Corneal inflammation: Description
Various inflammations can occur on the eye – both on the outside and inside the organ of vision. Depending on which structures are affected, one must expect complications, some of them dangerous. In the case of corneal inflammation (keratitis), the cornea, a very important component of the eye, is inflamed. Therefore, special caution is required in this disease.
What is the cornea and what is its function?
When you look at a human eye from the outside, the cornea is not noticeable at first because it is transparent. It sits on top of the eyeball in the middle 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 the light rays enter, then the cornea is the window glass, so to speak. This also explains why vision can be impaired in the case of corneal inflammation.
The cornea protects and stabilizes the eye. In addition, with its light-refracting properties, it is responsible together with the lens for bundling the incident light rays to a focal point on the retina. Without the cornea, sharp vision would therefore not be possible.
What is the structure of the cornea?
The cornea is slightly smaller than a 1-cent piece and evenly curved. It consists of several layers; from outside to inside these are:
- the epithelial layer, which absorbs 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
Corneal inflammation: symptoms
In the context of corneal inflammation, a variety of symptoms can appear on the eye. Which ones exactly depend on the cause of the disease. Possible typical symptoms of keratitis are:
- severe pain
- Foreign body sensation in the eye
- Eyelid spasm (blepharospasm): Due to the pain and the foreign body sensation, affected persons reflexively pinch the eye shut.
- Photophobia: Pain increases when looking into the light.
- Watering and possibly watery or purulent secretion.
- Eye redness
- growths and tissue damage on the cornea (corneal ulcers)
- reduced visual acuity (loss of visual acuity)
Corneal inflammation: causes and risk factors
Corneal inflammation is the body’s reaction to damage to the cornea. Most often, this occurs due to invading pathogens, sometimes due to other factors such as UV radiation or dehydration.
Infectious causes of corneal inflammation
The eye has some protective mechanisms (such as the blink) that prevent pathogens from entering as much as possible. Sometimes, however, germs do manage to overcome these hurdles.
Bacterial keratitis
Corneal keratitis is often caused by bacteria, especially staphylococci, streptococci, Pseudomonas aeruginosa, Proteus mirabilis and chlamydia. This bacterial keratitis shows a typical course:
The pain of a bacterial corneal inflammation usually begins discreetly and becomes stronger as it progresses. Purulent secretion is often formed. At the bottom of the anterior chamber of the eye, a white mirror may appear, which is caused by white blood cells (hypopyon). In severe cases, the cornea becomes scarred as a result of the inflammation to such an extent that vision in the affected eye becomes severely cloudy (leukoma). In addition, the pressure inside the eye may increase and lead to glaucoma.
Viral keratitis
Among viruses, herpes viruses in particular – more specifically, herpes simplex – can inflame the cornea (herpes keratitis). Most people become infected with these viruses at some point and then cannot get rid of them. Herpes viruses survive for life in nerve cells and can cause repeated outbreaks. These can also affect the cornea of the eye.
Varicella zoster viruses can also cause corneal inflammation. This virus is known primarily as the trigger of chickenpox. It belongs to the group of herpes viruses and also lies dormant in the body after the initial infection. If it becomes active again, it causes shingles (herpes zoster). It can also affect the eye and cause zoster ophthalmicus. You can find out everything important about this in the text “Shingles in the face”.
In addition, certain adenoviruses can underlie keratitis. They are highly contagious and often affect children. In addition to the cornea, the viruses also affect the conjunctiva, which is why doctors call it keratoconjunctivitis epidemica. In addition to severe itching, pain and secretion, there is a massive reddening of the eye. At first, superficial punctiform defects appear on the cornea. In the course, opacities may develop, sometimes persisting for months to years.
When a fungus triggers corneal inflammation, symptoms are similar to those of bacterial keratitis. However, the course of fungal corneal inflammation is usually slower and tends to be less painful.
Fungal infection in the eye often develops after the use of antibiotics or due to eye injuries with fungus-containing materials such as wood. The typical causative agents of fungal keratitis are Aspergillus and Candida albicans.
A rare variant of corneal inflammation is acanthamoebic keratitis. Acanthamoebae are single-celled parasites that, when they infect the cornea, lead to an annular abscess, among other symptoms. Affected individuals experience poorer vision and severe pain.
Contact lenses as risk factors
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.
Corneal inflammation can also be caused by foreign bodies entering the eye. Since the cornea is very sensitive, you usually notice it immediately when something gets into the eye. However, there are diseases in which the sensation in the eye is reduced or completely absent. Mostly a nerve paralysis is responsible for it, which can result from accidents, operations or chronic herpes infections. Then important protective reflexes are missing and the cornea is exposed to mechanical irritation by foreign bodies.
What many people underestimate is the damaging effect of UV radiation on the cornea. Strong ultraviolet light can damage the epithelial layer and cause very painful corneal inflammation after about six to eight hours (keratitis photoelectrica). One is exposed to high doses of ultraviolet light, for example, when welding without protective goggles, in the solarium as well as in the high mountains.
Corneal inflammation: examination and diagnosis
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 will indicate whether or not its sensation is disturbed. Furthermore, the intraocular pressure can be measured with a tonometer.
In order to find out which pathogen is behind an infectious corneal inflammation, the doctor can make a smear from the affected corneal areas (in the case of contact lens wearers, from the contact lens and accessories). This swab is examined more closely under a microscope.
Corneal inflammation: Treatment
The treatment of corneal inflammation depends on its cause:
Bacterial keratitis: therapy
In bacterial keratitis, local antibiotic preparations are usually used (e.g., antibiotic eye drops).
Because corneal inflammation can be very painful, many patients want to have anesthetic eye drops. Such eye drops are available, but they should not be used permanently! They cancel the protective corneal reflex, which then favors injuries. Therefore it is called in the long run with a corneal inflammation: Eye closed and through!
Especially in the case of bacterial corneal inflammation, perforation of the cornea is a feared complication. This is because a leak is created through which aqueous humor can escape from the inside of the eye to the outside. This can be prevented with a surgical intervention. For example, the cornea is covered with conjunctiva or – in an extreme emergency – a corneal transplantation is performed. Such an emergency corneal transplantation in case of existing inflammation is called keratoplasty à chaud.
Viral keratitis: Therapy
Furthermore, viral corneal inflammation is sometimes additionally treated with glucocorticoids (“cortisone”) (except keratitis dendritica). The agents are applied topically (locally).
Keratitis caused by other pathogens: Therapy
Corneal inflammation caused by fungi is treated with antifungal agents (antimycotics) such as natamycin or amphotericin B. They are applied topically or ingested. They are applied locally or ingested. If this does not help, emergency corneal transplantation (keratoplasty à chaud) becomes necessary.
If the keratitis is caused by acanthamoebae, the treatment consists of intensive local therapy. This involves a combination of antibiotics and disinfectants such as neomycin, propamidine and PHMB (polyhexane methylene biguanide). Emergency corneal transplantation (keratoplasty à chaud) may also need to be performed.
Non-infectious keratitis: Therapy
Corneal inflammation: course of the disease and prognosis
The exact course of corneal inflammation varies from case to case and depends above all on its trigger. It is important to see a doctor immediately if the eye symptoms persist. The earlier the appropriate treatment begins, the shorter the duration of the disease and the lower the risk of complications.
Thus, corneal inflammation can be well controlled in most cases with timely therapy. It is usually cured after one to two weeks. In more severe cases, however, the healing process can take several weeks. In the worst case, corneal inflammation leaves permanent visual damage.
Corneal inflammation: Prevention
If corneal inflammation is contagious (in the case of infectious keratitis), hygiene must also be observed so that it is not transmitted to nearby people. This includes, for example, that infected persons use a separate towel.
