Consensus 5

5^th Consensus Meeting: Glaucoma Screening

Fort Lauderdale, FL, April 26, 2008

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?
• 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?
• Are facilities for diagnosis and treatment available?
• Is there an appropriate, acceptable, and reasonably accurate screening test?
• Is the natural history of the condition, including development from latent to manifest disease, adequately understood?
• 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?
• Are angle closure (AC) and angle-closure glaucoma (ACG) important health problems?
• 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?
• Are facilities for diagnosis and treatment available?
• Is there an appropriate, acceptable, and reasonably accurate screening test?
• Is the natural history of the condition, including development from latent to manifest disease, adequately understood?
• 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?

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?

• 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.
• 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.

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.