Association of serum and vitreous homocysteine and uric acid concentrations with post-vitrectomy prognosis in patients with proliferative diabetic retinopathy

BACKGROUND: Proliferative diabetic retinopathy (PDR) is a major cause of vision loss, often requiring pars plana vitrectomy (PPV). Systemic and intraocular metabolic alterations, including dysregulation of homocysteine (Hcy) and uric acid (UA), may influence surgical outcomes. While prior studies suggest associations between these biomarkers and retinal pathology, the role of these biomarkers in postoperative prognosis remains unclear. This study hypothesized that elevated serum and vitreous Hcy and UA levels are associated with visual, structural, and microvascular changes following PPV in patients with PDR. AIM: To evaluate the associations between serum and vitreous Hcy/UA concentrations with postoperative outcomes in patients with PDR following PPV. METHODS: In this prospective observational study at a tertiary care center, 44 patients with PDR and 46 non-diabetic controls undergoing PPV between June 2021 and December 2022 were enrolled. Serum and vitreous Hcy and UA levels were measured. Best-corrected visual acuity, multimodal retinal imaging, and capillary density metrics were evaluated preoperatively and postoperatively. Correlation analyses assessed the relationships between biomarkers and clinical outcomes. RESULTS: Patients with PDR showed significantly higher serum and vitreous Hcy and UA concentrations compared to those of controls. Serum Hcy and UA levels correlated with vitreous levels. In patients with PDR, elevated vitreous Hcy correlated with worse best-corrected visual acuity at 1 day and reduced peripapillary retinal nerve fiber layer thickness at 7 days and 90 days. It also correlated with foveal avascular zone enlargement at 90 days and inferior superficial capillary plexus (SCP) width density at 7 days. Vitreous UA had negative correlations at 30 days with nasal SCP length density and temporal/inner ring SCP width density. CONCLUSION: Vitreous, but not serum, Hcy predicts post-PPV impairment, underscoring the prognostic value of the local ocular environment over systemic factors in PDR.