Recent epidemiologic studies on nutrition and cataract in India, Italy and the United States

Levels of Trace Elements in the Lens, Aqueous Humour, and Plasma of Cataractous Patients-A Narrative Review

Cataracts are one of the most common causes of effective vision loss. Although most cases of cataracts are related to the ageing process, identifying modifiable risk factors can prevent their onset or progression. Many studies have suggested that micro and macroelement levels, not only in blood serum but also in the lens and aqueous humour, may affect the risk of the occurrence and severity of cataracts. This systematic review aims to summarise existing scientific reports concerning the importance of trace elements in cataractogenesis. Many authors have pointed out elevated or decreased levels of particular elements in distinct ocular compartments. However, it is not known if these alterations directly affect the increased risk of cataract occurrence. Further studies are needed to show whether changes in the levels of these elements are correlated with cataract severity and type. Such information would be useful for determining specific recommendations for micronutrient supplementation in preventing cataractogenesis.

Risk factors of presenile nuclear cataract in health screening study

Background

To identify risk factors for the development of presenile nuclear cataract in health screening test.

Methods

The cross sectional study included a total of 532 eyes of 266 participants aged 30 to 49 years of Samsung Medical Center from February 2013 to April 2015. Presence of nuclear cataract was defined when the log MAR visual acuity with correction was greater than or equal to 0.2 and one or more of the following were met: Pentacam Nuclear Staging (PNS) grading score ≥ 1, average value of nuclear density ≥ 15%, maximum value of nuclear density ≥ 30%. Possible risk factors were obtained from blood tests and questionnaires of a health screening test of Samsung Medical Center. Association between nuclear cataract and risk factors was investigated using univariate and multivariate logistic regression analysis by generalized estimating equation (GEE) models.

Results

Five factors were significantly associated with presenile nuclear cataract: current smoking [odds ratio (OR) = 2.80, 95% confidence interval (CI), 1.10–7.12, p = 0.0310], non-exercise and high amount of daily physical exercise (OR = 3.99, 95% CI, 1.27–12.52, p = 0.0178; OR = 2.92, 95% CI, 1.38–6.22, p = 0.0053), asthma (OR = 8.93, 95% CI, 1.12–71.15, p = 0.0386), tuberculosis (OR = 4.28, 95% CI, 1.36–13.50, p = 0.0131), and higher total iron binding capacity (OR = 1.01, 95% CI, 1.00–1.02, p = 0.0059).

Conclusions

Presenile nuclear cataract is related to current smoking, non-exercise or high amount of physical exercise, asthma, tuberculosis, and iron deficiency status. The association of non-exercise group and presenile nuclear cataract seems to be related to co-morbidity. Patients with asthma, tuberculosis, or iron deficiency anemia are recommended to receive frequent ophthalmic examination to detect cataract.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0928-6) contains supplementary material, which is available to authorized users.

Relationship between Body Mass Index, Blood Pressure, and Visual Acuity in Residents of Esan West Local Government Area of Edo State, Nigeria

Aim. To study the relationship between body mass index (BMI) and blood pressure (BP) on visual acuity among apparently healthy residents of Ekpoma, Esan West Local Government Area of Edo State, Nigeria. Methodology. This is a cross-sectional descriptive study among 225 subjects (ages of 18–35 years) from whom BP, body weight, and height were collected. Visual acuity was measured using the Snellen chart following standard procedures of number of letters seen at 6-metre distance. The data were then analyzed using SPSS version 17. Results. The sampled population consists of 112 male and 113 female (mean age 31.72±14.2 years). Majority (180) of the respondents had normal visual acuity. However, compared with the respondents with normal BMI (R19.61±1.5; L19.67±1.70), visual acuity of underweight (R18.53±2.30; L18.53±2.70) and obese (R15.68±4.79; L17.73±1.70) were more deviated. Similarly, compared with respondent with normal BP (120–125/80–85 mmHg; R18.00±2.53; L18.07±3.11), hypotensive (R15.5±7.35; L15.00±10.20), and hypertensive (R15.01±21.25; L15.00±11.91) respondents had deviated visual acuity. Conclusion. Abnormal body weight (underweight and obese) and BP (hypotension and hypertension) have potential negative impacts on visual acuity. Based on the observed relationship between weights, BP, and visual acuity, eye examinations can be included as regular screening exercise for abnormal BMI and BP conditions.

Obesity and eye diseases

The prevalence of obesity has reached epidemic proportions in many countries. Although its impact on overall health is well documented, less is known about the ocular manifestations of obesity. Among different eye diseases, obesity has been linked with age-related cataract, glaucoma, age-related maculopathy, and diabetic retinopathy. Numerous population-based and prospective studies support an association between obesity and risk of age-related cataract. However, the nature and strength of these associations, particularly with the different cataract subtypes, remains to be determined. There is strong evidence that obesity is associated with elevated intraocular pressure, but there is no convincing data to support a more direct association between obesity and glaucomatous optic neuropathy. Studies to date have not found a consistent pattern of association between obesity and risk of age-related maculopathy or diabetic retinopathy. Thus, although obesity may be a risk factor for many ocular conditions, the present literature is inadequate to establish any convincing associations. Furthermore, whether weight loss reduces the risk of eye diseases remains unresolved. Because of the potential public health impact of obesity, there is a greater need to understand its ocular effects.

Comparative study of serum Na(+ )and K(+ ) levels in senile cataract patients and normal individuals

Many factors such as aging, changes in blood electrolytes levels, and possibly family history are involved in senile cataract formation. Changes in serum electrolytes levels can induce changes in aqueous electrolytes levels and effect on lens metabolism and probably cataract formation. In this paper, we study serum level of Na(+ )and K(+) in senile cataract patients and normal individuals. Methods and materials: 155 senile cataract patients scheduled for cataract surgery in eye clinic of Rasoul hospital and 155 normal individuals were selected. Serum Na(+) and K(+) levels were measured by Flame Photometry technique and means compared between two groups by t-test. Results: 1. Mean serum Na(+) level in senile cataract patients and normal individuals was 144.96 +/- 6.04 mEq/lit and 140.88 +/- 2.27 mEq/lit respectively, and there was statistically significant difference (P<0.0001). 2. Mean serum K(+) level in senile cataract patients and normal individuals was 4.20 +/- 0.34 mEq/lit and 4.15 +/- 0.32 mEq/lit respectively, and there was no statistically significant difference. Conclusion: Serum Na(+ )level in senile cataract patients was higher than normal individuals in this study. This result might suggest that diets with high Na(+) content are a risk factor for age-related cataract formation, as high Na(+) content of the diet leads to high level of serum Na(+), which in turn contributes to formation of age-related cataract.

Risk factors for nuclear, cortical and posterior subcapsular cataracts in the Chinese population of Singapore: the Tanjong Pagar Survey

AIM

To describe risk factors for nuclear, cortical, and posterior subcapsular (PSC) cataracts in Chinese Singaporeans.

METHODS

A population based cross sectional study was carried out on ethnic Chinese men and women aged 40-81 years. A stratified, clustered, disproportionate (more weights to older people), random sampling procedure was used to initially select 2000 Chinese names of those aged 40-79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a standardised ocular examination and interview at a centralised clinic, following which an abbreviated examination was conducted for non-respondents in their homes. Cataract was graded clinically using to the Lens Opacity Classification System (LOCS) III system. The main outcome measures were adjusted odds ratio for risk factors for specific cataract types (nuclear, cortical and PSC), any cataract and cataract surgery, examined in multiple logistic regression models.

RESULTS

Out of the 1232 (71.8%) examined, 1206 (70.2%) provided lens data for this analysis. Increasing age was associated with all cataract types, any cataract, and cataract surgery. There was no significant sex difference in presence of any cataract, specific cataract types or cataract surgery. After controlling for age, sex, and other factors, diabetes was associated with cortical cataract (3.1; 95% CI: 1.6 to 6.1), PSC cataract (2.2; 95% CI 1.2 to 4.1), any cataract (2.0; 95% CI: 0.9 to 4.5), and cataract surgery (2.3; 95% CI: 1.3 to 4.1). Lower body mass index was associated with cortical cataract (1.8; 95% CI: 1.1 to 2.9; lowest versus highest quintile) and any cataract (2.3; 95% CI: 1.3 to 4.0). Current cigarette smoking was associated with nuclear cataract (1.7, 95% CI: 1.0 to 2.9; more than 10 cigarettes per day versus none). A non-professional occupation was associated with nuclear cataract (2.9; 95% CI: 1.5 to 5.8; for production or machine operators and 2.6; 95% CI: 1.2 to 5.5; for labourers or agricultural workers, both versus professionals). Lower education was associated with nuclear cataract (2.3; 95% CI: 1.0 to 5.2, none versus tertiary), while lower household income was associated with PSC cataract (4.7, 95% CI: 1.1 to 20.0; income <S$2000 versus >S$4000).

CONCLUSIONS

Age related cataracts are associated with a variety of risk factors among Chinese people in Singapore, similar to those reported in European, Indian, and African derived populations. These data support common aetiological mechanisms for age related cataracts, irrespective of ethnic origin.

The Roche European American Cataract Trial (REACT): a randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract

CONTEXT

Funding surgery worldwide for age-related cataract (ARC), a leading cause of blindness, is a huge economic burden. Non-surgical means of slowing ARC progression could benefit patients and reduce this burden.

OBJECTIVE

To determine if a mixture of oral antioxidant micronutrients [mg/day] (beta-carotene [18], vitamin C [750], and vitamin E [600]) would modify progression of ARC.

DESIGN

REACT was a multi-centered, prospective, double-masked, randomized, placebo-controlled, 3-year trial.

SETTING

Consecutive adult American and English outpatients with early ARC were recruited.

PATIENTS

Four-hundred-and-forty-five patients were eligible; 297 were randomized; 231 (78%) were followed for two years; 158 (53%) were followed for three years; 36 (12%) were followed for four years. Twelve patients died during the trial (9 on vitamins; 3 on placebo (p = 0.07)). There were no serious safety issues.

INTERVENTION

After a three-month placebo run-in, patients were randomized by clinical center to the vitamin or placebo groups and followed every four months.

MAIN OUTCOME MEASURE

Cataract severity was documented with serial digital retroillumination imagery of the lens; progression was quantified by image analysis assessing increased area of opacity. This measure of area, 'increase % pixels opaque' (IPO), was the main outcome measure.

RESULTS

There were no statistically significant differences between the treatment groups at baseline. The characteristics of dropouts and the mean follow-up times by treatment group were the same. After two years of treatment, there was a small positive treatment effect in U.S. patients (p = 0.0001); after three years a positive effect was apparent (p = 0.048) in both the U.S. and the U.K. groups. The positive effect in the U.S. group was even greater after three years: (IPO = 0.389 (vitamin) vs. IPO = 2.517 (placebo); p = 0.0001). There was no statistically significant benefit of treatment in the U.K. group. In spite of nearly perfect randomization into treatment groups, the U.S. and U.K. cohorts differed significantly.

CONCLUSION

Daily use of the afore-mentioned micronutrients for three years produced a small deceleration in progression of ARC.

A possible role for vitamin C in age-related cataract

While many experimental studies have shown a protective effect of vitamin C in age-related cataract, other studies have revealed contrasting roles for this nutrient. Oxidative damage in the lens can be prevented by vitamin C. However, a pro-oxidant effect of vitamin C through H2O2 generation has been suggested. Vitamin C has also been shown to play a role in protein glycation, which is observed in cataract formation. A protective effect of dietary energy restriction appears to be inversely related to plasma vitamin C levels in rodents. Moreover, conclusions from human epidemiological and intervention studies are not uniform. The available evidence suggests that maintenance of sufficient plasma vitamin C is needed to prevent oxidative damage in the lens. More research will be needed in order to confirm the relative importance of of the different roles of vitamin C in the eye lens.

Anthropometric status and cataract: the Salisbury Eye Evaluation project

BACKGROUND

Weight or body mass index (BMI; in kg/m2) is frequently identified as a risk factor for cataract, but the nature of the association is unclear.

OBJECTIVE

We aimed to characterize the relation between BMI and stature and risk of different types of cataract.

DESIGN

We analyzed data from participants in the Salisbury Eye Evaluation (SEE), a cross-sectional survey of visual status and demographic, nutritional, and environmental factors conducted between 1993 and 1995 in a representative sample of community-dwelling older persons in Salisbury, MD. Multiple logistic regression techniques were used to compare risk factors between individuals with nuclear, cortical, or posterior subcapsular (PSC) opacities and individuals with no cataract.

RESULTS

Risk of nuclear opacification was greater in participants with lower BMIs [adjusted odds ratio of 1.13 (95% CI: 1.02, 1.27) with a BMI of 22.5 compared with 28.0] and of taller stature [1.12 (95% CI: 1.01, 1.25) with a stature of 170.5 cm compared with 164]. In contrast, risk of cortical opacification was greater in participants with higher BMIs and of taller stature, but the relation for stature diminished in magnitude and was not significant after adjustment for other risk factors. BMI was not related to risk of PSC opacities, but there was some evidence that taller stature is a risk factor for PSC opacification (P = 0.06) after adjustment for other risk factors.

CONCLUSIONS

Both BMI and stature are independent risk factors for cataracts in the SEE population, with the nature of the risk dependent on cataract type.

Antioxidant vitamins and nuclear opacities: the longitudinal study of cataract

OBJECTIVE

The association of antioxidant nutrients and risk of nuclear opacification was evaluated in the Longitudinal Study of Cataract.

DESIGN

Nutritional data were collected at baseline on the 764 participants, which included assessment of dietary intake, use of vitamin supplements, and plasma levels of vitamin E. Ophthalmologic and other data were collected at baseline and at yearly follow-up visits, including lens photographs, which were graded using the Lens Opacities Classification System III protocol.

MAIN OUTCOME MEASURES

Analyses examined whether the nutritional factors at baseline were related to increases in nuclear opacification at follow-up. The MULCOX2 approach, an extension of the Cox regression model, was used. Results are presented as relative risks (RRs) and 95% confidence intervals.

INTERVENTION

Intervention was not applicable.

RESULTS

The risk of nuclear opacification at follow-up was decreased in regular users of multivitamin supplements (RR = 0.69; 0.48-0.99), vitamin E supplements (RR = 0.43; 0.19-0.99), and in persons with higher plasma levels of vitamin E (RR = 0.58; 0.36-0.94).

CONCLUSIONS

In regular users of multivitamin supplements, the risk of nuclear opacification was reduced by one third; in regular users of vitamin E supplements and persons with higher plasma levels of vitamin E, the risk was reduced by approximately half. These results are similar to those obtained in our earlier case-control study. Because these data are based on observational studies only, the results are suggestive but inconclusive. The possible effect of nutritional supplements on the lens requires confirmation by ongoing clinical trials.

Antioxidants and age-related eye disease. Current and future perspectives

Oxidative mechanisms may play an important role in the pathogenesis of age-related eye disease, in particular cataract and macular degeneration, the two most important causes of visual impairment in older adults. For this reason, there is considerable interest in determining whether vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Basic research studies have shown that antioxidants can protect against the cumulative effects of oxidative stress in animal models of cataract and macular degeneration. Data from observational epidemiological studies in humans, however, are inconclusive. While results from several studies, primarily cross-sectional and case-control, are compatible with a possible protective role for micronutrients in disease development, data for specific nutrients or specific disease types have often been inconsistent. Further, these observational studies are limited because of the inherent imprecision of dietary exposure data and the likely effects of uncontrolled confounding. Thus, reliable data regarding a potentially important benefit of vitamin supplementation in eye disease will emerge mainly from well-designed, large-scale, randomized trials.

Some blood plasma constituents correlate with human cataract

AIMS

To look for differences between matched pairs of patients and controls in concentrations of various plasma constituents which might indicate dysfunctions associated with cataract.

METHOD

One thousand patients were taken from the cataract waiting list of a specialist eye hospital. For each patient a matched control of the same sex and half-decade of age but without cataract was taken from the patient list of the family doctor of the patient; the control was the next alphabetically after the patient on the doctor's list. The patients and controls were visited in their homes by a team of nurses who performed venepunctures and collected information for a questionnaire. Eye examinations were performed by a team of ophthalmologists.

RESULTS

Significant differences were found between the cataract and control groups in 10 of the 18 examined plasma constituents. A constellation of three--bilirubin, alkaline phosphatase, and gamma glutamyl transpeptidase--was significantly higher in the cataract group, suggesting subclinical liver dysfunction as a risk factor. Steroid treatment and diabetes increased cataract risk. Endogenous basal plasma cortisol levels were raised in the cataract group, irrespective of steroid use and diabetic status. Alkaline phosphatase, calcium, glucose, and sodium were all raised in the cataract group. Given the raised total protein and albumin also found in the cataract group, the lower albumin/(total protein-albumin) ratio (an approximation for albumin/globulin ratio) may imply an increase in globulin, suggestive of possible (chronic) infection. Total cholesterol was lower in the cataract group.

CONCLUSION

Human cataract in older age groups seems to be due to an accumulation of risk factors, even if individual mean concentrations are well within normal limits but, of course, differing significantly from the corresponding means in the control population.

Antioxidants and eye disease

Oxidative mechanisms are believed to play an important role in the pathogenesis of age-related eye disease, in particular, cataract and macular degeneration, the two most important causes of visual impairment in older adults. For this reason, there is considerable interest in determining whether vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Basic research studies have shown that antioxidants can protect against the cumulative effects of oxidative stress in animal models of cataract and macular degeneration. Data from observational epidemiologic studies in humans, however, are inconclusive. While results from several studies, primarily cross-sectional and case-control, are compatible with a possible protective role for micronutrients in cataract and macular degeneration, data for specific nutrients or specific disease types have often been inconsistent. Further, these observational studies are limited because of the inherent imprecision of dietary exposure data and the likely effects of uncontrolled confounding. Thus, reliable data regarding a potentially important benefit of vitamin supplementation in eye disease will emerge mainly from well-designed, large-scale, randomized trials. Such data are already being collected in the National Eye Institute-sponsored Age Related Eye Disease Study, as well as in the Physicians' Health Study and Women's Health Study.