Evidence Report/Technology Assessment: Number 38
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Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of the Full Report
Cataract and glaucoma are both common
conditions and are often present in the same
patient. Cataract surgery is the most commonly
performed surgical procedure on Medicare
beneficiaries. In 1998, approximately 1.4 million
cataract surgeries were performed on Medicare
beneficiaries. Primary open-angle glaucoma
affects at least 2.5 million individuals in the
United States, predominantly adults over 50 years
of age. The total direct cost expenditures for
glaucoma therapy have been estimated at $1.56
billion dollars per year.
Although guidelines exist for the indications
for cataract surgery in the otherwise healthy eye
and for glaucoma surgery in eyes with glaucoma,
there is controversy concerning the indications for
surgery when both cataract and glaucoma are
present. In addition, there is no clear consensus
about the appropriate timing of the surgery for
either condition, or about the best surgical
technique. Furthermore, there is no agreement
concerning the optimal management of these
disorders when coexistent. Therefore, the Agency
for Health Care Policy and Research, now
renamed the Agency for Healthcare Research and
Quality (AHRQ), awarded a contract to the
Johns Hopkins University Evidence-based
Practice Center to prepare an evidence report on
the topic. This evidence report was undertaken:
- To identify the most important questions pertinent
to surgical treatment of coexisting cataract and
- To assess the quality and content of the
evidence on surgical treatment of coexistent
cataract and glaucoma.
- To inform clinical
practitioners and identify areas where future
research is needed.
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Reporting the Evidence
The target population addressed in this
evidence report is adult patients with coexisting
cataract and glaucoma. Both open- and closed-angle
glaucoma were considered. The target
audience for the report is health care professionals
involved in the care of adult patients with
coexisting cataract and glaucoma.
The following questions were addressed in the
- What are the risks and benefits of staged
versus combined procedures for coexisting
cataract and glaucoma?
- What is the effect of cataract surgery on
short- and long-term intraocular pressure
(IOP) control in open-angle glaucoma
- What is the effect of glaucoma surgery (i.e.,
filtration surgery) on the development and
progression of cataract?
- What are the risks and benefits of antifibrosis
agents in the surgical treatment of coexisting
cataract and glaucoma?
- What are the risks and benefits of
trabeculectomy versus endoscopic laser versus
deep sclerectomy/viscocanulostomy in
patients with coexisting cataract and
- What are the risks and benefits of single-site
versus two-site operations for coexisting
cataract and glaucoma?
- What are the risks and benefits of nuclear
expression or phacoemulsification in patients
with coexisting cataract and glaucoma?
The interventions evaluated included two
commonly used methods for cataract extraction:
nuclear expression and phacoemulsification.
Several methods used for the surgical
management of glaucoma were studied, including
laser treatment, filtration surgery, and the newer
techniques of endoscopic cyclophotocoagulation
and the so-called nonpenetrating procedures.
The use of the antifibrosis agents 5-fluorouracil
and mitomycin C was also evaluated. The various ways in
which cataract and glaucoma surgery can be performed either
simultaneously or sequentially were studied.
The primary outcome assessed for the questions involving
glaucoma surgery was IOP, both in the immediate
postoperative period and long term. The articles reviewed
generally lacked useful data on optic nerve appearance and
visual fields, thereby precluding a meaningful review of those
outcomes. Likewise, the lack of information concerning
complications limited the ability to address the risk aspects of
each question. For the question concerning the development
of cataract after glaucoma surgery, both the observation of a
cataract and the performance of cataract surgery were assessed
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The literature searches were conducted using two electronic
databases, PubMed and CENTRAL, the Cochrane
Collaboration's database. The textwords and medical subject
heading (MeSH) terms we used included ("cataract" and
"glaucoma") and ("surgery" or "filtering surgery" or "cataract
extraction" or "sclerostomy" or "trabeculectomy" or
"phacoemulsification"). To retrieve the appropriate types of
studies, we included variants of "randomized controlled trials"
in the search as well as "case report" and "case series." We
limited the search to publications in English. Citations
spanned the period from 1980 to April 2000. The electronic
searches were augmented by a hand search of primary journals.
The abstracts of all identified citations were independently
reviewed by two members of the study team to determine if
they met eligibility criteria. When reviewing abstracts, the
following criteria were used to exclude articles from further
- Lack of adults in the study population.
- Lack of original data.
- Failure to include human data.
- Failure to address open-angle glaucoma or primary angle closure glaucoma.
- Neither a controlled trial nor a case series greater than or equal
to 100 eyes.
- Addressing only intracapsular cataract surgery.
- Addressing only full-thickness procedures.
Meeting abstracts and texts not in English were also excluded. Disagreements
between reviewers about the eligibility of a citation were
adjudicated at a meeting of the entire study team. We
reviewed the full text of the article for a 5-percent random
sample of rejected abstracts. None of these articles was
deemed eligible for inclusion in the full article review.
Two forms were developed and used to review eligible
citations. The quality assessment form contained questions
grouped into the following categories:
- Representativeness of study population-how completely
the authors described the study subjects.
- Bias and confounding, including completeness of
randomization and masking.
- Description of therapy-completeness of the description
of the study protocol and other treatments, if applicable.
Outcomes and followup, including explicit description of
the outcomes reported (e.g., assessment of IOP, cataract
assessment) and length of followup.
- Statistical quality and interpretation.
Quality scores for each controlled trial and cohort study
The article content assessment form was developed through
an iterative process. The study team discussed which
outcomes should be included on the form. Following these
discussions, selected relevant articles were reviewed to create a
standardized abstraction of reported outcomes in a manner
that was applicable across the range of studies. Finally, the
form was pilot tested on a sample of articles and revised as
necessary. Instructions for the use of the form were developed
by consensus for the purposes of consistency.
Each article identified by the search process and determined
to meet eligibility criteria through the abstract process was
reviewed by two reviewers. At least one of the reviewers was
trained in research methodology and at least one was trained
in ophthalmology or internal medicine.
Data from the article review process were entered into a
relational database. For each study question, one member of
the analysis team summarized the available data and reached a
conclusion about the answer to the question. The entire study
team assigned an evidence grade to the conclusions reached
about each study question.
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Of 919 unique, potentially relevant citations, 131 articles
were eligible for full article review. After 21 were excluded,
110 articles remained for data extraction. Study quality scores
were calculated for controlled trials and cohort studies,
comprising 81 articles. The mean overall study quality score
was 53 percent.
The findings are as follows.
Strongly Supported by the Literature
- Glaucoma surgery was associated with an increased risk of
- A glaucoma procedure added to cataract surgery lowers
IOP more than cataract surgery alone.
Moderately Supported by the Literature
- Limbus- and fornix-based conjunctival incisions provided
the same degree of long-term IOP lowering in combined
- In combined surgery using phacoemulsification, the size
of the cataract incision did not affect long-term IOP
- 5-fluorouracil was not beneficial in further lowering IOP
when used with combined procedures.
- Mitomycin C was efficacious in producing lower long-term
IOPs when used with combined procedures.
Weakly Supported by the Literature
- Combined procedures resulted in lower IOP at 24 hours
than cataract extraction alone.
- Extracapsular cataract extraction (ECCE) alone appears to
increase IOP at 24 hours.
- In the long term, cataract surgery alone lowered IOP by 2
to 4 mm Hg, combined cataract and glaucoma surgery
lowered IOP by 6 to 8 mm Hg, and the performance of a
glaucoma procedure alone provided even greater long-term
IOP lowering than combined cataract and glaucoma
- Combined surgery in which the incisions for the cataract
extraction and glaucoma procedure are separate provided
slightly lower long-term IOP than a one-site approach.
- Combined surgery in which phacoemulsification is used
provided slightly lower long-term IOP than nuclear
- The same complications occurred with combined surgery
as occur with cataract and glaucoma surgery performed
- 5-fluorouracil use was associated with epithelial defects.
- Hypotony was more likely after the use of antifibrosis
agents than after surgery performed without antifibrosis
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The literature addressing management of coexistent cataract
and glaucoma has important limitations that future research
should consider and address. First, those limitations
pertaining to the entire literature are described, and then those
that are specific to individual questions are described.
In terms of the management of glaucoma, because the
extant literature concentrates on IOP, this review was limited
to the effect of surgery on IOP. Future studies should assess
the effect of surgery on the appearance of the optic nerve,
visual field, and quality of life. Because of the chronic and
slowly progressive nature of glaucoma, these parameters need
to be evaluated in long-term (5 years or more) studies.
In terms of cataract, future studies should pay more
attention to the quantification of cataract and its effect on
vision. The existing literature is generally lacking in any
objective description of the ocular lens, whether clear or
cataractous. Quantifying lens opacity and assessing its effect
on vision and vision-related quality of life should be a priority
in future studies. Standardized grading systems for cataract
(already in use) should be employed.
Although the literature represented populations in North
America, Europe, and Asia, few of the reports included
significant numbers of black Americans. This population has
a high prevalence of glaucoma and may respond differently to
glaucoma surgery. Future researchers should strive to include
more black Americans in their studies.
Assessment of the evidence was limited by the quality of the
literature. In several of the study quality categories,
particularly bias and confounding, there was tremendous room
for improvement. A lack of comparability of study groups and
an absence of masking of observers greatly compromised the
validity of many studies. In future studies, it would be
valuable to strive for comparability of study groups and
statistical adjustment for baseline differences, as well as more
objective measures for assessing outcomes.
The following specific questions are areas for future
research, both because of their importance and the fact that
questions remain unresolved by the extant literature:
- Does trabeculectomy alone lower IOP more than
phacoemulsification plus trabeculectomy?
- Does phacoemulsification harm functioning filtering
- Does phacoemulsification reliably result in lower IOP on
the first day after surgery? If so, then it might not be
necessary to perform combined surgery.
- Does a two-stage procedure provide lower IOP than a
- What is the role of mitomycin C in combined procedures
and how should it be administered?
- Is the finding of decreased posterior capsular opacification
with the use of mitomycin C reproducible?
- Can better glaucoma procedures be developed to be used
in conjunction with cataract surgery?
- What are the risk factors for cataract development and
progression following glaucoma surgery?
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Availability of the Full Report
The full evidence report from which this summary was
derived was prepared for the Agency for Healthcare Research
and Quality by the Johns Hopkins University Evidence-based
Practice Center under contract 290-097-0006. Printed copies can be
obtained free of charge from the AHRQ Publications
Clearinghouse by calling 1-800-358-9295. Request Evidence
Report/Technology Assessment: Number 38, Surgical
Treatment of Coexisting Cataract and Glaucoma (AHRQ
Publication No. 03-E041.
The Evidence Report is also online on the National Library of Medicine Bookshelf.
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AHRQ Publication Number 01-E049
Current as of June 2001