Risk factors for cortical, nuclear, posterior subcapsular and mixed cataract: a case-control study

Impact of clinico-biochemical variations on the etiopathogenesis of cataract: a case-control study

Purpose:

Cataract is a major cause of blindness worldwide with a greater prevalence in developing countries like India. Owing to speculations about the relationship of various biochemical markers and cataract formation this case-control study was designed with the aim to know the impact of serum blood sugar, serum electrolytes and serum calcium on the etiopathogenesis of cataract in Kashmiri population.

Methods:

A total of 300 cases diagnosed with cataract and 360 healthy controls were taken for the study. Serum of all the cases and controls was analyzed for blood sugar and calcium using spectrometric techniques. Sodium and potassium were analyzed using Ion-Selective Electrode technology. All the investigations were done on ABBOTT c4000 fully automatic clinical chemistry analyzer.

Results:

Most of the patients in our study were ≥50 years of age having posterior subcapsular cataract. The mean levels of serum fasting blood sugar (mg/dL), serum sodium (mmol/L), serum potassium (mmol/L) and serum calcium (mg/dL) were 99.4 ± 7.7; 140.4 ± 2.5; 4.2 ± 0.5; and 8.9 ± 0.5, respectively, in cases compared to 107.7 ± 12.3; 142.9 ± 5.0; 3.8 ± 0.5; and 8.3 ± 1.7, respectively, in healthy controls. A significantly higher number of cataract cases had elevated serum glucose and sodium levels, low serum potassium and calcium levels compared to healthy controls.

Conclusions:

Hyperglycemia, hypernatremia, hypokalemia and hypocalcemia can independently increase the patients’ risk to cataracts. Corrections in these biochemical parameters may reduce cataract incidence.

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.

Hypertension and Hypercholesterolemia are Associated with Cataract Development in Patients with Type 2 Diabetes

INTRODUCTION

Patients with diabetes have up to five times higher incidence of cataract, mainly at a younger age, and cataract in these patients progresses more rapidly than senile cataract, especially in eyes affected with sight-threatening diabetic retinopathy (DR).

AIM

This study aimed to investigate the risk factors associated with cataract development in patients with type 2 diabetes (T2DM).

METHODS

This case-control cross-sectional study included 90 T2DM (56M/34F). Metabolic risk factors glycated hemoglobin (HbA₁c), total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides were determined using routine laboratory methods. Blood pressure was measured with a mercury sphygmomanometer after a 10-min resting period. Lens opacity was graded according to the Lens Opacity Classification System version III (LOCS III).

RESULTS

According to the LOCS III, patients were divided into two groups: group 1-patients with clear crystalline lens, and group 2-patients with initial cataract. Compared to patients with a clear crystalline lens, those with initial cataract had longer diabetes duration (p = 0.002), higher HbA₁c (p = 0.037), higher total cholesterol (p = 0.029), higher diastolic blood pressure (DBP) (p = 0.014), and lower creatinine clearance (p = 0.017). Cataract was positively associated with diabetes duration (p = 0.001), HbA₁c (p = 0.035), LDL cholesterol (p = 0.042), and DBP (p = 0.009), while negatively with creatinine clearance (p = 0.005). Logistic regression analysis showed that the influence of DBP (AOR = 1.06, p = 0.014) and creatinine clearance (AOR = 2.93, p = 0.045) on cataract development remained significant even after adjustment for diabetes duration and HbA₁c.

CONCLUSIONS

Diabetes duration and various metabolic risk factors, particularly poor glycemic control, hypercholesterolemia, DBP, and diabetic nephropathy's coexistence, are associated with cataract development in T2DM.

Is Dietary Milk Intake Associated with Cataract Extraction History in Older Adults? An Analysis from the US Population

BACKGROUND

Galactose accumulation in the lens tissue is known to be cataractogenic. Whether consistent dietary intake of lactose-which consists of glucose and galactose-predisposes to senile cataract remains unclear. This study was conducted to investigate the association between a number of dietary milk intake indicators and cataract extraction history in a representative sample of older adults from the US population. Methods and Materials. This is a cross-sectional, population-based study. Participants of the United States National Health and Nutrition Examination Survey 2001-2008 who were ≥50 years old and provided a complete history of their usual daily dietary intake were included. Exclusion criteria were special diets, extreme daily energy intake, and missing outcome (i.e., cataract extraction history). Indicators of milk intake used were early-life intake regularity, current daily milk/total dairy intake amounts, and estimated lifelong milk exposure. Odds ratios (OR) and 99% confidence intervals (99% CI) were calculated with fitting weights to better represent the population-based estimates.

RESULTS

Among the 5930 studied participants, early-life milk intake regularity was not associated with cataract extraction history in age/sex/ethnicity-adjusted and multivariable-adjusted models (p trend = 0.064 and 0.094, respectively). Current daily milk intake was associated with a slight reduction in the likelihood of cataract extraction in the age/sex/ethnicity-adjusted model (OR = 0.885 per cup equivalents, 99% CI = 0.795-0.986) and in the multivariable model (OR = 0.871 per cup equivalents, 99% CI = 0.746-0.993). However, no such association was observed between quartiles of current dietary milk intake and cataract extraction history (p trend = 0.064 and 0.094, respectively). Current daily milk intake was associated with a slight reduction in the likelihood of cataract extraction in the age/sex/ethnicity-adjusted model (OR = 0.885 per cup equivalents, 99% CI = 0.795-0.986) and in the multivariable model (OR = 0.871 per cup equivalents, 99% CI = 0.746-0.993). However, no such association was observed between quartiles of current dietary milk intake and cataract extraction history (p trend = 0.064 and 0.094, respectively). Current daily milk intake was associated with a slight reduction in the likelihood of cataract extraction in the age/sex/ethnicity-adjusted model (OR = 0.885 per cup equivalents, 99% CI = 0.795-0.986) and in the multivariable model (OR = 0.871 per cup equivalents, 99% CI = 0.746-0.993). However, no such association was observed between quartiles of current dietary milk intake and cataract extraction history (.

CONCLUSION

There appears to be no direct relationship between several indicators of dietary milk consumption and cataract extraction history in the general American population.

Hypertension is the Prominent Risk Factor in Cataract Patients

Background and objectives: The purpose of this study is to determine the impact of the most prominent cardiovascular and metabolic risk factors in patients undergoing cataract surgery. Materials and Methods: The study included 812 consecutive patients undergoing unilateral, uneventful cataract surgery by means of phacoemulsification, at the 2nd Department of Ophthalmology, Medical School, Aristotle University of Thessaloniki, Greece, during a calendar year. Patients were assessed for the type of cataract and the presence of three diseases, under pharmacological treatment, that have been reported as risk factors for the development of cataract (arterial hypertension, diabetes mellitus, and dyslipidemia). Results: There was a statistically significant difference between the types of cataract and individual risk factors (p < 0.001). Hypertension was the most frequentrisk factor, ranging from 43.8% in patients with subcapsular cataracts, 24.3% in patients with nuclear cataracts, 28.6% in patients with cortical cataracts, and 27.6% in patients with mixed type cataracts. There was a statistically significant difference as to the total number of risk factors per cataract type (p < 0.001); almost all patients with subcapsular cataracts had at least one risk factor (98.4%) while this percentage was 90.5% for patients with mixed cataracts, 85.7% for patients with cortical cataracts, and78.6% for patients with nuclear cataracts. Conclusions: Diabetes mellitus did not have a large incidence in our sample as a single risk factor, while hypertension did. This finding raises the importance of early detection of hypertension, a cardiovascular condition that typically progresses undetected for a number of years.

The Lens Opacities Classification System III Grading in Irradiated Uveal Melanomas to Characterize Proton Therapy-Induced Cataracts

PURPOSE

To evaluate the use of the Lens Opacities Classification System III grading (LOCS III) for the characterization of radiation-induced cataract, and to correlate the proton beam projection onto the lens with cataract location and grade as defined by the LOCS III.

DESIGN

Prospective, interventional case series.

METHODS

Fifty-two consecutive patients with cataract following proton therapy were included. All cataracts were graded using LOCS III. Relationships between proton beam and cataract subtypes, as well as between dose, proportion of lens irradiated, and extent of cataracts, were assessed.

RESULTS

Tumor diameter, volume, stage, and equatorial tumor location were associated with extent of posterior subcapsular cataracts (PSC) that were diagnosed at a median (interquartile range) 36 months (22;83) after treatment. In multivariate analysis, the tumor volume (P < .01) and an equatorial tumor location (P = .01) were risk factors for extensive PSC. Lens irradiation was avoided in 10 patients. In the remaining 42 patients (81%), the extent of PSC significantly correlated with the dose to the lens receiving 10, 26, and 47 Gy (P = .03, P = .03, and P = .04, respectively), the dose to the lens periphery receiving 10 and 26 Gy (P = .02 and P = .02, respectively), and the dose to the ciliary body receiving 10 and 26 Gy (P = .03 and P = .02, respectively). Nuclear color significantly correlated with the dose to the ciliary body receiving 10 Gy (P = .03) and 26 Gy (P = .02). After adjustment of the results on tumor volume and tumor location, the volume of lens receiving 10 Gy (P = .04) and 26 Gy (P = .03) remained significantly associated with the extent of PSC.

CONCLUSIONS

Proton dose correlated with the occurrence of PSC and nuclear color cataracts as defined by LOCS III grading. Better characterization of cataracts with the LOCS III after irradiation may help to further fill gaps in the current understanding of the mechanisms of radiation-induced cataracts.

Photoperiodic regime influences onset of lens opacities in a non-human primate

Background

Opacities of the lens are typical age-related phenomena which have a high influence on photoreception and consequently circadian rhythm. In mouse lemurs, a small bodied non-human primate, a high incidence (more than 50% when >seven years) of cataracts has been previously described during aging. Previous studies showed that photoperiodically induced accelerated annual rhythms alter some of mouse lemurs’ life history traits. Whether a modification of photoperiod also affects the onset of age dependent lens opacities has not been investigated so far. The aim of this study was therefore to characterise the type of opacity and the mouse lemurs’ age at its onset in two colonies with different photoperiodic regimen.

Methods

Two of the largest mouse lemur colonies in Europe were investigated: Colony 1 having a natural annual photoperiodic regime and Colony 2 with an induced accelerated annual cycle. A slit-lamp was used to determine opacities in the lens. Furthermore, a subset of all animals which showed no opacities in the lens nucleus in the first examination but developed first changes in the following examination were further examined to estimate the age at onset of opacities. In total, 387 animals were examined and 57 represented the subset for age at onset estimation.

Results

The first and most commonly observable opacity in the lens was nuclear sclerosis. Mouse lemurs from Colony 1 showed a delayed onset of nuclear sclerosis compared to mouse lemurs from Colony 2 (4.35 ± 1.50 years vs. 2.75 ± 0.99 years). For colony 1, the chronological age was equivalent to the number of seasonal cycles experienced by the mouse lemurs. For colony 2, in which seasonal cycles were accelerated by a factor of 1.5, mouse lemurs had experienced 4.13 ± 1.50 seasonal cycles in 2.75 ± 0.99 chronological years.

Discussion

Our study showed clear differences in age at the onset of nuclear sclerosis formation between lemurs kept under different photoperiodic regimes. Instead of measuring the chronological age, the number of seasonal cycles (N = four) experienced by a mouse lemur can be used to estimate the risk of beginning nuclear sclerosis formation. Ophthalmological examinations should be taken into account when animals older than 5–6 seasonal cycles are used for experiments in which unrestricted visual ability has to be ensured. This study is the first to assess and demonstrate the influence of annual photoperiod regime on the incidence of lens opacities in a non-human primate.

Prevalence of and factors associated with lens opacities in a Korean adult population with and without diabetes: the 2008-2009 Korea National Health and Nutrition Examination Survey

Objective

We examined the prevalence of and factors associated with lens opacities in a Korean adult population with and without diabetes.

Research Design and Methods

Among the 11,163 adults (≥19 years old) from the fourth Korea National Health and Nutrition Examination Survey in 2008–2009, the data from laboratory tests, nutritional surveys, and slit-lamp examinations of 10,248 persons (4,397 men, 5,851 women) were examined. Cataract was defined as the presence of any nuclear, cortical, subcapsular, or mixed cataract in at least one eye, using the Lens Opacities Classification System III.

Results

The weighted prevalence of cataracts were 23.5% [95% confidence interval (CI), 21.7–25.4] in a Korean adult population (19–39 years old, 1.8% [1.3–2.5], 40–64 years old, 25.2% [22.5–28.1],≥65 years old, 87.8% [85.4–89.9])and 54.7% [50.1–59.2] in a diabetic population(19–39 years old, 11.6% [4.5–26.5], 40–64 years old, 41.1% [35.4–47.0], ≥65 years old, 88.3% [83.5–91.8]). In a logistic regression analysis, age, myopia, and the presence of diabetes were independent risk factors. For young (age 19–39 years) and middle aged (age 40–65 years) adults with diabetes, the OR of having a lens opacity is 5.04 [1.41–17.98] and 1.47 [1.11–1.94], respectively, as those without diabetes, whereas for adults aged 65 and older, there was no difference in the prevalence of cataract.

Conclusions

According to these national survey data, ∼ 24% of Korean adults and ∼ 55% of people with diabetes have cataracts. The presence of diabetes was independently associated with cataracts in young and middle aged adults.

Fasting blood glucose levels and the long-term incidence and progression of cataract -- the Blue Mountains Eye Study

PURPOSE

To assess the associations between fasting blood glucose and the long-term incidence and progression of cataract.

METHODS

A total of 3654 persons aged 49+ years were examined at baseline with fasting blood glucose measured, and 2454 re-examined after 5 and/or 10 years. Lens photographs from each visit were used to assess cataract incidence and progression. Associations between baseline fasting blood glucose and incidence and progression of cortical, nuclear and posterior subcapsular (PSC) cataract were assessed using discrete logistic regression and change-point models.

RESULTS

After adjusting for potential confounders, baseline fasting blood glucose was associated with the 10-year incidence of cortical cataract with a threshold at blood glucose level of 6.0 mm (odds ratio [OR] 1.79, 95% confidence interval [CI] 1.25-2.57 for fasting glucose ≥6.0 mm compared to fasting glucose <6.0 mm). Each 1.0 mm increase in fasting glucose was also associated with higher 5-year progression of PSC (OR 1.25, 95% CI: 1.15-1.35), 10-year progression of cortical (OR 1.14, 95% CI: 1.01-1.27) and nuclear (OR 1.20, 95% CI: 1.01-1.43) cataract, with no thresholds detected.

CONCLUSIONS

In this primarily nondiabetic older population, baseline fasting blood glucose was associated with the long-term incidence of cortical cataract and long-term progression of all three cataract subtypes.

Prevalence of posterior subcapsular cataracts in volunteer cytapheresis donors

BACKGROUND

Granulocyte donors routinely receive dexamethasone orally before donation. Steroids may increase the risk of posterior subcapsular cataract (PSC) formation.

STUDY DESIGN AND METHODS

We recruited 100 granulocyte donors (four or more granulocyte donations; any number of platelet [PLT] donations) and 100 age- and sex-matched PLT donors (zero to three granulocyte donations, any number of PLT donations) to examine the risk of PSC. PSC was assessed by a masked ophthalmologist and reading center lens photograph gradings or medical record documentation of PSC as the reason for cataract extraction.

RESULTS

Fourteen eyes of 10 granulocyte donors and five eyes of four PLT donors had PSCs (odds ratio [OR], 2.82; 95% confidence interval [CI], 0.83-9.61; p = 0.10). Risk of PSC increased with number of granulocyte donations: compared to zero to three donations (4.0%), the risk for four to nine, 10 to 19, and 20 or more donations was 8.6% (OR, 2.25; 95% CI, 0.31-13.99; p = 0.30), 9.5% (OR, 2.53; 95% CI, 0.44-14.20; p = 0.21), and 13.0% (OR, 3.60; 95% CI, 0.48-22.81; p = 0.11), respectively (p = 0.06 for trend).

CONCLUSION

We did not demonstrate a statistically significant increased risk of PSC associated with granulocyte donation. However, although this makes a large risk unlikely, we cannot rule out a small to moderate risk and there is biologic plausibility that the steroid administration associated with granulocyte donation could be associated with PSC formation. Transfusion medicine professionals should advise granulocyte apheresis donors to maintain an appropriate frequency of eye examinations.

The epidemiology of cataract: a study in Greece

PURPOSE

We conducted a case-control study to identify risk factors for cataract in the Mediterranean Greek population. Three hundred and fourteen cases and 314 frequency-matched controls of both genders, aged 45-85, attending the ophthalmology department of a major teaching hospital in Athens, Greece, were included in the study.

METHODS

Cases were medically diagnosed and classified. Controls were healthy visitors without cataract. A detailed questionnaire, covering demographic, socioeconomic, somatometric, lifestyle and medical history variables, provided data on possible risk factors for cataract. Analyses were conducted through multiple logistic regression.

MAIN OUTCOME MEASURES

Cataract overall and by type: nuclear, cortical and posterior subcapsular (PSC).

RESULTS

  Statistically significant increased risk for cataract overall was found for current (OR = 1.99, 95%CI: 1.23-3.23) and ex-smokers (OR = 1.64, 95%CI: 1.02-2.70), history of coronary heart disease (OR = 2.25, 95%CI: 1.43-3.55), family history of ophthalmologic diseases (OR = 1.51, 95%CI: 1.03-2.20) and higher sunlight exposure at the beach (OR = 2.26, 95%CI: 1.37-3.72) as well as at work (OR = 2.03, 95%CI: 1.32-3.12). Use of measures protecting against sunlight at the beach, i.e. hat (OR = 0.58, 95%CI: 0.39-0.85) and vision repair spectacles (OR = 0.44, 95% CI: 0.30-0.65), were associated with reduced risk. RESULTS for cataract overall were also evident for the nuclear type and in most circumstances for PSC type, but were only suggestive for the cortical type of cataract.

CONCLUSION

We identified certain possible risk factors for age-related cataract. In a Mediterranean Greek population, we found that smoking, use of cortisone drops, cardiovascular heart disease and sunlight exposure increase the risk for cataract, while use of hat and vision repair spectacles act protectively.

Metabolic syndrome components in relation to risk of cataract extraction: a prospective cohort study of women

OBJECTIVE

To investigate the association between metabolic syndrome and some of its components with the incidence of cataract extraction.

DESIGN

Population-based prospective cohort study.

PARTICIPANTS

A total of 35,369 women, participating in the Swedish Mammography Cohort, aged 49 to 83 years, who completed a self-administered questionnaire about anthropometric measurements and lifestyle factors in 1997.

METHODS

The women were followed from September of 1997 to October of 2005. The cohort was matched with registers of cataract extraction in the study area.

MAIN OUTCOME MEASURES

Incident surgical extraction of age-related cataract.

RESULTS

We identified 4508 incident cases of cataract extractions during 98 months of follow-up. In multivariate analysis, women with a waist circumference >or=80 cm had an 8% increased risk of cataract extraction (rate ratio [RR], 1.08; 95% confidence interval [CI], 0.99-1.17). Women with diabetes had a 43% increased risk of cataract extraction (RR, 1.43; 95% CI, 1.10-1.86), and hypertension was associated with a 12% increased risk (RR, 1.12; 95% CI, 0.99-1.26). Women with all 3 components of the metabolic syndrome (waist >or=80 cm, diabetes, and hypertension) had a 68% increased risk of cataract extraction (RR, 1.68; 95% CI, 1.40-2.02) compared with women without any of these components. Among women aged less than 65 years at baseline with all 3 components of metabolic syndrome, the risk of cataract extraction was approximately 3-fold more (RR, 2.80; CI, 1.94-4.03).

CONCLUSIONS

Metabolic syndrome and its components, abdominal adiposity, diabetes, and hypertension, seem to be associated with an increased risk for cataract extraction, especially among women aged less than 65 years.

Lens opacities in adults in Pakistan: prevalence and risk factors

PURPOSE

To investigate the prevalence and risk factors for lens opacity (LO) amongst a nationally representative sample of the adult population of Pakistan.

METHODS

This national study of blindness and visual impairment (adults > or =30 years) used multistage, stratified, cluster random sampling. Grading of LO was conducted using the Mehra/Minassian classification system. LO, partly or wholly obscuring the red reflex, or previous cataract surgery were indicators of opacity.

RESULTS

16,402 (94.7%) adults were included in this analysis (study conducted 2002-2003). A total of 4,096 (standardized prevalence 20.9%, 95%CI: 20.3, 21.5%) adults were found to have LO. The highest prevalence of LO was found in Punjab province (22.2%), the lowest in Balochistan Province (18.0%). Significant positive associations were increasing age (multivariable odds ratio (OR) 3.2: 95%CI: 3.1, 3.4), hypertension (OR 1.2, 95%CI: 1.1, 1.3), history of diabetes (OR 2.6: 95%CI 2.0, 3.2) and smoking (OR 1.3: 95%CI: 1.1, 1.5). Higher body mass index (BMI) (OR 0.8: 95%CI 0.7, 0.9, heavy vs. normal BMI) and attendance to school (OR 0.6: 95%CI: 0.5, 0.8) were associated with lower risk of LO. Individuals in districts classified as hot were at significantly increased risk (OR 1.3: 95%CI: 1.1, 1.5), and those in wet districts (> 600 mm annual rainfall) had lower odds than individuals living in dry districts (OR 0.7: 95%CI: 0.6, 0.8).

CONCLUSIONS

Almost a fifth of the adult population had LO. Significant positive associations were age, smoking status, hypertension, diabetes, and increased deprivation level. Protective factors included high BMI and educational achievement. The climatic associations offer novel hypothesis for further research into cataractogenesis.

Dose-response relationship between ingested arsenic and cataracts among residents in Southwestern Taiwan

This association study was carried out to examine the effect of long-term exposure to ingested arsenic on various types of cataract. A total of 349 residents living in arseniasis-hyperendemic villages of southwestern Taiwan were recruited. Cumulative arsenic exposure was derived from the history of consuming artesian well water and the arsenic level in well water. The Lens Opacities System III was used to classify different types of cataract. The cataract surgery prevalence was 10% for the age group of 50 or more years. Cortical opacity was most common (35%), while nuclear and posterior subcapsular opacities were observed in 24% and 22% of subjects, respectively. Diabetes mellitus was a significant risk factor for all types of cataract. Occupational sunlight exposure was associated with cortical and posterior subcapsular opacities in a dose-response relationship. The cumulative exposure to arsenic from artesian well water and the duration of consuming artesian well water were associated with an increased risk of all types of lens opacity. But statistically significant dose-response relations with the cumulative arsenic exposure and the duration of consuming artesian well water were observed only for posterior subcapsular opacity (P=0.014 and P=0.023, respectively) after adjustment for age, sex, diabetes status, and occupational sunlight exposure. It was concluded that there was an increasing prevalence of posterior subcapsular opacity with the increase in exposure to ingested arsenic.

Lower intraocular oxygen tension in diabetic patients: possible contribution to decreased incidence of nuclear sclerotic cataract

PURPOSE

To report intraocular oxygen tension in eyes of diabetic and nondiabetic patients.

DESIGN

A prospective, interventional consecutive case series.

METHODS

Oxygen was measured with an optical oxygen sensor in patients who were undergoing vitrectomy. Before turning on the infusion fluid, intraocular oxygen tension was measured in two locations: adjacent to the lens and in the mid vitreous cavity.

RESULTS

Fifty eyes from 50 patients were included in the study. Twenty-one eyes were from diabetic patients and 29 eyes were from nondiabetic patients. The mean oxygen tension adjacent to the lens was significantly lower in diabetic than in nondiabetic patients (8.4 +/- 0.7 mm Hg vs 10.7 +/- 0.8 mm Hg; P < .05). Similarly, the mean oxygen tension in the center of the vitreous cavity was lower in diabetic than in nondiabetic patients (5.7 +/- 0.7 mm Hg vs 8.5 +/- 0.6 mm Hg; P < .001). In subgroup analyses, previous panretinal photocoagulation or cataract surgery did not affect oxygen levels significantly in the vitreous of diabetic or nondiabetic patients.

CONCLUSION

Eyes from diabetic patients have significantly lower intraocular oxygen tension than in eyes from nondiabetic patients. Because oxidative damage to the lens nucleus and increased intraocular oxygen tension have been associated with nuclear sclerotic cataract, these findings may help explain recent reports of an apparent protective effect of diabetes mellitus against nuclear sclerotic cataract.

Dietary carbohydrate intake and glycemic index in relation to cortical and nuclear lens opacities in the Age-Related Eye Disease Study

BACKGROUND

Little is known about the association between dietary carbohydrates and cataract in nondiabetic persons.

OBJECTIVE

The aim was to test whether recent dietary carbohydrate intakes or glycemic index (GI; a measure of carbohydrate intake quality) was associated with the presence of cortical or nuclear opacities.

DESIGN

A modified Block food-frequency questionnaire was used to obtain dietary information from 3377 participants (aged 60-80 y; 56% were women) in the Age-Related Eye Disease Study (AREDS). Lens status was evaluated by using the AREDS System for Classifying Cataracts. Associations were examined for eyes with only a single, or pure, type of lens opacity by using the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of a person.

RESULTS

For participants in the highest quartile, dietary GI was associated with a higher prevalence of all pure nuclear opacities [grade >2; odds ratio (OR): 1.29; 95% CI: 1.04, 1.59; P for trend = 0.02] and moderate nuclear opacities (grade > or =4; OR: 1.43; 95% CI: 0.96, 2.14; P for trend = 0.052). The OR in a comparison of the highest with the lowest quartile of intake was 1.27 (95% CI: 0.99, 1.63; P for trend = 0.09) for cortical opacities of any severity (>0% of area opaque), and the OR increased somewhat for moderate cortical opacities (>5% of area opaque; OR: 1.71; 95% CI: 1.00, 2.95; P for trend = 0.056).

CONCLUSIONS

Results from the cross-sectional analysis of AREDS baseline data suggest that dietary glycemic quality and dietary carbohydrate quantity may be associated with prevalent nuclear and cortical opacities, respectively.

Treatment of type 2 diabetes mellitus in a primary care setting in Taiwan: comparison with secondary/tertiary care

BACKGROUND

This study investigated the status of diabetes control and management in patients treated in a primary healthcare setting and compared the results with data previously obtained for secondary/tertiary care patients in Taiwan.

METHODS

This study was conducted at 51 primary healthcare stations randomly selected island-wide in Taiwan in 2001. A total of 1302 type 2 diabetes patients who had been followed-up for more than 1 year were included. Blood was collected for centralized HbA1c assay. The remaining data and information were collected by review of medical records and patient interview.

RESULTS

Compared with the results of a previous study on patients treated in a secondary/tertiary care setting, a significantly smaller percentage of primary care patients were receiving insulin therapy. Primary care patients also had a shorter duration of diabetes, a higher HbA1c level, better blood pressure control and a lower prevalence of complications. The proportion of patients achieving optimal control of glycemia and blood pressure was low. Patients aged < 65 years had a significantly shorter duration of diabetes, poorer diabetes control and better blood pressure control than elderly patients aged > or = 65 years. Primary care patients aged > or = 65 years had a significantly higher frequency of stroke than those aged < 65 years. The elderly group of secondary/tertiary care patients had a significantly higher frequency of coronary heart disease and stroke. Duration of diabetes and hypertension were the leading risk factors for complications in diabetes patients treated in both primary and secondary/tertiary care settings.

CONCLUSION

Diabetes control was poorer in primary care than in secondary/tertiary care patients, but control of blood pressure was better in primary care patients. The shorter duration of diabetes and better control of blood pressure in primary care patients and in patients aged < 65 years compared with their elderly counterparts might be related to a lower prevalence of complications.

A case-control study on risk factors for nuclear, cortical and posterior subcapsular cataract: The Casteldaccia Eye Study

PURPOSE

To investigate risk factors for nuclear, cortical and posterior subcapsular age-related cataract.

METHODS

A case-control study was carried out on subjects aged 40 years and older, living in Casteldaccia, Sicily. Twenty-seven potential risk factors were investigated. Nuclear, cortical and posterior subcapsular opacities of the lens were classified according to the Lens Opacities Classification System II. Subjects with advanced lens opacities represented the cases, while an identical number of subjects without or with early cataract, matched for sex and age, were recruited as controls from within the same population.

RESULTS

Univariate analysis showed that myopia and iris atrophy were significantly associated with nuclear cataract. Iris atrophy, use of corticosteroids, pseudoexfoliation syndrome and familial occurrence of cataract were positively correlated with cortical cataract. Myopia, iris atrophy, use of corticosteroids and familial occurrence of cataract presented an association with posterior subcapsular cataract. After multivariate analysis, the variables that remained significantly associated were myopia and iris atrophy for nuclear cataract; iris atrophy, pseudoexfoliation syndrome and familial occurrence of cataract for cortical cataract; and myopia, iris atrophy and familial occurrence of cataract for posterior subcapsular cataract.

CONCLUSION

In addition to well known risk factors such as myopia or use of corticosteroids, the Casteldaccia case-control study shows that iris atrophy represents a previously unrecognized risk factor for each of the three types of cataract.

Carbohydrate intake and glycemic index in relation to the odds of early cortical and nuclear lens opacities

BACKGROUND

Animal studies suggest a role for dietary carbohydrate in cataractogenesis. However, few published human studies have evaluated associations between carbohydrate nutrition and lens opacification.

OBJECTIVE

Our objective was to test the hypothesis that long-term carbohydrate intake and dietary glycemic index are associated with the odds of early cortical and nuclear opacities.

DESIGN

Subjects were 417 Boston-area members of the Nurses' Health Study cohort aged 53-73 y. Dietary information was based on an average from 5 semiquantitative food-frequency questionnaires collected over a 14-y period. Opacities were assessed by using the Lens Opacity Classification System III (LOCS III). We used eyes (n = 711) as the unit of analysis and generated odds ratios by using a generalized estimating approach to logistic regression to account for the lack of independence between the 2 eyes of each subject.

RESULTS

After multivariate adjustment, the odds of cortical opacities (LOCS III >/=1.0) among women in the highest tertile of carbohydrate intake (>/=200 g/d) was 2.46 times (95% CI: 1.30, 4.64; P for trend = 0.005) that among women in the lowest tertile (<185 g/d). This association was not affected by adjustment for dietary glycemic index, which was not associated with early cortical opacities. Carbohydrate nutrition was not associated with the odds of nuclear opacities (LOCS III >/=2.5).

CONCLUSIONS

These data suggest that carbohydrate quantity, but not carbohydrate quality, is associated with early cortical opacities, and that neither the quantity nor the quality of dietary carbohydrate affects the risk of nuclear opacities in middle-aged women.

Associations of cataract with antioxidant enzymes and other risk factors

PURPOSE

To determine the association of potential risk factors, including antioxidant enzymes, with the incidence of cataract.

DESIGN

Cohort study.

PARTICIPANTS

At baseline, the Age-Related Eye Diseases (Pathologies Oculaires Liées à l'Age, POLA) Study included 2584 residents of Sète (southern France) aged 60 years or older. From September 1998 to May 2000, a 3-year follow-up examination was performed on 1947 of the 2436 surviving participants (79.9%).

METHODS

Cataract classification was based on a standardized lens examination at the slit lamp, according to Lens Opacities Classification System III. Biologic measurements were performed at baseline from fasting blood samples.

MAIN OUTCOME MEASURES

At baseline and follow-up, the presence of cataract was defined as: NC or nuclear opalescence (NO) > or = 4 for nuclear cataract, C > or = 4 for cortical cataract, and P > or = 2 for posterior cataract (PSC) opacities, using opacity grades corrected for interobserver variability. Incidence rates were assessed separately for right and left eyes and for each type of cataract.

RESULTS

In the multivariate model, the incidence of cortical cataract was increased in subjects with high red blood cell superoxide dismutase activity (odds ratio [OR] 4.2 [1.5-12.1], P = 0.007). The incidence of PSC cataract was increased in subjects with a high level of plasma glutathione peroxidase (OR 1.8 [1.0-3.3], P = 0.05). In addition to age, gender, and opacities at baseline, significant risk factors for incident cataract were: long-duration diabetes (OR 5.8, P = 0.001 for cortical cataract) and lifetime heavy smoking (OR 2.9, P = 0.006 for PSC cataract).

CONCLUSIONS

Consistent with the baseline analysis, the results of this prospective study suggest that antioxidant enzymes might be implicated in the etiology of cataract.

Weight status, abdominal adiposity, diabetes, and early age-related lens opacities

BACKGROUND

The association between weight status and the risk of lens opacities has received little attention.

OBJECTIVE

We examined the cross-sectional relations of body mass index (BMI; in kg/m(2)), waist circumference, and diabetes with the presence of age-related lens opacities.

DESIGN

Eye examinations were conducted in 466 Boston-area women aged 53-73 y who were without previously diagnosed cataracts and were part of the Nurses' Health Study cohort. Weight, height, waist, and hip measurements were obtained by self-report. Lens status was evaluated by using the Lens Opacification Classification System III (LOCS III). BMI and waist circumference were used as measures of overweight and abdominal adiposity, respectively. Nuclear, cortical, and posterior subcapsular (PSC) opacities were defined as LOCS III scores > or = 2.5, > or = 1.0, and > or = 0.5, respectively. Diabetes was defined as a history of type 2 diabetes or as a fasting plasma glucose concentration > or = 7.0 mmol/L.

RESULTS

Women with diabetes were significantly more likely to have PSC opacities [odds ratio (OR): 4.1; 95% CI: 1.8, 9.4] than were women with fasting plasma glucose concentrations < 6.1 mmol/L. Women with a BMI > or = 30 had a higher prevalence of PSC opacities than did women with a BMI < 25 (OR: 2.5; 1.2, 5.2), and women with a waist circumference > or = 89 cm had a higher prevalence of PSC opacities than did those with a waist circumference < 80 cm (OR: 2.3; 1.0, 5.2). Diabetes and measures of adiposity were unrelated to the prevalence of cortical and nuclear opacities.

CONCLUSIONS

Diabetes is a strong risk factor for PSC opacities, and overweight and abdominal adiposity may be risk factors for PSC opacities.

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.

Cataract extraction and age-related macular degeneration: associations, diagnosis and management

Both cataract and age-related macular degeneration (ARMD) are common findings in our aging population. At issue is the progression of ARMD following cataract extraction. The purpose of this paper is to review the data relevant to this subject and to offer suggestions as to the management of cataract associated with macular degeneration. Published data are reviewed and an attempt is made to interpret the results. Topics discussed include the epidemiology and association between the incidence of cataract and ARMD, the role of photo-oxidative damage and inflammation in the pathogenesis of ARMD, and the possible contribution of cataract extraction to the exacerbation and acceleration of ARMD through increased photo-oxidative damage and intraocular inflammation. Recommendations for the cataract surgeon and specialist are formulated on the basis of existing literature.

High prevalence of lactose absorbers in Northern Sardinian patients with type 1 and type 2 diabetes mellitus

BACKGROUND

Increased intestinal lactase activity has been shown to occur in alloxan and streptozotocin diabetic rats.

OBJECTIVE

The objective of this study was to determine whether increased intestinal lactase activity is present in humans with diabetes mellitus.

DESIGN

We assessed the capacity to digest lactose by measuring breath-hydrogen production after oral administration of lactose in 50 patients with type 1 diabetes, 50 patients with type 2 diabetes, and 50 healthy control subjects from Sassari, Sardinia, Italy, a population characterized by a low prevalence of lactase persistence (lactose absorbers).

RESULTS

Fourteen percent of control subjects were lactose absorbers, compared with 48% of patients with type 1 diabetes and 52% of patients with type 2 diabetes (P < 0.005). The odds ratio of lactase persistence in patients with type 1 diabetes was 5.3 (95% CI: 2.0, 14.0) and in patients with type 2 diabetes was 5.5 (95% CI: 2.1, 14.5).

CONCLUSIONS

Diabetes is associated with increased intestinal lactase activity in humans. Consequently, there is a greater exposure to glucose and galactose in diabetic patients with high lactose consumption. This may explain the association between diabetes and the risk of cataract.

The epidemiology of cataract in Australia

PURPOSE

To describe the prevalence and risk factors for cataract in an Australian population aged 40 years and older.

METHODS

Participants were recruited by a household census and stratified, random cluster sampling to represent residents of Victoria, Australia, aged 40 years and older. The following information was collected: initial visual acuity and best-corrected visual acuity, demographic details, health history, dietary intake of antioxidants, lifetime ocular ultraviolet B exposure, and clinical eye examination, including lens photography. Cortical opacities were measured in sixteenths. Cortical cataract was defined as opacity greater than or equal to 4/16 of pupil circumference. Nuclear opacities were graded according to the Wilmer cataract grading scheme, and cataract was defined as greater than or equal to nuclear standard 2.0 of four standards. The height and width of any posterior subcapsular opacity was measured and recorded. Posterior subcapsular cataract was defined as posterior subcapsular opacity greater than or equal to 1 mm2. The worse eye was selected for analysis. Backward stepwise logistic regression was used to quantify independent risk factors for cataract.

RESULTS

A total of 3,271 (83% of eligible) of the urban residents, 403 (90% of eligible) nursing home residents, and 1,473 (92% of eligible) rural residents participated. The urban residents ranged in age from 40 to 98 years (mean, 59 years), and 1,511 (46%) were men. The nursing home residents ranged in age from 46 to 101 years (mean, 82 years), and 85 (21%) were men. The rural residents ranged in age from 40 to 103 years (mean, 60 years), and 701 (47.5%) were men. The overall weighted rate of cortical cataract was 11.3% (95% confidence limits, 9.68%, 13.0%) excluding cataract surgery and 12.1% (95% confidence limits, 10.5%, 13.8%) including cataract surgery. The risk factors for cortical cataract that remained in the multivariate logistic regression model were age, female gender, diabetes duration greater than 5 years, gout duration greater than 10 years, arthritis diagnosis, myopia, use of oral beta-blockers, and increased average annual ocular ultraviolet B exposure. Overall, 12.6% (95% confidence limits, 9.61%, 15.7%) of Victorians aged 40 years and older had nuclear cataract including previous cataract surgery, and 11.6% (95% confidence limits, 8.61%, 14.7%) had nuclear cataract excluding previous cataract surgery. In the urban and rural cohorts, age, female gender, rural residence, brown irides, diabetes diagnosed 5 or more years earlier, myopia, age-related maculopathy, having smoked for greater than 30 years, and an interaction between ocular ultraviolet B exposure and vitamin E were all risk factors for nuclear cataract. The rate of posterior subcapsular cataract excluding previous cataract surgery was 4.08% (95% confidence limits, 3.01%, 5.14%), whereas the overall rate of posterior subcapsular cataract including previous cataract surgery was 4.93% (95% confidence limits, 3.68%, 6.17%) . The independent risk factors for posterior subcapsular cataract in the urban and rural cohorts that remained were age in years, rural location, use of thiazide diuretics, vitamin E intake, and myopia.

CONCLUSIONS

The expected increase in the prevalence of cataract with the aging of the population highlights the need to plan appropriate medical services and public health interventions for primary and secondary prevention. Many of the identified risk factors for cataract in the population have the potential for being modified through public health interventions.

Statistical analysis of correlated binary data in ophthalmology: a weighted logistic regression approach

Ophthalmological studies often deal with correlated binary outcome variables. We propose a weighted logistic regression method to account for the intraclass correlations between eyes. Using simulation studies, we compared this method with two standard logistic regression approaches: a) based on eyes as the unit of analysis and b) treating individuals classified as cases if at least one eye is affected. The considered approaches were evaluated in terms of type I error, power and estimation properties. The simulation results reveal that the subject-based approach can lead to substantial bias in regression coefficient estimates when the correlation between eyes is heterogeneous across groups or when it is low, and that power is directly affected by this bias. Furthermore, the standard eye-based approach, which ignores intrasubject correlations, leads to inflated type I error rates. The proposed weighted approach performed well in all of the situations considered. This is a simple method which can be implemented using any current statistical or epidemiological package that includes logistic regression analysis.