Serum Serine as a Metabolic Marker of Optic Neuropathy in Patients with Type 2 Diabetes Mellitus After Vitreoretinal Surgeries.

Background: Optical neuropathy is a severe complication in patients with type 2 diabetes mellitus (T2DM) undergoing vitreoretinal surgeries. Early diagnostic indicators are critical to preventing irreversible vision loss. This study aimed to evaluate the alterations in blood serum amino acid profiles, with a specific focus on serine levels, and their potential clinical association with the severity of neuroretinal impairment. Methods: The clinical cohort included 28 patients aged 32 to 77 years with T2DM following vitreoretinal interventions. Visual field functional status was assessed using Humphrey automated perimetry, with mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI). Structural changes were quantified using optical coherence tomography (OCT) to measure peripapillary retinal nerve fiber layer (RNFL) thickness. Serum amino acid profiles were determined using an ion-exchange chromatography amino acid analyzer, alongside a reference group (n = 12). Results: All patients presented with moderate-to-severe visual field impairment. A profound decline in serum serine levels was observed in diabetic patients compared to the reference group (p < 0.001). The reduction in serine content closely mirrored both the degree of retinal sensitivity loss (MD and PSD values) and the number of thinned peripapillary RNFL sectors. Notably, the compensatory synthesis of serine via glycine cleavage appeared insufficient, as evidenced by a concomitant statistical decrease in glycine content (p < 0.05). No significant differences in serine levels were found between the subgroups when stratified strictly by age or isolated severity stages. Conclusions: It was demonstrated that the decline in serum serine levels in patients with T2DM following vitreoretinal interventions is significantly associated with the severity of optic neuropathy as assessed by optical coherence tomography (OCT). Consequently, serum serine may serve as a valuable dual biomarker, acting as a prognostic indicator for retinopathy progression and a predictive marker for early-stage neuropathy development.