Chapter 50
Introduction to Geographic and Preventive Ophthalmology
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In 1991, Dr. Alfred Sommer, the initial editor of this section, wrote that “geographic” and “preventive” ophthalmology share a common tradition and perspective, which explains the composition of this section. Both are firmly rooted in public health disciplines and public health pursuits; both are concerned with all aspects of an ophthalmic problem, from its root cause to its prevention and cure. A decade or more later, this is still true.

He emphasized that the careful study of individual patients would continue to provide important scientific insights. However, increasingly, the application of powerful epidemiologic tools to “groups” and “populations” or individuals has enhanced the ability to identify factors responsible for disease: from racial and genetic variations in the risk of chronic open angle glaucoma1,2 and age-related maculopathy3,4 to environmental5,6 and dietary factors7,8 that may be responsible for cataract. These same techniques provide rigorous means for evaluating treatment modalities and their long-term impact.9–12 These approaches and their interpretation are discussed elsewhere in this text. All ophthalmologists can benefit from the review: it can improve the quality of research and, more importantly, the ability to interpret and assimilate reports published in the clinical literature.13–15

At a time of increasing concern with health care costs, access, and quality, the “population” perspective to ocular morbidity and visual impairment has become even more compelling. For the first time, we have begun to develop truly representative estimates of the distribution and magnitude of visual impairment and blindness in the United States.16–21 Other chapters in this book lay the groundwork for understanding these issues of measures of visual function and the latest population estimates.

These data provide guidance for future directions and useful baseline yardsticks against which we can assess progress. The “good news” implementation of recommendations for appropriate management and care of type 1 diabetics not only saves sight but also is highly cost effective: ideal care is less expensive than just the cost of social security payments to those who would otherwise have gone blind.13 The “bad news”? At a time when cataract surgery has reached new heights of sophistication and ever more patients receive and benefit from earlier surgery, the single greatest cause of blindness in East Baltimore remains unoperated cataract.3 A better understanding of the totality and distribution of eye disease and the obstacles patients face in receiving care is clearly essential in designing appropriate and equitable eye care programs and convincing an increasingly reluctant public to support them. Robust, rigorous protocols for screening (discussed elsewhere in this volume) and diagnosis is one approach to effective intervention.

If a more holistic approach is needed to reduce the burden of avoidable blindness in the United States, it is absolutely crucial for poorer nations. Not only are they affected by the same blinding conditions as the West, but in many countries, these conditions are more common (glaucoma is 5 to 10 times more frequent in black populations in Africa and the Caribbean22), and developing countries have far less resources to deal with them. It is no surprise that cataract accounts for half of all blindness.23 Some African nations have less than one ophthalmic surgeon per million population, compared with one per 10,000 to 20,000 in the United States.

Ten years ago, a vigorous debate raged over the relative merits of intracapsular cataract surgery and aphakic spectacles versus intracapsular or extracapsular surgery with intraocular lenses (IOLs). Detailed clinical trials confirmed the clinical impression that even in areas in developing countries, IOL surgery was superior.24 Low cost ($5 to $10/lens) factories have developed in some of the poorest parts of Asia, driving this surgical revolution.25 Now the debate is about extracapsular cataract extraction (ECCE) or small incision surgery in these developing areas.

In addition to Western diseases and limited resources, developing countries also suffer from the neglected diseases that have yielded, in the West, to improved nutrition (xerophthalmia) and hygiene (trachoma) or that rarely occur outside the tropics to begin with (onchocerciasis). Each of these is dealt with in detail in this text: each is in flux. With the discovery that improvement in vitamin A status dramatically increases child survival, xerophthalmia, once the “Cinderella” of childhood blindness, has assumed mainstream attention.26 Epidemiologic studies have revealed that repeated reinfection is the prerequisite for trachoma blindness,27 and an integrated strategy is advocated for trachoma control.28 Mectizan, the first practical, effective, and safe microfilaricide has dramatically improved prospects for treatment and prevention of river blindness.29 Ocular complications of leprosy await a “magic bullet”; in the meanwhile, insufficient appreciation of the risks to sight and the management of those risks remain the greatest obstacles to tackling the problem.

The additional burdens afflicting developing countries explain varying patterns of blindness around the globe—and their impact on the outlook, experience, and challenges faced by our colleagues.

The global impact of eye disease and vision loss will double over the next 20 years as the number and proportion of older people increases. In both developed and developing areas, vision loss increases dramatically with age, whether resulting from cataract in developing countries or macular degeneration in developed areas. Having recognized this, the World Health Organization and nongovernment organizations under the leadership of the International Agency for the Prevention of Blindness, launched a Global Initiative for the Elimination of Avoidable Blindness, Vision 2020 the Right to Sight.23 This global initiative is likely to have a major impact over the next 20 years as it aims to eliminate avoidable blindness by 2020.

The disease-specific chapters will be immensely interesting to Western ophthalmologists concerned about blinding disease in the developing world. Suggestions for innovative use of scarce resources can be found elsewhere.

The past decade has witnessed an explosion of interest and discovery in all areas addressed by this section. Its chapters and contents will continue to be revised as new and pertinent data become available or as emerging, generic concerns require urgent changes in clinical practice.

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1. Tielsch JM, Sommer A, Katz J et al. Racial variations in the prevalence of primary open angle glaucoma: The Baltimore Eye Survey. JAMA 1991;266:369

2. Seah SKL, Foster PJ, Chew PT et al. Incidence of acute primary angle-closure glaucoma in Singapore. An island-wide survey. Arch Ophthalmol 1997;115:1436

3. Sommer A, Tielsch JM, Katz J et al. Racial differences in the cause-specific prevalence of blindness in East Baltimore. N Engl J Med 1991;325:1412

4. Smith W, Assink J, Klein R et al. Risk factors for age-related macular degeneration: Pooled findings from three continents. Ophthalmology 2001;108:697

5. Taylor HR, West SK, Rosenthal FS et al. Effect of ultraviolet radiation on cataract formation. N Engl J Med 1988;319:1429

6. McCarty CA, Mukesh BN, Fu C et al. The epidemiology of cataract in Australia. Am J Ophthalmol 1999;128:446

7. Leske MC, Chylack LT, Wu S-Y. The Lens Opacities Case-Control Study Group. The lens opacities case-control study. Risk factors for cataract. Arch Ophthalmol 1991;109:244

8. Congdon NG, West KP Jr. Nutrition and the eye. Curr Opin Ophthalmol 1999;10:464

9. Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema. Arch Ophthalmol 1985;193:1796:5

10. Macular Photocoagulation Study Group. Argon laser photocoagulation for neovascular maculopathy. Three-year results from randomised clinical trials. Arch Ophthalmol 1986;104:694

11. TAP Study Group. Photodynamic therapy of subfoveal choroidal neovascularization in age-related macular degeneration with verteporfin. Arch Ophthalmol 2001;119:198

12. Acyclovir for the prevention of recurrent herpes simplex virus eye disease. Herpetic Eye Disease Study Group. N Engl J Med 1998;339:300-6-256

13. Javitt JC, Canner JK, Frank RG et al. Detecting and treating retinopathy in type-1 diabetes mellitus. A health policy model. Ophthalmology 1990;97:483

14. The Glaucoma Laser Trial (GLT) and glaucoma laser trial follow-up study. 7. Results. Glaucoma Laser Trial Research Group. Am J Ophthalmol 1995;120:718

15. The COMS randomised trial of iodine 125 brachytherapy for choroidal melanoma, III: Initial mortality findings. COMS Report No. 18. The Collaborative Ocular Melanoma Study Group. Arch Ophthalmol 2001;119:969

16. Tielsch JM, Sommer A, Witt K et al. Blindness and visual impairment in an American urban population. The Baltimore eye survey. Arch Ophthalmol 1990;108:286

17. Klein R, Klein BEK, Linton KLP et al. The Beaver Dam Eye Study: Visual acuity. Ophthalmology 1991;98:1310

18. Klaver CC, Wolfs RC, Vingerling JR et al. Age-specific prevalence and causes of blindness and visual impairment in an older population. The Rotterdam study. Arch Ophthalmol 1998;116:653

19. Wang JJ, Foran S, Mitchell P. Age-specific prevalence and causes of bilateral and unilateral visual impairment in older Australians: The Blue Mountains Eye Study. Clin Exp Ophthalmol 2000;28:268

20. Dandona L, Dandona R, Srinivas M et al. Blindness in the Indian State of Andhra Pradesh. Invest Ophthalmol Vis Sci 2001;42:908

21. Weih LM, VanNewkirk MR, McCarty CA et al. Age-specific causes of bilateral visual impairment. Arch Ophthalmol 2000;118:264

22. Mason RP, Kosoko O, Wilson MR et al. National survey of the prevalence and risk factors of glaucoma in St. Lucia, West Indies. Part I. Prevalence findings. Ophthalmology 1989;96:1363

23. WHO Global Initiative for the Elimination of Avoidable Blindness. Geneva: World Health Organization. WHO/PBL/97.61, 1997

24. Prajna NV, Chandrakanth KS, Kim R et al. The Madurai Intraocular Lens Study. II: Clinical outcomes. Am J Ophthalmol 1998;125:14

25. Brian G, Taylor HR. Cataract blindness—Challenges for the 21st century. WHO Bull 2001;79:249

26. Keusch GT. Vitamin A supplements—Too good not to be true. N Eng J Med 1990;323:985

27. Taylor HR, Johnson SK, Prendergast RA et al. An animal model of trachoma. II. The importance of repeated reinfection. Invest Ophthalmol Vis Sci 1982;23:507

28. Mariotti SP, Pruss A. The SAFE Strategy: Preventing Trachoma. A Guide for Environmental Sanitation and Improved Hygiene. Geneva: World Health Organization WHO/PBD/GET/00.7

29. Cupp EW, Bernardo MK, Kiszewski AE et al. The effects of ivermectin on transmission of Onchocerca volvulus. Science 1986;231:740

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