Etiology of hypopyon in patients presenting acutely to the emergency eye department and characteristics of hypopyon uveitis.

Objective: To examine the etiology of undifferentiated hypopyon presenting acutely and to better characterize hypopyon uveitis.

Methods: Patients with hypopyon were retrospectively identified from presentations to the emergency eye department between January 2015 and 2022 and also from a uveitis database of 3,925 patients seen between January 2008 and January 2022. A total of 426 episodes of hypopyon occurred in 375 eyes in 359 patients, and medical records were reviewed for each patient.

Results: In all, 222 hypopyon episodes were due to uveitis, and 204 were due to nonuveitic causes. The most common cause of hypopyon was HLA-B27-associated uveitis in 146 patients (34.3%). The next most common causes were infectious keratitis in 125 patients (29.3%) and endophthalmitis in 63 patients (14.8%). Compared with those presenting with nonuveitic hypopyon, patients with uveitis tended to present younger (p < 0.001), were more likely to be male (p < 0.0001), had better initial and final visual acuities (p < 0.001), and had lower intraocular pressures (p = 0.030).

Conclusion: About half of the cases of hypopyon were secondary to uveitis, most of them being associated with HLA-B27 conditions with a good prognosis, and the other half were secondary to infectious keratitis and endophthalmitis with a poor prognosis.