated with corneal collagen cross-linking. This one-time procedure involves applying a vitamin B solution to the eye, which is then activated with ultraviolet light for about 30 minutes or less. The solution causes new collagen bonds to form, restoring and preserving some of the cornea's strength and shape.
Although treatment cannot completely return the cornea to normal, it can prevent vision from worsening and, in some cases, improve vision. The procedure may require removal of the thin outer layer of the cornea (epithelium) to allow riboflavin to penetrate the corneal tissue more easily.
ADVANCED STAGES
Intracorneal rings: In advanced keratoconus, wearing a standard contact lens can be very uncomfortable. The purpose of these rings is to correct the shape of the cornea. They also allow for better contact lens placement. Thanks to this procedure performed using topical anesthesia, the shape of the cornea can be corrected to some extent and vision is improved. These rings placed on the eye can be removed later upon the patient's request. The process takes approximately 15 minutes.
Corneal transplantation: Corneal transplantation is the latest method for keratoconus. Thanks to this extremely common method, tens of thousands of people overcome this problem every year. In corneal transplantation, a donor cornea replaces the patient's damaged cornea. Cornea transplants are usually done on an outpatient basis and take about an hour to complete. After the transplant, vision usually remains blurry for about three to six months, and medication must be taken to prevent transplant rejection. In almost all cases, the use of glasses or contact lenses is necessary to ensure the clearest vision after transplant surgery.