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Cataract Extraction Rates Among Chinese, Malays, and Indians in Singapore
A Population-Based Analysis
Arch Ophthalmol. 2001;119:727-732.
ABSTRACT
| |
Objective To describe the rates of cataract extraction among Chinese, Malays,
and Indians in an urban population in Asia.
Design Population-based incidence study using data from a medical savings fund.
Study Population Chinese, Malay, and Indian residents in Singapore.
Methods Data on all cataract operations performed for "senile cataract" (International Classification of Diseases, Ninth Revision, Clinical
Modification code 366.1) between 1991 and 1996 were retrieved from
Medisave, a population-wide, government-administered medical savings fund.
The Singapore census was used as a denominator to allow an estimation of age,
sex, and race-specific annual rates of cataract surgery.
Results Between 1991 and 1996, 61 210 cataract operations for "senile cataract"
were performed on Singapore residents, which is equivalent to an average rate
of 356.4 cataract operations per 100 000 persons per year (95% confidence
interval [CI], 353.6-359.2). The average rate was highest for Indians (age-sex
adjusted rate of 396.5 per 100 000/year), followed by Chinese (371.2
per 100 000/year), and lowest for Malays (237.2 per 100 000/year).
Women had higher rates of cataract extraction than men (age-adjusted relative
risk, 1.14; 95% CI, 1.11-1.17), with this pattern consistent across the 3
racial groups. The rate of cataract extraction increased by an average of
40 operations per 100 000/year (95% CI, 28.6-52.8) between 1991 and 1996.
Overall, the proportion of cataract extraction without concurrent intraocular
lens implantation was low (n = 762, 1.2%), but rates still decreased by an
average of 0.8 per 100 000 per year (95% CI, 0.03-1.5) during the 6 years.
Conclusions The rate of cataract extraction in Singapore is consistent with rates
seen in developed countries in the West. Racial variation in rates suggests
varying predisposition to cataract development and/or threshold for cataract
surgery between Chinese, Malay, and Indian populations in Singapore.
INTRODUCTION
CATARACT extraction accounts for more than half of all ophthalmic operations,
and it is the most common elective operation in many countries around the
world.1 Data on rates of cataract extraction
are important for optimal planning and allocation of ophthalmic resources,
but are available only from a limited number of countries, such as the United
States,2-4 Scandinavia,5-9
the United Kingdom,10-11 and Australia.12 In Asia, data on cataract extraction rates are lacking.
In Western populations, several distinct patterns in the rates of cataract
surgery have been observed. First, overall rates of cataract surgery have
increased 3- to 6-fold throughout the past 3 decades, from 100 operations
per 100 000 per year in the 1970s and 1980s, to approximately 300 to
500 operations per 100 000 per year in the 1990s.2, 4-5,8, 10, 12
Second, advances in microsurgery and intraocular lens (IOL) technology have
influenced the types of cataract extraction techniques. In Rochester, Minn,
for example, the proportion of cataract extractions with IOL implantation
has increased steadily from 63% in 1980 to 96% in 1987.4
Third, race and sex variations in rates have been described, with rates higher
in whites than blacks,13-14 and
higher in women than in men.4, 13-17
Whether similar time trends and demographic variations exist in Asian populations
is not known.
The purpose of this study was to describe cataract extraction rates
in Singapore, an urban, rapidly developing country in Asia. A unique opportunity
existed to evaluate racial variation in rates between Chinese, Malay, and
Indian people in the population, the majority of whom are first-generation
immigrants from the outlying provinces of China (Fujian and Guandong), the
surrounding islands of Malaysia and Indonesia, and southern India, respectively.
SUBJECTS AND METHODS
Singapore has a stable, multi-ethnic resident population of 3.16 million
people, of whom 77% are Chinese, 14% are Malay, 8% are Indian, and 1% is made
up of other ethnic groups.18 The study population
consisted of all Chinese, Malay, and Indian citizens and permanent residents
in Singapore who are identifiable by a unique identity card number assigned
to all Singapore residents. The institutional review board of the Singapore
National Eye Center approved this study.
CATARACT SURGERY DATA
The numerators were determined from a national medical savings fund
database—the Medisave database, which is managed by the Ministry of
Health's Epidemiology and Disease Control Division. The Medisave system is
a government-administered medical savings program that is available to all
Singapore citizens and permanent residents.19-20
The Medisave fund for Singapore and its use in other analyses has been described
in detail in other reports.21-23
In brief, all Singapore working individuals, including self-employed persons,
are required by law to contribute 6% to 8% of monthly income to a personal
Medisave account. The Medisave account may be used by the individual and his
or her family to pay for up to 80% of medical procedures costs in both the
public and private sector. As of 1995, there were 2.4 million Medisave accounts
(88% of the population).21 Medisave is linked
to 2 other national health financing plans—Medishield, which is a "catastrophic
illness insurance," and Medifund, which is a government grant for people without
adequate Medisave funds or family support. These 3 plans ensure virtually
universal health care coverage, including medically indicated elective ocular
surgery, for all Singapore citizens, permanent residents, and their families.19-20 Surgical procedures are classified
in the Medisave database according to complexity and cost of the operation,
with a total of 98 separate billing categories for ocular operations.
For this study, all possible cataract-related surgical procedures from
the Medisave database between January 1991 and December 1996 were initially
identified. These were categorized into the following 4 main groups of analysis:
(1) Cataract extraction with IOL implantation (including extracapsular cataract
extraction and phacoemulsification techniques); (2) cataract extraction with
no IOL implantation (including intracapsular cataract extraction and lensectomy
techniques); (3) cataract extraction combined with glaucoma surgery (including
trabeculectomy, filtering shunts, and other forms of glaucoma operations),
with or without IOL implantation; and (4) cataract extraction combined with
another surgical procedure (including combined cataract extraction with corneal
graft, combined cataract and vitrectomy, and other miscellaneous operations).
Next, only operations in which a primary diagnosis of "senile cataract"
was made and coded (code 366.1 of the International Classification
of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM]) were
included for analysis. Based on this definition, cataract extractions for
cases of congenital cataract (ICD-9-CM code 743.3), infantile, juvenile and
presenile cataract (code 366.0), traumatic cataract (code 366.2), cataract
secondary to ocular disorders (code 366.3), cataract associated with other
disorders (code 366.4), and other miscellaneous forms of cataract (codes 366.5,
366.8, and 366.9) were excluded. Further, operations in which senile cataracts
were not coded as the primary diagnosis (but could be coded as secondary diagnoses)
were not included. For example, combined cataract extraction and trabeculectomy
in which the primary coded diagnosis was "open-angle glaucoma" would not be
captured by the case definition. Finally, the case definition did not distinguish
between eyes. Thus, a person with bilateral cataract surgery would be counted
twice in the numerator.
Quality control measures are conducted by the Professional Medisave
Audit Unit in the Ministry of Health to prevent misuse of the Medisave funds,
and to ensure accuracy of the data.21-23
First, the reimbursement procedure follows strict guidelines. Second, annual
audits are carried out to assess the precision of the surgical coding of the
Medisave data. Between 5% and 10% of surgical codes are randomly checked against
the actual operations and the case records of each hospital during each audit.
At the Singapore National Eye Center, recent audits conducted on 100 operations
during October 1996, and on 57 operations during September 1997, revealed
no discrepancies between patients' case records and Medisave claims data (P.
L. Kwek, MD, written communication, Epidemiology and Disease Control Division,
Ministry of Health, Singapore, November 1997).
DENOMINATOR DATA
For the denominator, population data were drawn directly from the 1990
Singapore census and 1995 mid-decade census.18
Data for all other years in this study (1991, 1992, 1993, 1994, and 1996)
were based on projections by the Department of Statistics, Singapore.18 Ethnic groups were defined in the census according
to 1 of 4 main ethnic groups: Chinese (refers to persons of Chinese origin
such as Fujian, Guangdong, Hajia, etc), Malays (refers to persons of Malay
or Indonesian origin, such as Javanese), Indians (refers to persons with ancestry
originating on the Indian subcontinent), and others (comprising all persons
other than the first 3 categories, such as people of European, Eurasian, Middle
Eastern, and Japanese ethnicity). Persons of mixed heritage were classified
under the ethnic group of their fathers. As the "others" category includes
multiple ethnic populations, data on this group were not analyzed.
STATISTICAL ANALYSIS
Annual rates of cataract extractions for each subgroup (10-year age,
sex, and ethnic groups) were calculated by dividing the number of cataract
extractions by the population of that subgroup for that year. Age-adjusted
and age-sex–adjusted rates, and 95% confidence intervals (CI) were calculated
by direct adjustment using the appropriate Singapore census population in
1995 to compare rates between sex and race, respectively. Simple linear regression
models were constructed to evaluate the effect of time on rates of cataract
operations.
RESULTS
Between January 1, 1991, and December 31, 1996, there were a total of
63 730 cataract extraction operations for "senile" cataracts retrieved
from the Medisave database in Singapore. Of these, 2390 were operations on
those from the "others" group, and 130 had missing data on either age, sex,
or race, leaving 61 210 cataract operations for further analysis. The
number of cataract operations per year was 7538 in 1991, 7601 in 1992, 9065
in 1993, 10 640 in 1994, 12 380 in 1995, and 13 986 in 1996.
The majority of cataract operations were performed on persons of Chinese ethnicity
(n = 52 175; 85.2% of all operations), female sex (n = 34 615; 56.6%
of all operations), and above the age of 60 years (n = 46 556; 76.1%
of all operations). More than 95% of the operations were "cataract extraction
with IOL implantation," and only 762 operations (1.2%) were not associated
with simultaneous IOL implantation (Table
1).
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Table 1. Average Annual Rate of Cataract Extractions by Type of Surgery
(Singapore, 1991-1996)*
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The rate of cataract surgery averaged throughout the 6 years was 356.4
per 100 000 per year (95% CI, 353.6-359.2). There were variations in
the rate of cataract surgery by age, sex, and race (Table 2). Rates generally increased with age, were higher in women
than in men, and were highest in Indian, followed by Chinese, and lowest in
Malay patients.
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Table 2. Average Annual Rate of Cataract Extractions, by Sex, Age,
and Race (Singapore, 1991-1996)*
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After controlling for age and sex, Indians had 1.67 times, and Chinese
had 1.56 times higher rates than Malays (Table 3). Women had higher rates than men (with an age-adjusted
relative risk of 1.14; 95% CI, 1.11-1.17), with this pattern seen consistently
across all 3 groups. Overall, Indian women had the highest race-sex–specific
rates of cataract surgery, with 2.24 (95% CI, 2.18-2.30) times higher rates
than Malay men.
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Table 3. Age- and Age-Sex–Adjusted Rate of Cataract Extraction
(Singapore, 1991-1996)*
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There was a steady increase in the rate of cataract operations during
the 6-year period, rising from 277.4 per 100 000 per year in 1991, to
465.0 per 100 000 per year in 1996, which is equivalent to an increase
of 40 operations per 100 000 per year (linear regression coefficients: 
= 211.7 and  = 40.7; 95% CI, 28.6-52.8). After controlling for age,
the rate of increase was reduced to an average of 35 operations per 100 000
per year (Figure 1), suggesting
that an aging population partially accounted for the time trend. The excess
rates in women, after controlling for age (Figure 2), and in Indian and Chinese patients, after controlling
for age and sex (Figure 3), were
consistent throughout the 6 years.
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Figure 2. Age-adjusted rates of cataract
extraction (per 100 000 per year) by sex.
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Figure 3. Age-sex–adjusted rates of
cataract extraction (per 100 000 per year) by race.
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COMMENT
Cataract remains the most common cause of blindness in both developing
and developed countries around the world.1
To tackle this problem, the World Health Organization has set a rate of 350
cataract operations per 100 000 population per year as an "ideal" target
for developed countries.24 This target seems
to have been met and even exceeded in several economically developed nations.
In the United States, cataract extraction rates from 1980 to 1994 averaged
372 per 100 000 per year.4 In United Kingdom,
one study estimated a rate of 270 per 100 000 per year in 1990,10 while in Scandinavian countries, rates between 350
and 450 per 100 000 per year have been reported.5, 8
Data from Asia are not readily available. This study therefore provides timely
and useful information on the rates of cataract surgery in an urban, rapidly
developing country in Asia. An overall rate of 356 per 100 000 per year
was observed, within the goal set by the World Health Organization, and consistent
with other studies in Western countries.4-5,8, 10
In addition, increasing rates of cataract extraction over time (by approximately
40 operations per 100 000 per year) were seen. This trend has also been
noted in other countries,2, 7, 9, 11-12
although US rates may have plateaued since the 1993-1994 duration.4
What possible factors may explain the increasing rate of cataract surgery
in Singapore? Taylor1 observed 3 factors that
determine the number of cataract operations in a population: (1) the age structure
of the population; (2) the indications or thresholds for cataract surgery;
and (3) accessibility to cataract surgery among those who want or require
surgery.1 These factors, in combination, may
contribute to the increasing rate of cataract operations seen. After Japan,
Singapore is the second fastest aging nation in Asia, with the population
above 60 years having risen from 9.2% in 1990 to 12% in 2000, and expected
to rise 20% by the year 2030.18, 25
All other factors being constant, an aging population could explain increasing
rates of cataract surgery. However, an aging population did not fully account
for the time trend observed in this study, as age-adjustment only reduced
the rate of increase from 40 per 100 000 per year to 35 per 100 000
per year. Similarly, increasing rates of cataract surgery seen in the United
States between 1968 to 1976,2 in Denmark between
1980 and 1991,7 and in Australia between 1985
and 199412 could not be explained fully by
an aging population structure.
The second factor, changing thresholds or increasing "demand" for cataract
surgery, seems to be an important additional determinant. Visual function,
including visual acuity, is the major criterion in determining the need for
cataract surgery. Data from the Visual Impairment Project26
suggest that the number of cataract operations increases 2.5 times as the
visual acuity criterion changes from less than 20/200 to less than 20/80,
and 5-fold if it shifts to less than 20/40. In addition, advances in cataract
extraction and IOL technology, a shift toward local anesthesia and day surgery,
and greater patient expectation and demand for cataract surgery also contribute
to the changing threshold for cataract surgery seen in other countries.1-2,7, 12, 27
Similar trends in cataract surgery technology seem to be important in Singapore
as well. In a previous study of cataract extraction in Singapore, of the approximately
3000 cataract operations in 1982, only 32 reportedly involved an IOL implant.28 On the other hand, more than 98% of the operations
in this study involved IOL implants, with operations without IOL implants
decreasing by 0.8 per 100 000 per year throughout the 6 years. In the
1980s, fewer than 15% of cataract operations were performed as day surgical
cases; in 1992, this proportion was 95%.28
In 1992, the ratio of phacoemulsification vs extracapsular cataract extraction
was less than 1%; in 1996, this ratio was 25%.28
While no data are available, it is not unreasonable to suggest that greater
visual expectations in the population and lower visual acuity thresholds for
cataract surgery may also contribute to the increasing rate of cataract extraction
seen.
The third factor in explaining the increasing rate of surgery in Singapore
is increasing accessibility or increasing "supply" of cataract surgery services.
In the United States, "supply-side" variables, such as the increasing number
of ophthalmologists, seem to be important in determining the number of cataract
operations performed.2 In Singapore, the number
of ophthalmologists has increased more than 50% in decade; in 1989, there
were 53 ophthalmologists (1 per 50 000 persons), but by 1999, this number
had risen to 82 (1 per 38 000).
In this study, women were observed to have 14% higher rates of cataract
surgery than men after controlling for age, while Indian and Chinese patients
had 67% and 56% (respectively) higher rates than Malays after controlling
for age and sex. Sex variation in cataract operations has been investigated
elsewhere, and it seems to be related to variation in the incidence and prevalence
of cataract, threshold and indications for cataract surgery, and access to
cataract surgery between men and women.4, 13-17
The modest excess in rates for women in Singapore could be related to any
of the above factors.
More interesting, but more difficult to explain, was the variation in
cataract extraction rates between Chinese, Indian, and Malay patients. Several
explanations are possible. First, racial variation in accessibility to cataract
surgery in Singapore, as in other countries, should be considered.13-14 Although not proven, it is believed
that overall health care and socioeconomic status may be lower in Malays compared
with Indians and Chinese. This is suggested by studies that indicate lower
life expectancy in Malay persons,29 and poorer
glycemia and blood pressure control in Malay persons with diabetes and hypertension,
respectively.30 However, given the magnitude
of the variation in cataract surgery rates observed, and the fact that cataract
surgery can be paid for by Medisave in 90% of the population (with inexpensive,
subsidized operations available for the remaining 10%), accessibility is unlikely
the only explanation. A second and more probable explanation is racial variation
in indications or threshold for cataract surgery. Studies comparing mortality
rates in asthmatic persons in Singapore have suggested that Malays have higher
symptom thresholds prior to seeking medical attention.31
It is therefore possible that Malay persons have higher thresholds for cataract
surgery than Chinese or Indian patients with similar severity of lens opacity
and visual disability. Third, racial variation in incidence and prevalence
of cataract has been noted in other countries, and it may be significant in
Singapore as well.32-33 No local
data are available regarding racial variation in risk of cataract, but previous
studies have suggested that Malay persons have lower rates of cataract risk
factors such as ocular trauma,22 angle-closure
glaucoma,23, 34 myopia,35 and diabetes.36 Further
studies on the epidemiology of cataract among these 3 groups will provide
additional information.
The main strengths of this current study include a population-wide identification
of cataract extraction cases throughout a 6-year period, and accurate records.
However, there were some important limitations. The possibility of differential
underreporting and misclassification of cataract surgery between men and women
and racial groups could not be dismissed. In addition, if rates of second
eye cataract surgery were high, part of the demographic variation could be
explained by variation in rates of second eye cataract surgery.
In conclusion, this study provides data on the rate of cataract extraction
in an Asian population. First, an overall rate of 356 cataract operations
per 100 000 per year was observed, comparable with rates in other countries
in the West. Second, there were variations in rates between sex and race,
with an excess of cataract operations among women compared with men, and among
Indians and Chinese compared with Malays. In particular, the magnitude of
the observed variation suggests differences in risk of cataract and/or threshold
for cataract surgery between the 3 ethnic groups.
AUTHOR INFORMATION
Accepted for publication September 25, 2000.
Corresponding author: Tien Yin Wong, FRCS(Ed), MPH, Department of
Ophthalmology, National University of Singapore, 10 Kent Ridge Crescent, Singapore
119260 (e-mail: tienyinwong{at}yahoo.com).
Tien Yin Wong, FRCS(Ed), MPH
From the Singapore National Eye Center, Singapore Eye Research Institute
and National University of Singapore, Singapore; the Department of Ophthalmology
and Visual Sciences, University of Wisconsin, Madison; and the Department
of Epidemiology, Johns Hopkins University, Baltimore, Md.
REFERENCES
1. Taylor HR. Cataract: how much surgery do we have to do? Br J Ophthalmol. 2000;84:1-2.
FREE FULL TEXT
2. Nadler DJ, Schwartz B. Cataract surgery in the United States, 1968-1976: a descriptive epidemiologic
study. Ophthalmology. 1980;87:10-18.
ISI
| PUBMED
3. Stark WJ, Sommer A, Smith RE. Changing trends in intraocular lens implantation. Arch Ophthalmol. 1989;107:1441-1444.
FREE FULL TEXT
4. Baratz KH, Gray DT, Hodge DO, Butterfield LC, Ilstrup DM. Cataract extraction rates in Olmsted County, Minnesota, 1980 through
1994. Arch Ophthalmol. 1997;115:1441-1446.
FREE FULL TEXT
5. Stenevi U, Lundstrom M, Thorburn W. A national cataract register, I: description and epidemiology. Acta Ophthalmol Scand. 1995;73:41-44.
ISI
| PUBMED
6. Sletteberg O, Hovding G, Bertelsen T. Do we operate on too many cataracts? Acta Ophthalmol Scand. 1995;73:77-80.
ISI
| PUBMED
7. Norregaard JC, Bernth-Petersen P, Andersen TF. Changing threshold for cataract surgery in Denmark between 1980 and
1992: results from the Danish Cataract Surgery Outcomes Study, II. Acta Ophthalmol Scand. 1996;74:604-608.
ISI
| PUBMED
8. Ninn-Pedersen K, Stenevi U, Ehinger B. Cataract patients in a defined Swedish population, 1986-1990, I: resources
and epidemiology. Acta Ophthalmol (Copenh). 1994;72:1-9.
PUBMED
9. Bernth-Petersen P, Bach E. Epidemiologic aspects of cataract surgery, I: trends in frequencies. Acta Ophthalmol (Copenh). 1983;61:220-228.
10. Williams ES, Seward HC. Cataract surgery in South West Thames Region: an analysis of age-adjusted
surgery rates and length of stay by district. Public Health. 1993;107:441-449.
FULL TEXT
|
ISI
| PUBMED
11. Jay JL, Devlin ML. The increasing frequency of surgery for cataract. Eye. 1990;4:127-131.
12. Keeffe JE, Taylor HR. Cataract surgery in Australia 1985-94. Aust N Z J Ophthalmol. 1996;24:313-317.
ISI
| PUBMED
13. Sharkness CM, Hamburger S, Kaczmarek RG, Hamilton PM, Bright RA, Moore RM Jr. Racial differences in the prevalence of intraocular lens implants in
the United States. Am J Ophthalmol. 1992;114:667-674.
ISI
| PUBMED
14. Javitt JC, Kendix M, Tielsch JM, et al. Geographic variation in utilization of cataract surgery. Med Care. 1995;33:90-105.
ISI
| PUBMED
15. Carlsson B, Sjostrand J. Increased incidence of cataract extractions in women above 70 years
of age: a population based study. Acta Ophthalmol Scand. 1996;74:64-68.
ISI
| PUBMED
16. Lundstrom M, Stenevi U, Thorburn W. Gender and cataract surgery in Sweden, 1992-1997: a retrospective observational
study based on the Swedish National Cataract Register. Acta Ophthalmol Scand. 1999;77:204-208.
FULL TEXT
|
ISI
| PUBMED
17. Monestam E, Wachtmeister L. Cataract surgery from a gender perspective: a population based study
in Sweden. Acta Ophthalmol Scand. 1998;76:711-716.
FULL TEXT
|
ISI
| PUBMED
18. Department of Statistics. Yearbook of Statistics 1997. Singapore, Singapore; 1997.
19. Massaro TA, Wong YN. Medical Savings Accounts: The Singapore Experience. Washington, DC: National Center for Policy Analysis; April 1996.
NCPA Policy Report No. 203.
20. Phua KH. Savings for health. World Health Forum. 1987;8:39-41.
21. Wong TY, Tielsch JM, Schein OD. Racial difference in the incidence of retinal detachment in Singapore. Arch Ophthalmol. 1999;117:379-383.
FREE FULL TEXT
22. Wong TY, Tielsch JM. A population-based study on the incidence of ocular trauma in Singapore. Am J Ophthalmol. 1999;128:345-351.
FULL TEXT
|
ISI
| PUBMED
23. Wong TY, Foster PJ, Seah SKL, Chew PTK. Rates of hospital admissions for primary angle closure glaucoma among
Chinese, Malays and Indians in Singapore. Br J Ophthalmol. 2000;84:990-992.
FREE FULL TEXT
24. World Health Organization. Global Initiative for the Elimination of Avoidable
Blindness: An Informal Consultation. Geneva, Switzerland: World Health Organization; 1997. WHO publication
97.61.
25. The World Bank. World Development Report 1997: The State in a Changing
World. New York, NY: Oxford University Press; 1997.
26. McCarty CA, Keeffe JE, Taylor HR. The need for cataract surgery: projections based on lens opacity, visual
acuity, and personal concern. Br J Ophthalmol. 1999;83:62-65.
FREE FULL TEXT
27. Moorman C, Sommer A, Stark W, Enger C, Payne J, Maumenee AE. Changing indications for cataract surgery: 1974 to 1988. Ophthalmic Surg. 1990;21:761-766.
ISI
| PUBMED
28. Lee SY, Tan DTH. Changing trends in cataract surgery in Singapore. Singapore Med J. 1999;40:256-259.
PUBMED
29. Lun KC. Mortality analyses of the 1990 Singapore population, I: general life
tables. Ann Acad Med Singapore. 1995;24:382-392.
PUBMED
30. Epidemiology and Disease Control Department, Ministry of Health, Singapore. The National Heath Survey 1998, Singapore. Singapore, Singapore: Ministry of Health; 1999.
31. Ng TP, Tan WC. Temporal trends and ethnic variations in asthma mortality in Singapore,
1976-1995. Thorax. 1999;54:990-994.
FREE FULL TEXT
32. West SK, Munoz B, Schein OD, Duncan DD, Rubin GS. Racial differences in lens opacities: the Salisbury Eye Evaluation
(SEE) project. Am J Epidemiol. 1998;148:1033-1039.
FREE FULL TEXT
33. Taylor HR. Racial variation in vision. Am J Epidemiol. 1981;113:62-80.
FREE FULL TEXT
34. Seah SKL, Foster PJ, Chew PT, et al. Incidence of acute primary angle-closure glaucoma in Singapore: an
island-wide survey. Arch Ophthalmol. 1997;115:1436-1440.
FREE FULL TEXT
35. Au Eong KG, Tay TH, Lim MK. Race, culture and myopia in 110,236 young Singaporean males. Singapore Med J. 1993;34:29-32.
PUBMED
36. Tan CE, Emmanuel SC, Tan BY, Jacob E. Prevalence of diabetes and ethnic differences in cardiovascular risk
factors: the 1992 Singapore National Health Survey. Diabetes Care. 1999;22:241-247
FREE FULL TEXT
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