314 CHAPTER EIGHT of Nepal. Boys account for three-fifths of cases of Bitot's spots (59.3%) and active xerophthalmia (62.9%). The sex ratio for xerophthalmia is about 1.5:1 (boys to girls). Urban/rural prevalence rates are the same. The prevalence of Bitot's spots exceeds the WHO criterion in various geographic areas including the terai as a whole, villages at elevations less than 350 meters, the Eastern, Central, and Far Western B Regions, the zones of Sagarmatha, Janakpur, Narayani, and Mahakali, and in the sampling strata of the Eastern and Central Terai, Far Western Hills, and the urban sites. It seems ap- propriate to identify the area of the Eastern and Central Terai as the major geographic focus of xerophthalmia in Nepal. This area accounted for more than two-thirds of the Bitot's spots found in the Nepal Blindness Survey (see Figure 8.4). There is some concern that confounding due to seasonality may have influenced the con- centration of Bitot's spots found in this area. A second minor focus of xerophthalmia is located in the Far Western Hills and plains. Along with this geographic concentration of xerophthalmia cases, there is substantial evidence that xerophthalmia is concentrated in a particular group or groups of persons living in the high risk area. Nearly 90 percent of cases come from the Vaish and Shudra castes, none of whom own more than 40 ropanis of land -(5 acres) or have a radio, and very few of whom have watches in their households. The majority speak Maithili as their mother tongue. Gwala, Malla, and Teli communities are the most affected. Individual risk factors in xerophthalmia include living in crowded and unsanitary conditions, low consumption of a combination of vegetables, intermittent periods of food shortages, and, most impor- tant of all, a history of diarrhea. Whether diarrhea causes. xerophthalmia, xerophthalmia causes diarrhea, or whether both are related to other variables cannot be determined from the data. However, in some instances at least, diarrhea is the earlier event. In a case control study in which cases and controls were matched by age, sex, season, and village, cases were more than 20 times more likely than matched controls to have had diarrhea in the past 4 weeks. This was the strongest association between a disease and a risk factor found in the entire survey (p < .001), despite a small number of matched pairs (50). The tragedy of xerophthalmia in Nepal is that it places yet one more burden on precisely those who can least afford it, the children of families with low social and economic status. Xerophthalmia and keratomalacia are not synonymous with childhood blindness, however. Out of 11 blind children under the
