Age-related macular degeneration
Approximately 1 in 28 Americans aged older than 40 years is affected by low vision or blindness. Among community-dwelling adults, the prevalence of low vision and blindness increases dramatically with age in all racial and ethnic groups. Whites have higher rates of macular degeneration than African Americans, but glaucoma is more common among older African Americans. Between 2000 and 2020, the prevalence of blindness is expected to double.
Age-related eye diseases are costly to treat, threaten the ability of older adults to live independently, and increase the risk for accidents and falls. To prevent vision loss and support rehabilitative services for people with low vision, it is imperative for the public health community to address the issue through surveillance, public education, and coordination of screening, examination, and treatment.
Age-related macular degeneration (AMD) has several forms. The form known as wet AMD is caused by abnormal vascularization under the retina and is an important cause of central vision loss. Dry AMD, the most common form, tends to progress more slowly than the wet form. The most advanced form, geographic atrophy, also causes central vision loss. Although the pathogenesis of AMD is not totally understood, 54% of the cases of blindness in white Americans have been attributed to the disease. AMD increases dramatically with age in men and women, but no significant sex difference in rates has been found. AMD is less common in African Americans than in whites. According to community eye studies, as many as 16% of white women and 12% of white men aged 80 years and older have advanced AMD.
Several pathophysiological processes associated with aging have been proposed as etiologies for AMD, and research on the topic continues. In one study, high-dose supplements of vitamins C and E, beta carotene, and zinc slowed the rate of progressive vision loss somewhat over 5 years, but only when the condition was not extremely advanced. The recognition of a link between high-dose supplements of beta carotene in smokers and increased cardiovascular risk may have discouraged eye-care professionals and patients from using the vitamin-supplement regimen found to be effective. However, it has been estimated that in 300,000 people aged 55 years and older, additional vision loss over the next 5 years can be prevented if the supplementation study results are translated into widespread clinical practice. Laser therapy and photodynamic therapy can be used successfully for some forms of wet AMD, although the disease is particularly complex and challenging to treat. New forms of therapy, such as injecting antivascular endothelial growth factor, effectively reduced the progression of vision loss in a randomized trial of people with advanced wet AMD. No surgical interventions for the dry form of the disease exist, although the efficacy of laser photocoagulation of the macula to prevent progression of early disease is being studied. Rehabilitative interventions for individuals who are in their 80s and 90s and have low vision because of AMD are challenging, but quality of life can be improved. Helping the growing number of older adults with low vision to function independently will tax the already strained vision rehabilitation resources in many communities.
Impact of Age-related Eye Diseases on Public Health
The new prevalence estimates of age related eye diseases (AREDs), vision loss, and blindness in the United States have several important public health implications. First, a person often has more than one ARED, so aging individuals are at risk for multiple eye problems. Second, although The Eye Disease Prevalence Research Group studies demonstrated important disparities between African Americans and whites in the prevalence of individual AREDs, low vision, and blindness, the data were limited for several minority populations. The estimates were based on three eye studies that included African Americans; the prevalence of low vision and blindness among Hispanics was estimated from one study in southern Arizona. No information about American Indians or Asian Americans exists. Finally, little information is known about the way variable access to care or other factors may contribute to the striking variations in the prevalence of AREDs and loss of visual function. Investigators in east Baltimore, Md, estimated that half of the cases of blindness found in the community could have been prevented or reversed with proper care.
AREDs are common and costly. In a longitudinal analysis of Medicare claims for diabetic retinopathy, glaucoma, and macular degeneration, investigators documented that almost half of more than 20,000 Medicare beneficiaries had developed at least one of the three diseases in the 9-year follow-up period. From the longitudinal data, the investigators concluded that among people who live to age 65 years, the probability of acquiring at least one of the three conditions is 0.45. Decreased vision is associated with myriad problems in older adults, such as falls, hip fractures, family stress, and depression. Vision disorders are also a safety risk to all automobile drivers and passengers.
Reducing the level of disability caused by vision loss and blindness is challenging for public health professionals for many reasons. For example, the magnitude of the problem is not completely understood because it is hard to measure vision loss and blindness accurately by the usual surveillance methods. People with limited eyesight may be less likely to have necessary examinations or answer surveys commonly used to assess chronic conditions. State-based blindness registries have not successfully documented the prevalence, risk factors, and trends in vision loss. Comprehensive dilated-eye examinations for age-related macular degeneration are best performed by eye-care specialists — optometrists and ophthalmologists. It is easy for the general public to assume, erroneously, that a test of visual acuity associated with obtaining glasses or a driver’s license will detect sight-threatening conditions. In addition, the geographical distribution of eye-care specialists is not known, and areas such as rural and medically underserved communities may have shortages. Finally, medical services to detect and treat serious eye diseases may not be integrated with the services needed to improve quality of life and increase independence for people with low vision. Glasses and other aids to improve vision are not uniformly covered by health insurance. Rehabilitation services to help people with vision loss are administered by agencies experienced in helping individuals return to work but are not usually linked with public health or home health services for older adults. There is a public need for better understanding of access to eye-care and vision support services.
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