Utility values for age-related macular degeneration patients in Korea
Utility values for age-related macular degeneration patients in Korea
Seulggie Choi 0 3
Sang Min Park 0 1 3
Donghyun Jee 2 3
0 Seoul National University Graduate School, Department of Biomedical Sciences , Seoul , Republic of Korea
1 Seoul National University Hospital, Department of Family Medicine , Seoul , Republic of Korea
2 St. Vincent's Hospital, College of Medicine, Division of Vitreous and Retina, Department of Ophthalmology, Catholic University of Korea , Suwon , Republic of Korea
3 Editor: Gianni Virgili, Universita degli Studi di Firenze , ITALY
Sociodemographic factors and visual acuity are important factors in determining the quality
of life among AMD patients. Preserving BEVA, regardless of WEVA, may be associated
with improved quality of life.
Funding: This study was supported by a grant
from the Korea Health Technology R&D Project
through the Korea Health Industry Development
Institute (KHIDI), funded by the Ministry of Health
& Welfare, Republic of Korea (Grant number:
HI17C1234, URL: http://www.khidi.or.kr/eps). The
funders had no role in study design, data collection
and analysis, decision to publish, or preparation of
Age-related macular degeneration (AMD) is the most common cause for blindness in
developed countries [
]. A progressive disorder characterized by atrophy of the macula and central
vision function impairment, AMD primarily affects the elderly population [
]. Due to the
ever-increasing proportion of elderly adults, the incidence and prevalence of AMD are
expected to increase globally [
]. Due to the fact that AMD may lead to serious vision
impairment, one of the primary concerns for AMD patients is reduced quality of life.
Therefore, a major therapeutic goal for AMD management is maintaining the quality of life of the
patients at a socially acceptable cost. Identifying and controlling factors associated with
reduced utility values among AMD patients are needed in order to maximize the quality of life
for AMD patients.
Although multiple previous studies have evaluated the utility values for AMD patients,
most studies focused on visual acuity of AMD patients [
]. However, sociodemographic
factors such as household income and education are also important contributors to utility values,
indicating the need for studies investigating the impact of sociodemographic factors on utility
values among AMD patients. Moreover, there are limited studies on utility values for AMD
patients within Asian populations. Multiple reports have shown that AMD patients within
Asian populations differ from those within Western populations in prevalence of AMD
subtype, which could lead to different utility values among Asian populations . Furthermore, as
the innate differences in sociocultural and healthcare across regions may lead to different
utility values, studies evaluating the quality of life among AMD patients within Asian populations
Therefore, using a nationwide representative survey in Korea, we investigated the
sociodemographic and clinical factors associated with utility values among AMD patients.
Materials and methods
The Korean National Health and Nutrition Examination Survey (KNHANES) database
conducted from 2008 to 2012 was used for this study. A nationwide population-based
cross-sectional survey consisting of health records from health interviews and
examinations, KNHANES is conducted by the Division of Chronic Disease Surveillance from the
Korea Centers for Disease Control and Prevention. KNHANES represents the entire
noninstitutionalized population in Korea since approximately 4,000 households in 200
enumeration districts are selected annually by a stratified, multistage, clustered sampling
method. All participants signed informed consent forms agreeing to the use of their
information in this survey. The Korean Ophthalmologic Society had participated in KNHANES
from 2008 to 2012, which led to inclusion of ophthalmologic interviews and examinations
conducted by trained ophthalmologists.
All participants underwent a thorough ophthalmologic examination, which included a
45-degree digital retinal image for each eye. Early AMD was defined as the presence of a soft
drusen or any drusen with pigmentation changes in the macular retinal pigment epithelium
(RPE). Wet AMD was defined when detachment of the RPE or sensory retina, or subretinal
epithelial hemorrhages or scars were observed. Dry AMD was defined upon retinal
depigmentation spanning 175 ?m in diameter with visible choroidal vessels. A detailed description of
defining AMD patients can be found in a previous study [
]. Finally, visual acuity was
measured at 4 meters with an international standard vision chart based on the LogMAR Scale
(Jin's Vision Chart, Seoul, Korea).
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Among the 26,622 participants aged 19 years or more with data available on fundus images,
25,314 participants who did not meet the criteria for having AMD were excluded, resulting in
1,308 AMD patients (prevalence rate 4.9%). Among them, 4 participants without values on
education status, 20 participants without values on household income, and 1 participant
without values on martial status were excluded, ultimately resulting in a study population of 1,283
Measurement of utility value
The three-level version of EuroQol-5D (EQ-5D-3L), developed by the EuroQol group, is a
generic preference-based measure consisting of five questions that reflect the current health
status of the patient. The questions are composed of five dimensions: mobility, self-care, usual
activities, pain/discomfort, and anxiety/depression. Each question has three levels that indicate
(a) no problem, (b) some problems, or (c) severe problems. A possible 243 health states can be
described by EQ-5D-3L based on the five dimensions and three levels for each dimension.
EQ5D-3L have been widely used as a method of assessing the health status. EQ-5D-3L is useful
for comparison across regions due to its brevity, making it possible to compare utility values
across countries and populations. Following the EuroQol group-recommended procedure, the
Korean EQ-5D-3L was developed by the Korean Centers for Disease Control and Prevention.
The range for the Korean EQ-5D-3L utility score is from -0.171 (worst health status) to 1.000
(best health status). EQ-5D-3L is a continuous measure of utility, with values closer to 1.000
indicating the highest utility values. Since EQ-5D-3L is a continuous measure, no particular
cut-off points exist that indicate a certain level of utility, but rather is useful in comparing
utility values between certain groups by mean values.
Demographics and measures of AMD severity
Among patient demographics, age (years, less than 50, 50?59, 60?69, and 70 or more), sex
(men and women), education (elementary school or lower, middle school, high school,
technical college, and college or higher), employment status (yes and no), household income (1st,
2nd, 3rd, and 4th quartiles), and marital status (yes and no) were determined by a questionnaire.
AMD subtype (early and late), and vision loss (no vision loss and vision loss) defined when
visual acuity was measured at less than 0.1 in either eye, were determined by ophthalmologic
examinations. Based on the visual acuity determined by ophthalmologic examinations,
patients were categorized into 20/20 to 20/25, 20/30 to 20/40, 20/50 to 20/100, and 20/200
for both best-eye visual acuity (BEVA) and worst-eye visual acuity (WEVA). Finally,
participants were divided into 20/40: 20/200, 20/40:<20/200, <20/40 20/200, and <20/
40:<20/200 for the ratio between BEVA and WEVA values.
The proportions of the patient demographics and measures of AMD severity were calculated
in the number of patients and percent. For each patient demographic and measures of AMD
severity, the mean, standard deviation (SD), and 95% confidence intervals (CI) of EQ-5D-3L
utility values were calculated. Comparisons of utility values were done by the Kruskal-Wallis
test due to the expected non-normal distribution of values. For the analysis of utility values
according to sociodemographic factors, participants without AMD (n = 24,691) were
separately used to determine the utility values according to sociodemographic factors. Statistical
significance was determined at a p value of less than 0.05. All statistical analyses were
conducted with STATA 13.0 (StataCrop LP, College Station, TX, USA).
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Informed consent was obtained for all participants of KNHANES from 2008 to 2012 before
the survey. Since KNHANES is a publicly available database from the Korea Centers for
Disease Control and Prevention, approval from the Institutional Review Board was not needed.
All research methods adhered to the tenets of the Declaration of Helsinki.
In this study, we have shown that sociodemographic factors including age, sex, education,
employment status, and household income are important contributors to the quality of life
among AMD patients. Furthermore, patients with high BEVA tended to have greater utility
values compared to those with low BEVA, regardless of WEVA.
To our knowledge, only one other study investigated utility values for AMD patients within
an Asian population [
]. In 2012, Au Eong and colleagues revealed that the mean EQ-5D score
for 338 AMD patients was 0.89 [
]. This score is similar to our mean EQ-5D-3L score of
0.8765, which is significantly higher than that from studies within Western population. In a
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multi-center study investigating EQ-5D scores for AMD patients, Soubrane and colleagues
showed that the mean EQ-5D score for 401 patients from France, Germany, Spain, the United
PLOS ONE | https://doi.org/10.1371/journal.pone.0201399
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Kingdom, and Canada was 0.65 [
]. Similarly, Lotery and colleagues revealed that the mean
EQ-5D score for AMD patients from the United Kingdom was 0.67 [
Several reasons for the apparent difference in utility values of AMD patients among
Western and Asian populations may exist. First, polypoidal choroidal vasculopathy (PCV), an
AMD variant, appears to be more common among Asian populations, while neovascular
AMD is more common in Western populations [
]. While neovascular AMD leads to
progressive scarring, the natural history of PCV is characterized by less scarring, which could lead to
less severe visual impairment among Asian AMD patients [
]. Second, the innate differences
in sociocultural factors may have contributed to the patients' perception of the disease, as well
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as coping strategies, which could in turn result in differing utility scores according to region
. Specifically, it has been previously suggested that the fact that elderly adults, the main
population susceptible to AMD, have a greater tendency to reside alone or with only one
person among Western regions may contribute to the lower utility values within Western
]. As residing alone may lead to lower quality of life among elderly adults, such
sociocultural factors may have contributed to the lower EQ-5D scores for AMD patients in
Western populations compared to that from our study [
]. Indeed, higher utility scores for
Asian populations compared to those for Western populations are also observed among not
only AMD patients, but also glaucoma, diabetic retinopathy, and myopia patients [13?16].
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Only a few studies have investigated the effect of sociodemographic factors on utility values
among AMD patients. In a study investigating the quality of life for diabetic retinopathy and
AMD patients, Brown and colleagues have shown that among age, sex, and visual acuity, only
visual acuity was associated with quality of life among AMD patients [
]. This is in contrast
to the results from our study, in which both age and sex, along with visual acuity, was also
associated with utility values. Although the exact reasons for this discrepancy are unknown,
evidence from studies of utility values among the general population according to
sociodemographic characteristics seem to be more in line with the results from our study. For example,
greater age, lower education, unemployment, and lower household income may be associated
with decreased psychosocial well-being, an important factor that contributes to the quality of
life among AMD patients [
]. In our study, particularly as most patients did not experience
vision loss, sociodemographic factors such as education and employment have been shown to
be important drivers of the quality of life among AMD patients.
Previous studies are in line with the results from our study depicting decreased utility values
for those with worse visual acuity. In a study determining the impact of AMD on quality of
life, Espallargues and colleagues showed that visual acuity was significantly associated with
utility values among AMD patients [
]. Similarly, Brown and colleagues conducted a study
investigating the association between BEVA and utility values among AMD patients and
revealed that utility values among AMD patients are highly dependent on the degree of BEVA
]. Finally, in a study investigating the association between BEVA, WEVA, and utility values
among AMD patients, Sahel and colleagues depicted that both BEVA and WEVA influenced
quality of life, with BEVA contributing more significantly to general vision-related quality of
life compared to WEVA [
]. Although both BEVA and WEVA were associated with utility,
the lower utility values for those with low BEVA regardless of WEVA indicates the importance
of managing BEVA in order to maintain quality of life for AMD patients. Indeed, while
interventions aimed at minimizing visual acuity reduction on the worst-seeing eye are needed,
management of best-seeing eye may be imperative in maintaining the quality of life for AMD
Interestingly, there was no difference in utility values according to AMD subtype. Unlike
early AMD, late AMD patients generally undergo therapeutic interventions in order to delay
the progress of the disease. Although poorly managed late AMD could lead to reduced visual
acuity, late AMD patients did not have significantly lower utility values. One possible
explanation for this could be related to the high-level of care late AMD patients receive in Korea. Due
to the near-universal health care system and relative ease in which patients can receive care
from teaching hospitals, it is reasonable to assume that most late AMD patients in Korea have
assess to therapeutic management in a timely manner, which could ultimately lead to utility
values similar to those of early AMD patients [
]. However, the exact reasons for the lack of
discrepancy in quality of life according to AMD subtype are unknown and merit further
Several limitations must be considered when interpreting the results from our study. First,
utility value was measured by EQ-5D only. Although EQ-5D is a widely-used measure of
utility, other modes of utility measurement, such as time trade-off and standard game methods
are needed to validate the findings from this study. Second, the cross-sectional design of the
study only reveals the association between sociodemographic and clinical characteristics with
utility values. Therefore, future studies with longitudinal designs are needed. Third, other
clinical factors that may affect utility values, such as contrast sensitivity, were not included in our
study due to the lack of information. Finally, there may not have been enough participants
with vision loss and late AMD to adequately determine the difference in utility values
according to AMD subtype and vision loss. For example, power calculation for the number of
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participants with vision loss required revealed 479 patients (for alpha and power values of 0.05
and 0.80, respectively), which is far larger than the 48 patients with vision loss in our study.
Future studies with greater numbers of AMD patients with vision loss and late AMD are
required to adequately determine whether differences in utility values exist according to AMD
subtype and vision loss.
Despite these limitations, a number of strengths exist. First, the relatively large study
population and nationally-representative data enhance the generalizability of our findings. Second,
we took into account several factors in addition to visual acuity, including age, sex, household
income, education, employment, and martial status, revealing that such sociodemographic
factors are important contributors in determining the quality of life for AMD patients. Third, we
conducted the study within an Asian population, a study group little-studied previously.
Sociodemographic factors are important contributors to the quality of life for AMD patients in
Korea. Furthermore, high BEVA, regardless of WEVA, was associated with greater utility
value. Preventing BEVA reduction may be important in maintaining utility values for AMD
Conceptualization: Seulggie Choi, Sang Min Park, Donghyun Jee. patients.
Data curation: Seulggie Choi, Sang Min Park. Formal analysis: Seulggie Choi, Donghyun Jee.
Funding acquisition: Donghyun Jee.
Investigation: Seulggie Choi, Donghyun Jee.
Methodology: Sang Min Park, Donghyun Jee.
Project administration: Donghyun Jee.
Supervision: Sang Min Park, Donghyun Jee.
Writing ? original draft: Seulggie Choi, Sang Min Park, Donghyun Jee.
Writing ? review & editing: Sang Min Park, Donghyun Jee.
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