Purpose: To evaluate the differences in ocular biometric parameters between eyes with primary angle closure (PAC) with and without visible ciliary body processes (CBP) (PAC+CBP and PAC-CBP) and normal open-angle controls.
Study design: Cross-sectional study.
Methods: Eyes with PAC and normal open-angle controls underwent detailed ocular examinations and gonioscopy to determine the visibility of the CBP. The following ocular biometric parameters were determined using A-scan ultrasound biometry: axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous length (VL). The lens-axial length factor (LAF) and relative lens position (RLP) were also calculated. Continuous variables were assessed by analysis of variance with Bonferroni correction. Multiple linear regression analysis was performed to adjust for confounding factors. Area under the receiver operating characteristic curves were calculated to determine the diagnostic capability of biometric parameters.
Results: 84 PAC+CBP eyes, 57 PAC-CBP eyes, and 32 normal open angle control eyes were evaluated. The means of the ocular biometric values were significantly different among the three groups. AL, ACD, LT, VL, LAF, and RLP were also significantly different among the three groups in the multivariate regression analysis. AL, ACD, and VL were lower in the PAC+CBP group and LT, RLP, and LAF were greater in the PAC+CBP group than in the PAC-CBP and control groups. LAF ≥ 2.4 is the cutting point with the highest sensitivity and specificity to differentiate PAC+CBP from PAC-CBP.
Conclusions: The ocular biometric parameters in the PAC+CBP group were more strongly associated with a crowded anterior segment than in the other groups. Visibility of CBP in PAC-affected eyes may serve as a surrogate for an anterior segment crowding mechanism and help to select the most appropriate treatment in individual cases.
Keywords: Ciliary body processes; biometry; mechanism; primary angle closure.