CATARACT 225 TABLE 6-29. ESTIMATES OF INCIDENCE OF NEW CASES OF CURABLE CATARACT BLINDNESS IN NEPAL 1980-2000 Year-Est. Incidence Year-Est. Incidence 1980.-23,209 1981-24,021 1982-24,862 1983-25,732 19,84-26,633 1985-27,565 1986-28,530 1987-29,528 1988-30,562 1989-31,631 1990-32,739 1991-33,884 1992-35,070 1993-36,298 1994-37,568 1995-38,883 1996-40,244 1997-41,653 1998-43,110 1999-44,619 2000-46,181 Notes: Assuming constant age-specific incidence and 3.5 percent annual in- crease in cataract blindness incidence due to population growth in the age group with cataract and assuming no change in the rates of cataract operations. Throughout this chapter, estimates for surgical need should be under- stood as operations needed in addition to current levels of surgery. The incidence of cataract blindness was estimated to be 29,174 in 1980. Out of this total an estimated 4,221 were operated on (3,288 successfully). The remaining 24,956 form t-he number presumably added to the backlog in 1980. The same disqualifiers (corneal opacities, absence of pupillary reflex, posterior segment disease, etc.) as in the prevalence estimates have been used. Reducing 24,956 by the seven percent expected to be inoperable yields the estimate of 23,209 new cases of curable cataract blindness in 1980. Deaths among Cataract Blind: One of the greatest tragedies of cataract is the increased rate of death that has been reported in the unoperated blind. Five-year survival rates as low as 50 percent have been reported in some areas. The death rate among the unoperated cataract blind is not known. Since the average age at onset of cataract blindness in Nepal is nearly 60, the death rate is high in this age group, even in the absence of blindness. Tables 6- 30 and 6-31 show the effects of different hypothetical death rates on total deaths expected in the period 1981-1986 and on the result- ant 1986 point prevalence of surviving cataract blind. For the following example, assume a death rate of 100 per 1,000 in the newly blind. That is, of those not operated on, ten per- cent are expected to die within one year after becoming blind. The cataract blind in the backlog, however, are several years older and have already been blind an average of 4.5 years; for this group as- sume an annual death rate of 134 per 1,000 (this death rate is twice the death rate of nonblind individuals of the same age). Using the above assumptions (see Section 6.5), it can be estimated that
