AIM: To determine the levels of aquaporin-1 (AQP-1) in the lens epithelial cells (LECs) of primary glaucoma and to clarify its correlation with lens thickness. METHODS: This study comprised 64 eyes of 64 patients with primary glaucoma, who were divided into 3 groups: 25 eyes of 25 patients with acute primary angle-closure glaucoma (APACG), 19 eyes of 19 patients with chronic primary angle-closure glaucoma (CPACG) and 20 eyes of 20 patients with primary open angle glaucoma (POAG). This study also included 12 eyes of 12 patients with senile cataract as controls. The levels of AQP-1 in LECs were examined by real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry. The lens thickness was measured by A-scan ultrasonography. RESULTS: The AQP-1 mRNA levels of LECs were 0.84±0.27, 0.69±0.34, 0.44±0.19 and 0.51±0.21 in APACG, CPACG, POAG and senile cataract group, respectively. The levels of AQP-1m RNA were significantly higher in PACG groups compared with those in senile cataract and POAG group (all P<0.05). The immunohistochemistry showed the AQP-1 expression were strong-positive in PACG groups, but weak-positive in senile cataract and POAG group. A positive correlation was found between AQP-1 mRNA levels and the lens thickness (r=0.645, P<0.001). CONCLUSION: These findings show that the higher expression of AQP-1 in LECs may contribute to increased lens thickness, which might be associated with the occurrence and development of PACG.