Iritis means inflammation of the iris. The term is synonymous with anterior uveitis, when used to encompass inflammation of the iris root and ciliary body, but does not include more posterior inflammation.
It is uncommon, with an estimated annual incidence of 12-15 per 100,000 population. Every age may be affected, although it occurs most commonly between the third and fifth decades. Racial and genetic factors predispose susceptibility.
A triggering stimulus activates the inflammatory cascade that breaks down the blood - ocular barrier and releases white cells and fibrin into the anterior chamber.
The majority of episodes of acute iritis have no identifiable trigger, yet paradoxically it is a feature of many systemic and ocular diseases, especially those with infectious, traumatic and immune aetiology.
Ocular associations include trauma and infection. Trauma may be surgical, for example cataract surgery, or misadventure causing blunt or penetrating injury.
An especially fierce iritis is produced by retained organic ocular foreign body. Corneal infections cause iritis. Some medications, for example latanoprost drops, are also rarely associated.
Numerous systemic conditions are associated with iritis. Frequent culprits are sarcoidosis, HLA B27 spondyloarthropathies and autoimmune diseases in which altered immunity provokes inflammation of the iris.
Iritis is seen in conditions associated with lowered resistance to infection, as in systemic steroid use, AIDS and herpes zoster, and in infections such as TB, syphilis and other STIs.
Juvenile rheumatoid arthritis is the most common association with iritis in childhood, although granulomatous iritis is often due to sarcoidosis. Typically, iritis associated with active systemic disease responds poorly to standard treatment and may recur frequently.
Hypopyon in the anterior chamber of the eye in severe iritis
Iritis is one of three main intraocular causes of acute red eye (the other two being acute glaucoma and scleritis).
All three are distinguished from external red eye by the symptom triad of reduced vision, pain and photophobia.
In iritis, vision loss and pain are usually less severe, with photophobia being the prominent symptom.
Pen torch examination reveals conjunctival redness most marked around the periphery of the iris and a constricted pupil. If there have been previous episodes, the pupil may appear distorted because of fibrinous adhesions to the anterior lens surface. Commonly, ocular and systemic review is normal.
With slit lamp magnification, white cells can be seen floating in the anterior chamber and adhering to the internal corneal surface (keratic precipitates), sometimes with fibrin strands sticking the pupil to the anterior lens (posterior synecheae).
Severe cases may show clumps of white cells on the anterior iris or posterior cornea (granulomatous uveitis) or a fluid level in the inferior aspect of the anterior chamber (hypopyon).
Systemic investigation is not indicated for the first episode, unless it is unusually prolonged or robust inflammation is present. However, subsequent flare-ups should be worked up fully with immune profile serum ACE, ESR, tests for syphilis and radiology as indicated in the ocular and systemic review.
Iritis can be successfully treated with topical steroids and eye drops, but beware of complications
The principles of treatment are to reduce the inflammatory response with topical steroids, such as dexamethasone 0.1% drops 2-4 hourly; to prevent iris adhesion to anterior lens with cycloplegics such as cyclopentolate 1% drops once daily; and to treat the underlying cause if known.
Periocular steroid injection and systemic anti-inflammatory or immunosuppressive treatments may be indicated for very active iritis, although are usually reserved for inflammation involving posterior ocular tissue (pan-uveitis).
Once inflammation is under control, drops are gradually tapered in frequency and/or strength over several weeks as indicated by the response to treatment.
Very mild iritis is probably self-limiting and may not even present.
Promptly treated, even recurrent iritis has a good visual prognosis. However, if inflammation is not controlled cataract, glaucoma and degenerative corneal change (band keratopathy) occur as a complication of prolonged intraocular inflammation.
Long-term topical steroid use alone may cause cataract and glaucoma, in addition to making the cornea more vulnerable to infection, such as herpes simplex keratitis.
Therefore it is unwise to treat iritis with topical steroids without initial slit lamp examination and subsequent follow up of the treatment response and possible co-morbidities.
Idiosyncratic elevation of intraocular pressure can occur with topical steroids (steroid responder) and may need long-term glaucoma care even though the drops are stopped.
Iritis may present at any age, occurring in genetically-predisposed individuals, often with no apparent systemic association, a good response to topical steroids and no long-term sequelae.
However, iritis may also occur as a manifestation of other systemic or ocular disease and can cause permanent eye damage with consequent loss of sight, especially when managed sub-optimally.
Ms Vafidis is consultant ophthalmic surgeon at Central Middlesex Hospital, London Further reading
- Iritis and uveitis: www.emedicine.com/EMERG/topic284.htm
- Nussenblatt R, Whitcup S. Uveitis: Fundamentals and Clinical Practice, 3rd ed
- Philadelphia: Mosby/Elsevier Science, 2003.