Antioxidant Capacity in Fuchs’ Dystrophy and Its Relationship with Cataract: A Pilot Study

<b>Background/Objectives:</b> The aim of this study was to compare the level of total proteins and antioxidant capacity in the corneal endothelium of patients with endothelial decompensation, due or not due to a Fuchs' endothelial dystrophy (FECD), and analyze the influence of cataract formation. <b>Methods:</b> Endothelial cells from 27 patients with endothelial dystrophy and 6 from healthy human donors were used, distributed into four groups according to the presence of Fuchs' Dystrophy and cataract. <b>Results:</b> Protein levels differed significantly among the five study groups (Kruskal-Wallis H = 12.19, <i>p</i> = 0.016). Patients with FECD, particularly those with concomitant cataract, showed the highest median protein concentrations, whereas lower values were observed in non-FECD groups. Post hoc Dunn's test revealed a significant difference only between the non-FECD with cataract group and the controls (<i>p</i> < 0.05). The antioxidant capacity/protein ratio showed a marked variability across groups, with higher median values in non-FECD patients and greater dispersion in cataract groups; however, no statistically significant differences were detected (H = 5.58, <i>p</i> = 0.134). These findings highlight the differences in protein content and antioxidant defenses related to FECD and cataract status. <b>Conclusions:</b> Fuchs' endothelial dystrophy is associated with higher protein levels and a moderately elevated but heterogeneous antioxidant capacity in the corneal endothelium, reflecting adaptive responses to chronic oxidative stress. In contrast, no FECD eyes, particularly those with cataract, showed lower or more variable antioxidant capacity, indicating reduced or inconsistent protective mechanisms.