Uveitis is inflammation of the inside of the eye which affects one or more of the three parts of the uvea: the iris (which gives the eye its colour), the ciliary body (behind the iris, where the aqueous humour is produced) and the choroid (behind the retina). It is responsible for 10-15% of the cases of blindness in developed countries and may occur at any age. It is most common in young to middle-aged patients.

Types of uveitis are classified according to their anatomical localisation:

• Anterior uveitis: This is the most common form, it affects the iris (iritis) and, on occasions, the ciliary body (iridocyclitis). In this case, inflammation is prevalent in the anterior chamber of the eye.
• Intermediate uveitis: It affects the ciliary bodies and structures close to it, therefore inflammation is predominantly localised in the vitreous gel.
• Posterior uveitis: It affects the choroid (choroiditis), although it often affects the adjacent retina as it is in direct contact with it (chorioretinitis).
• Panuveitis: Sometimes the three parts of the uvea are compromised, leading to panuveitis.

The types of uveitis have different symptoms depending on the localisation. Anterior and intermediate uveitis present with redness, eye pain, tearing, photophobia (intolerance to light) and blurred vision. On the other hand, posterior uveitis usually presents with myodesopsia (perception of floaters), and a loss of vision which varies depending on the size and location of lesions.

Inflammation can occur in only one eye or both (simultaneously or separately in time). It can manifest itself acutely and suddenly or chronically with a more gradual and longer onset. Relapses or recurrences may be common.

The origins of intraocular inflammation may be very diverse. Uveitis may be the reflection of a disease occuring in other part of the body that has perhaps gone unnoticed, becoming a warning sign.

We can divide the causes of uveitis into infectious and non-infectious. The infectious agents that may cause intraocular inflammation include viruses (such as herpes), bacteria (such as tuberculosis, syphilis) or parasites (such as toxoplasmosis).

Toxoplasmosis is the most common infectious cause. This parasite, ingested in contaminated meat or vegetables, embeds itself in the retina and causes chorioretinitis which, once cured, leads to the appearance of a scar. When this occurs in the macula (the central part of the retina), the loss of vision is severe.

Non-infectious uveitis may affect the eye only or be related to general illnesses like idiopathic juvenile arthritis, ankylosing spondylitis, Behcet's disease, an inflammatory intestinal disease or sarcoidosis, etc.

We must remember that almost 35% of patients never get to the bottom of the cause or exact origin of the inflammation, so these are considered cases of idiopathic uveitis.

Treatment for uveitis depends on the cause of the inflammation, and should be started as soon as possible. In those of infectious origin, antibiotic treatment can cure it.

In most patients, corticosteroids are the mainstay of treatment in the acute phase, in form of eye drops, injections around or in the eye, or by systemic route (oral, intramuscular or intravenous).

In some cases of uveitis that are immunological, chronic and difficult to manage or have complications arising from the use of corticosteroids, it might be necessary to use immunomodulatory drugs to control inflammation (for a prolonged time or even lifelong). Some of these drugs might have side effects that require close monitoring.

In other cases, a surgical procedure with diagnostic purposes may be necessary in order to treat some of the complications associated with intraocular inflammation (especially in chronic forms), such as cataracts, glaucoma, persistent opacity of the vitreous body, intraocular bleeding, or retinal detachment.