Laboratory Workup in Pars Plana Diagnostic Vitrectomy: A Real-World Multidisciplinary Retrospective Case Series of Brazilian Patients with Uveitis

PURPOSE Diagnostic vitrectomy is a valuable tool for elucidating the etiology of uveitis, particularly when an intraocular malignancy is suspected. This study aimed to evaluate the diagnostic contribution of laboratory analyses performed on vitreous specimens obtained via vitrectomy at a Brazilian tertiary referral center.

METHODS We conducted a retrospective study of patients who underwent pars plana vitrectomy for diagnostic purposes between January 2014 and December 2025. Undiluted vitreous samples were submitted to interleukin profiling (0.1 mL), cytology (0.5 mL), flow cytometry (0.3 mL), polymerase chain reaction (PCR) (0.2 mL), and microbiological testing (0.1-0.3 mL); not all tests were performed in every case. Final diagnoses were based on comprehensive assessment of clinical history, disease course, therapeutic response, and intraocular fluid analysis.

RESULTS Twenty patients were included over an 11-year period. Median time from symptom onset to surgical intervention was 4.0 months (IQR 2.0-8.7). Diagnostic vitrectomy confirmed intraocular malignancy in 8 patients, established by cytology (n = 1), flow cytometry (n = 3), elevated IL-10/IL-6 ratio (n = 3), and a combination of all three methods (n = 1). Among patients with presumed infectious or non-malignant uveitis, final diagnoses included CMV retinitis (n = 1), ocular toxoplasmosis (n = 3), herpetic uveitis (n = 1), fungal endophthalmitis (n = 4), and idiopathic uveitis (n = 3).

CONCLUSION These findings provide a realistic overview of the diagnostic approach achievable in a multidisciplinary, real-world setting in South America. Strategic analysis of vitreous samples, guided by clinical suspicion and tailored laboratory testing, allows diagnostic vitrectomy to play a pivotal role in confirming infectious etiologies anduncovering masquerade syndromes associated with intraocular malignancies.