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How does corneal inflammation manifest itself?

by Josephine Andrews
Published: Last Updated on 352 views

In corneal inflammation (keratitis), the transparent part of the outer skin of the eye becomes inflamed, which causes severe pain. The triggers are often bacteria, viruses or parasites. However, keratitis can also have non-infectious causes such as UV radiation or foreign bodies that have penetrated the eye. In advanced stages, the disease can lead to permanent visual damage. Read the most important information about corneal inflammation here.

ICD codes for this disease:

ICD codes are internationally valid codes for medical diagnoses. They can be found, for example, in doctor’s letters or on certificates of incapacity for work.

H16

Corneal inflammation: description

Various inflammations can develop in the eye – both on the outside and on the inside of the visual organ. Depending on which structures are affected, one has to reckon with sometimes dangerous complications. In the case of corneal inflammation (keratitis), the cornea, a very important part of the eye, is inflamed. Therefore, special care should be taken with this disease.

What is the cornea and what is its function?

If you look at a human eye from the outside, the cornea (medical: cornea ) is not initially noticeable because it is transparent. It sits in the middle of the eyeball and forms the front surface of the eye in front of the pupil and the iris. If the pupil is the window of the eye through which light rays enter, then the cornea is the window glass, so to speak. This also makes it clear why vision can be impaired in the case of corneal inflammation.

Around the cornea is the dermis ( sclera ), which gives the white of the eye its colour. The boundary between the cornea and sclera is called the limbus .

The cornea protects and stabilizes the eye. In addition, with its refractive properties, together with the lens, it is responsible for the fact that the incident light rays are bundled to a focal point on the retina . Without a cornea, sharp vision would not be possible.

How is the cornea structured?

The cornea is slightly smaller than a dime and evenly curved. It consists of several layers; from outside to inside these are:

  • the epithelial layer that takes nutrients from the tear film and absorbs oxygen
  • the stroma , which gives hardness and elasticity to the cornea  
  • the endothelial layer , which absorbs nutrients from the aqueous humor inside the eye

There are countless small nerve endings in the cornea. This makes it very sensitive to any kind of damage. This makes perfect sense, because foreign bodies and diseases can be noticed very early on. In addition, the cornea has a high ability to regenerate – it can therefore quickly renew itself if damaged. The deeper the injury, the longer it takes to heal.

Corneal inflammation: symptoms

In the context of corneal inflammation, a variety of symptoms can occur in the eye. Exactly what these are depends largely on the cause of the disease. Possible typical signs of keratitis are:

  • strong pain
  • foreign body sensation in the eye
  • Eyelid spasm (blepharospasm): Due to the pain and the foreign body sensation, those affected reflexively pinch their eyes shut.
  • Aversion to light ( photophobia ): When looking into the light, the pain increases.
  • Dripping tears and possibly watery or purulent discharge
  • eye redness
  • Growths and tissue damage to the cornea (corneal ulcers)
  • decreased eyesight (loss of vision)

It is often not just a keratitis. The inflammation can spread to surrounding structures such as the conjunctiva (conjunctiva) or the iris (iris). The joint occurrence of corneal and conjunctivitis is called “keratoconjunctivitis”. The flow of secretion then usually increases and the eye is even more reddened. In addition, small swellings (chemosis) occasionally appear on the conjunctiva.

Corneal inflammation: causes and risk factors

Corneal inflammation is the body’s response to damage to the cornea. This usually happens due to invading pathogens, sometimes also due to other factors such as UV radiation or dehydration.

Infectious causes of corneal inflammation

The eye has a number of protective mechanisms (such as blinking) that prevent the penetration of pathogens as far as possible. Sometimes, however, germs manage to overcome these hurdles.

Bacterial keratitis

Corneal inflammation is often caused by bacteria, most notably staphylococci, streptococci, Pseudomonas aeruginosa, Proteus mirabilis, and chlamydia. This bacterial keratitis shows a typical course :

First, small, punctiform lesions develop in the epithelial layer of the cornea. This phase is called superficial punctate keratitis in technical jargon . The pathogens then spread in the cornea, often in the form of a ring. And finally, the so-called ” ulcus corneae serpens” occurs : the bacteria penetrate the corneal stroma, where they can multiply very quickly. Infections with Pseudomonas aeruginosa are particularly dangerous because the cornea is destroyed here within a short time.

The pain associated with bacterial corneal inflammation usually begins gently and gets worse as it progresses. It often forms purulent secretion. A white patch formed by white blood cells (hypopyon) may appear at the floor of the anterior chamber of the eye. In severe cases, the cornea scars as a result of the inflammation in such a way that the vision in the affected eye is severely clouded (leucoma). The pressure inside the eye can also increase, leading to glaucoma .

Viral keratitis

Among the viruses , herpes viruses in particular – more precisely: herpes simplex – are responsible for corneal inflammation. A large part of the population gets infected with this virus at some point in life (usually in childhood) and then never gets rid of it.

Herpesviruses last a lifetime in certain nerve cells and can lead to outbreaks from time to time, especially when the immune system is weakened. The viruses then migrate along the nerves to the surface of the body and lead to typical symptoms. Classically, these are the well-known cold sores (cold sores), but in rarer cases the cornea of ​​the eye can also be affected. Sometimes herpes simplex keratitis is transmitted from the outside, for example because the virus gets into the eye from the lip.

Depending on which level of the cornea is affected, three clinical pictures can be distinguished in herpes-related corneal inflammation:

  • Dendritic keratitis : In the epithelial layer, the viruses cause ramified erosions reminiscent of small trees. Typical of this epithelial keratitis is pain and often also reduced sensitivity (sensation to touch) of the cornea.
  • Keratitis herpetica interstitialis : Here the herpes viruses have attacked the stroma, which is why it is also called stromal keratitis. In the middle of the stroma there are accumulations of fluid similar to a target. However, the epithelium of the cornea remains intact. Symptoms include pain and a deterioration in vision.
  • Keratitis disciformis : It is also called endothelial keratitis because the herpes viruses have attacked the innermost layer of the cornea (the endothelium). This creates a disc-shaped corneal opacity that impairs vision. The iris is also sometimes affected – it is inflamed and/or loses its color in places. Unlike the other forms, disciform keratitis is not painful.

From the group of herpes viruses, herpes zoster can also lead to corneal inflammation. This virus is best known for causing shingles. When it causes symptoms in the eye area, it is called zoster ophthalmicus .

In addition to herpesviruses, certain adenoviruses are also possible triggers of keratitis. These pathogens are highly contagious and often affect children. In this form of the disease, known as epidemic keratoconjunctivitis , the corneal inflammation is accompanied by inflammation of the conjunctiva. In addition to severe itching, pain and secretion, there is massive reddening of the eye. Initially, punctiform superficial defects develop on the cornea (similar to superficial punctate keratitis). Over time, cloudiness may develop, which sometimes persists for months or years.

Corneal inflammation caused by fungi or parasites

When a fungus causes corneal inflammation, the symptoms are similar to those of bacterial keratitis. However, the course of fungal corneal inflammation is usually slower and less painful.

A fungal infestation in the eye often occurs after the use of antibiotics or as a result of eye injuries with materials containing fungi, such as wood. The typical causes of fungal keratitis are Aspergillus and Candida albicans .

A rare variant of corneal inflammation is acanthamoeba keratitis . Acanthamoeba are unicellular parasites which, when infested in the cornea, lead, among other things, to a ring-shaped abscess . Those affected see worse and have severe pain.

Contact lenses as risk factors

Basically, contact lens wearers have a higher risk of developing corneal inflammation than other people. On the one hand, the lenses can be contaminated with pathogens, on the other hand, the adhesive shells mean stress for the cornea, especially when wearing them for longer periods. Because as long as a contact lens is over the cornea, it is supplied with less oxygen, which makes it more susceptible to germ infestation. Acanthamoeba keratitis in particular is mainly found in contact lens wearers. According to studies from the USA, 30 percent of all keratids are related to wearing contact lines.

Modern contact lenses are significantly more permeable to oxygen than older models.

Non-infectious causes of corneal inflammation

The cornea can also become inflamed when no pathogens are involved. This can happen , for example, in the context of rheumatic diseases.

Dehydration can also trigger corneal inflammation, in conjunction with additional conjunctivitis (keratoconjunctivitis): Normally, the surface of the eye is always covered with a thin film of tears, which protects the cornea from drying out, among other things. Various glands in the eye produce the tear film, which is then distributed over the surface of the eye by blinking. If, for example, the eyelids cannot close completely when blinking (eg as a result of a stroke), then the tear film is not distributed correctly – the cornea dries out and becomes inflamed. The same can happen with Sjögren’s syndrome, for example – an autoimmune disease associated with dry eyes and mouth.

Corneal inflammation can also be caused by foreign bodies that have penetrated . Since the cornea is very sensitive, you usually notice it immediately if something gets in your eye. However, there are diseases in which the sensation in the eye is reduced or completely absent. Nerve paralysis, which can result from accidents, operations or chronic herpes infections, is usually responsible for this. Important protective reflexes are then absent and the cornea is exposed to mechanical irritation from foreign bodies.

What many people underestimate is the harmful effect of UV radiation on the cornea. Strong ultraviolet light can damage the epithelial layer and cause a very painful inflammation of the cornea (photoelectric keratitis) after about six to eight hours. One is exposed to high doses of UV light , for example, when welding without protective goggles, in the solarium and in the high mountains.

Corneal inflammation: examination and diagnosis

In order to be able to diagnose corneal inflammation, the ophthalmologist first collects a medical history (anamnesis) from the patient . He asks, for example, how long the symptoms have existed, whether they began gradually or suddenly and whether they are occurring for the first time.

With the slit lamp examination , the doctor can then examine the cornea and the anterior chamber of the eye for damage and signs of inflammation. He also checks the mobility and visual acuity of the eyes. A sensitivity test of the cornea shows whether its sensitivity is disturbed or not. The intraocular pressure can also be measured with a tonometer.

In order to find out which pathogen is behind an infectious corneal inflammation, the doctor can take a swab from the affected corneal areas (in the case of contact lens wearers from the contact lens and the accessories). This smear is examined more closely under the microscope.

Corneal inflammation: treatment

The treatment of corneal inflammation depends on its cause:

Bacterial keratitis: therapy

In the case of bacterial keratitis, local antibiotic preparations are usually used (e.g. antibiotic eye drops).

Sometimes medication to widen the pupil (mydriasis) is also useful. Because with bacterial corneal inflammation, cells (eg white blood cells) accumulate in the front chamber of the eye, which then lie between the cornea and the iris. The widening of the pupil prevents adhesions (synechiae) between these two components.

Because corneal inflammation can be very painful, many patients prefer numbing eye drops . There are such things, but they should not be used permanently! They lift the protective corneal reflex, which then promotes injuries. That’s why it’s ultimately a case of corneal inflammation: Close your eyes and go through with it!

Perforation of the cornea is a feared complication, particularly in the case of bacterial corneal inflammation. This creates a leak that allows aqueous humor to escape from the inside of the eye. This can be prevented with a surgical procedure . For example, the cornea is covered with conjunctiva or – in extreme emergencies – a cornea transplant is carried out . Such an emergency corneal transplant in the case of an existing inflammation is referred to as keratoplasty à chaud.

Viral keratitis: therapy

If viruses are the trigger of the corneal inflammation, patients receive antiviral drugs (usually aciclovir) – mostly in the form of preparations to be applied locally (topical application). Sometimes the doctor also prescribes antiviral drugs to be taken (systemic use).

In addition, a viral inflammation of the cornea is sometimes additionally treated with glucocorticoids (“cortisone”) (except for dendritic keratitis). The active ingredients are applied topically (locally).

Keratitis caused by other pathogens: therapy

A fungal corneal infection is treated with antifungal agents ( antifungals ) such as natamycin or amphotericin B. They are applied locally or ingested. If that doesn’t help, an emergency corneal transplant (keratoplasty à chaud) becomes necessary.

If the keratitis is caused by acanthamoeba , treatment consists of intensive local therapy. This involves combining antibiotics and disinfectants such as neomycin, propamidine and PHMB (polyhexane methylene biguanide). Under certain circumstances, an emergency corneal transplant (keratoplasty à chaud) must also be carried out.

Non-infectious keratitis: therapy

The therapy depends on the cause of the corneal inflammation. If, for example, strong UV radiation is responsible for the inflammation, the doctor prescribes an antibiotic eye ointment and possibly painkillers to be taken. If the inflammation is due to the cornea drying out as a result of a lack of wetting with tear fluid, tear substitute preparations are used.

Corneal inflammation: course of the disease and prognosis

The exact course of corneal inflammation varies from case to case and depends primarily on the trigger. It is important that you go to the doctor immediately if you experience persistent eye problems. The earlier the appropriate treatment begins, the lower the duration of the disease and the lower the risk of complications.

In most cases, corneal inflammation can be brought under control with timely treatment. It usually recovers after a week or two. In more severe cases, however, healing may take several weeks. In the worst case, corneal inflammation leaves permanent visual damage.  

Corneal inflammation: prevention

Keratitis can be prevented by protecting the eyes from harmful influences as much as possible. Above all, this means that mechanical damage caused by drying out and UV radiation is prevented. Contact lens wearers should also observe careful hygiene when handling the small visual aids.

If a corneal inflammation is contagious (in the case of infectious keratitis), attention must also be paid to hygiene so that it is not passed on to people close to you. This includes, for example, that infected people use a separate towel.

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