Purpose: To determine the incidence and prevalence of uveitis in a large, well-defined population in Northern California.

Design: Cross-sectional study using retrospective database and medical record review.

Participants: A group of 2070 people within 6 Northern California medical center communities (N = 731 898) who had a potential diagnosis of uveitis.

Methods: The patient database of a large health maintenance organization (2 805 443 members at time of the study) was searched for all patients who, during a 12-month period, had the potential diagnosis of uveitis. Detailed quarterly gender- and age-stratified population data were available. Medical records of patients who potentially had uveitis and who were members of the 6 target communities were reviewed by 2 uveitis subspecialists to confirm the diagnosis of uveitis and to establish time of onset. Demographic and clinical data were gathered for patients meeting the clinical definition of uveitis. Incidence rates were calculated by using a dynamic population model. Prevalence rates were based on the mid-study period population.

Main outcome measures: Presence and date of onset of uveitis.

Results: At midstudy, the population for the 6 communities was 731 898. During the target period, 382 new cases of uveitis were diagnosed; 462 cases of uveitis were diagnosed before the target period. These data yielded an incidence of 52.4/100 000 person-years and a period prevalence of 115.3/100 000 persons. The incidence and prevalence of disease were lowest in pediatric age groups and were highest in patients 65 years or older (P<0.0001). The prevalence of uveitis was higher in women than in men (P<0.001), but the difference in incidence between men and women was not statistically significant. Comparison between the group of patients who had onset of uveitis before the target period (ongoing uveitis) and the entire cohort of uveitis patients showed that women had a higher prevalence of ongoing uveitis than men and that this difference was largest in the older age groups (P<0.001).

Conclusion: In this largest population-based uveitis study in the United States to date, the incidence of uveitis was approximately 3 times that of previous U.S. estimates and increased with the increasing age of patients. Women had a higher prevalence of uveitis than men, and the largest differences were in older age groups.