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Chou R, Dana T, Bougatsos C. Screening for Visual Impairment in Older Adults: Systematic Review to Update the 1996 U.S. Preventive Services Task Force Recommendation [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2009 Jul. (Evidence Syntheses, No. 71.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

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Screening for Visual Impairment in Older Adults: Systematic Review to Update the 1996 U.S. Preventive Services Task Force Recommendation [Internet].

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1Introduction

Scope and Purpose

Impaired visual acuity is common in older adults. 1 In addition to a higher incidence and prevalence of primary ocular disease and systemic diseases associated with ocular disease in older compared to younger adults, older adults also experience normal age-related changes in vision. Because symptoms may be relatively mild or progress slowly, older adults may be unaware of or underreport impaired visual acuity. Older adults may also have difficulty recognizing or reporting impaired visual acuity due to the presence of co-morbidities such as cognitive impairment. Screening for vision disorders could help identify impaired visual acuity in older adults and lead to treatments that improve quality of life or functional capacity, or prevent or slow down progression of vision loss.

In 2008, the United States Preventive Services Task Force (USPSTF; see Appendix A for a comprehensive list of abbreviations) commissioned an evidence review on screening for impaired visual acuity in older adults, in order to inform an updated USPSTF guideline. The main purpose of the evidence review is to evaluate new evidence published since 1996 on screening for impaired visual acuity in older adults. 2

Condition Definition

Impaired visual acuity refers to decreased clarity or sharpness of vision. In addition to decreased visual acuity, vision impairment can also be associated with decreases in low light vision, color vision, binocularity, contrast sensitivity, or stereopsis, as well as visual field loss (areas in the field of view in which objects cannot be seen). Visual acuity is most commonly assessed using the Snellen eye chart, which assesses the ability of patients to recognize letters of different sizes arranged in rows from a pre-specified distance (typically 20 feet). Roughly speaking, a person with 20/100 vision according to the Snellen chart would need to be 20 feet away to read the smallest letters that someone with “normal” (20/20) vision could read at 100 feet. Visual acuity can also be described in meters (6/6 in meters is equivalent to 20/20 in feet) or using the decimal or the logarithm of the minimum angle of resolution (logMAR) scale (Table 1).

Table 1. Measurements of Visual Acuity.

Table 1

Measurements of Visual Acuity.

The severity of decreased visual acuity varies. Vision impairment has been defined as visual acuity of worse than 20/40 3 or 20/50 4 but better than 20/200 (the threshold for legal blindness). In this report, we use the term “impaired visual acuity” rather than “vision impairment” because the latter term implies functional limitations. In addition, vision impairment could occur for reasons other than visual acuity loss. Visual acuity worse than 20/20 but better than 20/40 or 20/50 is thought to have minimal effects on reading ability, functional capacity, or quality of life. Although no standardized definition for “mild” impairment in visual acuity exists, some studies have used a definition of visual acuity between roughly 20/40 and 20/80. 3, 4 This degree of impaired visual acuity is less likely to cause major functional limitations than more severe impairment in visual acuity, and may be more apt to be identified through screening.

This report focuses on impaired visual acuity associated with the following conditions: uncorrected refractive errors, cataracts, and age-related macular degeneration (ARMD). Diabetic retinopathy and glaucoma are addressed elsewhere by the USPSTF. 5, 6 Screening approaches for glaucoma (visual field assessment, fundoscopic examination, and intraocular pressure measurement) differ from the screening tests (visual acuity and central vision testing) typically used in primary care settings for the conditions included in this report. Screening for diabetic retinopathy typically occurs in the context of care for patients with known diabetes.

Prevalence and Burden of Disease

In 2000, approximately 1.8 million US adults older than 65 years were estimated to have impaired visual acuity (best-corrected vision worse than 20/40 but better than 20/200). 1 Based on mobile vision exams performed between 1999 and 2002, the National Health and Nutrition Examination Survey estimated an 8.8% prevalence of presenting impaired visual acuity in US adults greater than 60 years of age. 4 Impaired visual acuity rates in US adults were stable from 1986 through 1995. 7 Prevalence of impaired visual acuity rises with age in older adults, from 1.1% in persons 65 to 69 years of age to 16.7% in persons older than 80 years of age. 1 Impaired visual acuity is more prevalent in nursing home patients compared to community-dwelling older adults. 8, 9 In one survey of Baltimore area nursing home residents, the rate of impaired visual acuity was 18.8%. 9

Impaired visual acuity is consistently associated with decreased functional capacity and quality of life in older persons, including the ability to live independently, with more severe impaired visual acuity associated with greater negative impacts. 10 13 Impaired visual acuity can affect ability to perform both basic and instrumental activities of daily living, work, drive safely or obtain a driver's license, and increase risk of falls and other accidental injuries. 14 18

The link between visual impairment or specific causes of impaired visual acuity and mortality in older adults has been evaluated in a number of epidemiologic studies. Some data suggest an association between risk of mortality and impaired visual acuity (any cause), cataracts, or (to a lesser extent) ARMD, possibly because such conditions may be independent markers for increased cardiovascular risk. 19 25 However, other studies found any association largely attenuated or no longer present after adjustment for cardiovascular risk factors and other confounders. 26, 27

Uncorrected refractive errors, cataracts, and ARMD are common causes of impaired visual acuity in older adults. In 2000, refractive errors were estimated to affect 6.7 million US adults over 65 years of age. 28 In older adults with impaired visual acuity (including those currently using corrective lenses), approximately 60% have correctable (to better than 20/40) refractive errors. 4 In general, the prevalence of hyperopia increases sharply with age, with a prevalence 4.2 to 7.4 times higher in the persons ≥ 80 years of age compared to those 40 to 49 years of age. 28 Among white men, the prevalence of hyperopia ≥ +3.0 diopters (D) is 3.6% among those 40 to 49 years of age, 14.1% among those 65 to 69 years of age, and 23.5% among those greater than 80 years of age. An exception to increasing prevalence of hyperopia with age is adult black men, in whom the prevalence of hyperopia remains fairly constant across age groups, ranging from 1.5% to 3.9%. 28 Among adults over 65 years of age, the prevalence of myopia is relatively stable with increasing age, though prevalence varies among different ethnic/racial groups. For example, the prevalence of myopia < -1.0 D in black men aged 65 to 69 years is 8.1%, compared to 13.1% in Hispanic men and 17.7% in white men. 28

In persons with low vision (defined as best-corrected visual acuity < 20/40), cataracts are the cause in approximately half of cases. 1 The prevalence of cataracts increases sharply with age. Over 5 million US adults over 65 years of age were estimated to have cataracts (not necessarily associated with vision impairment) in 2000. 29 In white women, prevalence increases from 27.7% in persons 65 to 69 years to 76.6% in persons ≥ 80 years. Respective figures in black women are 28.5% and 60.9%, in white men 22.4% and 71.3%, and in black men 17.5% and 46.2%. Cataracts are the most common cause of blindness (best-corrected visual acuity < 20/200) in black US adults over 40 years of age (37%), but are a relatively less frequent cause of blindness in white (8.7%) and Hispanic (14.3%) persons. 1

In 2000, approximately 1.5 million US adults over 65 years of age were estimated to have ARMD and another 4.8 million were estimated to have drusen (a sign of early ARMD or increased risk for developing ARMD). 30 ARMD is not necessarily associated with impaired visual acuity, particularly in early stages. The proportion of patients with low vision attributable to ARMD ranges from 3% in black persons to 23% in white persons. 28 The prevalence of ARMD increases with age, rising from 1.1% among white men 65 to 69 years of age to 11.9% among those ≥ 80 years of age; a similar pattern is observed among white women (0.7% and 16.4%, respectively). 30 Prevalence is substantially lower among black men and women, even among older age groups (1.6% and 2.4% in persons older than 80 years of age, respectively). Advanced ARMD is more likely to be due to the neovascular or “wet” type of ARMD than to “dry” ARMD (geographic atrophy). ARMD is the most common cause of blindness among white persons (54% of cases) and accounts for a significant proportion of blindness among Hispanics (14.3%), but is a relatively infrequent cause of blindness among black persons (4.4%). 1

Etiology and Natural History

Refractive errors are a general term to describe conditions associated with the inability of cornea and lens of the eye to bring parallel rays of light into sharp focus on the fovea, resulting in blurry vision. In adults, common types of refractive errors are myopia, hyperopia, and astigmatism. Myopia occurs when images are focused in front of the fovea, affecting ability to clearly view more distant objects. 31 Hyperopia occurs when images are focused behind the fovea, which affects the ability to sharply view closer objects. Hyperopia often presents or worsens with older age because of presbyopia, which refers to age-related changes in the eye including decreased elasticity of the lens, reducing near-focusing ability. Astigmatism is a condition in which there are two or more focal points in the eye, resulting in distortion of images at various distances. Progression of myopia in older adults can be associated with development and progression of cataracts.

Cataracts are opacities in the lens of the eye, which result in decreased visual acuity and glare. 32 The main subtypes of cataracts are defined by their anatomic location within the lens and are classified as nuclear, cortical, and subcapsular, or some combination of these subtypes. Cataracts often occur bilaterally, though their presence and severity is frequently asymmetrical. Cataract opacities and severity of impaired visual acuity progress over time, with a variable rate of progression.

ARMD affects the macula, or area of the retina responsible for central vision. 33 Drusen, which are white to yellow retinal lesions, are an early sign of ARMD when they occur in the macula. Although their presence is not clearly associated with vision loss, presence of more or larger drusen is associated with a greater risk of developing advanced ARMD. Advanced ARMD is usually classified into “wet” or “dry” forms. The “dry” form of advanced ARMD (also referred to as ‘geographic atrophy’) is associated with atrophy of the retinal layers and retinal pigmented epithelial cells. The “wet” form of ARMD is associated with the development of abnormal blood vessels in the choroid layer underneath the retina (choroidal neovascularization). Both types of advanced ARMD can cause blurred central vision, distorted vision, and decreased low light vision. In severe cases, advanced ARMD results in central scotomas (complete loss of central vision).

Risk Factors

Rates of impaired visual acuity are higher among Hispanics, persons of lower socioeconomic or educational status, and those without private health insurance. 1, 4 Risk factors for specific conditions causing impaired visual acuity vary depending on the condition. A positive family history is a major risk factor for both myopia and hyperopia. 31 In both sexes and in various ethnic/racial groups, latent hyperopia tends to become manifest with older age due to a loss in accommodation, with the exception of black men, in whom the prevalence of hyperopia remains relatively low. 28 Risk factors for cataracts include older age, smoking, alcohol use, exposure to ultraviolet light, diabetes, and exposure to corticosteroids. 34, 35 Lower socioeconomic status and black race are associated with higher rates of unoperated cataracts. 36 Risk factors for ARMD are not completely understood, but are thought to include older age, smoking, and family history. 37 ARMD is substantially more common in white persons compared to other races/ethnicities. 1

Rationale for Screening/Screening Strategies

Impaired visual acuity due to uncorrected refractive error, cataracts, and age-related macular degeneration is common in adults and the prevalence increases with age. 1, 28 30 Impaired visual acuity in older adults may not be recognized or may remain unreported because vision changes can be relatively subtle, progress slowly over time, or occur in persons with cognitive dysfunction or other co-morbidities. However, even mildly impaired visual acuity can be associated with decreased quality of life and functional capacity and increase the likelihood of accidents and related injuries. 10 13 Screening for impaired visual acuity in the primary care setting is non-invasive and could potentially identify persons likely to benefit from referral for interventions to improve visual acuity or slow progression of ocular disease. 2, 38

Interventions/Treatment

A number of interventions are available to treat common causes of impaired visual acuity. Although impaired visual acuity may be identified in the primary care setting, most interventions require the involvement of an eye care provider. For uncorrected refractive error, the most common treatment is corrective lenses (eyeglasses and contact lenses). Photorefractive surgery including laser in-situ keratomileusis (LASIK), photorefractive keratectomy (PRK) or laser epithelial keratomileusis (LASEK) is associated with more up-front costs compared to corrective lenses and more commonly selected as a treatment option by younger adults. For patients with impaired visual acuity that is not sufficiently improved by correcting refractive error, reading aids (such as magnifiers) are a treatment option. 39 For cataracts causing significant impairment in visual acuity, the most common treatment is surgical cataract extraction and intraocular lens implantation. 40 Antioxidants and vitamins have been found to slow the progression of some types of ARMD, but have no proven benefit in slowing cataract progression. 41 44 No treatment is known to reverse the retinal damage associated with dry ARMD.

The wet form of ARMD accounts for most of the vision loss and blindness associated with advanced ARMD. Treatments for wet ARMD are aimed at the abnormal retinal vascular growth (choroidal neovascularization) associated with this condition and responsible for vision loss. Laser photocoagulation is an established treatment for wet ARMD, but causes blind spots due to retinal damage in areas of treatment. 45 It is generally considered a treatment option only in patients with extrafoveal (outside of the foveal area) neovascularization, in order to avoid causing central visual field defects. 45 47 Photodynamic therapy (PDT) with verteporfin, a photoreactive agent, is associated with less retinal scarring as compared to laser photocoagulation and is an option for subfoveal (under the fovea) neovascularization. Patients are intravenously injected with verteporfin, which preferentially adheres to newly-formed neovascular blood vessels. The verteporfin is then activated by exposure to low-intensity laser, with resulting thrombosis and destruction of abnormal blood vessels. Another treatment for wet ARMD is intravitreal injection of a vascular endothelial growth factor (VEGF) inhibitor such as ranibizumab or pegaptanib in order to suppress growth of abnormal blood vessels. Other treatments that have been studied for wet ARMD include surgical implantation of corticosteroids, 48 intravitreal interferon alfa, 49 radiation, 50 and surgical procedures (submacular surgery and macular translocation). However, these therapies have either not been proven to be effective or have limited indications for use.

Current Clinical Practice

The clinical standard for identifying presence of impaired visual acuity is by evaluation of distance visual acuity using the Snellen eye chart or another standardized test of visual acuity. Pinhole visual acuity testing can be used to estimate whether impaired visual acuity is due to correctable refractive error (vision corrects or improves upon pinhole testing). 51 Reading distance testing can also be assessed using a handheld card or other screening tool.

Clinically significant cataracts can be visualized via physical examination as opacities in the lens. Impaired visual acuity due to cataracts should not completely correct with pinhole testing, though partial correction may occur due to decreased light-scattering, particularly if myopia related to the cataract is present. 52

The Amsler grid consists of evenly spaced horizontal and vertical lines (making squares) on a sheet. 53 It is used to detect retinal defects affecting central vision including ARMD, which can be associated with distortion in the boxes on the grid or blank areas in the grid (scotomas). The Amsler grid can also be used by patients as a self-monitoring tool for early signs or progression of macular disease. 54, 55

Screening questions may be used to elicit self-perceived problems with vision. 56 Fundoscopic examination can also be performed in order to detect asymptomatic or early ARMD or other retinal disease. The frequency with which non-Snellen visual acuity tests, the Amsler grid, vision screening questionnaires, or fundoscopic examination is used in primary care is not known. 2, 38 Older adults with vision impairment are typically referred to an optometrist or ophthalmologist for further evaluation, correction of refractive error, and other treatments. About half of US adults over the age of 65 years report an eye exam within the last 12 months. 57

Recommendations of Other Groups

Several North American organizations recommend vision screening in older adults (Table 2). In general, the American Academy of Family Physicians 58, 59 and the Canadian Task Force on Preventive Health Care, 38 which issue guidelines for primary care physicians, recommend Snellen visual acuity testing at unspecified intervals. Both groups either do not recommend fundoscopy due to insufficient evidence or do not comment on the role of fundoscopic examination. The American Academy of Ophthalmology 60 and the American Optometric Association 61 both recommend a full eye examination in older adults, including fundoscopic exam, at an interval of one to two years.

Table 2. Vision Screening Recommendations.

Table 2

Vision Screening Recommendations.

Previous USPSTF Recommendation

In 1996, the USPSTF recommended routine vision screening with Snellen acuity testing for older persons (“B” recommendation). 2 The USPSTF made no recommendation regarding optimal frequency of screening or use of screening questions to identify persons at higher risk for impaired visual acuity. The USPSTF found insufficient evidence to recommend for or against routine fundoscopic examination by the primary care physician in asymptomatic older adults.

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