Screening Older Adults for Impaired Visual Acuity: A Review of the Evidence for the U.S. Preventive Services Task Force

The 2002 NHANES (National Health and Nutrition Examination Survey) estimated an 8.8% prevalence of impaired visual acuity (best-corrected vision of 20/50 or worse) in U.S. adults older than 60 years (1). In addition to having a higher incidence and prevalence of primary ocular disease and systemic diseases associated with ocular disease compared with younger adults, older adults also experience normal age-related changes in vision. Because symptoms may be relatively mild or may progress slowly, older adults may be unaware of or underreport impaired visual acuity or have difficulty recognizing or reporting impaired visual acuity because of comorbid conditions, such as cognitive impairment. Impaired visual acuity is consistently associated with decreased functional capacity and quality of life in older persons and can affect the ability to live independently or increase the risk for falls and other accidental injuries (25). Uncorrected refractive errors, cataracts, and age-related macular degeneration (AMD) are common causes of impaired visual acuity. In 2000, among U.S. adults older than 65 years, refractive errors, cataracts, and AMD were estimated to affect 6.7 million (6), more than 5 million (6), and 1.5 million persons (7), respectively. Advanced AMD is the most common cause of blindness in older, white U.S. adults, and cataracts are the most common cause of blindness in older black adults (8). Screening for vision disorders in primary care settings could identify impaired visual acuity in older adults and lead to treatments that correct or prevent vision loss. In 1996, the U.S. Preventive Services Task Force (USPSTF) recommended routine vision screening with a visual acuity test (for example, the Snellen eye chart) for older adults (a grade B recommendation) (9). In 2008, the USPSTF commissioned a new evidence review on the benefits and harms of screening for impaired visual acuity in adults 65 years or older to update its recommendations. The Appendix Figure shows the analytic framework and key questions used to guide our review. Appendix Figure. Analytic framework and key questions. KQ = key question. Methods Data Sources We searched the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews (through Issue 3, 2008) and MEDLINE databases (1996 to July 2008) for relevant studies (see Appendix Table 1, for the full search strategy). We supplemented these searches with reviews of reference lists of relevant articles, including the previous USPSTF review (9). Appendix Table 1. Search Strategies Study Selection The Figure shows the flow of studies from initial identification of titles and abstracts to final inclusion or exclusion. We selected studies pertaining to screening, diagnosis, and treatment of impaired visual acuity in older adults on the basis of predefined inclusion and exclusion criteria (Appendix Table 2). Two reviewers evaluated each study at the title or abstract and full-text article stages to determine eligibility for inclusion. Figure. Study flow diagram. AMD = age-related macular degeneration; KQ = key question; RCT = randomized, controlled trial; SR = systematic review; URE = uncorrected refractive error. * Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews. Identified from reference lists suggested by experts. Some studies were included for >1 KQ. Appendix Table 2. Inclusion and Exclusion Criteria The target sample was adults 65 years of age or older evaluated in primary care settings who were not known to have impaired visual acuity or had known but inadequately corrected refractive error. We defined impaired visual acuity as worse than 20/40 but better than 20/200. We included studies of vision screening in eye specialty settings but evaluated their applicability to primary care settings. We excluded studies of strictly community- or home-based vision screening but included mixed studies of home and clinic-based screening if 70% or more of patients were evaluated in clinic settings. For diagnosis, we evaluated accuracy of screening questions, visual acuity testing, the Amsler grid, and physical examination. For treatments, we evaluated corrective lenses and photorefractive surgery for uncorrected refractive errors; cataract surgery for cataracts; antioxidants or vitamins for dry AMD; and laser photocoagulation, photodynamic therapy, and vascular endothelin growth factor inhibitors for wet AMD. The full evidence report reviews other interventions (10). Outcomes of interest were visual acuity, vision-related function or quality of life, general function or quality of life, falls, accidents, death, and harms related to screening or treatment. We excluded studies of glaucoma or diabetes (11, 12). Screening for glaucoma is not based on evaluations of visual acuity and is addressed elsewhere by the USPSTF (11). Screening for diabetic retinopathy typically occurs in patients known to have diabetes. For diagnostic accuracy, we included studies that compared a screening test with a reference standard. We used randomized, controlled trials (RCTs) to assess the effectiveness and harms of screening and various treatments. If RCTs were not available or evidence was sparse, we also used controlled observational studies. Because many systematic reviews have been conducted on treatments for impaired visual acuity, we included good-quality systematic reviews of randomized trials on the effectiveness or harms of treatment and fair- or good-quality systematic reviews of observational studies when no randomized trials were available (after verifying data abstraction and statistical analyses). Data Extraction and Quality Assessment One investigator abstracted data, and another checked the abstracted data. We abstracted details about the patient sample, study design, data analysis methods, follow-up, and results. We used predefined criteria developed by the USPSTF to assess the internal validity of primary studies (13). We independently abstracted and rated all placebo-controlled RCTs, regardless of inclusion status in previously published systematic reviews (14). For randomized trials, we assessed methods of randomization, allocation concealment, and blinding; loss to follow-up; and use of intention-to-treat analysis. For cluster randomized trials (trials that randomly assigned patients in groups according to which clinic they attended), we also evaluated whether the study adjusted for the effects of clustering (cluster-correlation correction) (15). For systematic reviews, we abstracted information on search methods, dates of searches, selection of studies, and data synthesis methods. We rated quality by using criteria described in Appendix Table 3. Two authors independently rated the internal validity of each study as good, fair, or poor, on the basis of the number and seriousness of methodological shortcomings (13). We assessed the potential applicability of studies to primary care on the basis of whether patients were recruited from primary care settings, the proportion of patients with mild to moderate vision impairment, and whether the screening intervention was or could be done in most primary care settings. We resolved discrepancies in quality ratings by discussion and consensus. Appendix Table 3. Quality Assessment Criteria for Systematic Reviews For diagnostic accuracy studies, we used the diagti procedure in Stata, version 10 (StataCorp, College Station, Texas), to calculate sensitivities, specificities, and likelihood ratios. We used the cci procedure to calculate diagnostic odds ratios (ORs) with exact CIs. We classified likelihood ratios as large, moderate, or small on the basis of the criteria shown in Table 1 (16). Table 1. Interpretation of Likelihood Ratios Data Synthesis and Analysis We assessed the overall strength of each body of evidence by using methods developed by the USPSTF (13). For screening and diagnostic accuracy, we did not attempt to pool results of individual studies owing to heterogeneity in study samples, screening interventions, or diagnostic tests and results. For efficacy of treatments, we reported quantitative estimates for treatment effects from previously published systematic reviews that met quality criteria (14). When we identified RCTs not included in previous reviews, we calculated updated, pooled relative risks (RRs) by using the MantelHaenszel random-effects model (Review Manager, version 4.2.8, The Nordic Cochrane Center, Copenhagen, Denmark). Results Key Question 1 Does vision screening in asymptomatic older adults result in improved morbidity or mortality or improved quality of life? Three fair- or fair-to-goodquality cluster randomized trials (n= 4728) evaluated vision screening as part of a multicomponent screening intervention, with high applicability to screening in primary care settings (Table 2) (1719). Methodological shortcomings of all trials included lack of intention-to-treat analysis, unclear blinding status of outcomes assessors, and high loss to follow-up, which was due in part to advanced age and death in enrollees (Appendix Table 4). Only 1 (19) of the 3 trials applied a cluster-correlation correction (15). The screening intervention varied: 1 trial compared universal visual acuity testing (Glasgow acuity chart followed by pinhole testing for persons with visual acuity worse than 6/18) with targeted screening (19), 1 compared immediate with delayed vision screening (17), and 1 compared use of a screening question followed by visual acuity testing if positive with usual care (18). Duration of follow-up ranged from 6 months to 5 years. None of the trials found vision screening to be associated with beneficial effects on vision, likelihood of vision disorders, or functional impairment related to vision. Table 2. RCTs of Vision Screening in Older Adults Appendix Table 4. Quality Assessment of Randomized, Controlled Trials of Vision Screening in Older Adults The highest