Disparities between Ophthalmologists and Patients in Estimating Quality of Life Associated with Diabetic Retinopathy
Disparities between Ophthalmologists and Patients in Estimating Quality of Life Associated with Diabetic Retinopathy
Xiaofeng Zhu☯ 0 1
Qian Sun☯ 0 1
Haidong Zou 0 1
Xun Xu 0 1
Xi Zhang 0 1
0 Department of Ophthalmology, Shanghai First People's Hospital, affiliated Shanghai Jiaotong University , Shanghai , China
1 Editor: Chen-Wei Pan, Medical College of Soochow University , CHINA
Data Availability Statement: All relevant data are
within the paper.
Funding: This study was supported by a grant from
Shanghai Health Bureau and a grant from Hong Kong
K.C. Wong Education foundation.
Competing Interests: The authors have declared
that no competing interests exist.
This study aimed to evaluate and compare the utility values associated with diabetic retinopathy (DR) in a sample of Chinese patients and ophthalmologists.
Utility values were evaluated by both the time trade-off (TTO) and rating scale (RS)
methods for 109 eligible patients with DR and 2 experienced ophthalmologists. Patients
were stratified by Snellen best-corrected visual acuity (BCVA) in the better-seeing eye.
The correlations between the utility values and general vision-related health status measures were analyzed. These utility values were compared with data from two other studies.
The mean utility values elicited from the patients themselves with the TTO (0.81; SD 0.10)
and RS (0.81; SD 0.11) methods were both statistically lower than the mean utility values
assessed by ophthalmologists. Significant predictors of patients’ TTO and RS utility values
were both LogMAR BCVA in the affected eye and average weighted LogMAR BCVA. DR
grade and duration of visual dysfunction were also variables that significantly predicted
patients’ TTO utility values. For ophthalmologists, patients’ LogMAR BCVA in the affected
eye and in the better eye were the variables that significantly predicted both the TTO and
RS utility values. Patients’ education level was also a variable that significantly predicted
RS utility values. Moreover, both diabetic macular edema and employment status were sig
nificant predictors of TTO and RS utility values, whether from patients or ophthalmologists.
There was no difference in mean TTO utility values compared to our American and Canadian patients.
DR caused a substantial decrease in Chinese patients’ utility values, and ophthalmologists
substantially underestimated its effect on patient quality of life.
Diabetic retinopathy (DR) is the major cause of acquired vision loss and is the most common
microvascular complication of diabetes [
]. With rapid lifestyle changes occurring in China,
the estimated prevalence of diabetes has increased to 11.6% among Chinese adults [
], with at
least 20% of diabetic patients suffering from DR [
]. Visual impairment from DR places a
considerable burden on patients’ quality of life (QoL) [
In recent years, the QoL of DR patients has gradually become a concern among
ophthalmologists. A variety of vision-specific functioning and QoL questionnaires, such as the Visual
Functioning Index (VF-14) [
], the National Eye Institute’s Visual Function Questionnaire
], and the Impact of Vision Impairment (IVI) questionnaire [
offer tools for studying the QoL of DR patients. Outcome analyses of the questionnaires
showed that the QoL of DR patients was significantly lower than that of healthy individuals.
Nevertheless, these questionnaires have shortcomings, including a limited number of questions
and the incomplete assessment of DR patients’ QoL, their subjective desires and perceptions.
Utility measures of health-related QoL are preference values that patients attach to their
overall health status [
]. Conventionally, a utility value is a value between two extreme endpoints,
1.0 and 0.0, where 1.0 implies a perfect health state and 0.0 usually signifies death [
higher utility value reflects a higher patient QoL, including capacities for physical activities and
social and psychological health . Utility values for DR, using both the Standard Gamble (SG)
and time trade-off (TTO) methods, have been applied in several studies. However, the overall
utility values have considerable variability, which is likely caused by differences in study design,
methodology, sample size, and DR severity, with or without diabetic macular edema (DME).
After reviewing the English and Chinese literature, using PubMed and Chinese BioMedical
Literature (CBM) databases, we found that only one study assessed the utility values associated
with DR in a non-Western population [
]. However, China has the greatest public health
burden of DR in the world, and DR patients’ QoL relates to their culture and geography [
Furthermore, Brown suggested that it is important to appreciate the disparity in estimations of
utility values between age-related macular degeneration (AMD) patients and ophthalmologists
], and ophthalmologists should incorporate the needs and wants of the patient into
treatment decisions. To our knowledge, no published report has shown the disparities between
patients’ and ophthalmologists’ perceptions of QoL associated with DR.
The present study was performed to evaluate the utility values associated with DR in a
Chinese population using the rating scale (RS), another commonly used method for utility values,
and the TTO method to compare the assessed patient and ophthalmologist utility values and to
demonstrate some related indexes of these utility values. In addition, we investigated the
consistency of utility values among patients with DR through a comparison of our sample and the
other two samples obtained in a similar manner in different countries.
Materials and Methods
Study design and population
In this cross-sectional study, consecutive patients were recruited from a predominantly
vitreoretinal and comprehensive ophthalmologic outpatient service at the First People’s
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Hospital affiliated to Shanghai Jiaotong University, China, between October 2014 and March
The main inclusion criteria were that patients had a diagnosis of DR, at least a history of
diabetes mellitus (DM) associated with retinal microaneurysms, and had been suffering from
visual impairment (20/30 or worse in at least one eye). The latter was defined as either visual
impairment occurring primarily secondary to DR or the exclusion of primary visual
impairment caused by other reasons (such as cataract, glaucoma, or AMD), which have been
previously reported [
]. Patients were excluded from the study for inability or unwillingness
to answer the questions posed. In addition, patients with Alzheimer’s disease or other forms of
dementia who were poorly communicative were also excluded.
This study was approved by the institutional review boards of the First People’s Hospital
affiliated to Shanghai Jiaotong University and adhered to the tenets of the Declaration of
Helsinki. Moreover, written informed consent was obtained from all study patients.
All patients underwent a comprehensive ophthalmologic examination that included
determining the Snellen best corrected visual acuity (BCVA) in both eyes, an anterior segment
examination, dilated funduscopy, and an assessment of the DR grade [
] (according to the
annual meeting of the American Academy of Ophthalmology proposed international clinical
disease severity grading scale for DR in 2002) and the presence of DME.
A standardized interview was performed by experienced researchers trained in utility
valuation. Detailed demographic information including age, gender, years of formal education after
kindergarten, employment status, marital status, the number of systemic co-morbidities
(including cardiac, respiratory, neurologic diseases, and cancer), the duration of DM (time
since the onset of DM diagnosis), and the duration of visual dysfunction were collected in the
interview. The TTO and RS methods for calculating the utility values were used to evaluate the
patients’ health-related QoL.
TTO visual utility values from patients were measured using a standard methodology
described in other DR studies [
]. Patients were asked two hypothetical questions: (1)
how many years of remaining life they expect to live; and (2) in patients with abnormal visual
acuity (<20/30 in at least one eye), each was asked to quantify the maximum number of years
of remaining life, if any, they would be willing to trade in return for permanently perfect vision
in each eye. In patients with good bilateral visual acuity (20/20-20/25), each was asked to
quantify the maximum number of years of their remaining life, if any, that they would be willing to
trade in return for a guarantee of retaining good vision in each eye for the remaining years. The
utility value was calculated by these two pieces of data as follows: utility value = 1.0 –X
(X = time traded/time of remaining life). For example, if a 60-year-old patient expects to live
20 years and would be willing to trade in return 5 years for perfect vision, the utility value is
calculated as 1.0−5/20 = 0.75.
The RS was a vertical and calibrated visual analogue scale (0–100). The patients were asked
the subject question: On a scale where 0 represents blind and 100 represents perfect vision,
where would you rate your current vision? The score (Q) was chosen by patients, and the data
obtained were used to calculate the following: utility value = Q/100.
Ophthalmologists were asked to assume they had the same health status as each
corresponding patient and then to assess utility values according to his or her own perceptions. The
two ophthalmologists, with an average age of 40 and each having more than 10 years’ of
experience in vitreoretinal diseases, made their final assessments. Ophthalmologists who traded more
time or chose a lower scale than did actual patients (as indicated by lower utility values) may
have overestimated the impact that a medical condition has on QoL. Conversely,
ophthalmologists who opted to give up less time or chose a higher scale (as indicated by higher utility
values) may have underestimated patients’ suffering. The utility values assessment was
double3 / 15
masked so that neither the patient nor the ophthalmologist had access to the other’s utility
Data management and analysis
Before the study was undertaken, sample size was calculated employing values from a previous
] with SPSS Sample Power 3.0 (SPSS Inc., Chicago, IL, USA), with a 2-sided alpha of
0.05 and 90% power. A total of 94 patients was necessary to demonstrate a 10% difference in
mean utility values, and a total of 43 patients was necessary to demonstrate a 15% difference.
Snellen BCVA was converted to the logarithm of the minimum angle of resolution
(LogMAR) for statistical analysis [
]. The weighted average LogMAR BCVA of both eyes was
calculated as follows: the weighted average gave a 0.75 weighting to the better eye and a 0.25
weighting to the worse eye [
Descriptive statistical analyses were performed to characterize the demographic data, visual
acuity, clinical characteristics, and utility values. The paired, 2-tailed Student t test was used to
compare the mean utility values of the TTO and RS between patients and ophthalmologists.
Box-plots were used to provide a more detailed distribution of the utility values. Correlations
of the utility values from patients and ophthalmologists were analyzed with linear regression
analysis. A correlation coefficient (R2) 0.70 was considered to be a significant correlation.
The independent-samples t test and the Mantel-Haenszel chi-square test were used to compare
the major clinical characteristics of the patients.
Multivariate linear regression was used to evaluate the relationship of the utility values,
whether from DR patients or ophthalmologists, and the independent variables of age,
education, the number of systemic comorbidities, the duration of DM and visual dysfunction, DR
grade, LogMAR BCVA in affected eye, LogMAR BCVA in the better-seeing eye, and the
weighted average LogMAR BCVA at the same time point, using an entry p = 0.05 and an exit
p = 0.10. Bivariate analyses were performed to determine the association between the utility
values and the dichotomous variables of interest (gender, DME, employment and marital
status). Pearson correlation coefficients and analysis of variance (ANOVA) were used with
appropriate significance tests. One-way ANOVA and the Dunnett t test were used to compare our
TTO data with those of Brown and associates [
] obtained from 95 American patients with
DR and those of Sharma and associates [
] obtained from 186 Canadian patients with DR.
The study patients were divided into five groups according to the Snellen BCVA (LogMAR
BCVA) in the better-seeing eye: Group 1, 20/20 to 20/25 (1.0 to 0.8); Group 2, 20/30 to 20/50
(0.6 to 0.4); Group 3, 20/60 to 20/100 (0.3 to 0.2); Group 4, 20/200 to 20/400 (0.1 to 0.05); and
Group 5, worse than 20/400 (<0.05).
The data were analyzed using SPSS statistical software Version 13.0 (SPSS Inc., Chicago, IL,
USA). An alpha level of p < 0.05 was chosen as the criterion for significance.
A total of 120 patients were screened for the study; however, 11 were excluded because of their
inability to answer the questions. Thus, data from 109 (90.8%) patients with DR were included.
Patient demographic and clinical characteristics are shown in Table 1.
Utility values from patients and ophthalmologists
The TTO and RS utility values from the patients and ophthalmologists are shown in Table 2.
The difference between the mean TTO utility values and RS utility values overall from patients
was not statistically significant using the paired 2-tailed Student t test (p = 0.54). With the
exception of differences in the means for Group 1 (Snellen BCVA of 20/20 to 20/25 in the
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better-seeing eye) (p <0.05), the differences between the mean utility values from the patients
of each group using TTO versus RS methods were not statistically significant. However, with
the exception of differences in the means for Group 4 (Snellen BCVA of 20/200 to 20/400 in
the better-seeing eye) (p = 0.28) and Group 5 (Snellen BCVA worse than 20/400 in the
betterseeing eye) (p = 0.30), the differences between the mean utility values as assessed by the
ophthalmologists and each group using TTO and RS methods were statistically significant
Disparities between the ophthalmologists and patients
We compared the difference in the mean utility values from the patients and ophthalmologists
(Table 3). In addition to Group 4 (Snellen BCVA of 20/200 to 20/400 in the better-seeing eye)
and Group 5 (Snellen BCVA worse than 20/400 in the better-seeing eye), the differences in the
mean utility values between the patients’ and ophthalmologists’, overall, and each group using
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TTO, time trade-off; RS, rating scale; SD, standard deviation; CI, confidence interval.
* p value comparing the TTO and SG methods within each visual group using the paired two-tailed Student’s t test.
the paired 2-tailed Student t test were statistically significant (p <0.01) for both the TTO or RS
methods. Actually, compared to the ophthalmologist preferences, the DR patient-assessed
utility values were substantially lower than those of the ophthalmologists. Fig 1 shows box-plots
for the utility values from DR patients and ophthalmologists, stratified by TTO and RS
methods. In the total sample analysis, the utility values from DR patients and ophthalmologists had
no significant correlations, for either the TTO (Fig 2) or RS (Fig 3) method.
For DR patients, multivariate analyses using linear regression for both TTO utility values
and RS utility values as dependent variables are shown in Table 4 and Table 5, respectively.
LogMAR BCVA in the affected eye and the average weighted LogMAR BCVA were the
variables that significantly predicted both TTO utility values and RS utility values. In addition, DR
grade and the duration of visual dysfunction were also variables that significantly predicted
TTO utility values. Bivariate analyses were performed to determine which variables were
independently associated with TTO utility values and RS, as shown in Table 6. Both TTO utility
values and RS utility values were significantly associated with DME and employment status.
RS (t*, p*)
Fig 1. Distribution of utility values from diabetic retinopathy patients and ophthalmologists. The utility
values were measured by time trade-off and rating scale methods. Boxes indicate the 25th to 75th percentiles
of the utility values distribution, e.g., the interquartile range, and the bars inside the boxes represent the
median. The whiskers extend to the lower and the upper extremes defined as 25th percentile minus 1.5 times
the interquartile range and the 75th percentile plus 1.5 times the interquartile range. 〇, mild outliers; *,
Suffering from DME and unemployment were both factors independently associated with
lower utility values.
Furthermore, in the multivariate analysis of the utility values from ophthalmologists
(Table 4 and Table 5), patients’ LogMAR BCVA in the affected eye and in the better eye were
the variables that significantly predicted both the TTO utility values and RS utility values. In
addition, patients’ education levels also significantly predicted RS utility values. In the bivariate
analyses (Table 6), both TTO utility values and RS utility values were significantly associated
with patients’ DME (p <0.01) and employment status (p <0.05), which was similar to the
results from the patients.
Comparison trade-off method with previous studies
We used one-way ANOVA to compare our TTO data with those of Brown and associates [
obtained from 95 American patients with DR and from Sharma and associates [
from 186 Canadian patients with DR (Table 7). There was no difference in the mean utility
values of the Chinese, American, and Canadian patients (F = 1.05, p = 0.35). With the exception
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Fig 2. Scatter dot-plots of utility values from diabetic retinopathy patients and ophthalmologists, using the time trade-off method.
of differences in the means for Group 3 (Snellen BCVA of 20/60 to 20/100 in the better-seeing
eye) (F = 129.28, p<0.01), the differences among the mean utility values of each of the five
groups stratified by categorical Snellen BCVA were not statistically significant. We
simultaneously used the Dunnett t test to compare the difference between any two samples, and there
were no cross border differences noted in the mean utility values, overall or for groups.
Because patient perspectives play an integral role in guiding important decisions,
ophthalmologists are paying closer attention to the QoL of DR patients in the course of treatment. Although
a number of visual-specific functioning and QoL questionnaires [
], and even DR-specific
QoL questionnaires , have been developed and validated recently to measure the impact of
DR-related QoL, our evaluation and understanding remain limited due to the restricted ability
to fully assess QoL. Utility values were considered a useful tool to evaluate QoL associated with
visual loss from the DR patient’s point of view [
] because this theoretically takes into
account all aspects contributing to patient QoL and also provides an objective and
comprehensive view of consequences [
]. Furthermore, it is much more convenient for the
ophthalmologist to assess the patient’s QoL than to use visual-specific questionnaires composed of
multidimensional items. We used two main types of utility measurements in our study: RS and
TTO methods. The application shows that the RS method is an effective, simple and intuitive
way to evaluate utility values. However, Cunningham and Hunt [
] suggested that the RS
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Fig 3. Scatter dot-plots of utility values from diabetic retinopathy patients and ophthalmologists,
using the rating scale method.
method should be used in conjunction with one of the other methods (SG or TTO) because it
did not elicit valid cardinal utility measures. The TTO method has proven reliability, validity,
and reproducibility and is widely used in ophthalmic research [
]. Although the SG
method has been applied in many previous studies, we found it to be more difficult for patients
to understand compared to the TTO and RS methods; in fact, some patients were intimidated
by the concept of immediate death, no matter how small the chance . Therefore, both the
TTO, time trade-off; CI, confidence interval; BCVA, best-corrected visual acuity; DR, diabetic retinopathy.
*Backward linear regression with p = 0.1 cut-off for exclusion was used.
Beta coefficient (95% CI)
RS, rating scale; CI, confidence interval; BCVA, best-corrected visual acuity; DR, diabetic retinopathy.
*Backward linear regression with p = 0.1 cut-off for exclusion was used.
TTO and RS methods, which were used in our study rather than the SG method, are more
readily understood by patients, especially older patients.
For the present sample of 109 DR patients, the mean overall TTO or RS utility values were
0.81. To exemplify the TTO theory, if a patient’s expected remaining lifespan was 20 years and
he was willing to trade off 3.8 years for perfect vision, as previously described, the patient's
score in rating his current vision was 81, in a range of 1 to 100. This means that the overall
TTO utility value of DR patients in our study was slightly higher than the utility values of renal
transplantation patients (0.78) [
], which was equivalent to age-related macular degeneration
] and was very similar to the results of other previous studies [
Nevertheless, we noted a considerable variance, ranging from 0.55 to 0.84, in the mean TTO utility
values when the patients were grouped according to the severity of visual impairment in the
better-seeing eye. In particular, utility values of DR patients with Snellen BCVA in the
betterseeing eye of less than or equal to 20/200 (legal blindness in the USA) or less than 20/400 (legal
blindness in China), were just slightly higher than the utility values of severe angina (0.5) .
A discrepancy between the mean RS utility values and the mean TTO utility values existed,
especially in the low vision groups (Groups 4 and 5). This visual impairment may have the
greatest effect on DR patients’ RS utility values. Therefore, the RS method reflected the patients’
DR, diabetic retinopathy; TTO, time trade-off; RS, rating scale; DME, diabetic macular edema.
*Pearson correlation coefficients and analysis of variance (ANOVA) were used.
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F = 1.05, p = 0.35
F = 1.19, p = 0.31
F = 0.28, p = 0.76
F = 129.28, p
F = 1.05, p = 0.36
F = 0.07, p = 0.93
subjective evaluation of their own vision status. TTO utility values may contain more variables
that affect the QoL of DR patients, such as the degree of visual impairment, overall health
status, family support, economic situation and cultural background. Therefore, the TTO method
reflected individual differences in disease-related overall QoL. However, these two methods
had a positive correlation (r = 0.707). In short, our results demonstrate that both TTO and RS
utility values from DR patients showed good construct validity, as they were highly dependent
on the degree of visual loss, whether in the affected eye or the average weighted LogMAR
BCVA (Table 4), which is in accordance with conclusions from previous studies [
Thus, the greater is the degree of visual loss, the lower the mean utility values. In addition, DR
patients’ TTO utility values were linearly correlated with the DR grade and duration of visual
dysfunction. DR is mostly asymptomatic in its non-proliferative diabetic retinopathy (NPDR)
stages but may cause significant and disabling vision loss once it progresses to severe NPDR
and proliferative diabetic retinopathy (PDR) stages. There is an assumption that one could
better adjust to visual loss over time [
]; thus, the utility values with chronic visual loss compared
with more acute visual loss might be diverse. However, the conclusion from our study
obviously did not prove this hypothesis. Those who had visual loss for a longer time were more
willing to trade time for visual return. Furthermore, the level of education appeared to affect
the mean utility values using the t test; nevertheless, multivariate regression analysis failed to
confirm this association. Those with a high school education or less had lower utility values
than those with formal education beyond the high school years, which is consistent with the
results of a previous study [
]. We suspect that this discrepancy might be the result of
individual economic and social status differences. It is worth mentioning that patients with
substantially greater numbers of systemic comorbidities had similar utility values compared to those
with no or minimal comorbidities. This result revealed that visual impairment is an
independent and important factor impacting the QoL of DR patients.
DME and employment status also affected both the RS and TTO utility values, from both
patients and ophthalmologists. DME that causes centralized vision loss was obviously
associated with a negative impact on QoL [
]. However, in contrast to earlier views [
unemployed patients had lower utility values than those who were employed. It is generally assumed
that employed people require higher levels of visual function in order to perform better on the
job. We suspected that this discrepancy might be a result of the limited sample size, and thus,
we cannot be certain whether employment status was a significant confounder.
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When presented with the scenario of visual loss secondary to DR, ophthalmologists
substantially underestimated its effect on patients’ QoL. In our previous study [
rhegmatogenous retinal detachment and Brown’s study for AMD [
], differences between
ophthalmologists’ and patients’ perceptions of QoL were observed. Ophthalmologists, who are
usually concerned with the patient's visual acuity, the severity of the disease, and disease
progression, ignored the psychological burdens on the patient from the disease itself, such as fear
of blindness, the duration of visual dysfunction, and its impact on their daily life and work.
This perspective has been confirmed by an analysis and comparison of the various factors that
contribute to the patients’ experience of reduced QoL and the ratings provided by the
ophthalmologists. This observation reinforces the importance of considering DR patients' perspectives
and values when making significant health care decisions. At the focused level of individual
patient care, this indicates that patients should play a significant role in decisions involving
their treatment; at the broader level of health care policymaking, patients' preferences should
help determine how limited resources are allocated.
Our conclusions, based on the above results, were basically consistent with results from other
studies. Our hypotheses of how patients’ education levels and employment statuses significantly
predicted utility values are as follows: patients differed in the extent of visual impairment; the
number of DR patients with low vision was too small; our patients’ Snellen BCVA in the
betterseeing eye was not lower than counting fingers, while other studies included patients with no
light perception; and differences in social, economic, and cultural background.
As with any study, the present study has limitations. Although the sample size of our study
was sufficient to calculate the overall utility values of DR patients, the numbers of patients in
each group stratified by visual acuity were not sufficient. The utility values of DR patients
should be measured by repeated questions at a later date because it is important to prove the
reliability and repeatability of the results. Furthermore, the measurement of utility values,
whether by TTO or RS, could have its own limitations, such as a ceiling effect. Furthermore, we
were not able to take into account all variables that may affect the QoL of DR patients; it is
possible that the utility values of patients with DR reflect patient suffering from diabetes
systemically as a whole rather than DR alone. There is a danger that diabetes systemically acts as a
confounding factor of the relationship between DR and utility values.
Our data strongly suggest that DR causes a substantial decrease in Chinese patients’ utility
values, which appears to be highly dependent on the degree of visual loss, and that
ophthalmologists substantially underestimated its effect on patients’ QoL. Compared with previous studies
in different countries, our conclusions were fundamentally similar.
S1 Text. STROBE Statement—Checklist of items that should be included in reports of
S2 Text. PLOS ONE Clinical Studies Checklist.
This study was supported by a grant from Shanghai Health Bureau and a grant from Hong
Kong K.C. Wong Education foundation.
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Conceived and designed the experiments: HZ X. Zhu QS. Performed the experiments: HZ XX
X. Zhang X. Zhu. Analyzed the data: X. Zhu QS. Contributed reagents/materials/analysis tools:
X. Zhu XX. Wrote the paper: X. Zhu QS HZ.
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