AIM: To investigate the potential dissect element of elderly acute primary angle closure for early glaucoma prevention by measuring the parameters of anterior eye segment in the elderly with primary angle closure using ultrasound biomicroscopy(UBM)and A-scan ultrasonography.

METHODS: A retrospective study was performed based on the measured parameters with two samples. The first sample included 35 primary angle closure suspect eyes of 33 patients aging from 55 to 83 years old and the second sample included 25 healthy eyes of 25 randomly selected volunteers aging from 55 to 80 years old. The anterior chamber depth(ACD), angle opening distance(AOD500), iris-lens contract distance(ILCD),trabecular-ciliary process distance(TCPD), the ciliary processes around the scleral forward rotation angle(B angle),iris thickness(IT)were measured by UBM. Axial length(AL), lens thickness(LT), relative lens position(RLP)were measured by A-scan ultrasonography.

RESULTS: We compared the parameters measured for 35 primary angle closure suspect eyes and 25 healthy eyes. For Crystal related parameters, the RLP of angle closure suspect eyes decreased significantly(P<0.01)from that of healthy eyes, the LT of angle closure suspect eyes increased significantly(P<0.05)from that of healthy eyes, the ILCD of angle closure suspect eyes increased significantly(P<0.01)from that of healthy eyes; For ciliary body parameters, the TCPD, B angle of angle closure suspect eyes decreased significantly(P<0.01)from that of healthy eyes; For anterior chamber associated parameters, the ACD, AOD500 of angle closure suspect eyes decreased significantly(P<0.01)from that of healthy eyes. However, there was no difference in IT between the primary angle closure suspect eyes and the healthy eyes.

CONCLUSION: Lens forward positioning, lens thickness increase, and ciliary body position forward swing are high risk factors of elderly acute primary angle closure.