The term iritis, or anterior uveitis, is used in medical language to define inflammation of the anterior chamber of the eye and iris. It is the most common form of uveitis; in fact, in Western countries, 50% to 70% of all cases of uveitis are classified as anterior uveitis. Uveitis occurs predominantly in young and middle-aged people, with a slight prevalence in the female sex. In the most severe cases, it can cause loss of vision, which is why prompt intervention by a specialist is necessary.
Causes of iritis
L'iritis is often idiopathic, i.e. due to unknown causes, but can be triggered by genetic, immune, traumatic or infectious mechanisms. 20% of cases are due to blunt trauma to the eye.
When it is not caused by trauma, iritis is often associated with systemic diseases due to HLA-B27, a specific protein belonging to the HLA (Human Leukocyte Antigen) family, present on the surface of cells. These proteins enable the body to recognise its components and distinguish them from foreign proteins, such as those of viruses or cancer cells. In particular, the HLA-B27 antigen is present in approximately 8% of Caucasians and is associated with certain autoimmune diseases, such as ankylosing spondylitis, juvenile rheumatoid arthritis, reactive arthritis and iritis. It is therefore not uncommon for this form of anterior uveitis to be linked to autoimmune diseases.
Infectious causes, on the other hand, include: tuberculosis, chlamydia, herpes simplex, toxoplasmosis, varicella-zoster virus (which causes shingles).
Other causes of iritis include taking certain drugs, lymphomas, leukaemia and juvenile Xanthogranuloma.
What are the symptoms of iritis?
The symptoms of iritis are the consequence of uveal inflammation, which has a similar pattern to inflammation in other body tissues. However, due to the excessive vascularisation of the uveal tissue, there is an increased vascular response.
Iritis may present with ocular pain, mainly due to irritation of the ciliary nerves and spasms of the ciliary muscles. In addition, photophobia (i.e. a strong discomfort associated with light) may be present, caused by irritation of the trigeminal nerve due to ciliary spasm. The ophthalmologist, through slit-lamp examination, can observe the presence of cells and flare (white blood cells and protein transudate), which are due to the increased permeability of the blood vessels in the anterior chamber caused by inflammation.
In the case of traumatic iritis, microbial contamination and retention of necrotic debris at the site of trauma may be present. In contrast, if the iritis is infectious in nature, the symptoms are mainly caused by tissue damage due to the pathogen. Finally, in the case of iritis related to autoimmune causes, symptoms are due to the deposition of immune complexes.
Assessment and management of iritis
The clinical evaluation of iritis involves a series of eye examinations, but also additional laboratory or imaging tests that may be required if the underlying cause is suspected to be systemic or an infectious disease. Specific investigations in each patient are therefore necessary to identify the aetiology on the basis of clinical signs.
Among the most useful ophthalmic examinations, the visual acuity test allows identification of inflammatory activity and associated complications. Improvement in visual acuity, on the other hand, is an indicator of resolution of iritis and reduction of inflammation. It may also be useful to measure intraocular pressure (IOP), which can vary in some cases of iritis.
The treatment of iritis is mainly aimed at reducing inflammation and pain and preventing complications. First-line treatment involves topical cycloplegics (dilation of the pupil, prevention of pupillary spasm) and topical steroids (reduction of inflammation). Vitreous implants based on extended-release corticosteroids (fluocinolone acetonide, dexamethasone) are also available for the treatment of cases of inflammation-induced panuveitis. Approximately half of all patients with uveitis require more specific treatments, in addition to corticosteroids, to prevent vision loss.
With proper treatment, the prognosis for iritis is good. Close monitoring of the condition by the ophthalmologist is important, which should include repeated slit-lamp checks and intraocular pressure evaluations every few days. When the condition is stable, monitoring can be reduced to every 1-6 months. If not diagnosed and treated in time, neglected cases of iritis usually develop complications such as cataracts, glaucoma, retinal detachment and macular oedema.
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