Purpose: This study aimed to evaluate the prevalence of orbital conditions in a tertiary ophthalmic outpatient hospital in Sao Paulo, Brazil, with a focus on the main diagnoses and their distribution. Methods: A retrospective chart review was conducted involving patients registered and admitted to the orbital disease unit at the Department of Ophthalmology, University of S & atilde;o Paulo Medical School, from January 2004 to March 2018. A total of 838 medical charts were analyzed, of which 37 were excluded due to incomplete data. The remaining charts were categorized into eight diagnostic groups: Graves' orbitopathy, inflammatory disorders, tumors, vascular lesions, acquired structural abnormalities, congenital structural abnormalities, infectious diseases, and others. Results: Of the 837,300 ophthalmological appointments, 3,372 (0.4%) were related to orbital diseases. The study included 801 patients, of whom 63.45% were women. The patients' mean age was 42.86 years. Graves' orbitopathy was the most common (55%), followed by tumor (17%), inflammatory disorders (9%), vascular lesions (7%), acquired structural abnormalities (5%), congenital structural abnormalities (4%), others (2%), and infectious diseases (1%). The study found significant differences in the incidence and types of orbital diseases, indicating the specialized nature of tertiary care and referral biases. Conclusion: Published data on epidemiological orbital diseases is scarce. Therefore, this study focused on the diverse nature of orbital diseases and their low incidence among ophthalmology appointments. The major trends align with other epidemiological studies, demonstrating a preponderance of Graves' orbitopathy in middle-aged adults and a bimodal distribution of tumors. These findings are essential in shaping resident training programs and healthcare policies, particu larly in tertiary settings. Understanding the epidemiology of orbital diseases can improve diagnostic accuracy, treatment approaches, and patient outcomes as well as support future systemic prospective studies.
