Keratoconus (KC) is a controversial ophthalmological disease, often considered both multifactorial and multigenic with poor or not entirely understood etiopathogenesis. Corneal collagen crosslinking (CXL) procedure is the most common surgical therapy for KC which both slows corneal thinning and halts disease progression. While extensive studies provide consistent evidence on systemic oxidative stress in KC patients and animal models, little is known on the tear fluid oxidative stress markers such as antioxidant enzymes activity or lipid peroxidation markers. Also, little is known considering the oxidative status dynamics following CXL. In this way, we aimed to evaluate three oxidative stress markers in the tears of KC patients before and after CXL procedure. Total superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic activity and malondiladehyde (MDA) levels were assessed from the tears of 20 kC patients who received the recommendation for CXL procedure. Significantly decreased SOD activity (p = 0.0014) was observed in KC patients tears, as compared to age and sex-matched controls which could lead to significant lipid peroxidation boost (p < 0.001). Significantly higher GPx enzyme activity was observed in KC patients, as compared to control (p < 0.001), suggesting a compensatory response to intense lipid peroxidation. Following CXL, SOD activity significantly decreases and GPx activity extensively increases, as compared to baseline KC levels and controls (p < 0.001). This work provides additional evidence on oxidative stress status in the tears of KC considering general oxidative stress markers dynamics both before and after the CXL procedure. We also demonstrated that the CXL procedure could have further relevance in the management of this disorder.

中文翻译：

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角膜胶原交联之前和之后，圆锥角膜患者眼泪中的氧化应激标志物动力学。

圆锥角膜病（KC）是一种有争议的眼科疾病，通常被认为是多因素的和多基因的，其病因或病因尚不完全清楚。角膜胶原交联（CXL）手术是KC最常见的外科手术疗法，既可以减慢角膜变薄，也可以阻止疾病进展。尽管广泛的研究为KC患者和动物模型中的全身氧化应激提供了一致的证据，但对于泪液氧化应激标记（例如抗氧化酶活性或脂质过氧化标记）知之甚少。同样，考虑到CXL之后的氧化态动力学，人们所知甚少。通过这种方式，我们旨在评估CXL手术前后KC患者眼泪中的三种氧化应激标志物。根据接受CXL手术建议的20 kC患者的​​眼泪评估了总超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GPx）的酶活性和丙二醛（MDA）水平。与年龄和性别匹配的对照组相比，在KC患者眼泪中观察到SOD活性显着降低（p = 0.0014），这可能导致脂质过氧化作用明显增强（p <0.001）。与对照组相比，在KC患者中观察到明显更高的GPx酶活性（p <0.001），表明对强烈的脂质过氧化的代偿反应。与基线KC水平和对照相比，CXL后，SOD活性显着降低，GPx活性大幅提高（p <0.001）。考虑到一般氧化应激标记物在CXL手术前后的动力学变化，这项工作为KC眼泪中的氧化应激状态提供了补充证据。我们还证明了CXL程序可能在这种疾病的治疗中具有进一步的相关性。