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This draft Recommendation Statement is based on an evidence review that was published on February 19, 2013 (available at http://www.uspreventiveservicestaskforce.org/uspstf13/glaucoma/glaucomaart.htm).
The USPSTF makes recommendations about the effectiveness of specific clinical preventive services for patients without related signs or symptoms.
It bases its recommendations on the evidence of both the benefits and harms of the service, and an assessment of the balance. The USPSTF does not consider the costs of providing a service in this assessment.
The USPSTF recognizes that clinical decisions involve more considerations than evidence alone. Clinicians should understand the evidence but individualize decisionmaking to the specific patient or situation. Similarly, the USPSTF notes that policy and coverage decisions involve considerations in addition to the evidence of clinical benefits and harms.
This draft Recommendation Statement is available for comment from February 19 until March 18, 2013, at 5:00 PM ET. You may wish to read the entire Recommendation Statement before you comment.
Screening for Glaucoma: U.S. Preventive Services Task Force Recommendation Statement
DRAFT
Summary of Recommendation and Evidence
The U.S. Preventive Services Task Force (USPSTF) concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for primary open-angle glaucoma (POAG) in adults.This is an I statement.
See the Suggestions for Practice Regarding the I Statement in the Clinical Considerations for more information.
Table 1 describes the USPSTF grades, and Table 2 describes the USPSTF classification of levels of certainty about net benefit.
Rationale
Importance
Open-angle glaucoma affects approximately 2.5 million Americans and is a leading cause of impaired visual function (loss of peripheral vision) and blindness.Detection
The USPSTF found inadequate evidence on the accuracy of screening for POAG in adults. The evidence is limited by the lack of an established gold standard against which individual screening tests can be compared.Benefits of Detection and Early Treatment
The USPSTF found no studies directly evaluating the benefits of screening.The USPSTF found convincing evidence that treatment of adults with increased intraocular pressure (IOP) and early glaucoma reduces the number of persons who develop small, clinically unnoticeable visual field defects, and that early treatment of early asymptomatic POAG decreases the number of patients whose visual field defects worsen.
However, the USPSTF found inadequate evidence to determine if screening for or treatment of increased IOP or early asymptomatic POAG decreases the number of persons who will develop impairments in vision-related function or quality of life.
Harms of Detection and Early Treatment
There is no direct evidence on the harms of screening. The USPSTF found convincing evidence that treatment of increased IOP and early POAG results in a number of harms, including local eye irritation from medications and a risk of complications from surgery, such as early formation of cataracts; the magnitude of these harms for most individuals is small. There is a risk for false-positive and false-negative results, but the magnitude of this risk is unknown, given the considerable variability in reported test sensitivity and specificity. There is also a risk for overdiagnosis and overtreatment, as there is some evidence that most individuals with early increased IOP or POAG have an indolent long-term course, yet still receive treatment.The USPSTF concludes that the evidence of effectiveness of screening for glaucoma on clinical outcomes is lacking, and that the balance of benefits and harms therefore cannot be determined.
Clinical Considerations
Patient Population Under Consideration
This recommendation applies to adults without vision symptoms who are seen in a primary care setting.Assessment of Risk
Increased IOP, family history, older age, and African American race place an individual at increased risk for glaucoma (1, 2). Older African Americans have a higher prevalence of glaucoma and perhaps a more rapid disease progression, and if it is shown that screening for glaucoma reduces the development of visual impairment, African Americans would likely have greater absolute benefit than whites. People with a limited life expectancy would likely have little to gain from glaucoma screening.Screening Tests
The diagnosis of POAG is not made on the basis of a single test but on the results of a combination of tests showing characteristic degenerative changes in the optic disc and defects in visual fields (loss of peripheral vision). Although increased IOP has previously been considered an important part of the definition of this condition, it is now known that many people with POAG do not have increased IOP, and not all people with elevated IOP have or will go on to develop glaucoma; hence, using tonometry alone may be inadequate in screening for all cases of POAG. Measurement of visual fields can be difficult. The reliability of a single visual field measurement may be low; several consistent visual field measurements are needed to establish the presence of defects. Dilated ophthalmoscopy or slit lamp examination are used by specialists to examine changes in the optic disc; however, even experts vary in their ability to detect glaucomatous optic disc progression. Additionally, there is no agreed-upon single standard to define and measure progression of visual field defects. Most tests that are available in a primary care setting do not have acceptable accuracy to detect glaucoma.Treatment
The initial aim and efficacy assessment of primary treatments for POAG is reduction of IOP. Treatments include medications, laser therapy, and surgery. These treatments also effectively reduce the longer-term development and progression of small visual field defects as assessed by clinic-based examination. However, the magnitude of their effectiveness in reducing impairments in patient-reported, vision-related function, including development of blindness, is uncertain.Suggestions for Practice Regarding the I Statement
Potential preventable burden. There are approximately 2.5 million people in the United States with glaucoma; approximately 1.9% of these adults are older than age 40 years (3). The majority of individuals with glaucoma have POAG. POAG is defined as an optic neuropathy in the eye with a visibly open anterior chamber angle (between the iris and the anterior sclera/peripheral cornea) that is associated with progressive death of retinal ganglion cells and axons and associated visual field loss (1, 2, 4). Identifying and treating these individuals before they develop visual impairment is the goal of potential screening programs. It is unknown what proportion of these individuals are currently unidentified and will develop vision problems as a result of a diagnosis obtained through screening. The natural history of glaucoma is heterogeneous and not well defined. There is a subgroup of people with POAG in whom there is either no disease progression or the progression is so slow that the condition never has an important effect on their vision. The size of this subgroup is uncertain and may depend on the ethnicity and age of the population and initial findings of ophthalmologic testing. Screening asymptomatic individuals is likely to increase the size of this subgroup. Others experience more rapidly progressive disease, as determined by optic nerve damage, visual field defects, and development of visual impairment. Whether an individual's early glaucoma will progress to visual impairment cannot be precisely predicted. Whether the rate of progression of visual field defects remains uniform throughout the course of glaucoma is also unknown. Older adults and African Americans appear to be at increased risk for glaucoma and a more rapid progression of glaucoma.Potential harms. Harms caused by treatments for glaucoma include formation of cataracts, harms resulting from surgery, and harms of topical medication. There is a potential for overdiagnosis and overtreatment, as some people diagnosed and treated for glaucoma will never progress to visual impairment; the magnitude of overdiagnosis and overtreatment is unknown.
Costs. The cost of screening varies widely depending on the tests used. Testing with handheld tonometers and ophthalmoscopes can be done quickly and inexpensively. However, the diagnostic accuracy of these inexpensive tests is unknown. According to the National Business Group on Health, the average screening eye examination costs $71 (5). Screening with specialized tests for glaucoma and with newer computerized instruments is more expensive.
Current practice. Approximately 62% of Medicare patients received screening for glaucoma in 2009 (6). In 2008, approximately 53% of whites, 47% of African Americans, and 37% of Hispanic Americans reported an annual eye care visit (7).
Other Considerations
Research Needs and Gaps
The natural history of glaucoma, particularly the role of IOP and its relationship to the development of optic nerve damage, visual field defects, visual impairment, and blindness, is poorly understood. More evidence is needed on the link between the intermediate outcomes of optic nerve damage and visual field loss and the final health outcomes of visual disability and patient-reported outcomes. The ideal evidence for screening would be a randomized, controlled trial (RCT) of routine (or targeted) screening versus standard care with long-term followup. More studies on treatment are needed that are of long enough duration and large enough size to adequately assess important clinical outcomes (e.g., visual impairment and vision-related quality of life), or at least greater changes in visual fields.Discussion
Burden of Disease
Glaucoma can be characterized as primary (idiopathic) or secondary (due to a known cause, such as trauma or inflammation) and as closed angle or open angle. Closed-angle glaucoma may present with acute symptoms, such as eye pain and blurred vision, and is considered an emergency. POAG is the most prevalent type of glaucoma in the U.S. population, and is the focus of this recommendation. POAG is defined as an optic neuropathy in the eye with a visibly open anterior chamber angle (between the iris and the anterior sclera/peripheral cornea) that is associated with progressive death of retinal ganglion cells and axons and associated visual field loss (1, 2, 4). In most cases, damage to the optic nerve is due to increased pressure in the eye, also known as IOP. Approximately 2.5 million people in the United States have glaucoma, and many are unaware that they have it. Important risk factors include older age, family history of glaucoma, and African American race (7). The overall U.S. prevalence of glaucoma is estimated to be 1.9%. Age-adjusted estimates are approximately three times higher in African Americans than in white Americans (3).Scope of the Review
In order to update its 2004 recommendation on screening for glaucoma, the USPSTF reviewed evidence on the benefits and harms of screening for glaucoma. The USPSTF also reviewed the benefits and harms of medical and surgical treatment of early glaucoma. Beneficial outcomes of interest for the USPSTF included improvements in vision-related quality of life and reduction in the progression of early asymptomatic glaucoma to vision-related impairment. The USPSTF also considered evidence on the accuracy of screening tests for glaucoma.Accuracy of Screening Tests
The USPSTF considered evidence on the accuracy of the following tests for glaucoma: direct and indirect ophthalmoscopy, photography and computerized imaging of the fundus, corneal thickness measurement combined with another test for glaucoma, perimetry, and tonometry. The USPSTF did not consider evidence on tests that are experimental or are no longer commonly used in the screening or diagnosis of glaucoma.Evaluating the evidence on screening tests for glaucoma is complicated by the lack of an established standard for diagnosing glaucoma and a consequent lack of an established gold standard to evaluate accuracy. The USPSTF reviewed more than 100 studies on the accuracy of various tests to screen for glaucoma (1). Instead of an established gold standard, many investigators used confirmation of POAG at followup examination, diagnosis of POAG requiring treatment, and other individual tests or combinations of tests as the reference against which to evaluate accuracy. The tests with the most published studies on accuracy include optical coherence tomography, scanning laser polarimetry, confocal scanning laser tomography, frequency doubling technology, and the Humphrey visual field analyzer. There was appreciable variability among studies in the devices, parameters, thresholds for diagnosis, and measurement of outcomes. There were several methodological limitations in many of the studies, including the fact that most studies enrolled participants who were not representative of those who would receive the test in practice. Most studies did not blind personnel who interpreted test results to the results of the reference standard, and vice versa. Many studies used a reference test that included one or more tests comprising the candidate test, resulting in a significant concern for bias. Because of the methodological limitations, variability in study designs, and the lack of a diagnostic standard, the USPSTF was not able to make any conclusions about the overall accuracy of screening for glaucoma.
Effectiveness of Early Detection and Treatment
There are no studies that directly evaluate whether screening prevents visual field loss, visual impairment, or worsening quality of life. While there is evidence that medical and surgical treatment of early asymptomatic POAG decreases the number of patients whose visual field defects progress, there are no studies evaluating whether medical or surgical treatment reduces the progression to visual impairment or improves quality of life.The USPSTF reviewed one systematic review (of 10 studies) and 19 additional RCTs that evaluated whether medical treatment slows the progression of visual field loss (2). A systematic review published in 2007 (of 10 studies) concluded that medical treatment had a significant protective effect on incident visual field worsening when compared with placebo or no treatment (odds ratio, 0.62 [95% CI, 0.47 to 0.81]) (2, 8). The 19 additional primary studies reported mixed results with treatment; a few reported improvements in visual field parameters with medical treatment, seven reported no change, and nine reported worsening of visual field measures. Most of these studies were not large enough or long enough to detect differences in the rates of visual field loss or clinically relevant outcomes related to glaucoma, given the slowly progressive nature of the disease. Three large studies of long duration reported mixed results; two studies concluded that medical treatment reduced glaucoma progression and a third failed to find a difference between medical treatment and placebo (2, 9-11). A 2005 systematic review of five RCTs that randomized subjects to either medical and/or surgical treatment or to no treatment reported that subjects receiving medical and/or surgical treatment were less likely to experience progression of visual field loss and optic disc damage (hazard ratio for topical medications vs. no treatment, 0.56 [95% CI, 0.39 to 0.81]) (12).
Potential Harms of Screening and/or Treatment
The USPSTF did not find any studies addressing the harms of screening. Several studies on the harms of treatment of glaucoma were reviewed (2, 4). Eye redness was the most commonly reported side effect of topical medical treatments for glaucoma. In observational studies, the percentage of patients reporting eye redness ranged from 2% to 21%, depending on dose, length of use, and type of medication. Eye pain and burning was also commonly reported with topical medications, occurring in 1% to 3% of subjects in observational studies. Other reported adverse effects of topical medications include eye irritation, eye dryness, increased iris pigmentation, and cystoid macular edema. Surgical treatments of glaucoma are associated with hypotony, hyphema, shallow anterior chambers, cataract, and choroidal detachment. Penetrating surgical interventions (i.e., trabeculectomy) are associated with more frequent adverse effects than nonpenetrating procedures. Adverse effects more commonly reported in studies of surgical procedures than medications include cataracts, infection, bleeding, and synechiae.Estimate of Magnitude of Net Benefit
There is inadequate evidence on the accuracy of screening tests and the benefits of screening or treatment to delay or prevent visual impairment or improve quality of life. Therefore, the overall certainty of the evidence is low, and the USPSTF is unable to determine the balance of benefits and harms of screening asymptomatic adults for glaucoma.How Does Evidence Fit With Biological Understanding?
The exact cause of POAG is not known. Diagnosis of glaucoma is usually made using several tests that, when combined, evaluate the biologic structure of the optic nerve, function of the optic nerve, and IOP. Individuals with POAG may not have elevated IOP, and elevated IOP may not result in nerve damage and eventual visual impairment. This limits the development of a single gold standard to evaluate the accuracy of screening tests. Most people with glaucoma do not have symptoms. Once vision loss occurs—slow loss of side vision (peripheral vision)—the optic nerve is already damaged. Once severe enough, loss of vision impairs function and quality of life. Advanced glaucoma can lead to blindness. Treatments that lower IOP prevent the decline in the biologic structure and function of the optic nerve due to glaucoma. By doing so, these treatments slow worsening of visual field loss. However, the slowly progressive nature of glaucoma makes it difficult to evaluate the effectiveness of treatments, and may lead to detection and treatment of many asymptomatic individuals who will remain asymptomatic throughout their life (known as overdiagnosis and overtreatment).Recommendations of Other Groups
The American Academy of Ophthalmology recommends a comprehensive adult medical eye evaluation, including tests for glaucoma, with a frequency depending on the individual's age and other risk factors for glaucoma (13).The American Optometric Association recommends eye examinations every 1 to 2 years, with frequency depending on age and risk factors for glaucoma (14).
Table 1: What the Grades Mean and Suggestions for Practice
Table 2: Levels of Certainty Regarding Net Benefit
| Level of Certainty* | Description |
|---|---|
| High | The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies. |
| Moderate | The available evidence is sufficient to determine
the effects of the preventive service on health outcomes, but confidence
in the estimate is constrained by factors such as:
|
| Low | The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:
|
*The U.S.
Preventive Services Task Force defines certainty as "likelihood that the
USPSTF assessment of the net benefit of a preventive service is
correct." The net benefit is defined as benefit minus harm of the
preventive service as implemented in a general, primary care population.
The USPSTF assigns a certainty level based on the nature of the overall
evidence available to assess the net benefit of a preventive service.
References
1. Ervin AM, Boland MV, Myrowitz EH, Prince J, Hawkins B, Vollenweider D, et al. Screening for Glaucoma: Comparative Effectiveness. Comparative Effectiveness Review No. 59. AHRQ Publication No. 12-EHC037-EF. Rockville, MD: Agency for Healthcare Research and Quality; April 2012. 2. Boland MV, Ervin AM, Friedman D, Jampel H, Hawkins B, Vollenweider D, et al. Treatment for Glaucoma: Comparative Effectiveness. Comparative Effectiveness Review No. 60. AHRQ Publication No. 12-EHC038-EF. Rockville, MD: Agency for Healthcare Research and Quality; April 2012. 3. Friedman DS, Wolfs RC, O'Colmain BJ, Klein BE, Taylor HR, West S, et al; Eye Diseases Prevalence Research Group. Prevalence of open-angle glaucoma among adults in the United States. Arch Ophthalmol. 2004;122(4):532-8. 4. Boland MV, Ervin AM, Friedman DS, Jampel HD, Hawkins BS, Vollenweider D, et al. Comparative effectiveness of treatments for open-angle glaucoma: a systematic review for the U.S. Preventive Services Task Force. Ann Intern Med. 2013;158(4):271-9. 5. Grosse S, Biernath K. Vision evidence statement: screening. In: Campbell KP, Lanza A, Dixon R, Chattopadhyay S, Molinari N, Finch RA, eds. A Purchaser's Guide to Clinical Preventive Services: Moving Science Into Coverage. Washington, DC: National Business Group on Health; 2011. 6. National Committee for Quality Assurance. The State of Health Care Quality: Reform, the Quality Agenda, and Resource Use. Washington, DC: National Committee for Quality Assurance; 2010. Accessed at http://www.ncqa.org/portals/0/state%20of%20health%20care/2010/sohc%202010%20-%20full2.pdf on 11 February 2013. 7. Zhang X, Cotch MF, Ryskulova A, Primo SA, Nair P, Chou CF, et al. Vision health disparities in the United States by race/ethnicity, education, and economic status: findings from two nationally representative surveys. Am J Ophthalmol. 2012;154(6 Suppl):S53-62. 8. Vass C, Hirn C, Sycha T, Findl O, Bauer P, Schmetterer L. Medical interventions for primary open angle glaucoma and ocular hypertension. Cochrane Database Syst Rev. 2007;(4):CD003167. 9. Kass MA, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP, et al. The Ocular Hypertension Treatment Study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):701-13. 10. Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M; Early Manifest Glaucoma Trial Group. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268-79. 11. Miglior S, Zeyen T, Pfeiffer N, Cunha-Vaz J, Torri V, Adamsons I; European Glaucoma Prevention Study (EGPS) Group. Results of the European Glaucoma Prevention Study. Ophthalmology. 2005;112(3):366-75. 12. Maier PC, Funk J, Schwarzer G, Antes G, Falck-Ytter YT. Treatment of ocular hypertension and open angle glaucoma: meta-analysis of randomised controlled trials. BMJ. 2005;331(7509):134. 13. American Academy of Ophthalmology. Preferred Practice Pattern Guidelines: Comprehensive Adult Medical Eye Evaluation. San Francisco: American Academy of Ophthalmology; 2010. Accessed at http://one.aao.org/CE/PracticeGuidelines/PPP_Content.aspx?cid=64e9df91-dd10-4317-8142-6a87eee7f517 on 11 February 2013. 14. American Optometric Association. Optometric Clinical Practice Guideline: Comprehensive Adult Eye and Vision Examination. St. Louis, MO: American Optometric Association; 2005. Accessed at http://www.aoa.org/documents/CPG-1.pdf on 11 February 2013.
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