A recent population-based study in the Canadian province of British Columbia showed that, since the mid-1960s, there has been a significant increase in the incidence of retinopathy of prematurity-induced blindness in infants weighing 750 to 999 g at birth. To determine the impact of changing birth weight-specific survival on this new epidemic, all infants born in the province in the period 1952 through 1986 and known to the British Columbia Health Surveillance Registry as having retinopathy of prematurity-induced blindness were identified. In addition, the birth registration records for the 1 299 740 infants born in British Columbia in the same period and the death records of the 22 940 British Columbia-born infants who died in the province before the end of their first year of life were linked using a combination of probabilistic and manual record linkage techniques. These linked records and the records from the Health Surveillance Registry were used to calculate birth weight-specific incidence rates of retinopathy of prematurity-induced blindness in liveborn infants and first-year-of-life survivors. The rates, in 5-year intervals, showed that, in both liveborn infants and first-year survivors, the highest birth weight-specific rates occurred during the first epidemic of retinopathy of prematurity, which ended in British Columbia in 1954. Since the mid- to late-1960s, the incidence of retinopathy of prematurity-induced blindness in liveborn infants weighing less than 1000 g increased steadily whereas in infants weighing 1000 to 1499 g, incidence decreased slightly since the original epidemic ended. However, the experience of first-year-of-life survivors is substantially different. In survivors weighing 500 to 749 g at birth, incidence has decreased since the mid-1970s, whereas in survivors weighing 750 to 999 g, incidence has been stable since 1965. In infants weighing 1000 to 1499 g, the slight trend toward decreasing rates observed in livebirths since the end of the original epidemic is more pronounced. Thus, these results substantiate the idea that the new epidemic of retinopathy of prematurity-induced blindness in infants weighing less than 1000 g is a function of increasing birth weight-specific survival.
