Download The Economic Burden of Dry Eye Disease in the United States: A

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SPECIAL ARTICLE
The Economic Burden of Dry Eye Disease in the
United States: A Decision Tree Analysis
Junhua Yu, PhD,* Carl V. Asche, PhD,* and Carol J. Fairchild, PhD†
Purpose: The aim of this study was to estimate both the direct and
indirect annual cost of managing dry eye disease (DED) in the United
States from a societal and a payer’s perspective.
Methods: A decision analytic model was developed to estimate the
annual cost for managing a cohort of patients with dry eye with
differing severity of symptoms and treatment. The direct costs
included ocular lubricants, cyclosporine, punctal plugs, physician
visits, and nutritional supplements. The indirect costs were measured
as the productivity loss because of absenteeism and presenteeism.
The model was populated with data that were obtained from surveys
that were completed by dry eye sufferers who were recruited from
online databases. Sensitivity analyses were employed to evaluate the
impact of changes in parameters on the estimation of costs. All costs
were converted to 2008 US dollars.
Results: Survey data were collected from 2171 respondents with
DED. Our analysis indicated that the average annual cost of managing
a patient with dry eye at $783 (variation, $757–$809) from the
payers’ perspective. When adjusted to the prevalence of DED
nationwide, the overall burden of DED for the US healthcare system
would be $3.84 billion. From a societal perspective, the average cost
of managing DED was estimated to be $11,302 per patient and $55.4
billion to the US society overall.
Conclusions: DED poses a substantial economic burden on the
payer and on the society. These findings may provide valuable
information for health plans or employers regarding budget
estimation.
Key Words: dry eye, burden of illness, decision tree analysis,
presenteeism, absenteeism
(Cornea 2010;00:000–000)
D
in symptoms of discomfort, visual disturbance, and tear film
instability, with potential damage to the ocular surface.’’1 DED
causes degradation of visual acuity that can interfere with
many ordinary activities of daily living such as reading,
viewing a computer screen, and driving a car.2 DED may
impose an economic burden on patients and on society
because of the utilization of healthcare resources such as
physician visits, medications, and surgical procedures. Moreover, DED is associated with decreased productivity and days
missed from work.3
The economic impact of DED is magnified by its
prevalence. The 2007 Dry Eye WorkShop reported that the
global prevalence of dry eye ranged between 3.5% and
33.7%,4 depending on the age of the population and the
diagnostic criteria that were used. DED occurs more frequently
in older age groups5 and in females.6 Among US adults aged
50 years and older, the prevalence of DED has been reported as
1.68 million men7 and 3.23 million women.6 With projections
of longer life expectancy, an even larger economic burden of
DED on society can be expected.
Although the cost of DED management may be an
important economic burden for the healthcare system, very
few studies are available about the cost of this illness in the
United States. A comprehensive estimate of the economic
burden of DED is needed to provide insight into how much
society is spending on the disease and the potential impact that
an effective new treatment may offer.8 The objective of this
study was to evaluate the annual costs of caring for DED in the
United States, from both a societal perspective and a payer’s
perspective.
MATERIALS AND METHODS
Prevalence Approach
ry eye disease (DED) has been defined as ‘‘a multifactorial disease of the tears and ocular surface that results
Received for publication May 12, 2010; accepted August 12, 2010.
From the *University of Utah, College of Pharmacy, Pharmacotherapy
Outcomes Research Center, University of Utah, Salt Lake City, UT; and
†Alcon Research, Ltd, Fort Worth, TX.
Supported by Alcon Laboratories, Inc, Fort Worth, TX.
This work was conducted at the Pharmacotherapy Outcomes Research Center
at the University of Utah.
Reprints: Carl V. Asche, Pharmacotherapy Outcomes Research Center,
University of Utah, 421 Wakara Way, Suite 208, Salt Lake City, UT 84108
(e-mail: [email protected]).
Copyright Ó 2010 by Lippincott Williams & Wilkins
Cornea Volume 00, Number 0, Month 2010
Either the prevalence-based approach or the incidencebased approach can be used to establish the cost of an illness.9
Given the lack of existing longitudinal data about DED,
a prevalence-based cost-of-illness analysis was selected for
this study. Specifically, an internet-based survey was used to
assess the prevalence of mild, moderate, and severe symptoms
of DED and to assess the corresponding resource usage for
each group of subjects. Prevalence and resource usage were
assessed with respect to a 12-month treatment period, in
accordance with durations examined in previous economic
studies of DED.10,11 In the absence of longitudinal data about
changes in severity over time, we assumed that treatment
would not change significantly over a 1-year period.
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Yu et al
Subjects
The survey population was recruited via e-mail from the
Sjogren’s Syndrome Foundation and from the Harris Interactive’s Harris Poll online participant panel. Eligible subjects
had DED, were US residents aged 18 or older, and were
employed at least part time. DED was established by a previous
diagnosis of DED or Sjogren syndrome by an optometrist or
ophthalmologist or by an ocular surface disease index score in
the abnormal range (score .12 out of 100).12
Surveys
The survey contained questions regarding demographics, health history (dry eye and other conditions), current dry
eye treatments, physician visits, self-reported effectiveness of
treatment, and effect of dry eye on quality of life. The impact
of dry eye symptoms on work productivity was measured by
the Work Productivity and Activity Impairment Questionnaire,
a validated instrument for assessing productivity loss because
of various health conditions.13 This questionnaire elicits
information regarding the number of days and hours missed
from work (absenteeism), the extent of limitation at work
(presenteeism), and the impact of dry eye on usual daily
activities. The domain scores represent the percentage of
overall impairment in the past week.
Calculation of Costs
Five categories of healthcare resource use were assessed:
ocular lubricant treatment, cyclosporine, punctal plugs,
physician visits, and nutritional supplements. For topical
treatments, compliance rate was calculated from questionnaire
responses, to yield a ratio of actual use to prescribed use.
Ocular Lubricants
The average price per milliliter of ocular lubricant
treatment was obtained from prices and volumes that were
listed at pharmacy Web sites in 2008 for 32 products. Average
cost was converted to price per drop by assuming that each
drop had a volume of 0.05 mL.14 Subjects were assumed to use
ocular lubricant treatment throughout the 1-year study period.
The formula for calculating the yearly cost of ocular lubricant
treatment for patients who sought professional treatment was
as follows: mean price of each drop of ocular lubricant
treatment 3 the recommended number of daily drops 3
compliance rate 3 365 days. The formula for calculating the
yearly cost of ocular lubricants for subjects who did not seek
professional treatment was as follows: mean price of each drop
of ocular lubricant treatment 3 the average number of daily
drops for a dry eye population (5.7 uses per day)15 3 365 days.
Cyclosporine
For subjects who reported cyclosporine usage, cyclosporine therapy was assumed to have been used throughout the
study period. The yearly cost of cyclosporine was calculated as
follows: recommended 2 vials per day15 3 the price of each
vial of cyclosporine 3 compliance rate for cyclosporine 3 365
days. The price of each vial of cyclosporine was calculated by
dividing the cost per product ($117.46 for a pack of Restasis,
cyclosporine ophthalmic emulsion 0.05%; Allergan, Inc,
Irvine, CA)16 by the total number of units of doses (36 unit-
2
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Cornea Volume 00, Number 0, Month 2010
dose vials per pack)16 to yield a price per vial of $3.26 in 2008
dollars, as shown in Table 1.
Punctal Plugs
Subjects who reported having punctal plugs at the time
of the survey were assumed to have had 1 implantation
procedure in the past year. According to a study based on a
managed care database, the cost per procedure was estimated
to be $256 in 2005 dollars.10 This number was adjusted from
July 2005 dollars to July 2008 dollars via the consumer price
index (CPI) for medical care services, published by the Bureau
of Labor Statistics (http://data.bls.gov/cgi-bin/surveymost).
The formula was as follows: (CPI in July 2008/CPI in July
2005) 3 (July 2005 dollars) = July 2008 dollars. Therefore,
the cost per plug procedure was (385.4/337.8) 3 $256 = $292
(Table 1).
Oil-based Nutritional Supplements
Survey results were used to calculate the usage of
nutritional supplements among subjects who reported being
instructed by an eye care professional to take oil-based dietary
supplements, such as fish oil or flax seed oil. Results were
stratified by dry eye severity, to yield percentage of patients in
each severity group (mild, moderate, and severe) who reported
consumption of nutritional supplements at the time of the
survey. Prices for 3 oil-based nutritional supplements from
various manufacturers were obtained through an online search;
the average price was $0.52 per day in 2008 dollars. The
annual cost of nutritional supplements for each dry eye
severity group was calculated as follows: 365 days 3 mean
daily price of nutritional supplement 3 percentage of patients
reporting that they consumed nutritional supplements.
TABLE 1. Parameters for Cost Estimations
Variables
Value
Cyclosporine
Price per vial
Recommended no. vials per day
Ocular lubricant
Mean price per drop
Average no. drops per day
Cost of a plug surgery
Visit to an eye care professional
Price of the first visit
Price of the ophthalmic
follow-up visit
Weighted average price†
Average hourly wage
Cost of nutritional supplement
per day
Source
$3.26
2
Red Book
Roberts et al
$0.02
5.7
$292
Internet search
Roberts et al
Fiscella et al*
$180
2008 Physicians Fee &
Coding Guide*
2008 Physicians Fee &
Coding Guide*
Calculated
Bureau of Labor Statistics
Internet search
$100
$149.50
$15.95
$0.52
*Adjusted to 2008 July price using CPI method as explained in the Methodology
section.
†The weighted average price per ophthalmologist or optometrist visit was calculated
as 0.275 3 $180 (first visit) + $100 (follow-up visit), where 0.275 was the percentage of
patients who reported that the DED lasted less than 1 year and thus was assumed to
represent the percentage of first time visits.
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Cornea Volume 00, Number 0, Month 2010
Cost of Visiting a Healthcare Professional
The average annual numbers of visits per subject to
optometrists, ophthalmologists, and other eye care professionals were derived from the survey. The calculations took
into account the difference in cost between initial visits and
follow-up visits because the first consultation has a higher
charge than the follow-up visits.18 We assumed that the
subjects who reported having suffered DED for less than 1 year
were new patients. The cost per visit for an ophthalmologist or
optometrist was estimated as a weighted average of the fee for the
first visit and the follow-up visits, the formula for which was as
follows: the percentage of new patients 3 fee for the first office
consultation (Current Procedural Terminology code 99244)17,18 +
fee for the ophthalmic follow-up examination with treatment
(Current Procedural Terminology code 92014).17,18 Fees were
adjusted from 2007 July price to 2008 July price using the CPI
method as explained in the punctal plug section. The fees for
office visits are shown in Table 1. The total cost of visits to eye
care professionals was calculated as the total number of visits per
subject reported in the previous year 3 the weighted average cost
per visit.
Indirect Cost
Reductions in productivity because of absenteeism (the
loss of working hours) and presenteeism (the hours of reduced
effectiveness at work) were derived from the Work Productivity and Activity Impairment Questionnaire data. Lost
work time was ascertained by the following question: ‘‘During
the past 7 days, how many hours did you miss from work
because of your dry eye problems?’’ Lost work equivalent, the
hours of productivity lost because of reduced effectiveness
because of dry eye symptoms, was calculated from responses
to the following question: ‘‘During the past 7 days, how much
did your dry eye problems affect your productivity while you
were working?’’ Lost work equivalent was defined as the
number of usual weekly work hours 3 degree of impairment to
effectiveness (measured as a percentage). We assumed that the
past-week productivity and loss patterns were representative for
the year; therefore, the total annual indirect cost was calculated
as (lost work equivalent + lost work time) 3 hourly wage 3
48 working weeks. The average hourly wage was assumed to be
$15.95 per hour, according to data provided by the Web site of
the Bureau of Labor Statistics (http://data.bls.gov/cgi-bin/
surveymost?le).
Description of the Models
Dry Eye Treatment Pattern Model
Well-established treatment guidelines19–21 were used to
develop a decision tree model. Although the guidelines vary
slightly, they all recommend that therapy for DED should be
initiated in a stepwise fashion, in accordance with disease
severity. For patients with mild DED, the 3 guidelines
recommend initial treatment with an ocular lubricant, such
as artificial tears, lubricant eyedrops, and/or ointments. For
some patients with moderate DED, the 3 guidelines
recommend a topical antiinflammatory, such as cyclosporine.
For some patients with severe DED, the 3 guidelines
recommend punctal plugs. These consensus-based stepwise
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Dry Eye Economic Burden
treatments (ocular lubricants for mild DED, cyclosporine for
moderate DED, and punctal plugs for severe DED) were
included in the decision tree model.
Burden of Illness Model
Decision analytic models were employed to reflect
preferred treatment patterns and to evaluate the healthcare
utilization data in each treatment pattern under conditions of
uncertainty because of variability in DED treatment patterns in
the real world.22,23 Mutually exclusive categories of subjects
were identified to differentiate between severity of dry eye
symptoms and varying degrees of resource consumption. This
approach reduced model complexity and allowed for the
flexibility that real-world treatment patterns might deviate
from the recommended guidelines. Subjects were sorted into
2 groups: those who sought professional eye care and those
who did not. These groups were further classified as having
mild, moderate, or severe DED, as determined by the selfreported severity of symptoms for the past week. In each
severity group, subjects were further divided into 4 treatment
groups: neither cyclosporine nor punctal plugs; only plugs; only
cyclosporine; or both cyclosporine and plugs. This burden-ofillness model was used to calculate the direct medical costs to
payers (payer cost model) and to calculate the cost of DED to
society (societal cost model). The societal cost model included
direct medical cost and indirect cost because of presenteeism
and absenteeism.
Validation Model
To evaluate the validity of the payer cost model,
a validation model was constructed based on a cost-oftreatment report that used information from a published
retrospective healthcare claims database to calculate utilization
and costs of topical cyclosporine and punctal plugs over a
1-year period.10 In that study, the population consisted of
patients with DED that was treated with cyclosporine or
punctal plugs; so, their results were compared only with results
for our group of subjects similarly treated with cyclosporine or
plugs.
In the validation model, we assumed that all patients
with dry eye who were treated with either cyclosporine or
plugs were followed for 1 year after entry into the model. The
cohort of cyclosporine-treated patients was divided into
2 groups depending on whether they received punctal plugs
later in the 1-year period. Similarly, the plugs cohort was
divided into 2 groups depending on whether they received
cyclosporine in the 1-year follow-up period. The cost for
cyclosporine was calculated from the reported mean number of
prescriptions per year (3.93 per year)10 and from the mean days
of supply per prescription (31.51 days).10 In accordance with
the findings of their study, patients with plugs at entry into the
validation model were assumed to have a mean of 2.85
procedures per year,10 and the patients receiving cyclosporine
at entry into the validation model were assumed to have only
1 plug implantation procedure during the follow-up period.
Using the same calculation method as was used in the payer
cost model, we assigned path probabilities to each branch of
patients in the validation model and used their treatment costs
as payoffs to calculate the average costs per patient with dry
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Yu et al
that cyclosporine therapy was used throughout the study
period.
TABLE 2. Data Used for Validation Model*
Variable Name
Value
Cyclosporine
Mean number of prescriptions per year
Days supply per prescription
Compliance rate
Proportion of patients initiated with cyclosporine
Punctal plugs
Cost per plug procedure
Mean number of procedures, for those initiated with plugs
Combination plugs and cyclosporine
Proportion of patients using plugs after cyclosporine
Proportion of patients using cyclosporine after plugs
3.93
31.51
33.9%
50.86%
$270
2.9
21.1%
11.4%
*Source: Fiscella et al.
eye. Data for the validation model are given in Table 2.
Average treatment costs (cyclosporine and plugs) from the
validation model were compared with the corresponding
average treatment costs from the payer cost model.
RESULTS
Demographics
Among the 2171 respondents to the survey, 54% were
women and more than 50% characterized their dry eye
symptoms as mild. Table 3 shows the severity distribution of
DED among the study participants. DED was reported to have
lasted less than 1 year in 27.5% of patients, yielding a weighted
average cost of price per visit to an eye care professional of
$149.50 (Table 1). Resource usage among subjects who
sought professional eye care is shown in Table 4. Resource
usage among subjects who did not seek professional eye care
is shown in Table 5.
Confirmation of Assumptions
The mean reported duration of ocular lubricant
treatment was 47.1 months (95% confidence interval, 41.5–
52.7 months). Therefore, the assumption that subjects used
ocular lubricant treatment throughout the 1-year study period
was valid. The survey data indicated that the average treatment
duration for cyclosporine was 22.7 months (95% confidence
interval, 17.8–27.7 months), which validated our assumption
TABLE 3. Distribution of Dry Eye Subjects by Severity
of Symptoms
Subjects Seeking
Professional Eye
Care
Subjects Not Seeking
Professional Eye
Care
Proportion of Subjects
Mean
LCI
UCI
Mean
LCI
UCI
With Mild DED (%)
With Moderate DED (%)
With Severe DED (%)
53.9
34.0
12.0
49.5
29.9
9.2
58.3
38.1
14.8
59.9
31.4
8.7
53.2
25.1
4.8
66.6
37.8
12.5
LCI, lower confidence interval; UCI, upper confidence interval.
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Direct Costs
The average annual direct cost for patients seeking
medical care was calculated to be $783 per patient (Fig. 1).
Taking into account the US DED prevalence among adults
aged 50 years or older (1.68 million men7 and 3.23 million
women6), the overall burden of DED for the health care system
would be $3.84 billion. The average annual direct medical cost
per patient was $678 for patients with mild dry eye, $771 for
patients with moderate dry eye, and $1267 for patients with
severe dry eye. A detailed breakdown of the total medical cost
for each group of patients for plugs, cyclosporine, ocular
lubricant treatment, office visits, and nutritional supplements
TABLE 4. Utilization of Professional and Consumer Resources
for DED Among Patients Who Sought Professional Eye Care
Variables
Mean
Proportion of patients using plugs (%)
Mild DED
24.2
Moderate DED
12.8
Severe DED
15.5
Proportion of patients using cyclosporine (%)
Mild DED without plugs
4.1
Mild DED with plugs
16.1
Moderate DED without plugs
12.2
Moderate DED with plugs
16.3
Severe DED without plugs
30.3
Severe DED with plugs
35.2
Ratio of compliance with cyclosporine (%)
Mild DED
93.3
Moderate DED
93.1
Severe DED
72.2
Proportion of patients using ocular lubricants (%)
Mild DED
67.6
Moderate DED
81.3
Severe DED
86.9
Compliance with ocular lubricants (%)
Mild DED
94.2
Moderate DED
72.9
Severe DED
58.6
Proportion of patients using nutritional supplements
Mild DED
60.2
Moderate DED
63.3
Severe DED
71.5
Frequency of physician visits per year
To ophthalmologist
Mild DED
1.097
Moderate DED
1.137
Severe DED
1.847
To optometrist
Mild DED
0.899
Moderate DED
0.878
Severe DED
1.682
LCI
UCI
19.9
9.9
9.1
28.6
16.8
21.9
2.0
9.4
8.3
3.3
21.6
16.1
6.3
22.8
16.1
29.4
39.0
54.3
84.3
84.0
56.4
100.0
100.0
88.0
58.9
74.8
77.1
76.4
87.8
96.8
89.9
59.8
42.3
(%)
55.2
57.6
63.5
98.5
86.0
74.9
65.2
69.0
79.5
0.849
0.880
1.252
1.344
1.394
2.442
0.692
0.704
1.153
1.106
1.051
2.212
LCI, lower bound of confidence interval; UCI, upper bound of confidence interval.
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Dry Eye Economic Burden
TABLE 5. Utilization of Consumer Resources for DED Among
Subjects Who Did Not Seek Professional Eye Care
Variables
Mean (%)
LCI (%)
Proportion of subjects using ocular lubricants
Mild DED
51.5
37.4
Moderate DED
55.7
32.8
Severe DED
78.1
41.2
Proportion of subjects using nutritional supplements
Mild DED
49.4
40.5
Moderate DED
37.9
26.2
Severe DED
46.4
24.6
UCI (%)
did not interact with health care systems, the model estimated
that a cohort of 1000 subjects with varying severity of DED
had a mean direct cost of $543 per person per year (Fig. 1).
Indirect Costs
65.6
78.5
100.0
58.2
49.6
68.3
LCI, lower bound of confidence interval; UCI, upper bound of confidence interval.
is presented in Table 6. For each severity group, patients
treated with punctal plugs plus cyclosporine had the highest
annual direct expenditure: $2964 for mild patients, $2959 for
moderate patients, and $2698 for severe patients (Table 6;
groups 4, 8, and 12). The total annual direct costs to the payer
for a cohort of 1000 patients with varying severity of
symptoms would be $782,673.
The average annual direct cost for subjects who were self
medicating with ocular lubricant treatment or nutritional
supplements was calculated at $126 per subject (Fig. 1).
Taking into account the proportions of patients who did and
The average annual cost to society was calculated as
$11,302 per subject with DED (Fig. 2). The overall burden to
the US society was calculated at $55.4 billion.
The loss because of diminished productivity considerably outweighed direct costs of DED treatment (Table 6). In
a cohort of gainfully employed dry eye patients, the total
productivity loss per person ranged from $12,569 to $18,168
per year. As shown in Figure 3, the loss because of
presenteeism was substantially higher than the loss because
of absenteeism. The calculated mean number of lost work days
per year was 8.4 days for mild patients, 3.7 days for moderate
patients, and 14.2 days for severe patients, whereas the
equivalent lost work days because of affected performance was
equivalent to 91 days for mild patients, 94.9 days for moderate
patients, and 128.2 days for severe patients (Table 7). Subjects
who had not visited a physician during the past year lost fewer
days of productivity than subjects who had sought professional
eye care in the past year.
Sensitivity Analysis of Direct Medical Costs
Multiple 1-way sensitivity analyses were performed for
7 key variables (listed in Tables 4 and 5) to test the robustness
FIGURE 1. Decision tree used for estimating the direct cost per patient with dry eye.
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Yu et al
TABLE 6. Estimate of the Annual Direct and Indirect DED Costs of Patients Seeking Professional Eye Care*
Mild DED
No Plugs
Treatment group
Patients (%)
Costs
Indirect, total
Absenteeism
Presenteeism
Direct, total
Plugs
Cyclosporine
Ocular lubricant
Office visits
Nutritional supplements
Total (direct + indirect)
Moderate DED
With Plugs
No Plugs
Severe DED
With Plugs
No Plugs
With Plugs
No CS
Yes CS
No CS
Yes CS
No CS
Yes CS
No CS
Yes CS
No CS
Yes CS
No CS
Yes CS
1
38.6
2
1.6
3
10.7
4
2.0
5
26.6
6
3.6
7
3.8
8
0.8
9
7.2
10
3.1
11
1.3
12
0.6
$12,686
$12,686
$12,686
$12,686
$12,569
$12,569
$12,569
$12,569
$18,168
$18,168
$18,168
$18,168
$452
—
—
$39
$298
$114
$13,138
$2672
—
$2220
$39
$298
$114
$15,358
$744
$292
—
$39
$298
$114
$13,430
$2964
$292
$2220
$39
$298
$114
$15,650
$452
—
—
$30
$301
$120
$13,021
$2667
—
$2215
$30
$301
$120
$15,236
$744
$292
—
$30
$301
$120
$13,313
$2959
$292
$2215
$30
$301
$120
$15,528
$688
—
—
$24
$528
$136
$18,856
$2406
—
$1718
$24
$528
$136
$20,574
$980
$292
—
$24
$528
$136
$19,148
$2698
$292
$1718
$24
$528
$136
$20,866
*Costs for patients with DED who self medicated are not included in this table.
CS, cyclosporine.
of the results. The upper and lower limits for each of the model
variables are shown in Tables 3, 4, and 5. The 95% confidence
intervals around the mean values were constructed by
assuming a binomial distribution for binary variables and by
assuming a Poisson distribution for count variables. The
sensitivity analysis conducted on the list of variables is shown
in Figure 4. The tornado diagram indicates that the distribution
of severity of symptoms had a relatively large impact on the
FIGURE 2. Decision tree used for estimating the total annual cost per patient with dry eye (societal prospective).
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Dry Eye Economic Burden
comparable to the results from the payer cost model, in which
the annual cost for dry eye was calculated as $1092 for
subjects who reported being treated with plugs or cyclosporine
at the time of the survey.
DISCUSSION
FIGURE 3. Indirect costs because of productivity losses.
estimates. This was followed by a few treatment characteristics
for patients with mild DED (the frequency of ophthalmologist
visits, combined punctal plugs and cyclosporine treatment,
and frequency of optometrist visits) and compliance with
cyclosporine by severe patients. However, the change in the
magnitude around the mean direct cost of $783 was minimal,
ranging from $757 to $809 approximately.
Validation Results
In the validation model, the yearly medical cost of
cyclosporine and plugs was calculated to be $1123 per person
(Fig. 5). These results from the validation model were
TABLE 7. Impact of DED on Work Productivity
Subjects Who Visited
Physicians
Mean
LCI
UCI
Subjects Who Did Not
Visit Physicians
Mean
LCI
UCI
Lost work hours per week
Mild DED
1.40
1.07
1.74
0.04
0.01
0.10
Moderate DED
0.61
0.28
0.94
0.29
0.17
0.45
Severe DED
2.36
1.02
3.71
1.40
0.93
2.02
Affected performance (%)
Mild DED
37.9
32.1
43.7
1.6
7.8
14.3
Moderate DED
39.5
33.8
45.2
4.1
19.2
35.4
Severe DED
53.4
44.6
62.2
8.5
38.0
73.7
Lost work days per year, assuming 40 hours per week and 48 weeks
Mild DED
8.4
6.4
10.4
0.2
0.1
0.6
Moderate DED
3.7
1.7
5.6
1.7
1.0
2.7
Severe DED
14.2
6.1
22.3
8.4
5.6
12.1
Equivalent lost work days per year because of affected performance
Mild DED
91.0
77.1
104.9
4.0
18.6
34.3
Moderate DED
94.9
81.1
108.6
9.8
46.0
85.1
Severe DED
128.2
107.0
149.4
20.3
91.1
176.8
LCI, lower bound of confidence interval; UCI, upper bound of confidence interval.
q 2010 Lippincott Williams & Wilkins
To our knowledge, this is the first study about the cost
of DED in the United States. Reddy et al3 concluded that
previously available data were insufficient to estimate the US
cost of DED and therefore offered a conceptual framework for
future studies. We followed the practices that were established
by Clegg et al,11 who used the distribution of disease severity
to estimate the average annual cost for patients with dry eye in
Europe and used a sensitivity analysis to test the robustness of
their findings. However, we calculated the cost of managing
DED by using a decision tree analytical model, which is
a flexible tool to examine the impact of uncertainty of the
relevant parameters on the estimated costs. One advantage
of the decision tree analytical method is that the model
parameters and results can readily be updated when new
information becomes available from future studies.
The self-reported data from our survey revealed the
current utilization pattern of the mainstay therapies for DED,
including ocular lubricant treatment, prescribed eyedrops, and
the associated compliance rates. Therefore, the costs calculated from these survey data provided information that was
more comprehensive than information that can be obtained
from claims databases. Self-reported survey data do
have limitations in delivering comprehensive and generalizable information about resource use, but our results were
comparable to results from a model that used claims database
inputs.10 For example, the calculated annual cost of 2 mainstay
treatments (cyclosporine and punctal plugs) from the survey
data was only $31 lower than the annual cost that was
calculated from a claims database in the comparator study. The
consistency between the results of the 2 studies suggested that
the data obtained from the population-based survey generally
reflected the cyclosporine and plugs treatment pattern of dry
eye revealed in the large claims database. Hence, our results
represent a fairly complete and realistic costing of the burden
of DED in the United States in 2008.
The unique advantages of the survey data allowed us to
identify the resource utilization and productivity losses for
those dry eye sufferers who did not seek professional eye care
for DED in the previous year. This provided an opportunity to
measure the DED economic burden from both the society’s
and the payer’s perspective. We have not found any study that
has attempted to identify the cost associated with selfmedicating DED sufferers who remain outside the health care
system. An important finding of the study is that approximately 40% of the subjects with dry eye symptoms (of varying
degrees) did not seek medical care. This group incurred less
direct cost but had substantial societal cost because of
presenteeism and absenteeism.
All modeling studies have limitations imposed by the
structure of the model, by the inherent assumptions, and by the
source data. Given that the costs presented in this study were
based on treatment patterns and level of resource use derived
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Yu et al
Cornea Volume 00, Number 0, Month 2010
FIGURE 4. Tornado diagram for
average direct costs per patient
seeking professional eye care.
from recent population-based surveys, the level of accuracy of
self-reported data must be determined to further verify the
estimation results. However, dry eye epidemiological studies
rely on patient-reported symptoms to detect cases of DED.
Symptoms that are felt as inconvenient for some patients might
be considered debilitating by other patients, thus giving rise to
inconsistent reports of severity across individuals. Moreover,
studies have shown that patients’ self assessments of dry eye
symptoms are significantly more severe than the severity that
is perceived by their doctors.24 Physicians incorporate their
assessments of symptoms and clinical signs of ocular surface
diseases in determining severity. Therefore, care should be
taken when attempting to extrapolate the results of this study
to other populations.
Our results are comparable to those reported in the DED
burden-of-illness study by Clegg et al.11 The authors collected
resource use data from interviews with a randomly selected
sample of consultant ophthalmologists in Europe and estimated that the total annual health care cost of 1000 dry eye
sufferers ranged from $0.27 to $1.10 million US dollars in
2004.11 Our study found a comparable distribution of severity
and cost of DED ($0.78 million US dollars for 1000 sufferers).
The impact of dry eye on indirect costs is important. We
have included the indirect costs attributed to presenteeism and
absenteeism using the self-reported results from the work
productivity and activity impairment questionnaire. However,
because the survey data were based on the subjects who were
employed at least part time, the forgone productivity might be
an overestimate of the general dry eye population, some of
whom might be engaged in non–wage-earning or homeworking activities.
A surprising finding of the study was that loss because
of diminished productivity considerably outweighed direct
cost of care. These findings underscore the impact of DED in
the workplace and may provide valuable information to health
plans or employers regarding budget estimation. It is hoped
that information from this study can be helpful in setting
priorities for health care efficiency research.
We have presented a simplistic treatment and cost
structure in the model. Refinement of the model to allow more
sophisticated and detailed analysis would require additional
data that are not currently available in the United States.
Despite these limitations, this study improved upon previous
studies by incorporating the indirect costs and the
FIGURE 5. Expected direct medical costs for patients with dry eye in managed care database: cyclosporine and plug only.
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q 2010 Lippincott Williams & Wilkins
Cornea Volume 00, Number 0, Month 2010
nonprescription medications in the calculation of annual cost
of DED, with the aid of a rigorous decision tree model.
Therefore, we believe this study represents a significant
contribution to the field, given the lack of more robust data in
the peer-reviewed literature.
In summary, DED imposes a substantial economic
burden on the payer and on the society. The overall burden of
DED for the US health care system was calculated as
approximately $3.84 billion, with subgroup costs that varied
by severity of disease and by prevalence of those severity
subgroups. A surprising finding of the study was that loss
because of diminished productivity considerably outweighed
the direct cost of care. These findings underscore the impact of
DED in the workplace and may provide valuable information
to health plans or employers regarding budget estimation. The
information from this study can be helpful in setting priorities
for health care efficiency research.
ACKNOWLEDGMENTS
The authors are grateful for the editorial assistance from
Dana Wise and research assistance from Tran Le, Tracy Louie,
Anh Luong, and Brando Kyle Bellows.
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