Keratoconus guide

What is keratoconus?

The human cornea is the transparent outer lens of the eye. It usually has a ball-like shape. In keratoconus, the cornea thins and bulges into an irregular cone shape, resulting in loss of vision.

Keratoconus occurs in around one in 2,000 people. Usually, the disease begins during puberty and progresses to the middle of 30 years of age. It is impossible to foresee how the disease will progress. The corneal change usually affects both eyes, with one more affected than the other.

Although corneal diseases have been studied for decades, keratoconus is still poorly understood. In addition, the definitive cause of the disease is unknown, although a predisposition to developing it is believed to be present at birth.

Diagnostic tests

Keratoconus make changes to vision in two ways:

• As the cornea changes its shape from a ball to a cone, its smooth surface becomes wavy. It is called irregular astigmatism.
• As the front widens, vision becomes more myopic. It means that people can only see objects clearly when they are close. Everything further away looks blurry.

The main symptoms of keratoconus are as follows:

• Vision in one or both eyes gradually deteriorates, usually in late adolescence;
• Double vision;
• Bright lights look like they have halos around them.

Keratoconus is diagnosed by eye doctors - ophthalmologists. In addition to the examination, the doctor conducts the following tests:

• Topography of the cornea is the most accurate way to diagnose early keratoconus and track its progression. Create a map of the corneal curvature; the doctor takes a computerized image.
• Inspection with a slit lamp. Examining the cornea can help detect abnormalities in the outer and middle layers of the cornea.
• Pachymetry. This test is performed to measure the thinnest sections of the cornea.

Treatment methods

Treatment of keratoconus depends on the stage of the disease and is aimed at correcting vision. The following two methods are generally recommended to correct this condition. One of them is the use of different types of lenses.

• Glasses - are used to improve vision and treat astigmatism in mild cases.
• Soft contact lenses are ideal for correcting blurry or distorted vision in the early stages of keratoconus.
• Rigid gas permeable lenses are made of more durable material. Therefore, they are ideal for more advanced keratoconus.
• Hybrid contact lenses - have a rigid gas-permeable centre and a softer surrounding lens. These lenses might be more comfortable to wear than rigid gas-permeable ones.
• Scleral lenses are helpful for people with advanced keratoconus. These lenses hang over the cornea and rest on the whites of the eyes (sclera), creating a smooth optical surface.

Another treatment is a surgical procedure.

• Corneal collagen stapling or corneal cross-linking is a surgery used to strengthen the cornea. It is a minimally invasive outpatient procedure that lasts about an hour. First, the doctor applies riboflavin (vitamin B) eye drops. Then a particular ultraviolet light is directed directly to the cornea. It causes the formation of new corneal collagen cross-links. As a result, this leads to the thickening of the cornea itself.

The described methods of treatment stop the progression of the disease but do not eliminate the damage already done to the eyes.

New treatment options

Doctors usually only recommend surgery for severe cases that have caused significant changes to the cornea or vision.

There are two main surgical options available. The type of surgery depends on the location of the corneal protrusion and its severity. These options include:

• Penetrating keratoplasty is a complete corneal transplant in which donor tissue replaces the central part of the cornea (damaged area). Vision usually remains blurry for about three to six months after transplantation, and patients must take drugs to avoid rejection.
• Deep Anterior Layered Keratoplasty (DALK) - This procedure involves replacing the cornea's central anterior portion and preserving the inner lining. However, it is possible to avoid potential complications with complete corneal transplantation. Another advantage is eliminating the risk of transplant rejection and faster visual rehabilitation.

Both types of surgery are considered very safe operations and are successful in more than 90% of cases. However, most patients still require vision correction with glasses or contact lenses. The choice of lenses depends entirely on the level of astigmatism.

Statistics and prognosis

Traditionally, keratoconus has been described as a non-inflammatory disease. However, more recently, the association of the disease with inflammation of the eyes has been proven. As a rule, the disease develops in the second and third decades of life and progresses up to 40 years.

A comprehensive review of keratoconus has been published in Contact Lens & Anterior Eye. The publication evidence-proved how much the type of treatment depends on the severity and progression of the disease. Typically, mild cases are treated with glasses, moderate with contact lenses, and severe cases require corneal surgery. Contact lenses account for 87% of patient care.

Keratoconus is the main cause of corneal transplantation and implantation. Because of this disease, 58% of this type of operation occurs. However, with early diagnosis and surgical intervention, patients can maintain adequate visual function throughout their lives.

AiroMedical specialists, with the help of the world's leading ophthalmologists, ensure long-term success in patients with keratoconus. Most patients return to an active lifestyle thanks to timely diagnosis, properly selected treatment and visual rehabilitation.

References:

1. Dove Medical Press: Strategies for improving the early diagnosis of keratoconus
2. ЕyeWiki: Keratoconus
3. National Library of Medicine: Advances in the diagnosis and treatment of keratoconus
4. О ScienceDirect: Keratoconus: An updated review