Screening for retinopathy of prematurity after surfactant treatment

Surfactant administration in premature infants is supposed to induce rapid changes in tissue oxygenation. It might therefore modify the risk of developing retinopathy of prematurity (ROP). We have been using the so-called safety index $$\begin{gathered} SI = log_{nat} \hfill \\ = \frac{{GA (weeks) \times BW (kg)}}{{days in 0_2 + 1}} \hfill \\ \end{gathered} $$ to calculate the number of infants at low risk to develop ROP stage 3 or higher (SI≥1) after administration of two preparations of a surfactant. The study population consisted of 255 prematures of ≤2000 g birth weight treated with surfactant for respiratory distress syndrome in Switzerland between 1991 and 1993. Of these infants, 29 received a natural surfactant (Curosurf), and 226 infants were treated with the synthetic surfactant Exosurf. Reduction of fraction inspired oxygen (FiO2) was significant within 3 and 6 h and was more pronounced in infants having received natural surfactant. An SI≥1 was calculated in 106 of the 226 infants (47%) treated with Exosurf. Only one of these infants developed ROP stage 3 in one eye (no ROP in the fellow eye) whereas 12 infants with ROP stages 3 or 4 had an SI stage 2. According to this survey, the risk of developing severe stages of ROP does not increase in low birth weight infants who have been treated with surfactant. Irrespective of a surfactant therapy, the calculation of the SI is useful for substantially reducing the number of prematures who need intensive ophthalmological follow up.