Ophthalmologists who trained in the 1960s and 1970s believed that retrolental fibroplasia was a tragic, iatrogenic problem of the 1940s and early 1950s. In the 1960s and 1970s screening programmes were generally not in place, as this was the period of the “first lull”—the first epidemic (due to unmonitored supplemental oxygen, often given routinely to all premature babies)1 was over, and the “second epidemic” (due to increased survival of very low birth weight babies) had not really started. The paper by Rowlandset al suggests that we may be entering a “second lull.”2 The study reports the changing incidence of retinopathy of prematurity (ROP) in babies in one unit in the United Kingdom over a 10 year period (1989–98), and shows a significantly lower incidence of stage 3–5 ROP in babies examined in the second 5 year period compared with the first. This is despite babies in the second cohort being more preterm with lower birth weights as a result of improved survival of extremely low birthweight babies. If the risk factors for ROP had remained constant over the study period, one would expect a higher incidence in the second cohort, given that birth weight and gestational age are the most important risk factors. The authors conclude that the lower incidence of ROP in babies born more recently is attributable to improvements in neonatal care, in particular to the use of prenatal steroids and surfactant. However, this statement has to be interpreted cautiously, as historical cohort studies are subject to inherent weaknesses.

This paper raises several questions concerning the incidence of severe ROP. Firstly, has a fall in the incidence of ROP been reported in other studies, and if so, is this a universal trend? Secondly, if the trend is real, what are possible explanations? Thirdly, what are …