130 CHAPTER FOUR TABLE 4-20. DISTRIBUTION, ESTIMATED NUMBER OF CASES, AND PREV- ALENCE OF BLINDNESS BY ZONE (NBS 1981) Estimated Number of Cases Percentage of Nepal's Total Sample N Prevalence (per 100)a 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 39,887 5,525 12,685 11,575 11,212 11,415 14,963 5,574 11,262 1,291 5,805 2,100 9,906 7,489 6,821 117,623 0 0.64 (0.64j 0.95 (0.99) 0.92 (0.98) 0.78 (0.73) 0.69 (0.62) 1.00 (0.99) 0.50 (0.46) 0.84 (0.75) 0.79 (0.53) 0.80 (0.87) 1.13 (1.63 0.96 (1.26) 1.24 (1.24) 0.79 (0.80) 0.84 NA 4.7% 10.8 9.8 9.5 9.7 12.7 4.7 9.6 1.1 5.0 1.8 8.4 6.4 5.8 100.0 NA 100.0 Total 117,623 0.84 Source: FR4.003 AN.HM aFigures in parentheses are rates. age-sex-standardized blindness prevalence clear that there is much excess blindness in the Far West of Nepal. The cross-hatched area on Figure 4.1 represents the zones of Nepal with age-sex-standardized blindness prevalence rates exceeding the WHO criterion of 1 percent blindness prevalence. These zones are in the area of Nepal that is thought to have lower life expectancy, less access to medical care, and a greater share of poverty than many other areas in Nepal. It also has one of the greatest burdens of blindness. Sampling Strata: Table 4-'22 displays similar data using the sampling strata rather than administrative zones as the unit of analysis. Sampling strata are of less utility in programme plan- ning, because most programme implementation takes place at the zonal administrative level. However, sampling strata were created for the survey to bring together certain combinations of terrain (terai, hills, mountains) and regional (Eastern, Central, Western, Far Western A and B) characteristics to aid the search for local cir- cumscribed areas of disease foci. In addition to the previously discussed focus in the Far Western
