BACKGROUND: Glaucoma is a common cause of blindness in the world as well as in Vietnam. It is treated by many different methods but trabeculectomy is still the most popular and highly effective surgical method to treat this condition. AIM: To analyze the status of 5 years filtering blebs following trabeculectomy and to explore multiple factors associated with filtering blebs. METHODS: This is a retrospective, cross-sectional descriptive study. Eyes had been performed trabeculectomy for 5 years were included in these results. The filtering blebs were assessed using slit lamp and OCT. the OCT captured bleb area to evaluate fluid subconjunctival spaces, thickness and height of bleb and to evaluate the related factors RESULTS: A group of 106 primary glaucoma eyes of 97 patients (88 patients with 1 eye, 9 patients 2 eyes) had been performed trabeculectomy for 5 years were taken OCT anterior image. The proportion of female patients is 1.5 times that of male patients. IOP was controlled with or without topical medication in all eyes. The filtering bleb had a high echo reflection, which accounted for 42.5%, the average echo reflection was 38.6%, the low echo reflection response of 18.9%. 66% of the eyes had the aqueous space under the conjunctiva, 65.1% have the aqueous space under sclera flap, the average height of the bleb on OCT was 0.4 mm ± 0.3 mm. Young patients often have a higher rate of bleb fibrosis and loss of function than older patients CONCLUSION: OCT is capable of assessing the function of bleb. After 5 years of trabeculectomy, on the OCT image, most cases of blebs are maintaining drainage function.