Copper, Lysyl Oxidase Activity, and Collagen in Aqueous Humour of Primary Glaucoma: An Association with Clinical Parameters

Abstract

Introduction: To measure copper (Cu), lysyl oxidase (LOX) activity, and collagen levels in aqueous humour (AH) of primary glaucoma patients and correlate with clinical parameters. Methods: 120 patients with 40 each of primary open angle glaucoma (POAG), primary angle closure glaucoma (PACG), and cataract controls were recruited in this case-control study. AH samples were collected during the trabeculectomy and cataract surgeries. Cu levels were measured using an atomic absorption spectrophotometer. LOX unit activity was determined by Amplex Red assay and collagen concentration by Sirius red assay. Results: Significantly higher levels of Cu expressed as median (IQR) µmol/L were observed in POAG (p = 0.008) and PACG (p = 0.005) compared to controls. The LOX activity was increased in POAG and PACG (p = 0.04) compared to controls represented as median (IQR) µmol/min. The collagen levels given as median (IQR) mg/ml showed an insignificant increase in POAG and PACG compared to controls (p = 0.78). The LOX unit activity was correlated with visual field index (VFI), which showed a significant increase with the progression of the diseases (p < 0.05), whereas Cu levels were negatively correlated with LOX activity in AH. Cu and LOX activity showed weak correlation with YAG peripheral iridotomy (YAGPI), duration of anti-glaucoma medications, and highest preoperative intraocular pressure. Conclusion: Elevated Cu and LOX activity was observed in both POAG and PACG groups compared to controls. LOX activity showed notable increase with VFI as the severity of the disease. Although Cu levels are increased in glaucoma, it’s insufficient to significantly increase the activity of LOX.