## 4 Discussion
Among obesity indicators, waist circumference has demonstrated the highest correlation with visceral fat, suggesting its importance as a key measure of abdominal obesity [26]. Based on these findings, future studies should consider alternative indicators such as waist circumference, waist-to-hip ratio (WHR), waist-to-height ratio (WHTR), body fat percentage, and visceral fat area to better understand the relationship between obesity and cataract prevalence. The results of this study suggest that DII influences cataract prevalence via metabolic disease. Diets high in DII are high in saturated fats, simple sugars, trans fats, and high sodium, which increase the production of pro-inflammatory cytokines (IL-6, TNF-\(\alpha\), CRP, etc.) in the body as a mechanism of inflammation [15]. Chronic inflammation triggered by such a diet induces oxidative stress, impairs metabolic function, and increases the risk of metabolic diseases. Metabolic disease is an important mediating factor in the prevalence of cataracts, with diabetes impairing vascular function due to elevated blood glucose concentrations, disrupting glucose metabolism in the lens and inducing oxidative stress [27]. This oxidative damage can cause protein denaturation and lens opacity, thereby accelerating cataract formation [7]. Visual impairment caused by protein denaturation and lens opacity, such as reduced visual acuity, visual field defects, and visual distortion, can lead to difficulties in daily life and significantly impact physical functioning and quality of life [5]. Hypertension also impairs blood flow, reducing the supply of oxygen and nutrients to ocular tissues [8; 24]. Dyslipidemia leads to abnormalities in lipid metabolism in the blood, which increases lipid peroxidation reactions, which in turn induces oxidative stress, which can damage the lens cell membrane and increase the prevalence of cataracts [9; 25]. Thus, it can be interpreted that a diet high in DII increases inflammation levels in the body, leading to the development of metabolic diseases, and these metabolic diseases mediate cataract development through oxidative stress and impaired blood flow. This study used energy-adjusted DII values (per 1000 kcal intake) to account for differences in total energy intake among participants. The DII was categorized into tertiles, and SEM was used to analyze the mediating effect of metabolic diseases on the relationship between DII and cataract prevalence. As a result, cataract prevalence increased in the HIGH DII group, and the indirect effect of DII on cataract prevalence became significantly stronger when hypertension and dyslipidemia acted as mediators. These findings align with previous research, which has shown that higher DII levels increase the risk of metabolic diseases [17], and that these metabolic diseases, in turn, contribute to a higher risk of cataract development [28; 29]. Previous studies have reported that anti-inflammatory dietary patterns, including fruits, vegetables, fatty fish, nuts, and olive oil, have beneficial effects on metabolic health [30]. In particular, the Mediterranean diet, rich in antioxidant and anti-inflammatory components, has been shown to reduce systemic inflammation and lower the risk of metabolic diseases [31; 32]. These findings suggest that lowering DII may play a crucial role in not only preventing metabolic diseases but also reducing cataract risk. Based on these results, a structured anti-inflammatory diet may be particularly beneficial for individuals with metabolic conditions such as hypertension, diabetes, and dyslipidemia, contributing to cataract prevention and management. This study differs from previous research in that it did not merely analyze simple associations but instead utilized SEM to examine the mediating effect of metabolic diseases on the relationship between DII and cataract prevalence.