VISUAL IMPAIRMENT AND BLINDNESS 131 TABLE 4-21. DISTRIBUTION, ESTIMATED NUMBER OF CASES, AND PREV- ALENCE OF UNILATERAL BLINDNESS BY ZONE (NBS 1981) Estimated Number of Cases Percentage of Nepal's Total Sample N Prevalence (per 100) Zones Mechi Koshi Sagarmatha Janakpur Bagmati Narayani Gandaki Lumbini Dhaulagiri Rapti Karnali Bheri Seti Mahakali Subtotal Missing 2,476 3,645 3,697 4,008 4,247 4,092 3,279 3,783 484 2,031 489 3,141 1,769 2,402 39,543 344 8,747 21,804 13,620 29,465 19,107 19,814 16,648 25,871 2,595 11,737 6,370 23,055 14,314 20,465 233,612 NA 233,612 1.02 1.64 1.08 2.06 1.16 1.32 1.51 1.93 1.58 1.63 3.44 2.22 2.37 2.36 1.66 NA 1.66 3.7% 9.3 5.8 12.6 8.2 8.5 7.1 1.1 1.11 5.0 2.7 9.9 6.1 8.8 100.0 NA 100.0 Total 39,887 Source: FR4.003 AN.11M mountains, there is another focus of higher blindness prevalence in the Central Terai. Both strata exceed the 1.0 percent criterion. When age-sex-standardized blindness prevalence rates are ex- amined (Figure 4.2), these two foci are even more apparent. These two foci appear to have somewhat different explanations. The first focus, in the Eastern and Central Terai, is dominated by cataract as a cause of blindness. Although nearly two-thirds of the blindness in the Far Western Mountains was also related to cataract, there is also evidence of an old epidemic of smallpox that many years ago blinded hundreds in the Far Western Hills. Since smallpox has been eradicated, it is no longer a cause of additional blindness, and removing smallpox brings the rates of blindness in the Far Western Hills and Mountains to the same level as that in the Far Western Terai. In summary, over one-third (34.9%) of the blind in Nepal live in the Eastern and Central Terai. The corresponding zones (which are oriented North to South and include all terrains) are Koshi, Sagar- matha, Janakpur, and Narayani, which together include over 40 percent of the blindness in Nepal. As is shown in Chapter 6, this area corresponds to the area of highest cataract prevalence, in
