The number of blind people worldwide, already close to 40 million, is likely to double in the next 2 decades if there are not effective efforts directed toward blindness prevention. An estimated three of four people across the globe with vision impairment suffer it needlessly. That is, even without further medical research, a large reduction in the burden of blindness and visual impairment could be accomplished. Coordinated efforts initiated in the 1997 publication of The Global Initiative to Eliminate Avoidable Blindness outlined a global strategy and targets for the Vision 2020 program launched in 1999 by the World Health Organization and the International Agency for the Prevention of Blindness (IAPB). It is hoped that the growth in the number of people with blindness and visual impairment can be stopped in its tracks.
Over the past few decades, we have learned that blindness is not an equal opportunity calamity.
Close to 90% of all blindness occurs among the people of less developed nations; and across the globe, approximately two-thirds of the blind and visually impaired are older women.1,2 There are an estimated one million legally blind and 3.4 million visually impaired people in the United States, and 700,000 of the blind and 2.3 million of the visually impaired are women.3 The same pattern of gender inequity has been found worldwide where over 37 million are blind and another 124 million are visually impaired.2 In a systematic meta-analysis of over 70 population-based prevalence studies with a minimum sample size of 1000, pooled estimates revealed that two-thirds of those with visual impairment, including blindness, are women.1 A rarely mentioned fact is that inclusion of undercorrected refractive error would inflate these estimates by over 60% to an actual global burden of visual impairment of nearly 260 million.4 Given the salience of the unmet need for refractive correction, changes in the definition of visual impairment to incorporate levels of “presenting vision” are being proposed.2,5
One reason for the sex-related disparity in blindness and visual impairment is simple; most of the top causes of blindness—cataract, glaucoma, corneal scarring (largely trachoma), and age-related macular degeneration (AMD)—are age-related eye diseases, and, on average, women throughout the world tend to outlive men. However, women's greater longevity does not completely explain the inequality. In an analysis of the 23 surveys with sufficient information to adjust for age, women were still approximately two-thirds more likely to be blind and visually impaired whether they lived in Africa, Asia, or industrialized countries.1 So far, we can only guess at the other reasons underlying this disproportionate distribution.
In 2002, a group of researchers based primarily at the Schepens Eye Research Institute in Boston joined forces with colleagues from around the United States and the world to form the Women's Eye Health Task Force (WEHTF). The WEHTF, of which we are participants—Dr. Schaumberg as a founding member of the WEHTF Executive Committee and Dr. Nichols as a member of the group's International Advisory Committee—was formed in response to the fact that two-thirds of the world's blind and visually impaired are women, and that three-fourths of blindness and visual impairment could be prevented or treated without further research. Since its inception, the WEHTF, a member of the IAPB, has worked to emphasize the importance of considering the gender/sex disparity when planning research, vision care, and blindness prevention programs. Tied intimately to this message is the reality that women are often the major healthcare decision-makers and caregivers and in this role influence lifestyle choices and health-seeking behaviors of entire families.
As leadership members of the WEHTF and its effort, we recognize the key role of primary eye care providers. We hope to increase your awareness of the gender disparity in blindness and visual impairment and the strategies for translating awareness into public health action. Others already support and sponsor the WEHTF. They include The Lions Clubs International Foundation, The Lions Eye Health Program, The Schepens Eye Research Institute, and Harvard Medical School's Center of Excellence in Women's Health.
So why these staggering statistics? In addition to the greater longevity of women, there may be an inherent biologic predisposition (e.g., hormonal or immunologic) that contributes to a higher prevalence of some eye diseases. For example, dry eye syndrome is two to three times more prevalent in women than in men at any given age, and women are at higher risk of several autoimmune diseases with important ocular manifestations. Although these are not among the major causes of blindness and visual impairment, optometrists are likely to encounter them frequently in practice. Angle closure glaucoma, less common in the United States but an important cause of blindness worldwide, also affects women disproportionately.6 In contrast, evidence suggests that any gender difference in AMD is likely to be a result of women's greater longevity. On the other hand, there is good evidence to suggest that women are more likely to get cataracts, by far the leading cause of blindness and visual impairment in the world2 and the leading cause of visual impairment in the United States.7 Yet, despite the higher risk, women in many parts of the world are less likely to undergo cataract surgery.
Social or economic factors may also limit the access to and/or quality of women's eye care in general, and we need to support efforts to understand these often locally varying barriers.1 These factors appear to play a large role in the higher burden of cataract and trachoma blindness in developing countries.8,9 In the United States, the extent of these issues remains largely unexplored. The program for the upcoming Academy of Optometry Annual Meeting 2006 in Denver opens with a plenary session dedicated to “Challenges and opportunities in providing a lifetime of care to the underserved” demonstrating optometry's interest in addressing potential disparities. We certainly hope this editorial will help increase awareness of the greater burden of blindness and visual impairment experienced by women.
In countries like the United States, strides can be made by working with and educating the public to seek appropriate care from optometrists and other eye care professionals, to get tested for common eye diseases and those of higher risk, and to adopt healthy lifestyles. Behavioral and environmental factors that can increase the risk of eye diseases, although not limited by gender, include poor nutrition, obesity, and cigarette smoking. Smoking in particular and, to a somewhat lesser extent, obesity are proven risk factors for cataract and AMD, the leading causes of blindness in blacks and whites, respectively, in the United States. Obesity is also a key risk factor for diabetes and therefore impacts its consequences—diabetic retinopathy representing the leading cause of blindness among working age adults in the United States. Alarmingly, the most recent estimates show that we have been underestimating the prevalence of obesity by at least 50% in the United States.10 Smoking doubles the risk of blindness11 and may have an even greater impact on people genetically susceptible to AMD.12,13
However, there is a disturbing disconnect between the strong scientific evidence and the public's knowledge of these links. In a recent survey, 70% of smokers indicated that they would stop or cut down if they knew it could damage their eyesight. Yet less than 50% of people thought smoking could harm their eyes and an even smaller percentage had any awareness of AMD.
A notable exception to these statistics is found in Australia where 77% are aware that smoking can be harmful to sight.14 This is interesting because Australia is one of the few countries undertaking a major public awareness campaign to illustrate the harmful effects of smoking on eye health through mass media messages and warnings on tobacco products about the link between smoking and blindness. The fear of blindness can be a powerful incentive to adopt difficult lifestyle changes. Education by optometrists to their patients, colleagues, and policymakers about the risk of blindness and visual impairment caused by smoking and obesity may accordingly add a convincing new argument to ongoing smoking cessation and obesity reduction efforts.
Another effective message is the importance of regular eye examinations. It is well accepted that following a recommended eye examination schedule throughout life prevents blindness and visual impairment. This is an important message to deliver to women for their own vision care as well as vision care for their families. It facilitates early detection and treatment and enhances the opportunities for clinicians to relay important preventive health messages. Accessibility to appropriate refractive correction is another clear priority.
There is evidence that in developing countries, ongoing blindness prevention campaigns are having an impact on reducing the prevalence of blindness and visual impairment resulting from infectious causes. Unfortunately, there is little progress in decreasing the burden of visual impairment resulting from cataract, glaucoma, macular degeneration, and diabetic retinopathy.15 Recognition of the greater global burden of blindness and visual impairment among women, understanding its causes and the unique role women often play as caretakers in society, and translating the knowledge gained about modifiable risk factors into effective public health messages can help propel efforts forward. As optometrists, we are all united in the common goal of making sure that eye health is not neglected; and great strides can be made by working together to take these important messages to the public, healthcare professionals, and policymakers. The WEHTF would like to help in reaching this goal and has developed a variety of information and full-color educational pamphlets that are available free at www.womenseyehealth.org.
Debra A. Schaumberg
Kelly K. Nichols
1. Abou-Gareeb I, Lewallen S, Bassett K, Courtright P. Gender and blindness: a meta-analysis of population-based prevalence surveys. Ophthalmic Epidemiol 2001;8:39–56.
2. Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R, Pokharel GP, Mariotti SP. Global data on visual impairment in the year 2002. Bull World Health Organ 2004;82:844–51.
3. Vision Problems in the US. Prevalence of Adult Vision Impairment and Age-Related Eye Disease in America. Prevent Blindness America; 2002.
4. Dandona L, Dandona R. What is the global burden of visual impairment? BMC Med 2006;4:6.
5. Dandona L, Dandona R. Revision of visual impairment definitions in the International Statistical Classification of Diseases. BMC Med 2006;4:7.
6. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262–7.
7. Congdon N, O'Colmain B, Klaver CC. Causes and prevalence of visual impairment among adults in the United States. Arch Ophthalmol 2004;122:477–85.
8. Courtright P, West SK. Contribution of sex-linked biology and gender roles to disparities with trachoma. Emerg Infect Dis 2004;10:2012–6.
9. Lewallen S, Courtright P. Gender and use of cataract surgical services in developing countries. Bull World Health Organ 2002;80:300–3.
10. Ezzati M, Martin H, Skjold S, Vander Hoorn S, Murray CJ. Trends in national and state-level obesity in the USA after correction for self-report bias: analysis of health surveys. J R Soc Med 2006;99:250–7.
11. Evans JR, Fletcher AE, Wormald RP. 28,000 cases of age related macular degeneration causing visual loss in people aged 75 years and above in the United Kingdom may be attributable to smoking. Br J Ophthalmol 2005;89:550–3.
12. Despriet DD, Klaver CC, Witteman JC, Bergen AA, Kardys I, de Maat MP, Boekhoorn SS, Vingerling JR, Hofman A, Oostra BA, Uitterlinden AG, Stijnen T, van Duijn CM, de Jong PT. Complement factor H polymorphism, complement activators, and risk of age-related macular degeneration. JAMA 2006;296:301–9.
13. Schmidt S, Hauser MA, Scott WK, Postel EA, Agarwal A, Gallins P, Wong F, Chen YS, Spencer K, Schnetz-Boutaud N, Haines JL, Pericak-Vance MA. Cigarette smoking strongly modifies the association of LOC387715 and age-related macular degeneration. Am J Hum Genet 2006;78:852–64.
14. AMD Alliance International: Campaign Report 2005. Awareness of Age-related Macular Degeneration and Associated Risk Factors. AMD Alliance International; 2005.
15. Foster A, Resnikoff S. The impact of Vision 2020 on global blindness. Eye 2005;19:1133–5.