Purpose: (1) To measure the corneal endothelium-Descemet membrane (EDM) layer thickness in Descemet membrane detachment (DMD) patients in vivo using high-definition optical coherence tomography (HD-OCT), and to investigate its correlation with age. (2) To explore whether the detachment time will affect the EDM thickness. (3) To explore whether the EDM thickness of cornea with DMD was different from that without DMD. Participants: Patients with DMD were divided into three groups. Group 1 included twenty-three patients whose Descemet membrane (DM) was partial or complete detached from the corneal stroma after various ocular surgeries. Group 2 included eight patients from group 1 who underwent twice HD-OCT examination on different days before the DM reattached to the stroma. Group 3 included nine patients from group 1 who had clear grayscale boundary between the DM and stroma in HD-OCT images after DM reattachment. Methods: All patients underwent HD-OCT and EDM thickness was measured using Image -Pro Plus 6.0. In Group 1, regression analyses were used to evaluate the correlation between EDM thickness and age, and the thickness difference between the <= 50-year-old group and the >50-year-old group was analyzed by independent sample t-test. In Group 2, paired samples t-test was used to check whether detachment time would affect EDM thickness. In Group 3, paired samples t-test was used to check whether the EDM thickness of cornea with DMD was different from that without DMD. p < 0.05 was considered significant. Results: In Group 1, the EDM thickness measured on the first post-operative day was 27.8 +/- 3.6 mu m, and a positive correlation was found between EDM thickness and age (r = 0.619, p < 0.05). The EDM thickness of <= 50-year-old group and >50-year-old group were 23.9 +/- 3.2 and 29.2 +/- 2.6 mu m, and there was a significant difference between the two groups (p = 0.001). In Group 2, the first measurement of EDM thickness was 27.5 +/- 4.0 mu m, the second measurement was 27.6 +/- 4.2 mu m, the interval between the two measurements was 2.1 +/- 1.6 days, and there was no significant difference between the two measurements (p = 0.328). In Group 3, the EDM thickness with DM detachment was 28.3 +/- 3.5 mu m, with DM reattachment was 23.4 +/- 2.4 mu m, there was a significant difference between the two measurements (p = 0.002). Conclusions: The EDM thickness in the state of DMD is thicker than its actual thickness in normal cornea, and EDM thickness of the >50-year-old group is much thicker than that of the <= 50-year-old group.