CHILDHOOD BLINDNESS 315 age of 15 detected in the Nepal Blindness Survey, nutritional blind- ness accounted for only 2 cases. While the numbers are small and there are problems in interpreting the utility of prevalence data due to the increased risk of death following transient blindness from keratomalacia, it is clear that more than four-fifths of cases of childhood blindness detected in Nepal were not due to keratomalacia but were due to several other causes such as congenital cataract, in- fections, and trauma. Nutritional blindness was a small component of all blindness in Nepal, accounting for an estimated 1,095 cases out of the 117,623 estimated blind in Nepal. This low percentage (0.9%) may be an underestimate due to the difficulty of establishing the cause of blind- ness in persons with bilateral corneal scars or phthisis of undeter- mined etiology. In fact, of all the diseases studied in the Nepal Blindness Survey, the quality of data on xerophthalmia has the only serious limitations, due to problems such as low or unknown inter- observer agreement, a four-month survey period that may have missed the high incidence season for xerophthalmia, and the difficul- ty inherent in documenting the human tragedy of a disease like keratomalacia, which often causes swift and transient blindness en route to a high percentage of deaths. 8.1 Overview Childhood blindness is a widespread health problem in many less developed countries of South and Southeast Asia. In general, childhood blindness has been linked with nutritional deficiencies. Xerophthalmia, characterized by the epithelial disruption of the conjunctiva and the cornea, is generally linked to a vitamin A deficiency. The literature on this subject is limited, however, and the relationship between xerophthalmia, vitamin A deficiency, and other possible risk factors remains to be clarified. The term "xerophthalmia" means literally a dryness of the eyes. The first signs of xerophthalmia are conjunctiva! xerosis, characterized by dryness, thickening, wrinkling, and pigmenting of the conjunctiva. Associated with early xerophthalmia is the appearance of Bitot's spots, which are small, triangular plaques with foamy or cheesy surfaces. In children, these plaques consist of keratini2ied debris and saprophytic bacteria. More severe forms of xerophthalmia involve corneal xerosis and ulcerations that, if not treated, lead to keratomalacia, the necrosis and ultimate destruction of the cornea. Xerophthalmia is frequently but not always accompanied by night blindness, an early sign of the retina's loss of sensitivity to light.
