Most cases of uveitis occur because of the following factors:
- Autoimmune diseases (e.g., reactive arthritis, psoriasis, multiple sclerosis)
- Infections (e.g., Lyme disease, tuberculosis, herpes)
- Side effects of certain medications
- Injury to the eye
A significant proportion (up to 50%) of uveitis cases may occur without a known cause (termed as ‘idiopathic’ uveitis). 
The causes of uveitis vary by geographic location. A recent epidemiological review has shown that uveitis due to infectious causes is more common in developing countries (30–60% cases) whereas uveitis due to non-infectious causes is more prevalent in developed countries.