Ganglion cell layer thinning in diabetic patients without retinopathy: related or unrelated to total macular thickness?

ABSTRACT Purpose: Reduction of ganglion cell layer thickness may occur in diabetic patients without retinopathy. The relationships of this preclinical finding with retinal thickness or reduced parafoveal vessel density have not been established. This study investigated the relationships of ganglion cell layer thickness with retinal thickness and parafoveal vessel density in patients with and without diabetes. Methods: This was an observational, cross-sectional, prospective study that used optical coherence tomography angiography to compare non-diabetic patients (group 1) with diabetic patients without retinopathy (group 2). Ganglion cell layer thickness, macular thickness, and parafoveal vessel density (central, inner, and complete) medians were compared between groups (Mann-Whitney U test), and their relationships were assessed in each group (Spearman Rho test). Results: In total, 68 eyes were included in this study: 34 in group 1 and 34 in group 2. Ganglion cell layer thickness did not differ between groups in any sector. There were strong positive correlations between fields 2 (superior parafoveal), 3 (temporal parafoveal), and 4 (inferior parafoveal) of the optical coherence tomography macular thickness map and the ganglion cell layer thickness in all sectors in both groups. Central vessel density mean was lower in diabetic patients. In group 1 alone, thickness changes in the inferior and nasal inferior ganglion cell layer sectors were partially explained by inner vessel density (r2=0.32 and r2=0.27). Conclusions: Mean ganglion cell layer thickness was not lower in diabetic patients without retinopathy than in non-diabetic patients. Moreover, it exhibited a substantial correlation with total macular thickness. Parafoveal vessel density decreased before ganglion cell layer thinning was observed.

摘要
研究目的：无糖尿病视网膜病变的糖尿病患者可能出现神经节细胞层（ganglion cell layer, GCL）厚度降低，但该亚临床表现与视网膜厚度或凹旁血管密度降低之间的关联尚未明确。本研究旨在探讨合并与未合并糖尿病的患者中，神经节细胞层厚度与视网膜厚度及凹旁血管密度的相关性。
研究方法：本研究为观察性、横断面、前瞻性研究，采用光学相干断层扫描血管造影（optical coherence tomography angiography, OCTA）技术，比较非糖尿病患者（组1）与无糖尿病视网膜病变的糖尿病患者（组2）的相关指标。分别比较两组的神经节细胞层厚度、黄斑厚度及凹旁血管密度（中心区、内环区及全区域）的中位数（采用曼-惠特尼U检验），并在两组内分别评估各指标间的相关性（采用斯皮尔曼ρ检验）。
研究结果：本研究共纳入68只患眼，组1与组2各34只。两组各分区的神经节细胞层厚度均无显著差异。在两组中，光学相干断层扫描黄斑厚度图的2区（凹旁上方区）、3区（凹旁颞侧区）及4区（凹旁下方区）与所有分区的神经节细胞层厚度均呈强正相关。糖尿病患者的中心凹旁血管密度均值低于非糖尿病患者。仅在组1中，下方及鼻下方神经节细胞层分区的厚度变化可部分由内环区血管密度解释（r²=0.32及r²=0.27）。
研究结论：无糖尿病视网膜病变的糖尿病患者的平均神经节细胞层厚度并未低于非糖尿病患者。此外，该厚度与全黄斑厚度呈显著正相关。凹旁血管密度的降低早于神经节细胞层厚度的变薄。