AIM: To analyze the difference of the angle between the long axis of lacrimal sac and bony nasolacrimal duct(BNLD)in patients with chronic dacryocystitis and normal eyes, and discuss the relationship between the angle and chronic dacryocystitis.

METHODS:A total of 218 patients(248 diseased eyes)from Sichuan Province who visited the ophthalmology department of our hospital from January 2016 to March 2019 were collected retrospectively. All patients underwent computed tomography dacryocystography(CT-DCG)immediately after bilateral lacrimal duct irrigation, and three-dimensional reconstruction of the nasolacrimal duct structure was performed. The structures of the nasolacrimal duct, lacrimal sac and its surrounding tissues were observed in the coronal position, and the lacrimal sac-BNLD angles of the diseased eyes and the normal eyes were measured respectively.

RESULTS:The lacrimal sac-BNLD angle of the diseased eyes \〖23.55°(17.30°, 29.90°)\〗 was higher than that of the normal eyes \〖20.05°(15.40°, 28.35°)\〗(P<0.05). Among them, the angle of the diseased eyes in female patients \〖24.60°(17.75°, 31.00°)\〗 was significantly higher than that in normal eyes \〖21.15°(15.10°, 27.35°)\〗(P<0.05), while there was no significant difference in the angle between the diseased eyes and normal eyes in male patients(P>0.05). In addition, the angle of the diseased eyes in the age group of 41-60 a \〖25.20°(17.90°, 33.00°)\〗 was significantly higher than that in normal eyes \〖21.60°(15.25°, 29.05°)\〗(P<0.05).

CONCLUSION: The angle between the long axis of lacrimal sac and bony nasolacrimal duct increased in patients with chronic dacryocystitis, which may be one of the factors causing the onset of chronic dacryocystitis in middle-aged and elderly women.