Age-related cataract in the Tibet Eye Study

UV light and the ocular lens: a review of exposure models and resulting biomolecular changes

UV light is known to cause damage to biomolecules in living tissue. Tissues of the eye that play highly specialised roles in forming our sense of sight are uniquely exposed to light of all wavelengths. While these tissues have evolved protective mechanisms to resist damage from UV wavelengths, prolonged exposure is thought to lead to pathological changes. In the lens, UV light exposure is a risk factor for the development of cataract, which is a condition that is characterised by opacity that impairs its function as a focusing element in the eye. Cataract can affect spatially distinct regions of the lens. Age-related nuclear cataract is the most prevalent form of cataract and is strongly associated with oxidative stress and a decrease in the antioxidant capacity of the central lens region. Since UV light can generate reactive oxygen species to induce oxidative stress, its effects on lens structure, transparency, and biochemistry have been extensively investigated in animal models in order to better understand human cataract aetiology. A review of the different light exposure models and the advances in mechanistic understanding gained from these models is presented.

Prevalence of cataract and cataract surgery in urban and rural Chinese populations over 50 years old: a systematic review and Meta-analysis

AIM

To summarize the data of epidemiological studies on cataract prevalence over 50 years old in urban and rural areas of China from 2000 to 2020, and to analyze the prevalence of cataract and operation rate in China.

METHODS

By searching PubMed, EMBASE, Web of Science, Wanfang Data and CNKI, Chinese and English literatures on the prevalence of cataract in China were retrieved, and the relevant characteristic data were extracted. Then, Stata v15SE software was used for Meta-analysis and heterogeneity test. According to the results of heterogeneity, the corresponding effect models were selected to combine the extracted data.

RESULTS

A total of 20 studies were included in this study, with a total of 111 434 cases. Meta-analysis showed heterogeneity. According to the random effect model, the overall prevalence of cataract in Chinese people over 50 years old was 27.45%, that in rural was 28.79%, and that in urban was 26.66%. The overall coverage rate of cataract surgery was 9.19%.

CONCLUSION

The prevalence of cataract is high in China, and there is still room for improvement in surgical coverage, so it is very important to promote cataract screening and prevention.

Prevalence and risk factors of refractive error in Qinghai, China: a cross-sectional study in Han and Tibetan adults in Xining and surrounding areas

Background

Our study aimed to explore the prevalence and risk factors of refractive error (RE) in Han and Tibetan population aged 50–79 years in Xining and surrounding areas in Qinghai Province on Qinghai-Tibet Plateau.

Methods

As part of the China National Health Survey, our cross-sectional study compared the age-adjusted prevalence of RE in Han and Tibetan older adults aged 50–79 years in Xining and surrounding areas. A multivariate logistic regression model was used to identify risk factors for myopia and hyperopia.

Results

Among 769 Han participants and 476 Tibetan participants, the age-adjusted prevalence of myopia (spherical equivalent (SE) < − 0.5D), hyperopia (SE > + 0.5D), high myopia (SE < -6.0D) and astigmatism (cylindrical equivalent > = 0.5D) is 28.56, 22.82, 2.80, and 69.38%. Han participants have higher age-adjusted prevalence of myopia (32.93% vs 21.64%, p < 0.001), high myopia (3.93% vs 1.02%, p = 0.001) and astigmatism (72.14% vs 64.94%, p = 0.021) compared to Tibetan participants. Being Tibetan is the protective factor of myopia compared to being Han (OR 0.58, 95%CI 0.42–0.79, p < 0.001). Older age (p = 0.032), longer time length in rural area (p = 0.048), undergraduate/graduate education level (p = 0.031), lighter active level (p = 0.007) and lower BMI (p = 0.015) are risk factors for myopia. Older age (all p < 0.001) and pterygium status of the same eye (p = 0.013) also increase the hyperopia risk.

Conclusions

Our study found an overall prevalence of myopia of 28.56% in Xining and surrounding areas in adults older than 50 years. Han population has higher myopia risk than Tibetan population. More medical and social resources should be allocated to improve the vision and life quality of older adults.

Prevalence and service assessment of cataract in Tibetan areas of Sichuan Province, China: population-based study

OBJECTIVES

To assess the prevalence of visual impairment (VI) and blindness (BL) due to cataract and cataract surgical outcomes in remote dispersed and high-altitude Tibetan areas of China.

DESIGN AND SETTING

A cross-sectional study was conducted among people aged 50 and above in Tibetan Autonomous Prefecture of Kandze (TAPK), China, in 2017. The Rapid Assessment of Avoidable Blindness protocol was followed.

PARTICIPANTS

Of 5000 eligible participants, 4764 were examined (response rate 95.3%).

PRIMARY AND SECONDARY OUTCOME MEASURES

Cataract VI was defined as lens opacity at visual acuity (VA) levels of <3/60 (Blindness (BL)), ≥3/60 and <6/60 (severe visual impairment (SVI)), ≥6/60 and <6/18 (moderate visual impairment (MVI)), ≥6/18 and <6/12 (early visual impairment (EVI)).

RESULTS

The estimated prevalence of cataract BL was 0.61% (95% CI 0.42 to 0.87). With best corrected VA, the estimated prevalence of SVI from cataract was 0.86% (95% CI 0.63 to 1.17); MVI was 2.39% (95% CI 2.00 to 2.87) and EVI was 5.21% (95% CI 4.61 to 5.87). Women in TAPK had a significantly higher prevalence of cataract BL (0.82%, 95% CI 0.54 to 2.15) than men (0.34%, 95% CI 0.16 to 0.70). Women had lower cataract surgical coverage (CSC) by eyes (60.8%, 95% CI 55.5 to 65.8) compared with men (70.1%; 95% CI 63.7 to 75.7). The prevalence of cataract BL was higher among Tibetan (2.28%; 95% CI 1.98 to 2.62) than Han Chinese (1.01%%; 95% CI 0.54% to 1.87%). Overall CSC by person with BL (by better eye) was 82.0% (95% CI 75.2 to 87.6). Among cataract-operated participants, 71.2% had VA equal to or better than 6/18.

CONCLUSIONS

The study detected a low prevalence of VI and BL due to cataract with high CSC in the study area compared with many other places in China. Further actions should be taken to improve cataract surgical outcome.

Risk factors of age-related cataract in a Chinese adult population: the Taizhou Eye Study

IMPORTANCE

Cataract risk factors data will provide epidemic evidence for cataract prevention.

BACKGROUND

This study aimed to study the risk factors for age-related cataract in a Chinese adult population.

DESIGN

This is a population-based, cross-sectional study.

PARTICIPANTS

A total of 10 234 eligible subjects ≥45 years old (response rate: 78.1%) were included in the study.

METHODS

We conducted detailed eye examinations including presenting visual acuity, best-corrected visual acuity, slit lamp examination of lens opacities and fundus examination. Questionnaires about lifestyle were administered. Measurements of blood pressure, heart rate and body mass index were collected. Serological metabolic indicators, including fasting blood glucose, triglycerides, cholesterol, lipoprotein, were also evaluated. We used stepwise multivariate logistic regression model to evaluate the association of these risk factors with any cataract and subtypes of cataract.

MAIN OUTCOME MEASURES

Odds ratios of risk factors for cataract were calculated.

RESULTS

For any cataract, we found age, gender (female), increased outdoor activity, no outdoor eye protection, high myopia, high low-density lipoprotein, low high-density lipoprotein, lower education level and increased pickled food intake were independent risk factors. When further examined the risk factors of different subtypes of cataract, we found that these risk factors also existed, but there were slight differences among different subtypes. In addition, for cortical cataract, lower annual family income and high diastolic pressure were additional independent risk factors.

CONCLUSIONS AND RELEVANCE

Reduced outdoor activity, outdoor eye protection, prevention of high myopia, higher education level, controlled blood pressure, improved high-density lipoprotein and low-density lipoprotein levels and reduced pickled food intake may help to reduce the risk of age-related cataract development.

The Association of Outdoor Activity and Age-Related Cataract in a Rural Population of Taizhou Eye Study: Phase 1 Report

Purpose

To study the relationship between outdoor activity and risk of age-related cataract (ARC) in a rural population of Taizhou Eye Study (phrase 1 report).

Method

A population-based, cross-sectional study of 2006 eligible rural adults (≥45 years old) from Taizhou Eye Study was conducted from Jul. to Sep. 2012. Participants underwent detailed ophthalmologic examinations including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), intraocular pressure (IOP), slit lamp and fundus examinations as well as questionnaires about previous outdoor activity and sunlight protection methods. ARC was recorded by LOCSⅢ classification system. The prevalence of cortical, nuclear and posterior subcapsular cataract were assessed separately for the risk factors and its association with outdoor activity.

Results

Of all 2006 eligible participants, 883 (44.0%) adults were diagnosed with ARC. The prevalence rates of cortical, nuclear and posterior subcapsular cataract per person were 41.4%, 30.4% and 1.5%, respectively. Women had a higher tendency of nuclear and cortical cataract than men (OR = 1.559, 95% CI 1.204–2.019 and OR = 1.862, 95% CI 1.456–2.380, respectively). Adults with high myopia had a higher prevalence of nuclear cataract than adults without that (OR = 2.528, 95% CI 1.055–6.062). Multivariable logistic regression revealed that age was risk factor of nuclear (OR = 1.190, 95% CI 1.167–1.213) and cortical (OR = 1.203, 95% CI 1.181–1.226) cataract; eyes with fundus diseases was risk factor of posterior subcapsular cataract (OR = 6.529, 95% CI 2.512–16.970). Outdoor activity was an independent risk factor of cortical cataract (OR = 1.043, 95% CI 1.004–1.083). The risk of cortical cataract increased 4.3% (95% CI 0.4%-8.3%) when outdoor activity time increased every one hour. Furthermore, the risk of cortical cataract increased 1.1% (95% CI 0.1%-2.0%) when cumulative UV-B exposure time increased every one year.

Conclusion

Outdoor activity was an independent risk factor for cortical cataract, but was not risk factor for nuclear and posterior subcapsular cataract. The risk of cortical cataract increased 4.3% when outdoor activity time increased every one hour. In addition, the risk of cortical cataract increased 1.1% (95% CI 0.1%-2.0%) when cumulative UV-B exposure time increased every one year.

Cataracts among adults aged 30 to 49 years: a 10-year study from 1995 to 2004 in Korea

Purpose

To investigate the long-term characteristics of cataracts among adults aged 30 to 49 years in Korean over a span of 10 years.

Methods

Subjects between the ages of 30 to 49 years who underwent cataract surgery at St. Mary's Hospital from 1995 to 2004 (n = 976) were included. Patients with a history of ocular trauma, uveitis, other ocular or systemic diseases, and congenital cataracts were excluded. Additional information including type of lens opacity, urban/rural region, and pre- and postoperative visual acuities were analyzed. Lens opacity grading was conducted using Lens Opacity Classification System III. The Cochran-Armitage proportion trend test was used to analyze vision changes with the passage of time.

Results

Among the patients who had undergone cataract surgeries, 8.8% (976 / 11,111) met the inclusion criteria. The mean age was 41.7 ± 5.45 years. Gender breakdown of the patient population included 79.0% male and 21.0% female. In terms of home environment, 60.9% were from an urban region and 39.1% from a rural region. Opacity type included anterior polar (AP), posterior subcapsular (PSC), AP and PSC, cortical, and nuclear in 35.7%, 35.1%, 7.0%, 6.0%, and 5.4% of patients, respectively. At a 2-month postoperative follow-up appointment, 92.7% of patients showed a best-corrected visual acuity of more than 20 / 40.

Conclusions

Predominance of AP and PSC opacities as well as male patients was observed in this study population.

High Altitude and the Eye

The purpose of this study was to review the available data on the effect of high altitude on the eyes. We carried out electronic literature search on www.pubmed.com for articles published through year 2011. The search terms included high altitude and the eye, high-altitude retinopathy, eye problems in the Himalayas, and eye diseases in Tibet. Other terms like visual functions, intraocular pressure, corneal thickness, tear function, and ocular motility, at high altitude, were searched separately and in combination. Data were retrieved from both prospective and retrospective studies published in the English language.High altitude has both short-term and long-term effects on the eyes. The short-term effects include high-altitude retinopathy, change in corneal thickness, and photokeratitis. Long-term effects include pterygium, cataract, and dry eye syndrome. High-altitude retinopathy of mild degree does not affect vision but has a predictive value for the development of high-altitude cerebral edema. Change in corneal thickness at altitude induces refractive changes in eyes with radial keratotomy and in eyes with LASIK. High altitude does not adversely affect visual acuity and contrast sensitivity; scotopic vision may be affected if supplemental oxygen is not used.

Prevalence and associations of cataract in a rural Chinese adult population: the Handan Eye Study

BACKGROUND

Cataract remains the leading cause of blindness and visual impairment in the world and in China. However, data on the prevalence of cataract based on standardized lens grading protocols from mainland China are limited. This paper estimated the age- and gender-specific prevalence and risk factor for cataract

METHODS

In a population-based Chinese sample, participants underwent a comprehensive ophthalmic examination, including assessment of cortical, nuclear, posterior subcapsular (PSC) and mixed lens opacities from slit-lamp grading using the Lens Opacities Classification System III.

RESULTS

Of the 7,557 eligible subjects, 6,830 took part in the study (90.4% response rate), and 6,544 participants (95.8%, mean age 52.0 ± 11.8 years) had lens data for analyses. The prevalence of any cataract surgery in at least one eye was 0.8% (95% confidence interval [CI], 0.62, 1.06), with similar rates between men and women. The overall prevalence of any cataract or cataract surgery was 20.8% (95% CI, 19.8, 21.8), higher in women than in men after adjusting for age (23.6% vs 17.6%; OR: 1.78; 95% CI: 1.54-2.07). When distinct lens opacity was categorized in each eye as cortical, nuclear, PSC or mixed, based on one randomly selected eye, cortical cataract was the most common distinct subtype (12.3%), followed by mixed (3.2%), nuclear (1.7%), and PSC (0.2%) cataract. The prevalence of all lens opacities increased with age (P < 0.001). After excluding other causes for visual impairment, the proportion of people with best corrected visual acuity <20/60 was 21% among those with PSC, and 12% among those with mixed opacities in the better-seeing eye. In multivariable logistic regression models, myopia was associated with all cataract types, while higher fasting plasma glucose and diabetes were only associated with PSC cataract.

CONCLUSIONS

Cataract affects 20% of the population aged 30 years and older living in rural China, with cortical cataract the most common subtype. Risk factors for cataract include myopia and diabetes.

Lens autofluorescence is not increased at high altitude

PURPOSE

To study the relation between ambient environmental ultraviolet radiation exposure and lens fluorescence.

METHODS

Non-invasive lens fluorometry measurements were compared in healthy Bolivian and Danish subjects. Background ultraviolet radiation was 4.5 times higher in Bolivia than in Denmark.

RESULTS

No significant differences in lens fluorescence or transmittance were found between Bolivian and Danish volunteers.

CONCLUSION

Age-corrected lens fluorescence and transmittance were comparable for healthy participants living at high altitude near the equator and healthy volunteers living at sea level at 55 degrees northern latitude. These results suggest that lens ageing, as assessed by lens autofluorometry, is independent of exposure to ultraviolet radiation.

Prevalence and causes of low vision and blindness in a rural chinese adult population: the Handan Eye Study

PURPOSE

To describe the prevalence and causes of low vision and blindness in a rural population in Northern China.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

A study of 6830 Han Chinese aged 30 years and older was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, Northern China.

METHODS

Clustered samples of adults aged 30 years or more residing in 13 residential villages were selected randomly and were invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle resolution charts. Prevalence was age- and gender-standardized to the 2000 China Census.

MAIN OUTCOME MEASURES

Low vision was defined as VA <20/60 but >/=20/400, and blindness was defined as VA <20/400 following the Modified World Health Organization (WHO) definitions. Primary causes of low vision and blindness were determined by study ophthalmologists according to WHO definitions.

RESULTS

Six thousand eight hundred thirty (90.4%) of 7577 eligible individuals participated in the study, and 6799 (89.7%) had VA data available. Population-weighted prevalence of presenting bilateral blindness was 0.6% and bilateral low vision was 4.7% for persons 30 years of age and older. Based on best-corrected visual acuity (BCVA), the corresponding prevalence of blindness was 0.5% and that of low vision was 1.0%. Blindness and low vision were strongly age related (P<0.05). Cataract was the predominant cause of presenting bilateral blindness (36.6%), whereas undercorrected refractive error was the predominant cause of presenting low vision (78.4%). After refractive correction, cataract became the first leading cause of blindness (41.9%), and low vision (48.2%), myopic retinopathy (16.1%), glaucoma (9.7%), and corneal opacity (9.7%) were other common causes of blindness defined using BCVA.

CONCLUSIONS

A higher prevalence of blindness and low vision was seen in this rural Chinese sample than has been reported from urban Chinese populations. The estimated numbers with BCVA-defined low vision and blindness in 2020, based on best-corrected vision in rural Chinese adults aged 30 years or more, is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.

The epidemiology of age-related eye diseases in Mainland China

While many papers have been published regarding age-related eye diseases in Mainland China in the past two decades, the variable quality of those reports limit the conclusions that can be drawn. Many of these studies assessed blindness and low vision rates, and these estimates are likely accurate. However, due to lack of standardization of techniques for assessing cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy, estimates of the burden of these diseases on the population are less reliable. Owing to the rapid economic development of China in the last decade, resources to address eyecare problems are more likely to be available. Therefore, an accurate assessment of the burden of various eye diseases is needed in order to improve blindness prevention planning and program development.

Prevalence and risk factors of lens opacities in urban and rural Chinese in Beijing

OBJECTIVE

To determine the prevalence of lens opacities in the elderly Chinese population in an urban and a rural region of Beijing.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

The study included 4439 subjects of 5324 subjects invited to participate (response rate, 83.4%). The subjects were divided into a rural part (1973 subjects [44.4%]) and an urban part (2466 subjects [55.6%]). The study was limited to participants age 40 and older, and the mean age was 56.2+/-10.6 years (range, 40-101 years).

METHODS

Nuclear, cortical, and posterior subcapsular lens opacities were assessed based on standardized slit-lamp photographs of the lens using a modification of the grading score of the Age-related Eye Disease Study (AREDS).

MAIN OUTCOME MEASURES

Grading score of the AREDS.

RESULTS

Lens data were provided for 4378 subjects (98.6%) of 4439 persons examined, which consisted of 8724 eyes. Prevalence of any cataract surgery was 1.3% (95% confidence interval [CI]: 1.0-1.7), which was statistically independent of gender (P = 0.51; odds ratio [OR]: 0.86; 95% CI: 1.00-1.34), rural area versus urban region (P = 0.25), and level of education (P = 0.84). Prevalence of any nuclear lens opacity was 82.0% (95% CI: 80.8-83.2); prevalence of any cortical lens opacity was 10.3% (95% CI: 9.4-11.3); and prevalence of any posterior subcapsular opacity was 4.3% (95% CI: 3.7-4.9). If grade 2 of nuclear lens opacity was considered to be normal, prevalence of nuclear cataract was 50.3% (95% CI: 48.8-51.8), and the overall prevalence of any cataract was 53.1% (95% CI: 51.6-54.6), increasing from 6.5% (95% CI: 5.2-7.8) in those subjects 40 to 49 years of age to 52.3% (95% CI: 47.4-55.3) in those who were 50 to 59 years of age, and to 97.8% (95% CI: 96.4-99.2) in those 70 years and older (P<0.001). Frequencies of any cortical cataract and any subcapsular posterior cataract were 10.3% (95% CI: 9.4-11.3) and 4.3% (95% CI: 3.7-4.9), respectively.

CONCLUSIONS

Cataracts are common among adult Chinese residents in Beijing, with age as the most important associated factor. In view of the relatively low rate of cataract surgery performed so far, one may expect a marked increase in the number of cataract surgeries to meet the visual needs of the growing elderly population in China.

The epidemiology of age related eye diseases in Asia

In the past decade, several large population based studies have provided new information on the prevalence of visual impairment and the major age related eye diseases in Asia. These include epidemiological studies from India, Taiwan, Mongolia, Singapore, and Japan. In particular, the epidemiology of refractive errors and glaucoma has been well characterised, providing insights not only into the public health implications of these conditions, but also into anatomical changes of the eye with ageing. In contrast, there are few well conducted population based studies on diabetic retinopathy and age related macular degeneration in Asia, two conditions that are likely to be important causes of blindness in the future.

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.

Cataract surgical coverage and outcome in the Tibet Autonomous Region of China

BACKGROUND

A recently published, population based survey of the Tibet Autonomous Region (TAR) of China reported on low vision, blindness, and blinding conditions. This paper presents detailed findings from that survey regarding cataract, including prevalence, cataract surgical coverage, surgical outcome, and barriers to use of services.

METHODS

The Tibet Eye Care Assessment (TECA) was a prevalence survey of people from randomly selected households from three of the seven provinces of the TAR (Lhoka, Nakchu, and Lingzhr), representing its three main environmental regions. The survey, conducted in 1999 and 2000, assessed visual acuity, cause of vision loss, and eye care services.

RESULTS

Among the 15,900 people enumerated, 12,644 were examined (79.6%). Cataract prevalence was 5.2% and 13.8%, for the total population, and those over age 50, respectively. Cataract surgical coverage (vision <6/60) for people age 50 and older (85-90% of cataract blind) was 56% overall, 70% for men and 47% for women. The most common barriers to use of cataract surgical services were distance and cost. In the 216 eyes with cataract surgery, 60% were aphakic and 40% were pseudophakic. Pseudophakic surgery left 19% of eyes blind (<6/60) and an additional 20% of eyes with poor vision (6/24-6/60). Aphakic surgery left 24% of eyes blind and an additional 21% of eyes with poor vision. Even though more women remained blind than men, 28% versus 18% respectively, the different was not statistically significant (p = 0.25).

CONCLUSIONS

Cataract surgical coverage was remarkably high despite the difficulty of providing services to such an isolated and sparse population. Cataract surgical outcome was poor for both aphakic and pseudophakic surgery. Two main priorities are improving cataract surgical quality and cataract surgical coverage, particularly for women.

Prevalence of lens opacities in Latinos

OBJECTIVE

To estimate the age- and gender-specific prevalence of posterior subcapsular (PSC), nuclear, cortical, and mixed lens opacities in a population-based sample of Latinos 40 years and older.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Six thousand three hundred fifty-seven Latinos 40 years and older from 6 census tracts in Los Angeles, California.

METHODS

A population-based sample of Latinos underwent a complete eye examination, including assessment of presence and severity of lens opacification, using the slit lamp-based Lens Opacities Classification System II (LOCS II). All lens changes (including pseudophakia/aphakia); any nuclear, PSC, and cortical opacities; and nuclear-only, PSC-only, and cortical-only opacities were evaluated. Frequency distributions and chi-square test analyses were used to determine the age- and gender-specific prevalences for each opacity type.

MAIN OUTCOME MEASURES

Prevalences of cortical, nuclear, and posterior subcapsular opacities.

RESULTS

Of the 7789 eligible subjects, 6357 completed a clinical examination (82% participation rate). Of all participants with LOCS II grading, 20% had all lens changes, 7.6% had cortical-only opacities, 3.5% had nuclear-only opacities, 0.4% had PSC-only opacities, and 5.9% had mixed-type opacities. The prevalence of all types of lens opacities increased with age (P<0.0001). Of all participants with mixed opacities, 49% had monocular visual impairment and 20% had binocular impairment. Of all 6357 participants, 3.9% had undergone cataract extraction in at least one eye.

CONCLUSION

Our data provide the first population-based estimates of the prevalence and severity of lens opacities in Latinos. Cortical opacities were the most common type. The high rate of visual impairment from lens opacities suggests that programs that increase access to cataract surgery for older Latinos could help to reduce the burden of visual impairment in the United States.

Blindness and eye diseases in Tibet: findings from a randomised, population based survey

BACKGROUND

Public health officials of the Tibet Autonomous Region (TAR) of China requested a survey of blindness, eye diseases, and eye care service utilisation to assist the development of a 10 year blindness prevention and treatment plan. The objective of the survey was to determine the prevalence of blindness and visual impairment, as well as cataract surgical coverage and surgical outcome in the TAR.

METHODS

The Tibet Eye Care Assessment was a cross sectional prevalence study of three of the seven prefectures (provinces) of the TAR (Lhoka, Nakchu, and Lingzhr) selected to represent its three main environmental regions. The survey sample was selected using a random multistage cluster method. Two teams conducted the survey in a standardised fashion in each prefecture, Lhoka during May and Nakchu during June 1999, and Lingzhr during May 2000. Visual acuity, cause of vision loss, trachoma, and vitamin A deficiency were included in the clinical examination.

RESULTS

Among the 15,900 people enumerated, 12,644 were examined for an overall response rate of 79.6%. The crude prevalence of blindness (presenting better eye visual acuity of less than 6/60) was 2.3%; age and sex adjusted blindness prevalence was 1.4% (95% CI 1.3 to 1.5). Visual impairment (better eye presenting visual acuity of 6/24 to 6/60) was found in 10.9% (95% CI 10.5 to 11.2) of the population (age and sex adjusted). Cataract was the primary cause of blindness (50.7%), followed by macular degeneration (12.7%) and corneal opacity (9.7%).

CONCLUSION

Blindness is a serious public health problem in Tibet, with prevalence higher than in similar studies in eastern China. As elsewhere in the world, women have an excess burden of blindness compared to men. About 75% of blindness in Tibet can be either prevented or treated. Eye care planning for Tibet must focus on cataract, particularly among women.

Prevalence of lens opacity in Chinese residents of Singapore: the tanjong pagar survey

OBJECTIVE

To determine the prevalence of lens opacity among Chinese residents of Singapore.

DESIGN

Population-based, cross-sectional survey.

PARTICIPANTS

Chinese men and women aged 40 years or more in Singapore.

METHODS

A stratified, clustered, random sampling method, with more weights given to the older age groups, was used to initially select 2000 Chinese persons aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a comprehensive ocular examination at a centralized clinic, after which nonrespondents were examined in their homes with portable instruments.

MAIN OUTCOME MEASURES

Lens opacity, as determined clinically at the slit lamp using a modification of the Lens Opacity Classification System III. Prevalence rates were age adjusted to the 1997 Singapore census population.

RESULTS

Of the 1232 persons examined (71.8%), 1206 (70.2%) provided lens data for this analysis. The age-adjusted prevalence of any cataract surgery was 5.1% (95% confidence interval [CI], 3.6, 6.5), with similar rates between men and women. The age-adjusted prevalence of specific types of lens opacity was 22.6% (95% CI, 19.8, 25.4) for any nuclear opacity, 23.9% (95% CI, 21.0, 26.8) for any cortical opacity, and 7.0% (95% CI, 5.3, 8.8) for any posterior subcapsular opacity. The overall age-adjusted prevalence of any cataract or cataract surgery was 34.7% (95% CI, 31.5, 38.0), increasing from 7.0% in those 40 to 49 years and to 94.3% in those 70 years and older (P < 0.001, test for trend for age). When the prevalence of distinct types of lens opacity in an eye was considered, the most common was mixed (age-adjusted prevalence, 11.5%, based on right eye data), followed by nuclear only (9.7%), cortical only (8.3%), and posterior subcapsular only (0.6%). For all cataract types, the prevalence was similar in men and women and was higher in persons examined at their homes than in those examined at the study clinic.

CONCLUSIONS

These population-based data suggest that cataract is common among adult Chinese residents in Singapore, despite ready access to cataract surgical services. Persons accepting the offer of free eye examinations were less likely to have cataract than those who did not take up this offer.

Ocular phototoxicity

The human eye is constantly exposed to sunlight and artificial lighting. Therefore the eye is exposed to UV-B (295-320 nm), UV-A (320-400 nm), and visible light (400-700 nm). Light is transmitted through the eye and then signals the brain directing both sight and circadian rhythm. Therefore light absorbed by the eye must be benign. Damage to the young and adult eye by intense ambient light is avoided because the eye is protected by a very efficient antioxidant system. In addition, there are protective pigments such as the kynurenines, located in the human lens, and melanin, in the uvea and retina, which absorb ambient radiation and dissipate its energy without causing damage. After middle age there is a decrease in the production of antioxidants and antioxidant enzymes. At the same time, the protective pigments are chemically modified (lenticular 3-hydroxy kynurenine pigment is enzymatically converted into the phototoxic chromophore xanthurenic acid; melanin is altered from an antioxidant to pro-oxidant) and fluorescent chromophores (lipofuscin) accumulate to concentrations high enough to produce reactive oxygen species. We have known for some time that exposure to intense artificial light and sunlight either causes or exacerbates age-related ocular diseases. We now know many of the reasons for these effects, and with this knowledge methods are being developed to interfere with these damaging processes.

Low-cost high-volume extracapsular cataract extraction with posterior chamber intraocular lens implantation in Nepal

OBJECTIVE

To improve current clinical practices and ways of thinking about the problem of curable Third-World blindness resulting from cataract.

DESIGN

A two-site prospective, nonrandomized, comparative clinical trial.

PARTICIPANTS

Patients from 2 distinct surgical venues underwent cataract surgery following the same carefully outlined protocol: 62 consecutive cases from the Tilganga Eye Centre in Katmandu, Nepal, and 207 cases from a remote eye camp in rural Chaughada, Nepal.

INTERVENTION

Extracapsular cataract extraction with posterior chamber intraocular lens (IOL) implantation surgery using a technique developed by Dr. Sanduk Ruit of the Tilganga Eye Centre in conjunction with the Medical Directorate of the Fred Hollows Foundation of Australia. Also presented is the teaching method used to help make local doctors proficient in this technique.

MAIN OUTCOME MEASURES

Visual acuity recorded at 2 months after surgery as well as surgical complications.

RESULTS

Preoperative visual acuities for the 62 patients from the Tilganga Eye Centre ranged from 20/60 to light perception only (4 patients were untested). At 2 months after surgery, 87.1% had a best-corrected visual acuity of 20/60 or better. There were zero major surgical complications reported from the Tilganga group. Of the 207 patients at the Chaughada eye camp, preoperative visual acuities (recorded for 177 [85.5%]) ranged from 20/200 or greater to light perception only. One hundred eighty-nine (91.3%) of the patients returned for an examination at 2 months after surgery, at which time 54.5% had an uncorrected visual acuity of 20/60 or greater, improving to 74.1% with correction. There were six (2.9%) surgical complications documented at Chaughada.

CONCLUSIONS

Because the average operative time using the technique presented here is less than 10 minutes per case and the cost per surgery is less than $20, the surgical results are significant in addressing the massive problem of cataract blindness in the Third World. With some changes in preoperative care, a simplified surgical technique, the development of local lens factories, and the implementation of teaching programs, effective lens implantation cataract surgery can be done in high volume at affordable costs in remote areas of underserved nations.

Diabetes, hypertension, and central obesity as cataract risk factors in a black population. The Barbados Eye Study

OBJECTIVE

The increased cataract prevalence of black populations, especially of cortical cataract, remains unexplained. The authors evaluate the relationships of diabetes, hypertension, and obesity patterns to lens opacities, by age, among 4314 black participants in the Barbados Eye Study.

DESIGN AND PARTICIPANTS

Prevalence study of a random sample of the Barbados population, ages 40 to 84 years (84% participation).

MAIN OUTCOME MEASURES

Associations with age-related lens changes (grade > or = 2 in the Lens Opacities Classification System II at the slit lamp) were evaluated in logistic regression analyses by age (persons < 60 years and > or = 60 years). Results are presented as odds ratios (OR) with 95% confidence intervals.

RESULTS

Of the 1800 participants with lens changes, most had cortical opacities. Diabetes history (18% prevalence) was related to all lens changes, especially at younger ages (age < 60 years: OR = 2.23 [1.63, 3.04]; age > or = 60 years: OR = 1.63 [1.22, 2.17]). Diabetes also increased the risk of cortical opacities (age < 60 years: OR = 2.30 [1.63, 3.24]; age > or = 60 years: OR = 1.42 [1.03, 1.96]); additional risk factors were high diastolic blood pressure (age < 60 years: OR = 1.49 [1.00, 2.23]) and higher waist/hip ratio (all ages: OR = 1.36 [1.00, 1.84]). Diabetes was also related to posterior subcapsular opacities. Glycated hemoglobin levels were positively associated with cortical and posterior subcapsular opacities. Overall, 14% of the prevalence of lens changes could be attributed to diabetes.

CONCLUSIONS

The high prevalence of cortical opacities was related to diabetes, hypertension, and abdominal obesity, which also are common in this and other black populations. Interventions to modify these risk factors, especially in populations in which they are highly prevalent, may have implications to control visual loss from cataract, which is the first cause of blindness worldwide.

Comparative pupil dilation using phenylephrine alone or in combination with tropicamide

OBJECTIVE

A prevalence survey of actinic and other eye diseases was conducted in Nambour, Queensland, Australia, in 1992. Pupils were dilated with phenylephrine alone for cataract identification because there were concerns that patient discomfort, due to cycloplegia occurring with the usual dilating agents of tropicamide and phenylephrine, may influence future compliance in an associated intervention study. This validation study was undertaken to measure the possible underestimation of cataract prevalence in this community study, which may have occurred because of inadequate dilation from phenylephrine alone.

DESIGN

The study design was a repeated measures experimental design.

PARTICIPANTS

Forty-seven normal subjects participated in the study. Both eyes were tested.

INTERVENTION

Pupil diameter after dilation with three drops of 10% phenylephrine alone was compared with pupil diameter after dilation with three drops of 10% phenylephrine together with three drops of 1% tropicamide. The two regimens were given to the same subjects 1 week apart. Reversal was attempted with thymoxamine hydrochloride 0.5%.

MAIN OUTCOME MEASURES

Pupil diameter was assessed using a Neitz cataract camera, and accommodation reserve also was measured. Subjects' subjective appreciation of return of ocular function was assessed by a questionnaire. Repeated measures analysis of variance, paired t test, McNemar's test, and Wilcoxon signed rank test were used to analyze outcomes.

RESULTS

Mean maximum pupil size with 10% phenylephrine and 1% tropicamide was significantly larger than pupil size after the use of 10% phenylephrine alone (F1,19 = 18.99, P = 0.0003). However, there was no significant difference between the two dilation regimens when comparing the proportion of subjects who dilated to 6 mm or more (McNemar's X(2)1 = 2.7, P > 0.1). Compared with 10% phenylephrine and 1% tropicamide, pupil diameters were significantly smaller (t46 = 16.77, P = 0.0001), and accommodation reserve greater (t46 = 4.14, P = 0.0001), 40 minutes after reversal with thymoxamine in the group dilated with 10% phenylephrine alone.

CONCLUSION

Pupil dilation with 10% phenylephrine alone, if allowed at least 40 minutes to act, will be as satisfactory for the identification of cataracts in a normal population as 10% phenylephrine and 1% tropicamide and is more acceptable because of reduced problems with glare and accommodation.

The prevalence of cataract in two villages of northern Pakistan with different levels of ultraviolet radiation

To study the effect of ultraviolet (UV) light on the development of age-related cataract, a community-based cross-sectional study was undertaken in two villages in the mountainous Northern Areas of Pakistan. The relative UV light exposure was calculated by the UK Universities Global Atmospheric Modelling Program using the variables direct sunlight hours per day, latitude and ground reflectivity. A total of 797 subjects (410 men, 387 women) over the age of 40 years from both villages were examined for the presence of cataract. The prevalence of cataract increased with age (p < 0.001) and was significantly higher in women at all ages (p < 0.01). There was no significant difference in the overall prevalence of cataract between the two villages. The male population in each village was subdivided into those who worked predominantly indoors and those who worked predominantly outdoors. All women worked outdoors. There was no significant difference in the prevalence of cataract between the male outdoor workers in the two villages. The indoor workers in the village with higher UV light exposure (Hunza) had a significantly higher cataract prevalence (p < 0.001) than the indoor workers in the village with lower UV light exposure (Nomol). In the village with lower UV light exposure (Nomol), the male outdoor workers had a significantly higher prevalence of cataract than the male indoor workers (p < 0.001). There was no significant difference in the prevalence of cataract between the male indoor and outdoor workers in the village with higher UV light exposure (Hunza). Overall, these results are not strongly supportive of UV light being of major importance in cataractogenesis, but they are consistent with a saturation model of UV light as a risk factor for cataract formation.

Distribution of cataract types in the Italian-American case-control study and at surgery in the Parma area

PURPOSE

To compare the distribution of cataract types at surgery with the distribution detected in an ophthalmology clinic-based case-control study in the same geographic area (Parma, Italy).

METHODS

The distribution of cataract type assessed according to the Lens Opacities Classification System I in 284 consecutive patients 45 years of age or older, who were admitted for cataract surgery to the Institute of Ophthalmology in Parma during 1994, was compared with the distribution assessed in 1008 participants in the Italian-American case-control study of age-related cataract in the Parma metropolitan area from 1987 to 1989.

RESULTS

Analysis of cataract distribution indicates in the surgical group, compared with the case-control population, a significant increase of nuclear (N) and posterior subcapsular (PSC) opacities (any), a reduction of pure forms of cortical and N cataracts, and a marked increase of mixed types of opacities with a simultaneous N and PSC component.

CONCLUSION

Although cortical opacities are probably the most prevalent type of age-related lens change in the general population of Parma metropolitan area, the type of cataract most frequently responsible for the decision of patients to undergo cataract surgery is a mixed type of opacity with an N-PSC component.

Population based cataract epidemiological surveys utilising a photodocumentation system

For the past 10 years, the authors have performed cataract epidemiological surveys in several places. All of them were principally population based and applied new types of photodocumentation systems which were developed by our department. The survey places in Japan were Noto, our main survey field located in the centre of the main island of Japan, one village in the subtropical island of Okinawa, a village in the northern island of Hokkaido and one village (Bukittinggi) in West-Sumatra, Indonesia, very close to the equator. The survey methods applied including an interview and ophthalmological examinations, were almost identical in each place and the authors believe that the quality of the examinations was at high level. The cataract classification and grading systems applied were those established by the Japanese Co-operative Cataract Epidemiology Study Group. At present, no significant prominent difference of cataract prevalence and distribution of cataract types have been found in the three Japan survey places. The distribution of cataract types in the Indonesian subjects however, was different from the Japanese subjects. The lens transparency ratio in the Noto survey was quite similar to that of a Dutch study. From photographic images of both opaque and transparent lenses much objective information which be cannot detected through naked eye observation is obtainable. Furthermore, data obtained from the images are comparable because of their objectivity. Although the methodology seems to be rather sophisticated and is costly, the above advantages make it an important asset in this type of cataract research. For example, lens transparency changes with ageing can be indicated quantitatively from image analysis data.(ABSTRACT TRUNCATED AT 250 WORDS)

Casteldaccia eye study: prevalence of cataract in the adult and elderly population of a Mediterranean town

Prevalence of cataract was studied in a population based survey performed in adults aged 40 years or more living in Casteldaccia, a small Sicilian town. Lens opacities of moderate or severe grade (type II or worse, according to the Lens Opacity Classification System II) were found at the following rates: nuclear opalescence in 18.5%, cortical cataract in 12.9%, posterior subcapsular cataract in 10.8%. All these types of cataract were much more frequent in the elderly population and were about 1.5 times more common in women than in men. Late cataract was found in about 1/3 of subjects aged 60 to 69 years, in 2/3 of subjects aged 70 or more, but rarely under 60 years of age. However, early cataract was rather common among younger subjects. Cataracts causing a reduction of visual acuity under 0.7 in the worst eye were found in 4%, 8.7% and 21.5% respectively in the three age groups ranging from 40 to 49, 50 to 59 and 60 to 69 years and in 54.4% of subjects 70 years old or over.

Senile and presenile cataract. Survey of patients undergoing cataract surgery

Two groups of patients operated on because of cataract were compared: 106 patients from Poland and 103 patients from Norway. Mean age in the Polish group was 60 years and in the Norwegian 76 years. To explain the difference in age at operation the incidence of some cataract risk factors--diabetes, myopia, rural residence, outdoor occupation, cataract in family, steroid therapy, smoking and alcohol intake--were evaluated. Significant differences between these two groups were found only for rural residence, alcohol intake and cigarette smoking. The author suggests another possible factor causing earlier cataract formation among Polish patients.

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

A case-control study was conducted to evaluate risk factors for cortical, nuclear, posterior subcapsular and mixed cataract. The 385 cases and 215 controls (age range 40-75 yrs) included in the study underwent a complete ophthalmological examination and laboratory blood tests, and were interviewed about behavioral variables, environmental exposure and their medical history. Lens opacity was classified using the 'Lens Opacity Classification System II' (LOCS II). On multivariate analysis, the risk factors for cortical cataract were the presence of diabetes for more than five years (OR = 3.7) and increased serum K+ and Na+ levels. A history of surgery under general anesthesia and the use of sedative drugs were associated with reduced risk (OR = 0.4). Posterior subcapsular cataract was associated with the use of steroids (OR = 18.2) and diabetes (OR = 8.1), and nuclear cataract with calcitonin (OR = 5.7) and milk intake (OR = 0.25). Mixed cataract was associated with a history of surgery under general anesthesia (OR = 0.5). Some of these results are consistent with the findings of similar studies performed in different geographical areas, others are not. The results suggest a possible role of electrolyte imbalance in the development of senile cataract.

Ultraviolet light exposure and lens opacities: the Beaver Dam Eye Study

OBJECTIVES

Exposure to sunlight may be a risk factor for the development of cataract. The relationships between exposure to sunlight and to the ultraviolet-B (UVB) component of light and the prevalence of lens opacities were examined in the Beaver Dam Eye Study.

METHODS

Persons 43 to 84 years of age residing in Beaver Dam, Wisconsin, were examined using standardized photographic assessments of lens opacities. A questionnaire about medical history and exposure to light was administered.

RESULTS

After adjusting for other risk factors, men who had higher levels of average annual ambient UVB light were 1.36 times more likely to have more severe cortical opacities than men with lower levels. However, UVB exposure was not found to be associated with nuclear sclerosis or posterior subcapsular opacities in men. Moreover, no associations with UVB exposure were found for women, who were less likely to be exposed to UVB.

CONCLUSIONS

Exposure to UVB light may be associated with the severity of cortical opacities in men. However, the lack of an association in women, the group more likely to have cortical opacities, suggests that other factors may be more important in the pathogenesis of lens opacities.

The photophysics and photobiology of the eye

The eye consists of three major segments: the cornea, lens and retina. The main function of the anterior ocular tissue, the cornea and the lens is to transmit and focus light on the retina without distortion. They also filter out UV light (less than 400 nm) and prevent it from reaching the retina. Much of the light reaching the retina is used for sight. However, light can have numerous other effects on the constituents of the eye, both beneficial and deleterious. This article reviews the interaction of light with the eye, various protective mechanisms, the possible role of light in aging and disease states and the role of light in biological processes other than sight such as mood, hormonal secretions and the cyclic growth and phagocytosis of the rods and cones.

Photoinduction of cataracts in rat lens in vitro. Preventive effect of pyruvate

Intact rat lenses were incubated in riboflavin-containing Tyrode solution or medium-199, generating photochemically active species of oxygen and the oxidative stress measured in terms of the decrease in active accumulation of rubidium, and the fall in the levels of glutathione and ATP. Addition of pyruvate to the medium prevented the tissue against oxidative damage as evidenced by a greater accumulation of rubidium and higher levels of glutathione and ATP. Pyruvate was thus found to be effective against the toxicity of oxygen derivatives, particularly the hydrogen peroxide. In dark experiments also, conducted in glucose-free medium, the uptake of rubidium was substantially greater in the presence of pyruvate. The levels of ATP were also higher. These results, therefore, suggest that this ketoacid is beneficial to the tissue through its ability to decompose H2O2 as well through providing a metabolic support. The development of in vitro cataract under the photochemical effects of riboflavin and oxygen was also effectively thwarted by pyruvate. The results are thus potentially useful from the point of view of developing pyruvate and similar compounds as effective anticataract agents.

Distribution of lens opacities in the Italian-American Case-Control Study of Age-Related Cataract. The Italian-American Study Group

The Lens Opacities Classification System I (LOCS I) was used to classify lens opacities in the clinic-based Italian-American Case-Control Study of Age-Related Cataract. Data on the distribution of cataract types among the 1008 patients (age range, 45-79 years) are presented. A single type of cataract was found in 65% of all cases in whom both lenses could be graded. Among all patients and among patients with only one type of cataract, cortical opacities occurred most frequently and posterior subcapsular opacities least frequently. In patients with bilateral cataracts there was a high degree of concordance of cataract type and severity. The high degree of concordance of cataract type between eyes and the decreasing prevalence of unilateral cataract with increasing age suggest that patients with unilateral cataract are at high risk of developing the same opacity in the fellow eye. Cortical cataracts were found more frequently in women, and in patients with unilateral cataract, the left eye was more frequently affected. Clinic-based data on the distribution of cataract may be of assistance in planning future clinical studies of cataract.