Introduction: Obesity is a chronic disease whose prevalence is increasing and is now considered a global epidemic. Eye diseases are also on the rise worldwide and have a serious impact on quality of life, increasing healthcare costs. The relationship between obesity and ocular pathology has not been well elucidated, nor is it pathologically homogeneous: they appear to be related to some extent to excess body fat, in particular to the distribution of adipose tissue and its ectopic deposition. A recent foreign review summarized the relationship between obesity and eye disease.
Through systematic searches of MEDLINE/PubMed, CINAHL, EMBASE and Cochrane Library databases from 1984~2024, and browsing related websites, the following conclusions were drawn: there is clear evidence that obesity is associated with several eye diseases, and waist circumference (WC) and waist-to-hip ratio (WHR) have a stronger positive correlation with eye diseases than body mass index (BMI).
Obesity, the "root of all evil".
Globally, at least 2.8 million people die each year from overweight or obesity-related pathologies, and an estimated 35.8 million people (2.3%) worldwide are caused by overweight or obesity. Increased BMI is an important risk factor for NCDs, and the risk of developing it increases with BMI.
Several common diseases caused by obesity:
1. Cardiovascular diseases (mainly heart disease and stroke) have been the leading cause of death in recent decades;
2, type 2 diabetes;
3. Musculoskeletal diseases (especially osteoarthritis, a highly disabling degenerative joint disease);
4. Certain cancers (including endometrial cancer, breast cancer, ovarian cancer, prostate cancer, liver cancer, gallbladder cancer, kidney cancer and colon cancer);
5. Eye diseases.
Figure 1. Trends in the prevalence of obesity among people aged ≥ 20 years in the world from 1980~2019
"Stealing the Light" eye disease
Like obesity, eye disease is a serious public health problem. According to the Global Burden of Disease Study (2021), the number of people with moderate to severe visual impairment worldwide is expected to increase from 216.6 million in 2015 to 587.6 million in 2050 by 2050.
Little is known about the effects of being overweight on eye health. There are many eye diseases associated with obesity, among which the most studied are glaucoma, cataracts, age-related macular degeneration (AMD), diabetic retinopathy (DR), and dry eye syndrome (DES). The effects of obesity on the ophthalmic system are complex and diverse, among which inflammation, oxidative stress, and hormonal imbalance are important causes, and metabolic syndrome and related cardiovascular diseases may also be involved in the pathogenesis of ocular diseases.
What is the relationship between obesity and eye diseases?
In a systematic review of prospective studies, the relationship between obesity and different anthropometric methods (BMI, WC, WHR) and 4 major and age-related ocular pathologies (cataract, glaucoma, AMD, and DR) was explored.
In Asian populations, there was a significant association between BMI and increased intraocular pressure (IOP). In Western populations, obesity was positively associated with AMD, but not in Asian populations. Similarly, obesity was positively correlated with DR in Western populations and negatively associated with Asian populations. In addition, the study also showed that WC is often a better risk indicator for AMD and DR than BMI in Western, Asian, and other non-Western populations.
More longitudinal studies are needed to clarify consistent observations about the role of obesity and visceral fat in eye disease, particularly on the effectiveness of abdominal obesity and weight loss in preventing or improving age-related eye diseases.
Obesity and cataracts
A 2000 report showed that BMI and WHR were found to be independent risk factors for cataract development in 17,150 men who were followed for 5 years. Elevated levels of CRP, a systemic marker of inflammation, are associated with an increased risk of cataracts; In addition, obesity may be associated with subclinical systemic inflammation and oxidative stress, which should be aggressive and promote the development of cataracts. There are also well-established systemic risk factors for adult-onset cataract and are often associated with obesity, such as hypertension, hyperlipidemia, diabetes mellitus, and insulin resistance.
Overall, the evidence suggests that obesity due to BMI is associated with an increased risk of age-related cataracts, posterior subcapsular cataracts, and cortical cataracts in adults.
Obesity and glaucoma
Glaucoma is a multifactorial eye disease that is the leading cause of irreversible blindness worldwide. The most common type of glaucoma is primary open-angle glaucoma (POAG). Elevated intraocular pressure (IOP) is the most common risk factor for POAG, and other important risk factors include high BMI, high education, and high hematocrit.
A prospective cohort study of African-American women in United States showed that POAG was significantly associated with BMI, WC, WHR, and prolonged and high-intensity smoking. In conclusion, evidence from the literature is still scarce, but it suggests a significant association between BMI, WC, WHR and glaucoma risk, and these observations can be applied to the prevention and treatment of glaucoma.
Obesity and papilledema
Papilledema is a condition characterized by edema of the optic nerve head secondary to elevated intracranial pressure (ICP). The most common cause is idiopathic intracranial edema, particularly idiopathic intracranial hypertension (IIH). The most common symptoms of IIH are chronic headache, cognitive dysfunction, and visual disturbances due to papilledema, which are more common in women, and obesity is a major risk factor, with obesity in 90% of patients.
In summary, the severity of papilledema and vision loss is associated with an increase in BMI in patients with IIH. People with severe obesity require diet or bariatric surgery to avoid loss of vision function and other complications.
Obesity and age-related macular degeneration (AMD)
AMD is a classic disease of old age and is the most common cause of blindness in developed countries. A risk factor for advanced AMD is smoking.
The exact mechanism of the association between obesity and AMD risk is unknown. A ≥3% reduction in WHR has been reported to be associated with a reduced incidence of AMD. One meta-analysis concluded that physical activity had a protective effect on AMD; There is also epidemiological evidence that antioxidant supplementation and adherence to the Eastern Mediterranean diet, high intake of vegetables and whole grains, and low intake of red meat are associated with a reduced risk of early and late AMD; Conversely, heavy alcohol consumption is associated with a greater risk of developing AMD.
In summary, smoking, nutrition, and physical activity are important factors influencing the occurrence and development of AMD.
肥胖和糖尿病性视网膜病变（DR）
Obesity and diabetes are positively associated with the occurrence and development of DR and its complications in the elderly in United States. In a prospective cohort study in 2024, visceral obesity as measured by visceral fat index (VAI), lipid accumulation products (LAP), and Chinese VAI (CVAI) was found to be independently associated with an increased risk of new-onset DR in Chinese patients with type 2 diabetes.
Hyperleptinemia in both obese and diabetic patients not only promotes oxidative stress, but also increases ocular vascular endothelial growth factor, which constitutes a pathogenic cofactor for proliferative DR neovascularization. Hypertension and hyperlipidemia are often associated with obesity and can also lead to endothelial dysfunction.
Obesity and retinal vasculopathy
Retinal vascular diameter is a surrogate marker of microvascular disease and a predictor of cardiovascular events. Retinal microangiopathy can occur in individuals with cardiovascular disease associated with obesity. In particular, there is an association between high BMI and waist-to-height ratio (WHtR) in children and retinal arteriolar stenosis, especially in middle age. Low NO levels in obese children may be a factor in narrowing the diameter of arterioles. There is also evidence that inflammatory markers are associated with venous occlusion in the retina, and inflammation may be one of the main mechanisms by which obesity alters retinal microcirculation. Studies from the 1999~2006 National Health and Nutrition Examination Survey showed that a high BMI was associated with an increased risk of diabetes and retinal vein occlusion (RVO).
肥胖和干眼综合征(DES)
DES is a very common eye disease that seriously affects quality of life and may be associated with systemic discomfort diseases, topical eye diseases, or commonly used medications.
Studies have shown a moderate positive correlation between body fat percentage and DES: women with a body fat value of ≥ 30% and men with a body fat value of ≥ 20% are more likely to report dry eye on the SFDEQ (Brief Dry Eye Questionnaire).
As life expectancy increases and people age, people tend to have sedentary habits, and this lifestyle is one of the leading causes of obesity and related diseases and/or complications, including hypertension, diabetes, and metabolic syndrome. Adipose tissue, the source of low-grade inflammation in obesity, is rich in pro-inflammatory macrophages that produce pro-inflammatory markers that negatively affect tears, thus linking pathogenic obesity and DES. In conclusion, weight loss, calorie restriction, and an active lifestyle were associated with significant improvements in patients with DES.
Obesity and obstructive sleep apnea syndrome (OSAS)-related eye diseases
Similar to obesity, OSAS can negatively affect multiple organs and systems, especially related to the cardiovascular system, and some other OSAS-related diseases, such as arterial hypertension, insulin resistance, systemic inflammation, visceral fat accumulation, and dyslipidemia, are also associated with obesity. There is a strong independent association between OSAS, visceral obesity, and insulin resistance.
Obesity can lead to certain ocular diseases associated with OSAS, including ptosis syndrome, central serous chorioretinopathy, non-arteritic anterior ischemic optic neuropathy, and normal intraocular pressure glaucoma.
Figure 2. Effects of visceral obesity and OSAS on skeletal muscle, liver and ocular pathology
brief summary
Obesity must be considered an important risk factor for ocular disease. Therefore, a multidisciplinary and multidimensional approach to the treatment of obesity is also essential for eye health. Lifestyle factors, particularly diet and physical activity, as well as weight changes, should not be overlooked in the prevention and treatment of obesity-related eye diseases. Further research is needed to explore the effects of weight loss on the prevention of vision loss.
参考文献：Bosello F, Vanzo A, Zaffalon C, et al. Eat Weight Disord. 2024 May 6; 29(1):33. doi: 10.1007/s40519-024-01662-8.