Glaucoma is known as one of the 3 major causes of blindness, along with age-related macular degeneration and diabetic retinopathy. In early stages of its development, patients rarely experience noticeable symptoms, leading to significant advancement of the disease by the time they visit a hospital [1]. As such, eye diseases associated with vision loss do not allow for the recovery of damaged optic nerves [2]. They can severely diminish a patient’s quality of life, including physical limitations. Therefore, the importance of early diagnosis and treatment should be emphasized. Currently, the elderly accounts for 18.4% of the Korean population [3]. The number of patients with severe ophthalmic diseases such as glaucoma is increasing as the aging population accelerates. The socio-economic burden is also increasing, making ophthalmic diseases a major health problem [2].

Glaucoma is a disease in which visual field defects occur due to abnormalities in the optic nerve that transmits light received by the eyes to the brain and is defined as progressive optic neuropathy. It is a serious eye disease that eventually leads to blindness if left untreated and undetected at an appropriate time [4]. According to previous studies, the prevalence of glaucoma among adults aged 30 or older in Korea was 0.2% [5], and the number of people with glaucoma is expected to increase steadily as the population ages rapidly [6]. Glaucoma is sometimes caused by aging [7], but aging is not the only cause of glaucoma. It is also known to be caused by various factors such as family history, myopia, high blood pressure, diabetes, smoking, eye pressure, and diet [8]. Recently, studies have emphasized the importance of nutrient intake in suppressing the progression and onset of glaucoma [9], and it has been reported that the intake of certain antioxidant nutrients inhibits the progression of glaucoma [10].

Many studies have been conducted on health and behavioral factors related to glaucoma, but studies on the relationship between nutrient intake and glaucoma are insufficient [2]. In particular, there is a lack of research in Korea that reveals the relationship between eye diseases and nutrition, and previous studies that have attempted analysis did not find significant differences between eating habits and eye diseases [11]. Therefore, this study was conducted to provide a basis for the need for diet and nutrition management in preventing and managing ophthalmic diseases, which have recently emerged as a major health problem, by comparing the food and nutrient intake of subjects according to the prevalence of glaucoma.

Using data from KNHANES 2017 and 2018, this study attempted to lay the basis for the need for dietary habits and nutritional management to prevent and manage eye diseases by comparing nutrient intake according to the prevalence of glaucoma in Korean seniors aged 60 or older. As a result, 3 considerations could be made.

First, when comparing the vitamin C intake between the glaucoma group and the non-glaucoma group, it was found that the non-glaucoma group had a higher intake of vitamin C than the glaucoma group. Studies by Ramdas et al. [13] have reported a positive effect of vitamin C intake from the diet on glaucoma, and studies by Wang et al. [14] have also indicated that vitamin C intake can reduce the prevalence of glaucoma. Furthermore, studies conducted by Giaconi et al. [15] have supported the beneficial effect of vitamin C intake on glaucoma, suggesting that a higher consumption of vitamin C-rich foods such as vegetables and fruits may lower the risk of developing glaucoma. In this study, although the average vitamin C intake of the non-glaucoma group was higher than that of the glaucoma group, it was much lower than the recommended intake of 100 mg/day, and the difference between the 2 groups was also small. Therefore, it is necessary to investigate the correlation between vitamin C intake and glaucoma in a different study design.

Second, comparing niacin intake of glaucoma group and non-glaucoma group, the amount of niacin intake in the glaucoma group was higher than in the non-glaucoma group. According to previous studies on niacin and glaucoma, the higher the intake of niacin, the lower the likelihood of developing glaucoma [16]. Jung et al. [17] studies also reported that niacin intake was significantly lower in glaucoma patients. However, according to a study on the link between eye pressure and niacin intake, known as a major risk factor for glaucoma, the higher the niacin intake, the higher the eye pressure, and the possibility of glaucoma risk was indirectly increased [18]. Lee et al. [19] reported there was no significant link between the niacin intake. Currently, there is a lack of prior research on niacin intake and glaucoma, and inconsistent results have been shown, so further research on the relationship between niacin and glaucoma is necessary.

Third, comparing omega-3 fatty acid intake of glaucoma group and non-glaucoma group, the omega-3 fatty acid intake in the non-glaucoma group was higher than in the glaucoma group. The intake of omega-3 fatty acids has been reported to decrease intraocular pressure, reducing the risk of glaucoma [102021]. Nguyen et al. [22] reported that an increase in intraocular pressure was a strong factor in glaucoma progression and that the risk of glaucoma increases by 11% with every 1 mmHg increase. Experiments with mice supported the notion that omega-3 fatty acid intake helped reduce intraocular pressure. These experiments suggested that the intake of omega-3 fatty acids increased aqueous outflow and resulted in a decrease in intraocular pressure in mice [23]. Based on these findings, it is suggested that adequate intake of omega-3 fatty acids may reduce the risk of glaucoma in individuals aged 60 and above. Therefore, it is recommended for older adults to ensure sufficient consumption of omega-3 fatty acids.

Fourth, the glaucoma group had lower intake of meats, fish, and shellfish compared to the non-glaucoma group. Numerous studies have investigated the associations between glaucoma and specific food groups. However, a definitive correlation has not yet been established. Previous studies have suggested that a well-balanced diet rich in green vegetables can inhibit the development and progression of glaucoma [24]. Furthermore, the intake of fruits and vegetables that are rich in vitamins has been linked to a reduced risk of glaucoma [15]. Additionally, Kim [11] found that consuming blue-backed fish had a positive effect on glaucoma, which aligns with the findings of the present study. However, further research is needed to determine whether the intake of specific food groups is indeed related to glaucoma. Therefore, future investigations should focus on exploring the relationships between glaucoma and various food groups.

Our study has several limitations. Firstly, this study utilized 24-h recall data from the KNHANES. The 24-h recall is a method used to investigate the type and quantity of food consumed in the past 24 h or the previous day. Considering that the subjects in this study were over 60 yrs old, it is believed that the survey was more challenging compared to a younger age group. Additionally, relying solely on this data may not accurately represent the usual food consumption or intake amounts of the subjects. Secondly, current study was a cross-sectional study and conducted as part of the KNHANES, which limits our ability to establish a causal relationship between nutrient intake and glaucoma. To clearly confirm any causal relationships, future studies utilizing prospective cohort surveys are needed. Thirdly, there was a significant difference in the number of subjects between the 2 groups, with a smaller number of subjects in the glaucoma group.

In summary, the results of the present study revealed that the glaucoma group showed lower intakes of meats, fish, shellfish, omega-3, and vitamin C compared to the non-glaucoma group. Therefore, there was an association between food and nutrient intake and glaucoma in older adults. A prospective study is needed to clarify the causal relationship between food, nutrient intake, and glaucoma for future research.