Uveitis is an inflammation inside the eye that we see in our examinations. In many cases, it is an underlying disease of the entire body, where the inflammatory reaction in the eye is particularly noticeable. Often an underlying inflammatory disease, and sometimes an infection is the cause.
GENERAL, CLARIFICATION OF TERMS
Often, the exact trigger of the inflammation cannot be clarified. In the case of a typical clinical picture, an infection can sometimes be suspected, or even proven. Only in exceptional cases is the tissue damage directly infectious, for example, in cytomegalovirus retinitis in AIDS patients, or in incipient bacterial keratitis. Mostly, however, the clinical picture is determined by the inflammatory reaction of the body to the pathogen. For this reason, the symptoms improve with steroids, but may worsen if the pathogen suddenly gains the upper hand, because of reduced inflammation. Causative treatment of the infection must therefore be carried out together with anti-inflammatory therapy. In addition, anti-infective therapy (for example, in toxoplasmosis) must be continued not only consistently, (until the lesions have healed) but with a safety margin within which all pathogens have been reached. Relapse prophylaxis is sometimes necessary to prevent reactivation.
In contrast to keratitis of the cornea, infectious uveitis of the choroid is usually secondary to an infection of the entire body. Only rarely does the pathogen first enter the eye, and spread from there. Chronic fungal, or bacterial colonization of the paranasal sinuses, and the lacrimal ducts can sometimes spread to the mucous membranes of the eye.
Systemic infectious diseases often enter through the eye, and almost always first cause an infection of the highly perfused choroid (choroiditis) and spread from there, to other eye tissues. Depending on the pathogen, a typical clinical picture is sometimes recognizable. Toxoplasmosis is an example of this, and often new foci of inflammation are seen adjacent to old scars. An exception to this, is herpes viruses, which often spread and reactivate along nerve fibers. Typical clinical findings are found in both diseases.
Some forms of infectious uveitis do not appear in the eye until the second wave of infection. The cause is not fully explained; however, this makes it difficult to detect the pathogen in the blood. Moreover, the inflammatory activity cannot be determined by the antibodies in the blood, so we have to rely on the clinical examination.
In unclear cases, or in the absence of a response to therapy, continued, more invasive diagnostics are required, simultaneously from the aqueous humor of the eye and the blood serum. Since aqueous humor is quickly renewed, these examinations should be performed rapidly. Sometimes, no pathogen can be detected after a few days. Only rarely a vitreous biopsy, and very rarely a chorioretinal biopsy is necessary to detect the pathogens.
The following, important systemic infections may also affect the eye: toxoplasmosis, tuberculosis, syphilis, lyme disease. Less common, are bartonellosis and, very rarely in our latitudes, leprosy. Apart from toxoplasmosis, parasitic infections are rare in Europe and North America. However, depending on the nature and location of previous travels, toxocariasis, very rarely cysticercosis and cryptococcosis, may occur. The latter, especially in patients with severe immunodeficiencies, or immunosuppression. Onchocerciasis, as a cause of river blindness, can also be acquired during a trip. Viral infections of the eyes also occur frequently \here in Switzerland, with the family of herpes viruses in the foreground. Herpes simplex (trigger of “cold sores”) and Varicella zoster virus (trigger of chickenpox and shingles) rarely manifest in the posterior segment of the eye, but predominantly in the anterior segment. Cytomegalovirus (CMV), on the other hand, can cause severe retinitis, especially in immunosuppressed and AIDS patients. Rubella viruses can cause severe infections and disabilities of the unborn child during pregnancy.
In the case of uveitis, an infection must always be considered. Depending on the clinical picture, further clarification is then planned in a targeted manner, be it in the direction of an infectious, or non-infectious cause. This includes questions sometimes about all organ systems, as well as specific blood sampling and imaging of the eye, also of the lungs and head.
The severity of the inflammation, and course of the disease depend on the pathogen, as well as the patient’s immune system and defense response. For example, at first onset of infection, the inflammatory response is often more vigorous than at reactivation.
The aggressiveness of diagnosis and therapy are based on the dynamics and progression of systemic, or local inflammatory activity. It is important to know, that in many parasitosis and fungal infections, a chronic state of irritation persists even after successful therapy. Inactive remnants of the pathogen may be sufficient for this.
Systemic infections, as cause of uveitis, are frequent. Nevertheless, clarification is difficult in the majority of cases, because ocular involvement with uveitis, usually does not occur until the infection is reactivated. Often, the clinical picture of the uveitis presentation and course, provide the most important clues for differential diagnosis. During the workup, attention should be paid to which dispositional factors influence the current situation, as this will have an impact on the therapeutic strategy. On the one hand, therapy is directed against the infectious cause, and is usually systemic since the source of infection is the entire organism. On the other hand, control of the inflammatory response by local and, if necessary, systemic steroids is usually additionally required to prevent inflammatory tissue damage as far as possible. Anti-inflammatory therapy alone leads to an exacerbation of the infectious activity in higher doses, and is therefore not sufficient.