Association of Plasma Complement C3 Levels With Primary Angle-Closure Glaucoma in Older Women

Purpose: The plasma complement component (C)3 concentration and clinical characteristics of primary angle-closure glaucoma (PACG) subjects were analyzed to evaluate whether C3 levels were correlated with PACG severity.

Methods: Peripheral blood samples from subjects with PACG (n = 237) and normal controls (n = 158) were collected. The plasma levels of C3 were measured by immunoturbidimetry. The assessments of intraocular pressure; vertical cup/disc ratio (VCDR); central corneal thickness; axial length; anterior chamber depth; visual field-derived mean deviation; and mean sensitivity were performed by glaucoma specialists. Based on their sex and age, the PACG subjects were categorized into female (0-49 years, 50-59 years, 60-70 years, and 70+ years) and male (0-49 years, 50-59 years, 60-70 years, and 70+ years) subgroups.

Results: The mean plasma levels of C3 (101.71 ± 21.17 mg/dL) were significantly lower (P < 0.001) in PACG subjects compared with controls (110.68 ± 17.63 mg/dL). Plasma C3 concentrations were significantly lower (P < 0.001) in female subjects with PACG (100.74 ± 19.83 mg/dL) compared with controls (113.58 ± 18.80 mg/dL). A similar result was observed when plasma levels of C3 were compared between the PACG and control groups with respect to age (≥50 years). The mean plasma levels of C3 were lowest in the severe PACG group followed by moderate PACG and mild PACG, and the differences were significant (P = 0.003). Multivariable regression analyses showed that there was a significant correlation between C3 levels and VCDR (B = -0.310, P = 0.047).

Conclusions: Older women with PACG have lower plasma C3 levels, which were further demonstrated to be negatively associated with PACG severity. These findings suggest the involvement of C3 in the pathomechanisms of PACG in older women.