Corneal and refractive error astigmatism in Singaporean schoolchildren: a vector-based Javal's rule

BACKGROUND

Traditional approaches to Javal's rule do not use data from subjects with oblique astigmatism and have not been used to make predictions about subjects with oblique astigmatism. Vector approaches to analyzing refractive error can circumvent these problems.

METHODS

Subjects were 993 Singaporean schoolchildren. We performed linear regression of refractive error astigmatism on corneal astigmatism, using J0 vectors to describe with-the-rule and against-the-rule astigmatism and J45 vectors to describe oblique astigmatism.

RESULTS

We obtained the following statistically significant regression relationships: RJ0 = 0.931 x CJ0 - 0.276 and RJ45 = 0.638 x CJ45 + 0.010, where R and C denote refractive error astigmatism and corneal astigmatism, respectively.

CONCLUSION

Our vector-based Javal's rule gives closer predictions of refractive astigmatism than the original Javal's rule and the simplified Javal's rule and can be applied in cases of corneal oblique astigmatism.

Familial clustering and myopia progression in Singapore school children

BACKGROUND

Familial factors may be related to the progression of myopia in children. A cohort study was conducted to determine the relationship between familial factors and myopia progression in children.

METHODS

From a larger clinical trial (n = 311), 153 Singapore children aged 6--12 years were recruited to participate in a cohort study of the risk factors for myopia progression. An in-person interview was conducted whereby information on the history of myopia in first-degree relatives was obtained. Other information collected included housing type, parental education and income. Cycloplegic refractive error as measured by subjective refraction and autorefraction were ascertained every six months. The average length of follow-up was 28 months.

RESULTS

The adjusted mean rate of progression of myopia was -0.60 (95% confidence interval -0.66, -0.55) diopters per year. The average rate of progression of myopia for children with a parental history of myopia was -0.63 (95% confidence interval -0.69, -0.56) diopters per year compared to -0.42 (95% confidence interval -0.57, -0.27) diopters per year for children whose parents were not myopic. The different measures of family history of myopia were related to rate of change in refractive error and refractive error in the final visit. There was no association between close work and myopia progression.

CONCLUSIONS

A positive family history is related to the progression of myopia and final refractive error in Singapore children, thus supporting evidence that hereditary factors may play an important role in myopia progression.

Academic achievement, close up work parameters, and myopia in Singapore military conscripts

AIM

To determine the relation of refractive error to environmental factors, including close up work, in Singapore military conscripts.

METHODS

A cross sectional study was conducted on 429 Singapore military conscripts. Non-cycloplegic refraction and A-scan biometry were performed in both eyes. A detailed questionnaire was administered by in-person interview to obtain information about current and past near work activity, extra tuition lessons, educational experiences, and family demographics.

RESULTS

Myopia associated with the conscript having been educated in the (gifted, special, or express) educational streams (adjusted odds ratio (OR) = 3.8, 95% confidence interval CI 2.0-7.3), and having completed pre-university education (OR=4.1, 95% CI 1.9-8.8). The reported close up work activity at age 7 years did correlate with age of onset of myopia (p<0.001). In parallel, supplemental tuition lessons in primary school has (OR=2.6, 95% CI 1.4-4.9) associated with conscript myopia. Parental myopia was positively associated with myopia (p<0.001), but this relation disappeared when adjusted for environmental factors. Current (p=0.83) and past close up work activity at age 7 years (p=0.13) did not correlate with myopia.

CONCLUSION

Educational level and educational stream positively related to myopia. A relation was observed with reported close up work activity in early childhood and with tuition classes during elementary school, but not with current close up work activity. These results underscore the strong influence of environment in myopia pathogenesis but a role for close up work activity remains indeterminate.

A population-based prevalence survey of skin diseases in adolescents and adults in rural Sumatra, Indonesia, 1999

Skin disorders are one of the most common presenting health problems and pose a considerable public health problem in developing and developed countries. A population-based survey (n = 917) was conducted in October and November 1999 to determine the prevalence of skin diseases in 3 rural villages in Indonesia (Riau province, Sumatra). The overall individual response rate was 96%. Household interviews were conducted to obtain information on skin conditions, basic socio-demographic factors and lifestyle habits. Trained doctors performed a thorough clinical skin examination of each subject in the household. The overall prevalence of skin disease in the 3 villages was 28.2% (95% confidence intervals 24.6-31.8). The prevalence of fungal infections (12.0%) was twice as high as dermatitis (5.1%). As skin conditions are common in rural Indonesia, it is advisable to improve the training of nurses and doctors in the prevention and treatment of skin disorders.

Does education explain ethnic differences in myopia prevalence? A population-based study of young adult males in Singapore

PURPOSE

To study interethnic variation in myopia prevalence and severity in young adult males in Singapore and to determine whether these variations are related to differences in education level.

METHODS

A population-based survey of refractive errors in a cohort of 15,095 military conscripts between July 1996 and June 1997 using noncycloplegic autorefraction and a standard questionnaire. Prevalence rates of myopia (<-0.5 D) and severe myopia (<-6.0 D) were determined for Chinese, Malay, and Indian men; prevalence rate ratios were compared after adjusting for education level.

RESULTS

Singapore has one of the highest prevalences of myopia (79.3%) and severe myopia (13.1%), with Chinese having higher rates (82.2%, 95% confidence interval 81.5, 82.9) compared with Indians (68.7%, 95% confidence interval 65.1, 67.1) and Malays (65.0%, 95% confidence interval 62.9, 67.1). Education was strongly associated with prevalence and severity of myopia. However, significant interethnic variation persisted after adjusting for education.

CONCLUSIONS

There is a high prevalence of myopia in Singapore. Although prevalence and severity of myopia were strongly associated with education, interethnic variation observed was not fully explained by differences in education level.

Myopia and night lighting in children in Singapore

AIM

To examine the role of night time lighting and myopia in children in Singapore

METHODS

A cross sectional study was conducted on 1001 children in two Singapore schools. Cycloplegic refraction and A-scan biometry measurements were made in both eyes. A detailed questionnaire was completed by the parents to obtain information on night time lighting, near work activity, educational and demographic factors.

RESULTS

There was no difference in myopia prevalence rates in children exposed to night time light (33.1%) compared with children who slept in the dark (31.4%) before age 2. In addition, vitreous chamber depth was not related to night light (p = 0.58) before age 2. These results remained even after controlling for near work.

CONCLUSION

Myopia is not associated with night light in Asian populations.

Myopia in Singapore kindergarten children

PURPOSE

The purpose of this study was to examine whether close-up work was related to myopia in Singapore kindergarten children.

METHODS

One hundred twenty-eight children, ages 3 to 7 years, from a kindergarten in Singapore were examined by cycloplegic autorefraction. The parents also completed a questionnaire on the different types of close-up work activities each child was engaged in, socioeconomic status, and parental history of myopia.

RESULTS

Myopic children spent 3.0 hours per day (median) on close-up work activity, while nonmyopic children spent 2.0 hours per day (median) on close-up work activity. The prevalence of myopia in the sample was 8.6%.

CONCLUSION

Close-up work activity was not related to myopia in pre-school children.

Near-work activity and myopia in rural and urban schoolchildren in China

PURPOSE

To examine the prevalence of myopia in rural and urban schoolchildren in Xiamen, China, and to assess the impact of environmental factors on rates of myopia.

METHODS

Second-grade children attending either a city (n=119) or rural (n=91) school in Xiamen, China, were examined using cycloplegic autorefraction and biometry. Detailed questions on socioeconomic status, near-work activity, reading and writing habits, and family histories of myopia were asked in a face-to-face interview using a standard questionnaire.

RESULTS

The prevalence of myopia was 19.3% (95% confidence interval [CI], 12.3, 29) in the city and 6.6% (95% CI, 2.4, 14.3) in the countryside. The average hours per day children spent reading and writing outside of school was 2.2 hours in the city compared with 1.6 hours in the countryside (P<.0001). In both schools, the odds ratio for total reading and writing, adjusted for parental history of myopia, was 2.2 (95% CI, 1.1, 4).

CONCLUSION

These data suggest the prevalence of myopia is higher in the city than in the countryside. One possible explanation for these different rates could be that schoolchildren in the city spend more time reading and writing outside of school compared with children in the countryside. Myopic children in both the city and the countryside spent more time reading and writing compared with nonmyopic children. This increased near-work activity may contribute to the prevalence of myopia.

The design and assessment of questionnaires in clinical research

Questionnaires are one of the most commonly used tools for data collection in clinical research. Despite its simplicity and convenience of use, the design of questionnaire instruments that accurately measure health status and their determinants is nevertheless a difficult and challenging task.We review the two most important issues which are reliability and validity. Reliability can be defined as the degree to which a measure gives 'consistent' or 'reproducible' values when applied in different situations. Validity refers to the extent in which the true value of a variable is correctly measured by the instrument. For different types of questionnaire measurement instruments, specific issues of content, construct and criterion validity should be appropriately addressed. Accuracy in questionnaire-based measurement in clinical studies is achieved by paying attention to the relevant specific issues of reliability and validity during development and testing of such questionnaires.

Risk factors for hip fracture in Asian men and women: the Asian osteoporosis study

The objectives of the Asian Osteoporosis Study (AOS) were to determine risk factors for hip fracture in men and women in four Asian countries, that is, Singapore, Malaysia, Thailand, and the Philippines. A total of 451 men and 725 women (aged 50 years and over) with hip fractures were compared with an equal number of community controls. A standardized questionnaire was administered by interview. The following relative risks (RRs) were found in women and men by multiple logistic regression: dietary calcium intake < 498 mg/day, 2.0 for women (95% CI, 1.5-2.8) and 1.5 for men (95% CI, 1.0-2.2); no load bearing activity in the immediate past, 2.0 for women (95% CI, 1.4-2.7) and 3.4 for men (95% CI, 2.3-5.1); no vigorous sport activities in young adulthood, 7.2 for women (95% CI, 4.0-13.0) and 2.4 for men (95% CI, 1.6-3.6); cigarette smoking, 1.5 for men (95% CI, 1.0-2.1); alcohol consumption 7 days a week, 2.9 for women (95% CI, 1.0-8.6) and 1.9 for men (95% CI, 1.1-3.2); fell twice or more in the last 12 months, 3.0 for women (95% CI, 1.8-4.8) and 3.4 for men (95% CI, 1.8-6.6); a history of fractures after 50 years of age, 1.8 for women (95% CI, 1.1-2.9) and 3.0 for men (95% CI, 1.6-5.6); a history of stroke, 3.8 for women (95% CI, 2.0-7.1) and 3.6 for men (95% CI, 1.8-7.1); use of sedatives, 2.5 for women (95% CI, 1.0-6.3) and 3.0 for men (95% CI, 1.0-9.7); and use of thyroid drugs, 7.1 for women (95% CI, 2.0-25.9) and 11.8 for men (95% CI, 1.3-106.0). Women who were 1.56 m or taller had an RR of 2.0 (95% CI, 1.3-3.0) for hip fracture and men who were 1.69 m or taller had an RR of 1.9 (95% CI, 1.2-3.1) for hip fracture. Based on these findings, primary preventive programs for hip fracture could be planned in Asia.

Genetic, dietary, and other lifestyle determinants of plasma homocysteine concentrations in middle-aged and older Chinese men and women in Singapore

BACKGROUND

Epidemiologic studies have identified the plasma homocysteine concentration as a risk factor for atherothrombotic vascular disease. There is little information on the distributions and determinants of homocysteine concentrations in Asian populations.

OBJECTIVE

The present study was designed to examine the relations between genetic and lifestyle factors and plasma homocysteine concentrations among Chinese in Singapore.

DESIGN

Plasma total homocysteine, folate, vitamin B-12, and vitamin B-6 concentrations and genetic variation at the methylenetetrahydrofolate reductase (MTHFR) locus were measured in 486 Chinese men and women aged 45-74 y in Singapore. Data on dietary and other lifestyle factors were collected in face-to-face interviews.

RESULTS

Men had higher plasma concentrations of total homocysteine than women (P = 0.0001). Age was positively associated with plasma homocysteine in both sexes (P for trend = 0.0001). Plasma concentrations of folate, vitamin B-12, and vitamin B-6 were inversely associated with homocysteine concentrations. Among individuals with low plasma folate, those possessing 2 copies of MTHFR mutant alleles had significantly higher homocysteine concentrations than did those with > or = 1 copy of the wild-type allele. Cigarette smoking, daily coffee consumption, and physical inactivity were positively related to plasma homocysteine concentrations in both sexes (P < 0.05). However, these associations disappeared after adjustment for plasma folate concentrations.

CONCLUSIONS

Age, sex, plasma folate, vitamin B-12 and B-6 concentrations, and MTHFR genotype are independent determinants of plasma homocysteine in middle-aged and older Chinese in Singapore. These factors combined could account for up to 40% of the total variation in homocysteine concentrations in this Asian population.

Hip fracture incidence rates in Singapore 1991-1998

In this population-based study, we determined the incidence rates of hip fracture among Singapore residents aged 50 years and above. Information was obtained from a centralized database system which captured admissions with the primary diagnosis of a closed hip fracture (ICD-9 codes 820, 820.0, 820.2 and 820.8, n = 12,927) from all health care establishments in the country from 1991 to 1998 inclusive. After removing duplicates, hospital transfers, readmissions and non-acute care admissions, the total number of hip fractures was 9406. Based on the national population census 1990 (n = 464,100) and yearly population estimates, the age-adjusted hip fracture rates for 1991-1998 (per 100,000) were 152 in men and 402 in women. This was 1.5 and over 5 times higher than corresponding rates in the 1960s. From 1991 to 1998, these hip fracture rates tended to increase by 0.7% annually in men and by 1.2% annually in women. Among the three major racial groups, in men, the Chinese had significantly higher age-adjusted hip fracture rates (per 100,000): 168 (95% confidence interval (CI) 158-178) compared with 128 (95% CI 105-152) for Indians and 71 (95% CI 54-88) for Malays. A similar pattern occurred in women: 410 (95% CI 395-425), for Chinese compared with 361 (95% CI 290-432) for Indians and 264 (95% CI 225-303) for Malays. Since the 1960s, the main increases in hip fracture rates have been seen in the Chinese and Malays, with the rates in Indians appearing to decrease. Hip fracture incidence rates in Singapore have risen rapidly over the past 30-40 years, particularly in women, and are now among the highest in Asia. Significant racial differences in hip fracture rates occur within the same community. Time trends in hip fracture rates differed between races.

The incidence of hip fracture in four Asian countries: the Asian Osteoporosis Study (AOS)

The Asian Osteoporosis Study (AOS) is the first multicenter study to document and compare the incidence of hip fracture in four Asian countries. Hosital discharge data for the year 1997 were obtained for the Hong Kong SAR, Singapore, Malaysia and Thailand (Chiang Mai). The number of patients who were 50 years of age and older and who were discharged with a diagnosis of hip fracture (ICD9 820) was enumerated. The age-specific incidence rates were deduced and were directly adjusted to the US white population in 1989. The age-adjusted rates for men and women (per 100,000) are as follows: Hong Kong, 180 and 459; Singapore, 164 and 442; Malaysia, 88 and 218; Thailand, 114 and 289; compared with US White rates of 187 in men and 535 in women, published in 1989. We conclude that there is moderate variation in the incidence of hip fracture among Asian countries. The rates were highest in urbanized countries. With rapid economic development in Asia, hip fracture will prove to be a major public health challenge.

Cross-sectional study of near-work and myopia in kindergarten children in Singapore

INTRODUCTION

In view of the high and increasing myopia rates amongst young Singaporean children, we aimed to assess the relationship between near-work and myopia in 414 pre-school children aged 4 to 6 years.

MATERIALS AND METHODS

We measured near-work indices such as tuition classes outside school and other possible risk factors via a questionnaire. We then measured myopia with a hand-held autorefractor.

RESULTS

Children who had 3 or more hours per week of near-work classes outside school had a higher rate [odds ratio 1.39 (95% confidence interval 1.02, 2.53)] of myopia.

CONCLUSIONS

This suggests that there may be an association between near-work and myopia, even at such a young age. Given the increasing emphasis on near-work in Singapore, it may be important to call for increased visual health awareness, although further studies will be needed to establish if near-work causes myopia.

Factors related to the progression of myopia in Singaporean children

PURPOSE

To examine the possible factors related to the progression of myopia in Singapore children.

METHODS

One hundred fifty-three Singapore children aged 6 to 12 years were recruited to participate in a concurrent cohort study of the risk factors for the progression of myopia. Socioeconomic status, outdoor activity, and near-work activity were documented in a face-to-face clinic interview. The changes in cycloplegic subjective refraction and autorefraction were ascertained with the use of a Nidek ARK 900 over a 2-year period.

RESULTS

The average rate of progression of myopia as measured by subjective refraction was -0.59 D per year (95% confidence interval -0.52, -0.66). Younger children and children who were more myopic at the beginning (refractive error worse than -2.0 D) of the study had higher myopia progression rates.

CONCLUSIONS

Myopia progression was faster for younger children and for children who had more severe myopia at baseline. Socioeconomic status and near-work activity were not related to myopia progression.

Clinical drug trials: practical problems of phase III

INTRODUCTION

Phase III randomised clinical trials provide the highest level of evidence to support the superior effectiveness of a new drug or therapy. The main practical problems encountered in the initiation, design, conduct and completion of both investigator-initiated and sponsor-initiated phase III clinical drug trials will be reviewed.

METHODS

A Medline search of clinical drug trials conducted in Singapore as well as journal articles highlighting important methodological considerations and practical problems encountered in phase III clinical trials was performed.

RESULTS

Several phase III randomised clinical trials have been conducted in Singapore which include the investigation of interventions that include tramadol, estradiol patch and colloidal bismuth subcitrate. The main problems encountered in phase III clinical drug trials include difficulties with recruitment of subjects for the study, proper filing of case report forms, special problems in children and the elderly, adequate compensation for adverse events and the adequate archival of documents of the completion of trials. In investigator-initiated trials, careful attention should be given to identifying a suitable study question, choice of study design, sample size calculations and data analysis. In sponsor-initiated trials, a good working relationship with the sponsor is essential and publication terms should be spelt from the onset of the trial.

CONCLUSIONS

Well-planned clinical trials led by a team of competent investigators are essential for the conduct of rigorous sponsor-initiated and investigator-initiated clinical trials.

Temporal variations in myopia progression in Singaporean children within an academic year

PURPOSE

Excessive nearwork is believed to be associated with myopia development and progression. To investigate this further, we studied refractive error changes and their correlation with nearwork in a cohort of grade school children in Singapore.

METHODS

Cycloplegic autorefraction was performed 5 times over 10 months on 168 children aged 7, 9, and 12 years who were further divided into myopic and nonmyopic subgroups based in their initial refractive errors. Information about nearwork was obtained through diaries filled out over 24 h at the commencement of the study.

RESULTS

Myopia progression was high (overall mean: -0.87 D per year) and largely linear throughout the year, but significantly higher rates were seen after the final school examinations in 7-year-old myopes and nonmyopes. Overall, myopic groups exhibited higher progression rates than nonmyopic groups, although 33.6% of subjects from the latter groups had become myopic by the end of the study. Nearwork scores derived from the diaries were generally not well correlated with overall myopia progression.

CONCLUSIONS

The tendency for myopia progression rates to increase after the final school examinations in 7-year-olds is interpreted as a delayed effect of the intense nearwork associated with preparing for them. The timing of nearwork-diary data collection at the beginning of the study could be responsible for the poor correlation between these data and overall myopia progression rates.

Eye cancer incidence in Singapore

AIM

To describe the epidemiological characteristics of patients with primary intraocular, conjunctival, and orbital cancers seen in Singapore from 1968 to 1995.

METHODS

Epidemiological data of all cancers diagnosed in Singapore are collected by the Singapore Cancer Registry. The data of all cases of Singapore residents with eye cancers (ICD-9, site 190) were retrieved for analysis. This includes intraocular, conjunctival, and orbital cancers but excludes cancer of the eyelids.

RESULTS

There were 125 patients of which 67 (53.6%) were male and 58 (46.4%) were female. The average annual age standardised incidences for male and female Singapore residents were 1.89 and 1.81 per million respectively. The most common cancer was retinoblastoma (53.6%), followed by malignant melanoma (19.2%) and squamous cell carcinoma (11.2%). The most common cancer among patients younger than 15 years was retinoblastoma (95.7%) and that for those 15 years and older was malignant melanoma (42.6%). The most common subsite was the retina (53.6%), followed by conjunctiva (12.8%), orbit (8.8%), and lacrimal gland (6.4%).

CONCLUSION

The annual age standardised incidence have been stable for the 28 years studied. Retinoblastoma is much more common than melanoma in Singapore. These expanded epidemiological characteristics serve to provide ophthalmologists and epidemiologists with a foundation to monitor future disease patterns in Singapore and provide a basis for comparison with other selected populations elsewhere.

Outdoor work and the risk of pterygia: a case-control study

AIM

To investigate the relationship between outdoor work and pterygium formation in a hospital-based case-control study in Singapore.

METHOD

Sixty-one patients with pterygium (49 males, mean age 54.2 years) and 125 controls (41 males, mean age 50.2 years), excluding patients with cataract and age-related macular degeneration presenting at outpatient clinics of the Singapore National Eye Centre were interviewed face-to-face with a standard questionnaire. Demographic data and information on outdoor work and eye protection, were collected.

RESULTS

Thirty-eight subjects (20.4%) were outdoor workers and 148 (79.6%) were indoor workers. Outdoor workers were more likely to be male smokers and alcohol drinkers with lower family income and higher sunlight exposure than indoor workers. The crude odds ratio for pterygium in outdoor workers was 7.0 (95% confidence interval 3.2, 15.3). The adjusted odds ratio was 4.2 (95% confidence interval 1.7, 10.1).

CONCLUSION

There is a statistically significant association between outdoor work and pterygium formation, which may be related to the higher exposure to sunlight and dust in outdoor workers. Efforts may be made to educate outdoor workers to wear proper equipment to protect their eyes against excessive sunlight.

Refractive errors in Singapore and Xiamen, China--a comparative study in school children aged 6 to 7 years

PURPOSE

To compare and contrast the prevalence of myopia and other refractive errors in Xiamen city, Xiamen countryside (Southern China), and Singapore.

METHODS

One hundred thirty-two schoolchildren aged 6 to 7 years from Xiamen city, 104 from Xiamen countryside, and 146 from Singapore city were recruited to join the study. Cycloplegic autorefraction, keratometry, and biometry measurements were performed on all children.

RESULTS

The prevalence of myopia was 12.3% in Singapore city, 9.1% in Xiamen city, and 3.9% in Xiamen countryside. The prevalence of astigmatism was higher in Singapore compared with Xiamen. The rates of hyperopia and anisometropia were similar in all three locations.

CONCLUSIONS

The myopia rate in Singapore city was higher than in Xiamen city; the lowest rates were found in Xiamen countryside. As the Chinese population from all three sites is of similar genetic stock (predominantly from Southern China), it is postulated that the differences in myopia rates in these three localities may be related to environmental factors.

Ophthalmic involvement in cranio-facial trauma

OBJECTIVES

This is a retrospective descriptive case study which will look into the spectrum of ophthalmic involvement in cases with orbital and eye injuries after cranio-facial trauma and to analyse the visual and motility outcome.

MATERIAL

One hundred and four cases with ophthalmic involvement after cranio-facial trauma that were referred to and seen in the eye department of a tertiary teaching hospital in Singapore between 1991-97 were included in the study.

METHODS

The case records of 104 such patients were traced. The demographic data, the mode of injury, the type of fracture sustained and presence of serious eye injury were noted. The details about visual acuity, significant diplopia and enophthalmos at the first and last visits were charted. Presence of traumatic optic neuropathy including the type of treatment given was recorded.

RESULTS

There was a male preponderance (82%). The industrial accidents were 21%, only next to road traffic accidents, which constituted approximately 36.5%. The predominant types of fractures seen were blow-out orbital fractures, complex fractures comprising of Le-Fort II, III, panfacial and fronto-basilar skull fractures. Diplopia was the most common presenting feature (40%) with visual acuity disturbance (23% having <6/60) as the next most common finding. Traumatic optic neuropathy was seen in 20% of patients and serious eye injury was present in 9% of patients. The incidence of traumatic optic neuropathy was significantly higher (p<0.001) in patients with complex fractures and fronto-basilar fractures, as compared to the blow-out and zygomatico-maxillary fractures. Analysis of final results indicated 15% as having significant diplopia in one or more gazes and 12.5% as having a vision of <6/60.

CONCLUSION

Diplopia and visual acuity disturbances seem to be the most common ophthalmic presentations in cranio-facial trauma. A significant number of patients suffer from poor vision and significant diplopia despite treatment.

Myopia: gene-environment interaction

INTRODUCTION

Myopia has reached epidemic proportions in Japan, Hong Kong, Taiwan and Singapore. This review summarises the evidence for environmental and genetic factors as well as gene-environment interaction for myopia for both epidemiologic studies as well as animal models.

METHODS

A literature review was conducted after a Medline search on articles on the genetic or environmental aetiology of myopia in animal or epidemiologic studies. Articles on the methodology of gene-environment studies were also reviewed. All articles reviewed were articles published in peer-reviewed journals.

RESULTS

Cross-sectional studies have found a positive association between myopia and near work activity such as reading and writing. Likewise, laboratory research has shown that environmental factors such as visual deprivation may lead to the development of myopia in animals. While linkage studies in humans are currently being conducted to identify possible markers for myopia in the human genome, several neurotransmitters, modulators and growth factors that influence refractive development have already been identified in animal models that may help identify candidate genes. Epidemiologic studies have also evaluated the combined effects of hereditary factors, environmental factors and gene-environment interaction on myopia development.

CONCLUSIONS

Both genes and environmental factors may be related to myopia. There are no conclusive studies at present, however, that identify the nature and extent of possible gene-environment interaction. Further linkage analysis, affected sib-pair studies, and family-based association studies may better identify the nature of gene-environment interaction.

Risk factors for the development of pterygium in Singapore: a hospital-based case-control study

PURPOSE

A hospital-based case-control study, designed to evaluate the risk factors for the development of pterygium in Singapore.

METHODS

Sixty-one cases and 125 controls were interviewed at the Singapore National Eye Centre. Information on present and past (5 and 10 years ago) exposure to sunlight on weekdays and weekends, sociodemographic data, behavior lifestyle and family history of eye disease was collected.

RESULTS

Patients with pterygia were mostly males, smoked and drank alcohol more often, had lower combined family incomes and were more likely to have a family history of eye disease. The adjusted odds ratios for the development of pterygia were 1.27 (95 percent confidence interval 1.06 to 1.54) and 1.31 (95 percent confidence interval 1.09 to 1.57) for participants who had spent more time in the sun five and ten years ago respectively.

CONCLUSIONS

Pterygium is an important public health problem in Singapore and its development is related to the amount of sunlight exposure.

Incidence and survival characteristics of retinoblastoma in Singapore from 1968-1995

PURPOSE

To describe the incidence and survival of 69 Singapore residents with retinoblastoma in all Singapore hospitals from 1968-1995.

METHODS

Data of all Singapore residents diagnosed with retinoblastoma from 1968-1995 were collected by the Singapore Cancer Registry based on notifications from physicians, pathology records, hospital discharge records, and death certificates. The medical records of 46 patients were traced, and information on laterality of tumor, spread of tumor, mode of treatment, and family history of retinoblastoma was obtained. Time trends and survival characteristics of the cohort were described.

RESULTS

The incidence rate of retinoblastoma was 2.4 per 1 million for children <9 years and 11.1 per 1 million for children <5 years. The incidence of retinoblastoma has been almost uniform over time from 1968-1995, except for an apparent increase in 1988-1992. The 3-year survival rate for retinoblastoma was 83%. Survival rates were higher in children <2 years because children who present at a younger age may have tumors diagnosed at earlier stages of the disease. There was no difference in survival rates for sex, race, laterality, family history of retinoblastoma, treatment, or year of diagnosis.

CONCLUSION

Retinoblastoma is the most common eye cancer in children that may cause blindness or death. The incidence rates of retinoblastoma in Singapore have remained fairly stable over 28 years, and the survival rate is higher in younger children. This study will be helpful in monitoring future disease patterns in Asian populations.

The prevalence and pattern of contact lens use in a Singapore community

PURPOSE

We conducted a cross-sectional survey to determine the prevalence, socio-demographic patterns, and characteristics of contact lens use in an electoral community in Singapore.

METHODS

One thousand eight hundred fifteen persons aged between 12-55 years from 768 households were surveyed using a standardized pre-tested questionnaire.

RESULTS

The percentage of contact lens wearers in the survey populations was 9.0%. Forty-two percent of surveyed individuals were myopes, 21.8% of whom wore contact lenses. Contact lens wearers tended to be young Chinese females with higher level education and incomes. Most wore monthly disposable or daily wear soft contact lenses. Convenience and cosmesis were the main reasons cited for contact lens wear. Optometrists, who prescribed the bulk of contact lenses, were also the most influential in determining consumers' choice of lenses.

CONCLUSION

Information gathered in this population-based survey may be used to facilitate national eye-care planning and provide a baseline for comparison with rates of lens wear found in other countries and in future surveys.

Estimating the magnitude of close-up work in school-age children: a comparison of questionnaire and diary instruments

BACKGROUND

Numerous scientists have noted a relationship between close-up work and myopia.

METHODS

A questionnaire and four 24-hour diaries were developed to estimate close-up work activity in a cohort study of close-up work and myopia progression in Singapore children. The number of hours per day that children engaged in each type of close-up work activity over a weekday and weekend during the school term, during the examination period, and in the vacation were estimated.

RESULTS

The children spent an average of 6.6 hours per day on total weighted average close-up work, of which 4.3 hours were spent on reading and writing. The intra-class correlation coefficient for the reproducibility of the questionnaire was 0.87 (95% CI 0.85-0.91). The intra-class correlation coefficient for total weighted close-up work was 0.50 (95% CI 0.34-0.66) when the questionnaire was compared with the four 24-hour diaries. The amount of close-up work activity increased with age.

CONCLUSIONS

A questionnaire for close-up work was developed and proven to be reproducible and comparable to four 24-hour diaries.

Pterygium: prevalence, demography and risk factors

Pterygium is not just a degenerative disease, but may be a proliferative disorder of the ocular surface. The etiology of pterygia has intrigued researchers for centuries. Several surveys have consistently shown that countries nearer the equator have higher rates of pterygia. A possible reason for this geographic variation is that (ultraviolet) UV B light may be a risk factor for the development of pterygia. UV B radiation may induce cellular changes in the medial limbus of the cornea. Several case-control and cross-sectional studies have attempted to accurately quantify UV light exposure and document its relationship with pterygia. Genetic attributes and other lifestyle behaviors may also contribute to the development of pterygia. However, further research efforts are needed to enable us to better understand the relative contribution of the different risk factors and how each risk factor may be linked to pterygium formation. In addition, the underlying mechanism of the effects of UV radiation needs to be further evaluated. By readdressing these unresolved issues in a newly proposed epidemiological study, new measures might be taken to reduce incidences and improve clinical managements of diseases, in addition to preventing UV exposure by eliminating other contributory factors. Meanwhile, preventive measures such as protection of the eyes by the wearing of sunglasses with UV B protective lenses and brimmed hats outdoors are recommended.

Homocysteine and atherosclerotic disease: the epidemiologic evidence

Homocysteine is a sulphur-containing amino acid formed during metabolism by one of two pathways by remethylation and transsulfuration. Altered homocysteine metabolism may be implicated as a factor in atherosclerosis, cerebrovascular disease or peripheral vascular disease. It is postulated that homocysteine may damage endothelial cells or acts as a direct causal factor in the thromboembolic process. Several studies have reported that there are a number of factors that may influence levels of homocysteine in humans. Serum homocysteine levels may be associated with low levels of folate, vitamin B6 and vitamin B12. These studies showed that serum homocysteine levels were higher in men and older adults, and some showed that there was a direct relationship between homocysteine and cigarette smoking, diabetes, obesity, and hypertension. Subjects who consume larger amounts of coffee were also noted to have higher serum homocysteine levels. Several cross-sectional, case-control, and cohort studies have linked homocysteinaemia with cardiovascular disease morbidity and mortality. In the Framingham Heart Study, the cohort study in Tromso, Norway, and the Atherosclerosis Risk in Communities (ARIC) Study, homocysteine levels were found to be higher in adults with asymptomatic or symptomatic coronary artery disease. In the British Regional Heart Study, homocysteine levels were found to be significantly higher in patients with stroke. Thus, there are suggestions that vitamin therapy and alteration of lifestyle habits such as cigarette smoking may lower homocysteine levels. There may be less coronary heart disease morbidity and mortality with lower homocysteine levels.

Relation between work and myopia in Singapore women

BACKGROUND

Work and related activities may be connected to myopia development and progression. We investigated the relationship between working activities and the onset as well as worsening of myopia.

METHODS

Information on the working status of the mothers of 374 children, the number of hours of close-up work activity, and whether the mother was short-sighted, was obtained by a face-to-face interview. In addition, a subsample of 84 mothers was interviewed over the telephone and asked whether the myopia occurred in adulthood and, if so, the age of cessation of myopia.

RESULTS

The adjusted odds ratio for myopia in working women was 1.9 [95% confidence interval (CI) 1.2 to 3.2] and the adjusted odds ratio for high myopia (> -6.0 D) was 1.6 (95% CI 0.8 to 3.0). Women who were working also had higher rates of adult-onset myopia, odds ratio 4.4 (95% CI 0.9 to 21.2), and a later age of cessation of myopia than nonworking women.

CONCLUSIONS

In our study, work was related to myopia in Singapore women. Work may be a surrogate for another risk factor, close-up work activities such as reading, writing, and computer use.

Distance, lighting, and parental beliefs: understanding near work in epidemiologic studies of myopia

PURPOSE

To develop measures and indices of factors (distance of eye from object, posture, and lighting) that may modify a possible effect of near work activity on myopia.

METHODS

The duration of near work, the distance of an object from eye, lighting conditions, and other sociodemographic characteristics were asked in an interview. Both distance and lighting information from the questionnaire were compared with more precise measurements.

RESULTS

Diopter hours were quantified as the duration of near work multiplied by the reciprocal of the distance which the activity was performed. The intraclass correlation coefficient of the reliability of distance information for each type of near work activity ranged from 0.43 to 0.91. Home light meter readings were significantly higher for children who were reading under both room and reading light, and the distances from the questionnaire were comparable to the measured distances.

CONCLUSIONS

Measures of posture, distance, and lighting factors have been developed to study the possible effect modifiers of the effects of near work on myopia.

Incidence of eyelid cancers in Singapore from 1968 to 1995

AIM

To describe the epidemiological characteristics of patients with eyelid malignancies seen in all hospitals in Singapore from 1968 to 1995.

METHOD

The Singapore Cancer Registry has been collecting epidemiological data of all cancers seen in Singapore since 1968. The data of all cases of Singapore residents with eyelid cancers diagnosed from 1968 to 1995 (ICD-9, sites 172.1 and 173.1) were retrieved for analysis.

RESULTS

There were 162 male patients (49.8%) and 163 females (50.2%). The median age at diagnosis was 63 years in males and 66 years in females. The average annual age standardised incidence rate among male Singapore residents was 6.5 per million and 5.5 per million among female Singapore residents. Between 1993 and 1995, the average annual rate for females was 6.8 per million, compared with 3.1 per million between 1968 and 1972. The most common cancer was basal cell carcinoma (84.0%), followed by sebaceous adenocarcinoma (10.2%) and squamous cell carcinoma (3.4%).

CONCLUSION

The annual age standardised incidence for male residents has remained relatively stable. The incidence for female residents has shown a steady increase over the past 28 years. The incidence for males is generally higher than that for females. These expanded epidemiological characteristics may serve to provide a foundation to monitor future disease patterns and to promote further research into the aetiology of these cancers.

Myopia in children born premature or with low birth weight

PURPOSE

To evaluate the association of myopia or astigmatism in children without retinopathy of prematurity (ROP) born premature or with low birth weight.

METHODS

This cross-sectional study was conducted in Singapore where 527 children from three kindergartens aged 2 to 7 years without a history of ROP were recruited. Information on birth weight and gestational age at birth was obtained from a personal booklet and the refractive error in spherical equivalents was measured using distance photoretinoscopy. The data was analysed with univariate analysis and logistic regression models.

RESULTS

There was no difference in the prevalence of myopia in children born premature or with low birth weight. There was also no difference in astigmatism in children born premature or with low birth weight.

CONCLUSION

This study shows no relationship between astigmatism or myopia with prematurity or low birth weight in children born without retinopathy of prematurity.

The epidemiology of obesity: a review

Obesity is a major public health problem worldwide contributing to increased morbidity and mortality. There are several indices of obesity which include body mass index, waist-hip circumference ratio and skinfold thickness. The prevalence of obesity varies from 7% in France to 32.8% in Brazil. However, the comparison of obesity across different countries is difficult as there are different age structures of the population, measurement techniques are not the same and surveys may not be population-based. Trends in developed and developing countries suggest that the rates of obesity are increasing. This rising trend may be contributed by factors such as low levels of physical activity, high calorie intake and long hours of watching television. Cohort and cross-sectional studies have shown that obesity may be linked to an increased risk of coronary heart disease, hypertension, diabetes mellitus and gallstones. There is also a positive association between obesity and cancer. The mortality of obese adults, adolescents and children is higher than that of the general population. Multi-prolonged intervention strategies are needed to prevent obesity and its associated complications.

Gene therapy for cystic fibrosis: a potential cure

Cystic fibrosis is a lethal autosomal recessive disorder. In 1989, the cystic fibrosis gene was isolated on chromosome 7. Positional cloning, linkage analysis, saturation cloning, and chromosome jumping enabled the isolation and cloning of the gene that encodes the cystic fibrosis transmembrane conductance regulator. Current work focuses on the safe, efficient delivery of a functional cystic fibrosis transmembrane conductance gene to patients who are afflicted with cystic fibrosis and the expression of the gene in somatic cells to correct the genetic defect and restore chloride channel function. It is hoped that successful gene therapy will be a feasible and cost-efficient approach that will lead to a cure.

Cigarette smoking and bladder cancer in Washington County, Maryland: ammunition for health educators

To investigate the frequency of cigarette smoking in patients who have been diagnosed with bladder cancer, data were obtained for 1507 subjects listed in the 1975 private census of Washington County, Maryland. Case subjects were defined as persons at least 18 years of age diagnosed with bladder cancer (ICD code = 188.0 to 188.9) between 1975 and 1992 for whom smoking information was available. Control subjects were defined as a random sample of persons frequency matched by age and sex to the cases. Controls were free of bladder cancer and had smoking information available. The odds ratio for current smokers for the association between smoking and bladder cancer adjusted for age and sex was statistically significant (OR = 1.68, 95% confidence intervals, 1.22 to 2.32). The chi-square trend test of the dose-response results was significant (chi-square = 11.69, df = 1, P < .01).