What is keratoconus? Symptoms, diagnosis & treatment options (crosslinking)

Here you can find out everything about keratoconus. What causes the protrusion of the cornea? Which risk factors promote its occurrence? At what stage do which symptoms occur? And above all: what treatment methods are available, when are they advisable, how do they work and what are the benefits, risks and side effects?

EyeLaser clarifies:

Corneal protrusion (keratoconus) at a glance

Keratoconus is a progressive eye disease that affects the structure of the cornea, the clear front part of the eye. In this disease, the cornea gradually thins and deforms into a conical, irregular shape. This deformation leads to a considerable distortion of vision, as light is no longer properly focused on the retina.

Patients with keratoconus typically experience symptoms such as blurred or distorted vision, increased sensitivity to light and difficulty seeing at night. The exact cause of keratoconus is not fully understood, but genetic predispositions and external factors such as excessive eye rubbing are thought to play a role. If left untreated, keratoconus can progress and lead to serious visual impairments that significantly affect daily life.

Keratoconus frequency and distribution

Keratoconus is a relatively rare eye disease that affects around 1 in 2,000 people worldwide. However, the prevalence can vary depending on geographical region and ethnic group. Some studies report that the prevalence may be higher in certain population groups, such as people from the Middle East or South Asia. The condition is most commonly diagnosed in adolescents and young adults, with the first symptoms typically appearing during puberty or early adulthood. Both eyes are frequently affected, but often to varying degrees. Due to the progressive nature of keratoconus, early diagnosis and treatment is crucial.

Causes of keratoconus and risk factors

  • Genetic predisposition: There is evidence that genetic factors play a role, as keratoconus tends to run in some families. Certain genetic mutations can increase susceptibility to the disease.
  • Biomechanical weakness: A weakening of the collagenous support structure of the cornea can lead to its thinning and deformation.
  • Enzymatic changes: Changes in enzyme activity in the cornea can affect the stability of the tissue and contribute to the development of keratoconus.

Risk factors

  • Family history: People with first-degree relatives who suffer from keratoconus have a higher risk of also developing the disease.
  • Excessive eye rubbing: Frequent and vigorous rubbing of the eyes, often due to allergies or dry eyes, can damage the cornea and increase the risk of keratoconus.
  • Certain diseases:
    • Atopic diseases: Allergies, eczema and asthma are common in patients with keratoconus.
    • Systemic diseases: Conditions such as Down syndrome and Marfan syndrome are associated with a higher risk of keratoconus.
  • Hormonal changes: The disease often occurs during puberty or pregnancy, indicating a possible influence of hormonal changes.
  • Environmental factors: High levels of UV exposure and oxidative stress can also play a role in the development of keratoconus.

Keratoconus symptoms & diagnosis:

3D model of an eye with keratoconus.

Keratoconus often begins insidiously and can be difficult to recognize in the early stages. The first signs include

  • Blurred vision: Frequent adjustment to new spectacle strengths without any noticeable improvement in vision can be an early sign.
  • Sensitivity to light: Those affected often notice an increased sensitivity to bright light and glare.
  • Ghost images: Double vision or the perception of shadows around objects, especially in low light conditions.
  • Eye irritation: Frequent rubbing of the eyes due to discomfort or itching.
  • Night vision: Difficulty seeing at dusk or at night, often accompanied by light scattering and halos around light sources.

Over time, the condition can worsen and the symptoms become more intense and debilitating:

  • Significant visual deterioration: Vision can deteriorate quickly, making it difficult to read, drive and perform everyday tasks.
  • Astigmatism: Increasing irregular astigmatism caused by the deformation of the cornea leads to further distortion of vision.
  • Deformation of the cornea: Visible changes in the corneal structure that can be detected by medical examinations in advanced keratoconus.
  • Contact lens intolerance: In advanced stages, wearing contact lenses can become uncomfortable as the cornea is too irregular to tolerate a lens well.

The symptoms of keratoconus usually develop over several years. Early detection and regular ophthalmologic examinations are crucial to slow the progression of the disease and take appropriate treatment measures. If left untreated, keratoconus can lead to significant vision loss and in severe cases may require a corneal transplant.

Keratoconus diagnosis: How is the corneal disease recognized?

Patient being examined for keratoconus.

Slit lamp examination

A slit lamp is a microscope that allows the ophthalmologist to examine the cornea and other structures of the eye in detail. Through this examination, early signs of keratoconus, such as small tears or scars in the cornea, can be detected.

Corneal topography

This procedure is the most important tool for diagnosing keratoconus. Corneal topography creates a detailed map of the corneal surface and measures its shape and curvature. In keratoconus, the topography shows characteristic conical deformations and thinning of the cornea.

Pachymetry

Pachymetry measures the thickness of the cornea. In keratoconus, the cornea is typically thinner than normal, especially in the central area. This measurement helps to determine the severity of the disease.

Keratometer and keratoscope

These instruments measure the curvature of the cornea. A keratometer projects light onto the cornea and measures the reflections to determine the curvature. A keratoscope uses rings of light projected onto the cornea to detect distortions.

Optical coherence tomography (OCT)

OCT uses light waves to create detailed images of the cornea. This highly precise procedure can visualize the layers of the cornea and helps to detect subtle changes that indicate keratoconus.

Retinoscopy

During retinoscopy, a beam of light is directed into the eye to measure reflections from the retina. This helps to detect irregular astigmatism, which is often associated with keratoconus.

Corneal biomechanics analysis

This newer procedure measures the biomechanical properties of the cornea, such as its elasticity and firmness. Changes in these properties can indicate keratoconus.

Crosslinking for keratoconus: The best treatment method

Crosslinking, also known as corneal collagen cross-linking (CXL), is an innovative treatment method for stabilizing the cornea in keratoconus. The aim of this therapy is to strengthen the cornea and stop or slow down its progression. The cornea is treated with vitamin B2 (riboflavin) and UV-A light, which forms new cross-links between the collagen fibers of the cornea.

How does crosslinking work?

  1. Preparation: First, the top layer of the cornea (epithelium) is removed to facilitate the penetration of riboflavin.
  2. Riboflavin application: Riboflavin drops are applied to the cornea and left to act for about 30 minutes until the vitamin has penetrated sufficiently into the tissue.
  3. UV-A irradiation: The cornea is irradiated with UV-A light for about 30 minutes, which triggers a chemical reaction that leads to the formation of new cross-links between the collagen fibers.

Advantages of crosslinking:

1. stabilization of the cornea

Crosslinking strengthens the structure of the cornea by forming additional cross-links between the collagen fibers. This significantly slows or stops the progression of keratoconus, keeping the cornea stable and functional.

2. avoidance of more serious surgical interventions

Early use of crosslinking can often avoid the need for invasive procedures such as corneal transplantation. This reduces the risks and complications associated with major surgery.

3. improvement in the quality of vision

Patients often report an improvement in their quality of vision after the procedure. Although the main goal of crosslinking is stabilization, the increased corneal strength can also lead to a reduction in irregularities that impair vision.

4. long-term effectiveness

Studies have shown that the positive effects of crosslinking can last for many years. The stabilization of the cornea through crosslinking is effective in the long term, which means that patients can experience a lasting improvement in their vision and quality of life.

5. minimally invasive treatment

Crosslinking is a minimally invasive procedure that is usually performed on an outpatient basis. This means that patients can usually return to their normal activities quickly after a short recovery period.

6. security profile

Crosslinking is considered safe and effective, with a low rate of complications. Most patients report only temporary side effects such as pain or a foreign body sensation in the eye, which subside within a few days.

7. compatibility with other treatments

Crosslinking can be used in combination with other treatments. For example, special contact lenses or other refractive corrections can be used after crosslinking to further improve vision.

8. low repetition rate

The need to repeat the procedure is minimal. Once performed, crosslinking proves to be a robust solution against the progression of keratoconus, which sustainably improves the quality of life of those affected.

Risks and side effects:

  • Pain and discomfort: Pain and a foreign body sensation in the eye may occur after the procedure, but this usually subsides after a few days.
  • Infection and inflammation: As with any surgical procedure, there is a small risk of infection or inflammation.
  • Visual impairment: In rare cases, temporary or permanent visual impairment may occur.
More about crosslinking at EyeLaser

Further treatment methods for keratoconus

Glasses and contact lenses for keratoconus

In the early stages of keratoconus, spectacles can be an effective method of correction. As the corneal deformation is still slight at the beginning, conventional spectacle lenses can compensate for the visual defects caused by the irregular cornea. However, as keratoconus progresses, spectacles often no longer provide the necessary visual correction as they cannot sufficiently correct the increasing irregularities of the cornea.

Contact lenses are a widely used and effective treatment method for keratoconus, especially when glasses are no longer sufficient. There are different types of contact lenses that can be used for keratoconus:

  1. Soft contact lenses:

Advantages: Comfortable to wear and easy to adjust.

Disadvantages: Often do not provide enough correction for advanced irregular astigmatism.

  1. Dimensionally stable (rigid gas-permeable) contact lenses:

Advantages: Hold their shape on the cornea, resulting in a smoother surface for better vision correction.

Disadvantages: Can be uncomfortable at first and take a long time to get used to.

  1. Hybrid contact lenses:

Advantages: Combine a rigid core with a soft lens to increase comfort while providing effective vision correction.

Disadvantages: Can be more expensive and are not suitable for all patients.

  1. Scleral lenses:

Advantages: Cover most of the cornea and rest on the sclera (the white part of the eye), which is particularly helpful for advanced keratoconus. They provide excellent comfort and stable vision.

Disadvantages: Require special customization and care, which can lead to higher costs.

  1. Piggyback systems:

Advantages: A soft contact lens is worn under a rigid lens to increase comfort and improve vision correction at the same time.

Disadvantages: Requires maintenance and management of two sets of lenses, which can be more complex.

Intacts for keratoconus

Intacs are small, curved plastic segments that are implanted into the cornea of the eye to change the shape of the cornea and improve the quality of vision. These segments are made of biocompatible material that is well tolerated by the eye. The procedure is usually performed under local anesthesia and is minimally invasive.

Procedure

  1. Preparation: First, the cornea is prepared with a special laser or surgical instrument to create small channels into which the Intacs are inserted.
  2. Implantation: The Intacs segments are then inserted into these channels, where they slightly lift and smooth the cornea to reduce the conical deformation.
  3. Adjustment: The position of the Intacs can be adjusted slightly after implantation to achieve the optimum correction.

Advantages of Intacs

  • Improved quality of vision: Intacs can smooth the corneal surface and reduce refractive errors, resulting in improved quality of vision. This is particularly helpful for patients who do not respond adequately to other correction methods such as glasses or contact lenses.
  • Minimally invasive: The procedure is less invasive than a corneal transplant and requires a shorter recovery time. Most patients can return to their normal activities just a few days after the procedure.
  • Reversibility: One of the biggest advantages of Intacs is their reversibility. The segments can be removed or replaced if necessary, which offers flexibility in treatment.
  • Stability of the cornea: By providing structural support to the cornea, Intacs help to slow or stop the progression of keratoconus.
  • Compatibility with other treatments: Intacs can be used in combination with other treatment methods, such as crosslinking, to further improve stability and quality of vision.

Risks and side effects

  • Complications: As with any surgical procedure, there are risks associated with the implantation of Intacs, such as infection, displacement of the segments or inadequate vision correction.
  • Visual complaints: Some patients report glare or halos around light sources, especially at night.

Corneal transplantation is the last resort:

A corneal transplant, also known as keratoplasty, is a surgical treatment method for patients with advanced keratoconus for whom other therapies are no longer sufficient. The patient’s diseased cornea is partially or completely replaced with a healthy donor cornea. There are two main types of corneal transplantation:

  1. Penetrating keratoplasty (PK): The entire thickness of the cornea is transplanted. This method is often used for severely damaged or very thinned corneas.
  2. Lammellar keratoplasty (LK): Only part of the cornea is replaced, either the anterior or posterior layer, depending on the extent of the damage. This method has the advantage of faster healing and lower rejection rates.

Advantages of corneal transplantation

  • Restoration of vision: Transplantation can lead to a significant improvement in the quality of vision, especially in patients who do not respond to other treatment methods.
  • Long-term solution: A successful transplant can last for years or even a lifetime, providing a permanent solution for severe cases of keratoconus.
  • Extended treatment options: Corneal transplantation can also be considered after unsuccessful other surgical procedures such as Intacs or crosslinking.

Risks and side effects

  • Rejection reactions: As with any transplant, there is a risk that the body will reject the donor tissue, which requires careful aftercare and possibly long-term medication.
  • Infections and complications: Postoperative infections and other complications such as increased intraocular pressure or graft failure can occur.
  • Long recovery time: Complete healing can take several months to a year, with regular follow-up examinations required.

The decision to undergo corneal transplantation should be made after careful consideration of all risks and benefits and after comprehensive consultation with a specialist ophthalmologist. This treatment offers many patients with advanced keratoconus the chance of a significant improvement in their vision and quality of life.

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Author:

Dr. Victor Derhartunian

Nachdem er sein Handwerk von den beiden Pionieren der Laserchirurgie gelernt hat, gehört Dr. Victor Derhartunian zu den führenden Augenlaser-Chirurgen. Er leitet die Praxis in Wien und kann seine Patienten in fünf Sprachen beraten.