Keratoconus

In a keratoconus, the cornea of the eye becomes thinner and bulges like a cone. This deformation manifests itself in the person concerned mainly by a blurred or distorted vision noticeable. In addition, the vision usually deteriorates quickly. Keratoconus often develops only in one eye, later the second one also changes.

The exact causes of keratoconus are not yet fully understood. Apparently, those affected have changes in comparison to the healthy cornea, which makes the cornea less stable and thus more easily deformable. Genetic influences probably play a role in the development of keratoconus.

Light to medium keratoconus stages are usually treated well with contact lenses. If the corneal cone continues to increase, however, the contact lenses will no longer adhere well at some point. Then different operative methods are possible. So you can for example:

• Replace parts of the ocular cornea or the whole cornea with donor material (corneal transplantation).
• Insert halves of a small plastic ring (so-called intrastromal ring segments) between the corneal layers to flatten the keratoconus.

A relatively new method of treating keratoconus is called corneal crosslinking. Here, the doctor wears off the top cell layer of the cornea and then treats the eyes with vitamin B2 drops and UV radiation. This should improve the cross-linking of the molecules within the cornea and make them more stable and less deformable. The ocular malformation progresses more slowly.

So far, there is no causal treatment of keratoconus, a cure in the true sense is therefore not possible. With appropriate therapy, however, the eyesight of those affected can be improved.

Keratoconus: What Is It?

Keratoconus is a malformation in which the cornea of the eye (cornea) gradually becomes thinner and bulges like a cone. A keratoconus usually occurs on both sides, but usually arises only in one eye.

The term keratoconus consists of the word part kerato-, which goes back to the Greek word kéras (= horn), and the Latin word cone (= cone) together.

Keratoconus is one of the most common abnormalities of the cornea. It occurs statistically in about 4 to 600 out of 100,000 people. However, the frequency of keratoconus varies according to the source of the literature. At the time of diagnosis, most people are between 15 and 30 years old.

While corneal change is more common in women than in men, according to some sources, other sources suggest that the disease is equally common in both women and men.

What Are The Causes?

The exact causes of keratoconus (corneal cone) are not yet known. However, previous findings indicate that the molecular structure of the cornea differs slightly in those affected compared to people without keratoconus. Especially with the collagens and some enzymes there are deviations, whereby the cross-linking within the cornea is worse. As a result, it is less stable and gives way more easily.

There is probably a genetic component in the development of this eye disease. This is because the risk of keratoconus is increased if cases of this corneal change have already occurred in the family.

The thinning and conical protrusion of the cornea should also occur more frequently in connection with various diseases, such as in:

• Eye diseases like
  • Retinopathia pigmentosa (genetic retinal degeneration)
  • Retinopathy of prematurity
• Allergic diseases, e.g.
  • Eczema
  • Allergic conjunctivitis (so-called spring conjunctivitis)
• Metabolic diseases
• Hereditary diseases, e.g.
  • Down syndrome (trisomy 21)
  • Marfan syndrome (connective tissue disease)
  • Leber's congenital amaurosis (retinal defect)
  • Ehlers-Danlos syndrome (connective tissue disease with distensible skin and over-moving joints)
  • Vitreous bone disease (bone defect)

Also, regular, extreme eye rubbing should be able to contribute to the emergence of keratoconus, the underlying mechanisms are unclear.

Some experts believe that years of contact lens wear favors keratoconus. However, this may only be the case in those who had previously unrecognized, undiagnosed keratoconus.

Keratoconus: Symptoms

A keratoconus (corneal cone) can have a variety of symptoms that can change with the progression of the disease. Possible symptoms include:

• progressive deterioration of vision
• fluctuating eyesight
• blurred or distorted vision
• increased photosensitivity
• deteriorated night vision
• sudden deteriorated eyesight, fog-like vision

Usually only one eye forms a keratoconus. Later, the cornea also changes in the second eye.

Keratoconus: Diagnosis

To diagnose a keratoconus (corneal cone), the ophthalmologist examines the victim's eyes and asks him about existing complaints and illnesses. To diagnose keratoconus, various eye examinations can contribute, such as:

• Slit lamp: With the slit lamp, the doctor can better recognize altered structures in the eye.
• Placido disk: The Placido disk is an illuminated, round disk with colored concentric circles. If the person concerned looks at the disc, the doctor can observe how the circles on the cornea are reflected. If the circles look distorted, this indicates an irregular corneal surface.
• Ophthalmometer: A measurement of the cornea with the ophthalmometer (keratometer) shows how hard the cornea of ​​the eye is curved.
• Corneal Topography (Videokeratoscopy): A scanner records the surface and thickness of the cornea.
• Refraction test: With the refraction test, the ophthalmologist determines the visual acuity of the affected person.
• From a certain strength of the keratoconus, the conical corneal deformation can be seen without further aids. The lower edge of the lid is now deformed by the corneal cone (so-called Munson sign) and resembles the letter V.

Keratoconus: Therapy

For a Keratokonus (corneal cone), there are various therapy options. Which treatment is right depends on how advanced the keratoconus is in the affected person and how quickly the eye disease worsens.

Lighter keratoconus cases can usually be treated with spectacle lenses or contact lenses. However, when the keratoconus is more advanced, contact lenses often can not be worn because they can hold badly on the cone-shaped cornea and fall out. In later stages, therefore, eye surgery (corneal transplantation) may be necessary in which the cornea is completely or partially replaced by donor material. Corneal grafts are usually well tolerated.

Contact lenses, eyeglasses

Frequently, contact lenses are sufficient to treat keratoconus.

• Glasses or Soft Contact Lenses: In early keratoconus stages, glasses or soft contact lenses can correct the blurred or distorted vision. However, usually frequent adjustments of the lenses or spectacle lenses are necessary because the cornea can deform further.
• Hard contact lenses: In contrast to soft lenses, hard contact lenses can be adjusted to a certain degree to the individual corneal deformities and are therefore used in many keratoconus sufferers.
• Piggyback lenses: If you have problems with hard contact lenses, you can try so-called piggyback lenses or "add-on lenses". In this variant, the person concerned wears a soft contact lens under a hard contact lens.
• Hybrid contact lenses: Hybrid contact lenses are a kind of mixture of soft and hard lenses. In the middle is a dimensionally stable core, surrounded by a soft outer ring.
• Scleral lenses: Scleral lenses treat corneal irregularities and, to a degree, advanced keratoconus cases. While other contact lenses lie directly on the cornea of ​​the eye, the slightly larger scleral lens is located on the dermis, ie on the white of the eye. There is no contact with the cornea. The above the cornea lying tear film of the eye reaches up to the scleral lens and fills the "gap" from. Thus, corneal deformations can be compensated.

Eye surgery

Eye surgery may be appropriate if:

• The cornea is scarred.
• The cornea is getting thinner.
• The vision is bad despite strong contact lenses.
• Contact lenses can no longer be worn due to advanced keratoconus.
• Contact lenses can not be tolerated.

Depending on which part of the cornea protrudes and how advanced the keratoconus is, different operative methods can be considered, for example:

• Intrastromal ring segments
• Corneal transplant

Intrastromal ring segments

In this method, during eye surgery, the doctor inserts two small, half-moon, plastic ring segments between the corneal layers. In this way, the conical protrusion flatter and the vision improves. Also, contact lenses usually fit better after such an intervention again. The corneal implants can be removed if necessary.

Corneal transplantation (keratoplasty)

In advanced cases of keratoconus, which are associated with scarring and thinning of the cornea, a corneal transplantation (keratoplasty) may be useful - a complete or partial replacement of the own cornea against donor material. There are different ways:

• Perforating Keratoplasty: The cornea is replaced in full thickness.
• Anterior lamellar keratoplasty (DALK): the outer layer of the cornea is replaced.

Corneal Crosslinking

The so-called corneal cross-linking is still a relatively new method to treat keratoconus in its early stages. Before the actual treatment, the uppermost layer of the cornea (corneal epithelium) is removed. Subsequently, the affected person drops vitamin B2 (riboflavin) into the eye and is then irradiated for 30 minutes with UV light (320 nm). During the irradiation is further dripped so that the cornea does not dry out.

This method is intended to stimulate the cornea to form more crosslinks and thereby strengthen them. The cornea becomes slightly stiffer and less deformable in this way. The disease progresses more slowly. The corneal cross-linking is especially in early keratoconus stages in question.

Course and Prevention

A keratoconus proceeds untreated mostly slowly, but in spurts. In part, the disease comes for a long time by itself to a standstill. Although the "corneal cone" can not heal in the true sense, a treatment can slow down the progression of the disease and relieve discomfort.

Complications

About one in ten sufferers experience so-called acute keratoconus. This complication usually occurs when, in an untreated corneal cone, the lowest two layers of the cornea tear as a result of the constant stretching. Then aqueous humor can penetrate the cracks, causing the cornea to cloud. In the affected person, this is noticeable by the following symptoms:

• a suddenly deteriorated view
• eye pain
• photosensitivity
• watery eyes

Since genetic factors probably play a role in the development of keratoconus (corneal cone), the disease can not really be prevented.