Association Between Serum Complement C3 Levels and Age-Related Cataract.

Purpose: The serum complement component 3 (C3) concentration and clinical characteristics of age-related cataract (ARC) subjects were analyzed to evaluate whether serum C3 levels are correlated with ARC.

Methods: A total of 492 ARC patients and 466 normal subjects from the Department of Ophthalmology and Visual Science, Eye and ENT Hospital of Fudan University, Shanghai, China, were consecutively recruited into this study between June 2014 and May 2017. Immunoturbidimetry was used to measure the serum C3 levels. Clinical information (intraocular pressure, visual acuity, central corneal thickness, axial length, vertical cup/disc ratio) and demographic information were obtained. Based on sex and age, the ARC subjects were categorized into female (50-60 years, 61-70 years, and 71+ years) and male (50-60 years, 61-70 years, and 71+ years) subgroups.

Results: The mean serum C3 level was significantly lower in the ARC group (100.97 ± 18.22 mg/dL) in comparison to the control group (123.27 ± 22.51 mg/dL) (t = 16.888, P < 0.001). A similar result was also observed when the serum C3 levels were compared between the ARC and control groups with respect to sex and age. The mean serum C3 level was lowest in the nuclear ARC subgroup (98.63 ± 18.76 mg/dL) followed by the cortical ARC subgroup (102.26 ± 18.04 mg/dL) and the posterior subcapsular ARC subgroup (103.80 ± 17.20 mg/dL), and the differences were significant (P = 0.037). Logistic regression analyses revealed that complement C3 (odds ratio [OR] = 0.924, 95% confidence interval [CI] = 0.913-0.935) was associated with ARC.

Conclusions: ARC patients have lower serum C3 levels, which were further demonstrated to be correlated with the onset/development of ARC. These findings suggest the involvement of C3 in the pathomechanisms of ARC.