Download Global Burden of Eye and Vision Disease as Reflected in the

Research
Original Investigation
Global Burden of Eye and Vision Disease as Reflected
in the Cochrane Database of Systematic Reviews
Lindsay N. Boyers, BA; Chante Karimkhani, BA; John Hilton, MSc, MPhil; William Richheimer, MD;
Robert P. Dellavalle, MD, PhD, MSPH
IMPORTANCE Eye and vision disease burden should help guide ophthalmologic research
Supplemental content at
jamaophthalmology.com
prioritization. The Global Burden of Disease (GBD) Study 2010 compiled data from 1990 to
2010 on 291 diseases and injuries, 1160 disease and injury sequelae, and 67 risk factors in 187
countries. The Cochrane Database of Systematic Reviews (CDSR) is a resource for systematic
reviews in health care, with peer-reviewed systematic reviews that are published by
Cochrane Review Groups.
OBJECTIVE To determine whether systematic review and protocol topics in the CDSR reflect
disease burden, measured by disability-adjusted life-years (DALYs), from the GBD 2010
project. This is one of a series of projects mapping GBD 2010 medical field disease burdens to
corresponding systematic reviews in the CDSR.
DESIGN AND SETTING Two investigators independently assessed 8 ophthalmologic conditions
in the CDSR for systematic review and protocol representation according to subject content.
The 8 diseases were matched to their respective DALYs from the GBD 2010 project.
MAIN OUTCOMES AND MEASURES Cochrane Database of Systematic Reviews systematic
review and protocol representation and percentage of total 2010 DALYs.
RESULTS All 8 ophthalmologic conditions were represented by at least 1 systematic review in
the CDSR. A total of 91.4% of systematic reviews and protocols focused on these conditions
were from the Cochrane Eyes and Vision Group. Comparing the number of reviews and
protocols with disability, only cataract was well matched; glaucoma, macular degeneration,
and other vision loss were overrepresented. In comparison, trachoma, onchocerciasis,
vitamin A deficiency, and refraction and accommodation disorders were underrepresented.
CONCLUSIONS AND RELEVANCE These results prompt further investigation into why certain
diseases are overrepresented or underrepresented in the CDSR relative to their DALY. With
regard to ophthalmologic conditions, this study encourages that certain conditions get more
focus to create a better representation of what is causing the most disability and mortality
within this research database. These results provide high-quality and transparent data to
inform future prioritization decisions.
Author Affiliations: Author
affiliations are listed at the end of this
article.
JAMA Ophthalmol. 2015;133(1):25-31. doi:10.1001/jamaophthalmol.2014.3527
Published online September 18, 2014.
Corresponding Author: Robert P.
Dellavalle, MD, PhD, MSPH,
Dermatology Service, Department of
Veteran Affairs Medical Center, 1055
Clermont St, Box 165, Denver, CO
80220 (robert.dellavalle
@ucdenver.edu).
25
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Research Original Investigation
Global Burden of Eye and Vision Disease
T
he process of setting research agendas and priorities
is complex and multifactorial, with the aim to provide the greatest public health benefit.1 While a uniform approach to establishing health research priorities is
not appropriate for the unique situation and context in
which agendas are set, 9 common themes of good practice
have been identified including, but not limited to, determination of criteria that will guide prioritization decisions,
determination of decision makers, and transparency.1 The
Cochrane Collaboration serves as an example of a large network of researchers that has established a diversity of
priority-setting methods by its various review groups.2 The
10 guiding principles of Cochrane’s work are collaboration,
building on the enthusiasm of individuals, avoiding duplication of effort, minimizing bias, keeping up to date, striving for relevance, promoting access, ensuring quality, continuity, and enabling wide participation.3
Within the Cochrane Library, the Cochrane Database of
Systematic Reviews (CDSR) contains reviews produced by 53
Cochrane Review Groups. The CDSR serves as a source of peerreviewed systematic reviews in health care. It aims to provide evidence-based information to inform decision making
for individuals, health care professionals, and policy makers
alike.4,5 Until now, Cochrane reviews have mainly focused on
treatment effectiveness assessed in randomized clinical trials,
although guidance on incorporating evidence from studies with
other designs is being developed.
One of the Cochrane Review Groups, the Eyes and Vision
Group, registered with Cochrane in 1997 and has 200 members from 30 countries.6 This group seeks to create, sustain,
and encourage access to systematic reviews that synthesize information regarding all aspects of prevention and treatment
of eye disease and visual impairment.7 Its scope extends to aid
those affected by visual impairment or blindness in the adjustment to their disability. Prioritization strategies for the
Cochrane Eyes and Vision Group specifically emphasize chief
causes of blindness worldwide and regions with a large range
of clinical practices and outcomes.7 The compiled systematic
reviews rely on data from randomized and quasirandomized
clinical trials and create descriptive compilations where such
information is scarce. Primary outcome measurements are visual function such as visual acuity, assessment of visual field,
and assessment of vision-related quality of life.7
There are various efforts underway to help drive agendas
and priorities within the field of ophthalmology.8 For instance, the Sight Loss and Vision Priority Setting project, initiated in 2011, is supported and guided by the James Lind
Alliance.9 The priorities set by this group are within the context of the UK National Health Service. This organization uses
the input of patients, caregivers, and health care professionals to identify and prioritize unanswered questions or overlooked issues regarding ophthalmology treatment, diagnosis, and prevention.9 The results are publicized to research
commissioning bodies to be considered for funding.9 Li et al10
conducted an eye and vision prioritization exercise on the topic
of open-angle glaucoma. This study focused on creating and
evaluating a framework to determine evidence gaps and prioritize clinical questions by using clinical practice guidelines
26
and systematic reviews. Unlike the Sight Loss and Vision Priority Setting project, this work aimed to respond to clinicians’ needs and was thus limited to the professionals’
perspective.10
When it comes to research prioritization, burden of disease is one of many factors that may be considered. In particular, the Global Burden of Diseases (GBD), Injuries, and Risk
Factors Study 2010 is the result of a worldwide collaboration
of 500 researchers that scientifically and systematically quantified various health metrics of loss to diseases, injuries, and
risk factors by age and sex.11 The GBD 2010 included 291 diseases and injuries, 67 risk factors, 1160 sequelae (nonfatal
health consequences) for 21 regions, 187 countries, and 20 age
groups. The GBD 2010 uses improved methods for the estimation of disability weights, which quantify the severity of health
loss associated with a particular disease state. Disabilityadjusted life-years (DALYs) are a metric established by the GBD
to analyze and compare years of healthy life lost. The DALY is
a combination of years lost owing to premature death and years
lived with disability. These data metrics enable comparison of
health data across boundaries of geography and time in a way
that is more comprehensive, internally consistent, and comparable than previous data sources.12-14
The aim of the current study was to assess representation of 8 ophthalmologic categories studied by the GBD
2010 within the CDSR and whether representation corresponds to GBD 2010 disability estimates for each category.
The current study is part of a larger series intending to map
all 291 diseases studied by the GBD 2010 to representation in
major research databases.15,16
Methods
The following 8 ophthalmologic categories were studied by the
GBD 2010: refraction and accommodation disorders, cataracts, macular degeneration, glaucoma, trachoma, onchocerciasis, vitamin A deficiency, and other vision loss. The other vision loss category included a total of 57 eye conditions including
choroidal degeneration, central retinal artery occlusion and diplopia (see eTable 1 in the Supplement for a complete list of conditions in the other vision loss category). Each ophthalmologic category was explored in the CDSR by searching the
condition name under title, abstract, keywords (see Table 1 and
eTable 1 in the Supplement for International Statistical Classification of Diseases, 10th Revision [ICD-10] definitions and
search terms for each ophthalmologic category).18 Both systematic reviews and protocols were considered to assess ophthalmologic disease representation in the database.
Certain GBD categories were ultimately excluded
because ophthalmologic conditions were not the focus and
GBD metrics could not be attributed solely to the ophthalmologic conditions. These categories included sense organ
diseases, other sense organ diseases, and other noncommunicable diseases. The category of vitamin A deficiency was
predominantly eye conditions (ICD codes of nonophthalmologic conditions were E50.8. E50.9, and E64.1); thus, it was
included.
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Global Burden of Eye and Vision Disease
Original Investigation Research
Table 1. GBD 2010 Ophthalmologic Conditions, the ICD-10 Codes That Define Them, and Terms Searched
on the Cochrane Library
Ophthalmologic
Condition
ICD-10 Codes Populating
Ophthalmologic Category
in GBD 2010a
Terms Entered Into Search Query
Refraction and
accommodation
disorders
H49-H52
Refraction, accommodation disorders, paresis of accommodation,
spasm of accommodation, paralytic strabismus, third nerve palsy,
oculomotor nerve palsy, fourth nerve palsy, trochlear nerve palsy,
sixth nerve palsy, abducent nerve palsy, ophthalmoplegia,
Kearns-Sayre syndrome, strabismus, esotropia, exotropia, hypertropia,
hypotropia, heterotropia, cyclotropia, microtropia, monofixation
syndrome, heterophoria, esophoria, exophoria, brown sheath
syndrome, traumatic limitation of duction of eye muscle, Duane
syndrome, binocular movement, palsy of conjugate gaze, convergence
insufficiency, convergence excess, internuclear ophthalmoplegia,
hypermetropia, myopia, astigmatism, anisometropia, aniseikonia,
presbyopia, internal ophthalmoplegia
Cataracts
H25-H26
Cataracts, senile cataract, senile incipient cataract, subcapsular polar
senile cataract, water clefts, senile nuclear cataract, cataracta
brunescens, nuclear sclerosis cataract, Morgagnian type, senile
hypermature cataract, infantile cataract, juvenile cataract, presenile
cataract, traumatic cataract, complicated cataract, cataract in chronic
iridocyclitis, glaucomatous flecks, drug-induced cataract, secondary
cataract, Soemmerring ring
Macular
degeneration
H35.3
Macular degeneration, angioid streaks of macula, cyst of macula,
drusen of macula, degeneration of macula, hole of macula, puckering
of macula, Kuhnt-Junius degeneration, senile macular degeneration,
toxic maculopathy
Glaucoma
H40
Glaucoma, glaucoma suspect, ocular hypertension, primary openangle glaucoma, primary angle-closure glaucoma, glaucoma
secondary to eye trauma, glaucoma secondary to eye inflammation,
glaucoma secondary to other eye disorders, glaucoma secondary to
drugs
Trachoma
A71, A74.0, and B94.0
Trachoma, trachoma dubium, trachomatous, chlamydial conjunctivitis,
paratrachoma
Onchocerciasis
B73
Onchocerciasis, Onchocerca volvulus infection, Onchocercosis, river
blindness, Robles disease
Vitamin A
deficiency
E50.0-50.7 (E50.8,
E50.9, and E64.1
excluded because
not ophthalmologic
conditions)
Vitamin A deficiency with conjunctival xerosis, vitamin A deficiency
with Bitot spot, vitamin A deficiency with corneal xerosis, vitamin A
deficiency with corneal ulceration, vitamin A deficiency with
keratomalacia, vitamin A deficiency with night blindness, vitamin A
deficiency with xerophthalmic scars of cornea, ocular manifestations
of vitamin A deficiency, cerophthalmia due to vitamin A deficiency,
vitamin A eye, vitamin A blindness, vitamin A ocular
A systematic review or protocol was matched to 1 of the 8
ophthalmologic categories according to its subject content, and
the particular Cochrane Review Group that published each review and date of publication were determined. For a review
or protocol to be classified under a disease, the disease was required to be a predominant focus of the abstract objectives and
main results. If the systematic review or protocol included the
search term in the title, it was automatically included. Reviews or protocols with more than 1 category as a predominant focus were counted once within each respective category. For instance, if a review pertained to both cataracts and
glaucoma, it was counted twice.
Methods used by the GBD 2010 to generate DALY estimates have been previously described.13,14 As previously mentioned, the DALY metric combines years of life lost owing to
premature mortality and years lived with a disability.19 Disability-adjusted life-year metrics for each of the 8 ophthalmologic categories, expressed as the percentage of total DALYs of
291 conditions measured in the GBD 2010, were obtained from
the GBD Compare interactive time plot.20 Using this tool, search
parameters of time plot, DALYs metric, global place, all ages, both
sexes, and % units were selected for each ophthalmologic condition. The DALY rankings for the 8 ophthalmologic categories compared with 176 conditions measured in the GBD 2010
were obtained from the GBD interactive arrow diagram.21 Aljamaophthalmology.com
Abbreviations: GBD, Global Burden of
Disease; ICD-10, International
Statistical Classification of Diseases,
10th Revision.
a
Specific ICD-10 codes used by GBD
2010 are published in a study by
Lozano et al.17
though the GBD project studied 291 conditions, rankings only
include 176 conditions, excluding conditions for which the project made no explicit estimates such as etiologies of diarrhea,
pneumonia, and more specific conditions under maternal or
congenital. Search parameters of global place, all conditions,
both sexes, DALY metric, and age standardized were used. The
DALY percentage change from 1990 to 2010 was also obtained
from the GBD interactive arrow diagram for each ophthalmologic condition. Age standardization was used in the interactive arrow diagram for DALY ranking and percentage change
to eliminate effects of population growth and aging over the
20-year span.
Matching of the CDSR representation with GBD disability
estimates was accomplished by creating a data plot of representation vs disability to generate a linear line of best fit with
a coefficient of determination (R2) and qualitatively determining whether conditions were well matched or not well matched.
Because research prioritization of a major database, such as
the CDSR, was not expected to solely correlate with a single
factor, qualitative rather than quantitative methods were used
to match funding with disability.
Two authors (L.N.B. and C.K.) collected data independently, with consensus review during March 2014. Because the
current study solely involved nonhuman subjects, institutional review board approval was not necessary.
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27
Research Original Investigation
Global Burden of Eye and Vision Disease
Table 2. Representation in the CDSR and DALY Metrics for 8 Ophthalmologic Conditions Studied by GBD 2010a
Ophthalmologic
Condition
No. of
Systematic
Reviews and
Protocols in
the CDSR
Cochrane
Group
Contributions
% of Total
2010 DALY
(Of 291
Conditions)
DALY %
Change of
DALY From
1990 to
2010
2010
DALY Rank
(Of 176
Conditions)
Other vision loss
26 (23 reviews,
3 protocols)
19 Eyes and Vision,
5 Neonatal, and
2 Stroke
0.25
+2
67
Refraction and
accommodation
disorders
15 (12 reviews,
3 protocols)
15 Eyes and Vision
0.23
+1
68
Cataracts
19 (16 reviews,
3 protocols)
16 Eyes and Vision
and 3 Anesthesia
0.19
−30
74
Macular
degeneration
20 (19 reviews,
1 protocol)
20 Eyes and Vision
0.054
+56
132
Glaucoma
30 (20 reviews,
10 protocols)
30 Eyes and Vision
0.038
+31
147
Trachoma
4 (4 reviews,
0 protocols)
4 Eyes and Vision
0.013
+48
165
Onchocerciasis
1 (1 review,
0 protocols)
1 Eyes and Vision
0.02
−31
163
Vitamin A
deficiency
1 (1 review,
0 protocols)
1 Acute Respiratory
Infections
0.032
−9
153
Results
A total of 116 reviews and protocols represented the 8 ophthalmologic categories, with 106 (91.4%) of these being from
the Cochrane Eyes and Vision Group (Table 2). Glaucoma had
the greatest representation in the CDSR, with 30 reviews and
protocols, followed closely by the other vision loss category,
with 26 reviews and protocols, and macular degeneration, with
20 reviews and protocols. Those categories with lower representation were trachoma, with 4 reviews, and onchocerciasis
and vitamin A deficiency, both with only 1 review. A list of all
included review and protocol titles for each condition is available in eTables 2 and 3 in the Supplement and a list of all excluded titles in eTables 4 and 5 in the Supplement. The range
of review and protocol publication year was from 1999 to 2014,
with 73.3% occurring from 2010 to 2014; the median and mode
year was 2012.
Looking at the global GBD 2010 DALY metrics, other vision loss had the greatest percentage of total DALY (0.25%), followed by refraction and accommodation disorders (0.23%)
(Table 2). Vitamin A deficiency had the lowest percentage of
total DALY (0.032%) of the conditions assessed. The conditions that experienced an increase in DALY from 1990 to 2010
listed from greatest to least were macular degeneration (percentage change in DALY from 1990 to 2010 was +56%), trachoma (+48%), glaucoma (+31%), other vision loss (+2%), and
refraction and accommodation disorders (+1%). The conditions that experienced a decrease in DALY from 1990 to 2010
listed from greatest to least were onchocerciasis (percentage
change in DALY from 1990 to 2010 was −31%), cataracts (−30%),
and vitamin A deficiency (−9%). The 2010 DALY ranks for the
8 ophthalmic conditions assessed ranged from 67 for other vision loss to 153 for vitamin A deficiency.
Comparing the CDSR representation with DALY metrics,
the overall R2 was 0.23, indicating an overall poor correlation
between these variables (Figure). Specifically, cataract was the
28
Abbreviations: CDSR, Cochrane
Database of Systematic Reviews;
DALY, disability-adjusted life-year;
GBD, Global Burden of Disease;
a
Arranged in order of decreasing
percentage of total 2010 DALY.
only category that was well matched (Table 2). Glaucoma,
macular degeneration, and other vision loss were overrepresented when matched with corresponding DALYs. Conversely, trachoma, onchocerciasis, vitamin A deficiency, and
refraction and accommodation disorders were underrepresented in the CDSR relative to corresponding DALYs.
Twenty-six systematic reviews and protocols covered 57
ophthalmologic conditions defined by the GBD 2010 other vision loss category (see eTable 1 in the Supplement for ICD codes
and conditions that comprise the other category; see eTable 3
in the Supplement for included titles and eTable 5 for excluded titles). The Cochrane Eyes and Vision Group was responsible for 73.1% of the systematic reviews in the CDSR for
these 57 ophthalmologic conditions.
Discussion
The 8 ophthalmologic categories assessed were represented
by a total of 116 reviews and protocols in the CDSR, with most
(91.4%) published by the Eyes and Vision Group. While the
CDSR covers a broad diversity of ophthalmologic conditions,
prioritization is not solely guided by burden of disease data.
This was exemplified by the poor correlation between the CDSR
representation and DALYs for the ophthalmologic categories,
which yielded an R2 of 0.23. Other factors and considerations
play critical roles in the prioritization process by the CDSR. In
addition, the fact that most reviews and protocols were published from 2010 to 2014 provided evidence of the current and
frequently updated nature of the CDSR content.
Conditions for Which CDSR Representation Appeared
Well Matched With Disability Metrics
Cataract was the only category that was well matched with respect to DALY and CDSR representation. Although cataracts had
the third highest DALY, the condition experienced the greatest decrease in DALY from 1990 to 2010 of the conditions stud-
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Global Burden of Eye and Vision Disease
Original Investigation Research
Figure. Comparison of Ophthalmology Representation in Cochrane Database of Systematic Reviews
to Percentage of Total 2010 Disability-Adjusted Life-Years
35
R2 = 0.23
Cochrane Systematic Reviews and Protocols, No.
30
Glaucoma
Other vision loss
25
20
Macular degeneration
Cataracts
Refraction and
accommodation disorders
15
10
5
Trachoma
Onchocerciasis
Vitamin A deficiency
0
0
0.05
0.1
0.15
0.2
0.25
Total 2010 Disability-Adjusted Life-Years, %
ied. Age-related cataracts are the leading cause of blindness,
causing an estimated 51% of all blindness and affecting 19.7 million people worldwide.22 In addition, surgery for cataracts and
refractive errors are among the most cost-effective interventions in health care.22
Conditions for Which CDSR Representation Appeared
Overmatched With Disability Metrics
Glaucoma, macular degeneration, and other vision loss were
overrepresented when compared with their DALY metrics.
Glaucoma not only had the greatest number of CDSR reviews
and protocols, but also experienced a 31% increase in DALY
from 1990 to 2010. Similarly, macular degeneration experienced the greatest increase in DALY (+56%) of all the categories. The apparent overrepresentation of these 2 conditions in
the CDSR is more accurately reflected by their 20-year disability trends.
Representing 57 eye conditions, the other vision loss category was second in terms of CDSR representation, with 29 reviews and protocols and has the greatest DALY and highest
DALY ranking of all the categories. This category experienced
a DALY percentage change increase of 2%, the smallest of the
3 conditions that were overmatched.
Conditions for Which CDSR Representation Appeared
Undermatched With Disability Metrics
Trachoma, onchocerciasis, vitamin A deficiency, and refraction and accommodation disorders were underrepresented in
the CDSR relative to their disability estimates. Of the conditions studied, refraction and accommodation disorders had the
second greatest DALY. While uncorrected refractive errors are
responsible for 43% of all visual impairment and affect apjamaophthalmology.com
0.3
The correlation coefficient (R2) equals
0.23 for the number of Cochrane
systematic reviews and protocols
compared with the global percentage
of total 2010 disability-adjusted
life-years for 8 ophthalmologic
conditions.
proximately 120 million people worldwide, most of these cases,
such as near sightedness, far sightedness, or astigmatism, could
be corrected with the assistance of eyeglasses, contact lenses,
or refractive surgery.23 Perhaps this existing knowledge of effective interventions contributed to a relatively constant DALY
from this category (+1%) from 1990 to 2010. Similarly, vitamin A deficiency and onchocerciasis demonstrated the lowest 2010 DALYs of the 8 ophthalmologic conditions, in addition to large decreases in DALY from 1990 to 2010. Their low
CDSR representation may thus reflect the relative decreased
burden of disease over time. In contrast, trachoma was underrepresented in the CDSR but experienced the second greatest 20-year increase in DALY (+48%) of all the conditions assessed. While trachoma is the leading cause of infectious
blindness in the world, the condition is irreversible and highly
contagious.23 Active efforts, such as those led by the World
Health Organization’s Alliance for the Global Elimination of
Trachoma, predominantly focus on prevention at the population level.24
Limitations and Future Directions
Limitations of this study were related to synthesizing ophthalmologic presence in the CDSR and the use of GBD metrics. First,
quantification of reviews and protocols in the CDSR was subject to how the reviews and protocols were compiled. For instance, multiple conditions may be covered in one review with
a broader focus, referred to as lumping. Alternatively, several
reviews may cover the same information, each with a more narrow focus, referred to as splitting.25 Hence, consideration of a
systematic review as one unit of representation may not be appropriate for certain topics. In addition, the CDSR reviews synthesize studies and the best evidence in the literature. For this
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Research Original Investigation
Global Burden of Eye and Vision Disease
reason, meta-analyses for topics that lack studies in the literature are generally not possible in the CDSR. Variables beyond Cochrane research prioritization determine database presence. Additionally, the assignment of a particular review or
protocol by the study authors to a particular ophthalmologic
category was not completely objective; the use of independent data collection by 2 authors with consensus review strove
to minimize this source of error.
Second, this study was also subject to limitations of the
GBD 2010 such as inconsistent or scarce data sources.26 The
ICD codes comprising disease categories were established by
GBD collaborator consensus. These ICD codes were used to generate search terms and may not have generated all search results pertaining to each topic. Several GBD categories were excluded from the current study that did not focus exclusively
on ophthalmologic conditions because the DALYs could not be
solely attributed to the ophthalmologic condition. In addition, the GBD 2010 does not provide disability estimates for
individual diseases in the other vision loss category. Further
breakdown of this category would enable a more in-depth and
inclusive study of disease impact. As GBD data become available on an annual basis, analysis of the relationship and trends
between database representation and GBD disability over time
can be explored further. Finally, this study did not explore the
contributions of disease inclusion in the CDSR other than global
disease burden such as the skewed financial burden of diseases that disproportionately cause vision impairment in
developed populations.
Conclusions
Overall, the global burden of ophthalmic conditions was
poorly proportioned to the reviews and protocol representa-
ARTICLE INFORMATION
Submitted for Publication: May 13, 2014; final
revision received June 24, 2014; accepted July 4,
2014.
Published Online: September 18, 2014.
doi:10.1001/jamaophthalmol.2014.3527.
Author Affiliations: Georgetown University School
of Medicine, Washington, DC (Boyers); Columbia
University College of Physicians and Surgeons, New
York, New York (Karimkhani); Cochrane Editorial
Unit, The Cochrane Collaboration, London, England
(Hilton); Department of Ophthalmology, University
of Colorado Anschutz Medical Campus, Denver
(Richheimer); Department of Dermatology,
University of Colorado Anschutz Medical Campus,
Denver (Dellavalle); Department of Epidemiology,
Colorado School of Public Health, University of
Colorado Anschutz Medical Campus, Denver
(Dellavalle); Department of Dermatology, Denver
Veterans Administration Hospital, Denver, Colorado
(Dellavalle).
Author Contributions: Ms Boyers and Dr Dellavalle
had full access to all of the data in the study and
take responsibility for the integrity of the data and
the accuracy of the data analysis.
Study concept and design: Boyers, Karimkhani,
Hilton, Dellavalle.
30
tion in the CDSR. There are likely a variety of factors contributing to the lack of correlation. Diseases with known
cures, but with significant public health and economic barriers to treatment, such as vitamin A deficiency, were
underrepresented in the CDSR. Furthermore, economic
impact of diseases disproportionally affecting wealthy
populations may contribute to overrepresentation in the
CDSR. This article highlighted ophthalmic diseases where
global burden fails to correlate with current research and
reviews. We suggest that considerations be taken of such
underrepresented and overrepresented ophthalmic conditions in pursuit of future research, reviews, and funding.
Overall, global burden of disease comprises one of many
factors guiding research prioritization of ophthalmic conditions by Cochrane Review Groups. The process of mapping systematic reviews with disability metrics, such as DALY, provides reproducible, transparent, and valuable data for use in
future research prioritization discussions. Certainly, the allocation of research funds and topic prioritization is an intricate process guided by many factors.1 Within Cochrane, prioritization processes are largely determined and maintained
by individual Cochrane Review Groups.
This study is part of a series that aims to map all conditions studied by the GBD to representation in various major
databases such as the CDSR.16 In the future, we hope that this
initial manual mapping will become automated, using the advanced and large-scale methods possible with computer programs and technological advances. Global burden of disease
is a useful metric that may guide prioritization decisions. The
GBD has created unprecedented public access of electronic information. As GBD metrics become increasingly used by health
care professionals, policy makers, and individuals alike, the
global burden of disease may ultimately help to reduce research gaps and profoundly impact the human population.
Acquisition, analysis, or interpretation of data:
Boyers, Karimkhani, Richheimer.
Drafting of the manuscript: Boyers, Richheimer.
Critical revision of the manuscript for important
intellectual content: All authors.
Administrative, technical, or material support:
Boyers, Karimkhani, Dellavalle.
Study supervision: Richheimer, Dellavalle.
Conflict of Interest Disclosures: All authors have
completed and submitted the ICMJE Form for
Disclosure of Potential Conflicts of Interest. Ms
Boyers and Dr Dellavalle are both employees of the
US Department of Veterans Affairs. Dr Dellavalle is
also chair of the Colorado Skin Cancer Task Force.
Mr Hilton is an employee of The Cochrane
Collaboration. No other disclosures were reported.
Funding/Support: Dr Dellavalle receives a salary
from the US Department of Veterans Affairs. Dr
Dellavalle is also supported by grants from the
Centers for Disease Control and Prevention and
National Institutes of Health.
Role of the Funder/Sponsor: The funders had no
role in the design and conduct of the study;
collection, management, analysis, and
interpretation of the data; preparation, review, or
approval of the manuscript; and decision to submit
the manuscript for publication.
Disclaimer: The opinions expressed herein do not
necessarily reflect those of the US Department of
Veterans Affairs, the Centers for Disease Control
and Prevention, the National Institutes of Health, or
The Cochrane Collaboration.
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