[Retinopathia praematurorum: risks and critical timing].

Two prospective studies were performed to characterize the retinopathy of prematurity (ROP) risk in preterms further. In the first study the gradual relationship between birth weight, gestational age and duration of oxygen therapy and the incidence of ROP was evaluated. A total of 487 preterms were enrolled in this survey. Seventeen percent (67 babies) of 389 surviving children presented clinical signs of acute ROP. Among the analyzed risk factors "gestational" age provided the best correlation with the manifestation of acute ROP. According to the nonlinear regression model the risk of acute ROP can approximately be calculated as: R = 2(39-SSW).0.5 (R = relative risk of ROP in %). The second study focused on the relationship between individual risk factors and the age at stage III onset. The mean age of the first ROP stage III diagnosis was 66 days after birth at an average gestational age (post-menstrual age) of 37.0 weeks. Multifactorial analysis clearly demonstrated that birth weight was most informative among the tested set of parameters concerning the age at onset of ROP stage III. Best fitted linear regression of this relation was: LAT = 100-BW.34 (LAT = age at onset of ROP III expressed as postnatal days; BW birthweight measured in kg). It is suggested to take this approximation into account for the timing of ROP screening.