Consensus 5

5th Consensus Meeting:
Glaucoma Screening

Fort Lauderdale, FL, April 26, 2008

cons5

edited by Robert N. Weinreb, Paul R. Healey and Fotis Topouzis
2008. xiv and 11 tables and 57 figures, , of with 1 in full colour. Hardbound.
ISBN-10: 90 62992 188.
ISBN-13: 978-90-6299-218-8
Published by Kugler Publications.
Click here for more information on all publications in the Consensus series.

See meeting photos

Summary Consensus Points

Is OAG an important health problem?

  • Glaucoma is the leading cause of preventable irreversible blindness.
  • The goal of glaucoma screening is to prevent visual impairment, preserve
    quality of life and visual functioning.
  • Each society should determine its own criteria, including the stage
    of disease, for the allocation of an affordable proportion of its resources
    for glaucoma care and screening.
  • The prevalence of open-angle glaucoma has been determined for some populations
    of European, African and Asian ancestry
    Comment: Prevalence, incidence and
    severity data are needed still for many regions of the world.
  • Long-term data show a substantial frequency of glaucoma blindness in
    some populations.
    Comment: Additional population based data are needed on
    the rates and risks of vision loss

Is there an accepted and effective treatment for patients with the disease
that is more effective at preventing morbidity when initiated in the early,
asymptomatic stage than when begun in the later, symptomatic stages?

  • High-quality randomized trials (treatment vs. no treatment) and meta-analyses
    have shown that topical ocular hypotensive medication is effective in delaying
    onset and progression of open-angle glaucoma (OAG).
  • Treatments are effective, easy to use, and well tolerated.
  • It is not known whether postponing ocular hypotensive therapy affects
    the rate of subsequent conversion from ocular hypertension to OAG or the
    rate of progression of visual field loss once OAG has developed.
  • It is not known whether the reduction in progression rate from intraocular
    pressure (IOP) lowering therapy varies according to disease stage.
    Comment: Asymptomatic disease may include early, moderate, or at times severe stages
    of OAG.
  • Current evidence suggests that glaucoma therapy itself is not associated
    with a measurable reduction of quality of life.
  • Patients’ perceived vision-related quality of life (VRQOL) and visual
    f unction is correlated with visual field loss, especially binocular visual
    field loss, in OAG.

    Comment: the greater the visual field loss, or the later
    the stage of the disease, the more symptomatic the disease.

Are facilities for diagnosis and treatment available?

  • The resources for diagnosis and treatment of glaucoma vary worldwide.

    Comment: Many countries have insufficient facilities to provide care at
    Summary consensus points 147 present practice standards relative to developed
    countries. There is a need to identify areas without facilities to help
    plan resource allocation.

  • Fewer resources are required to diagnose glaucoma at moderate to advanced
    asymptomatic stages compared to very early stages.
  • Treatment of glaucoma requires facilities for regular long-term monitoring.
    There is a need to study barriers to access for glaucoma care so that available
    facilities can be used optimally

Is there an appropriate, acceptable, and reasonably accurate screening test?

  • The best single test or group of tests for open-angle glaucoma screening
    is yet to be determined.
  • Optimal screening test criteria are not yet known.

    Comment: Screening
    test criteria depend upon health care system, location, and prevalence of
    open-angle glaucoma (OAG).

    Comment: The sensitivity and specificity of tests
    for population-based screening are unknown, as most have been tested only
    on selected groups, not populations.

  • Diagnostic test accuracy may vary according to the severity of the disease.
  • The tests available and effective for case-finding are not necessarily
    the same as those for population- based glaucoma screening which requires
    a very high specificity to be cost-effective.
    Comment: Screening requires
    a test with a high specificity. Diagnosis requires a test with a high sensitivity.

    Comment: Individuals at high risk require highly accurate tests.

Is the natural history of the condition, including development from latent
to manifest disease, adequately understood?

  • Open-angle glaucoma (OAG) incidence rates are known for untreated and
    treated patients with ocular hypertension.
  • OAG progression rates vary greatly among patients.
    Comment: More research
    is required to determine the extent and basis of progression rate variation.
  • Progression event rates for patients (in clinical trials, under clinical
    care or observation) in terms of percent of patients/eyes progressing per
    year are available both for OAG and ocular hypertension.
  • Progression data expressed as rate of disease progression (i.e., expressed
    in dB/year or in % of full field/year) are very sparse.

Is the cost of case finding (including diagnosis and treatment of patients
diagnosed) economically balanced in relation to possible expenditure on medical
care as a whole?

  • The best evidence to date, based on two modeling studies, suggests:
    1. Screening of high-risk subgroups may be more cost-effective than screening
      the entire population. 148 Summary consensus points
    2. Screening may be
      more cost-effective as glaucoma prevalence increases
    3. The optimal screening
      interval is not yet known
    4. Screening may be more cost-effective when initial
      assessment is a simple strategy that could be supervised by non-medical
      technicians.

    Comment: More research is needed for the implementation of
    the best screening program for glaucoma.
    Comment: Expert consensus is required on how cost data should be collected and reported in glaucoma care. This
    includes reporting visually relevant outcomes on a per-patient basis.
    Comment: Additional data are required to develop a glaucoma disease staging system
    based on disability.

  • Population-based screening studies are required to determine optimal
    screening strategies and their cost-effectiveness.
  • Multi-eye disease screening needs to be evaluated as to whether it would
    be more cost-effective than glaucoma-only screening.

Are angle closure (AC) and angle-closure glaucoma (ACG) important health
problems?

  • Primary angle-closure glaucoma (PACG) accounts for approximately 25%
    of all glaucomatous optic neuropathy worldwide, but 50% of bilateral glaucoma
    blindness.
  • Visual impairment from primary angle closure (PAC) and PACG can result
    from ocular damage other than glaucomatous optic nerve damage (e.g., corneal
    decompensation, cataract, ischemic optic neuropathy).
  • Some Asian populations have a high prevalence of advanced angle-closure
    glaucoma.
  • PACG is predominantly asymptomatic.
  • PACG is a problem of sufficient magnitude that public health intervention
    should be evaluated.

Is there an accepted and effective treatment for patients with angle-closure
glaucoma (ACG) that is more effective at preventing morbidity when initiated
in the early, asymptomatic stage than when begun in the later, symptomatic stages?

  • Angle closure is a progressive condition that can lead to glaucoma.
  • Iridotomy or iridectomy is the preferred initial treatment for cases
    of PAC and PACG.
    Comment: Iridotomy or iridectomy eliminates pupillary block.
  • There is no evidence to support medical treatment alone for PACG in
    the absence of iridotomy or iridectomy.
  • Medical treatment may be indicated for lowering IOP after iridotomy
    or iridectomy, following risk assessment.
    Comment: Research is needed to
    determine whether a residual increase in IOP following iridotomy or iridectomy
    requires treatment
  • Iridotomy or iridectomy will not always alleviate irido-trabecular apposition
    since mechanisms other than pupillary block may be present, such as plateau
    iris or phacomorphic angle closure.
    Comment: Peripheral iridoplasty may
    be effective in further opening the angle and preventing further closure.
    Unlike iridotomy or iridectomy, peripheral iridoplasty sometimes needs to
    be repeated.
  • There is good evidence that preventive iridotomy or iridectomy will
    eliminate the risk of acute angle closure when performed on the fellow eye
    of patients who have experienced acute angle closure.
  • There is insufficient evidence for deciding which PACG patients should
    undergo lens extraction alone (without trabeculectomy).
    Comment: Lens extraction
    alone may be considered in eyes with mild degree of angle closure (less
    than 180º of PAS), mild optic nerve damage/ visual field damage or those
    that are not on maximum tolerated medical treatment.

    Comment: There is limited evidence for recommending lens extraction alone in eyes with mild PACG.
    Similarly there is limited evidence for recommending lens extraction alone
    in eyes with more advanced PACG.
    Comment: Published studies to date have
    been non-randomized, with small sample sizes and short follow-up.

  • Although commonly performed, there is limited evidence about the effectiveness
    of combined cataract extraction and trabeculectomy in eyes with PACG.
    Comment: There is a need for studies comparing this form of surgery with separately
    staged cataract extraction and trabeculectomy.

Are facilities for diagnosis and treatment available?

  • There is a need for a systematic assessment of the clinical capacity
    to identify and treat angle closure (AC).
  •  Gonioscopy is essential for diagnosis and treatment. Comment:
    Inadequate clinical training and limited use of gonioscopy are major obstacles
    to successful case finding.

Is there an appropriate, acceptable, and reasonably accurate screening test?

  • There is evidence that limbal anterior chamber depth (LCD) may be an
    appropriate screening test for angle closure.
    Comment: Using a LCD of 25%
    corneal thickness as a cut-off all those cases falling below this level
    would require gonioscopy. Approximately 4% of occludable angles may be missed
    by this method.
    Comment: More research is required concerning alternative
    screening tests.
    Comment: A screening test should not be used as a substitute
    for definitive diagnosis. 150 Summary consensus points
  • Clinic-based case-detection should target established primary angle
    closure (PAC) and primary angle closure glaucoma (PACG) as blindness can
    still be prevented when interventions are implemented at these stages.
  • Comment: The evidence supporting early detection and prophylactic treatment
    of primary angle closure suspects (PACS) is limited at present and cannot
    be justified where prevalence of PACS is high.
  • Gonioscopy is the current gold standard of angle examination and is
    the appropriate test for diagnosing angle closure.
    Comment: Gonioscopy alone may not be suitable as a screening test.
    Comment: Gonioscopy combined with optic disc examination and intraocular pressure measurement may enable optimum
    detection of PAC, PACG and open angle glaucoma (POAG) in a clinic setting.
  • For accuracy of clinic-based case detection of PAC/G improve, there
    needs to be a significant increase in the level and use of gonioscopy and
    disc examination training for ophthalmologists.

Is the natural history of the condition, including development from latent
to manifest disease, adequately understood?

  • An episode of symptomatic acute angle closure (AAC) places the unaffected
    fellow eye at high risk of a similar fate.
  • The current best estimate for progression from primary angle closure
    suspect (PACS) to primary angle closure (PAC) or PAC to primary angle closure
    glaucoma (PACG) is approximately 20-30% over 5 years.
    Comment: The data
    on the natural history of PACS/PAC/PACG are sparse and would benefit from
    confirmation in further studies.
  • Asymptomatic angle closure is associated with later presentation and
    more advanced loss of vision than symptomatic angle closure where facilities
    for treatment are readily available.

Is the cost of case finding (including diagnosis and treatment of patients
diagnosed) economically balanced in relation to possible expenditure on medical
care as a whole?

  • In assessing the cost-effectiveness of a screening program for angle
    closure and angle closure glaucoma, we must consider fully the costs and
    benefits of the program.
  • Evaluation must consider the perspective of the decision maker, the
    incremental cost of the proposed program versus current programs and how
    we measure effectiveness.
  • A thorough cost effectiveness analysis is not possible at present.
    Comment: In order to determine the cost-effectiveness of screening for primary angle
    closure (PAC)/primary angle closure glaucoma (PACG) we will need to be able
    to define clearly key elements of the screening process and the potential
    benefits of screening.

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