Purpose: Human blood contains low levels of protoporphyrin IX (PP IX), a photoactive compound that produces reactive oxygen species when exposed to light. It has been proposed that photoactivation of PP IX and subsequent generation of potentially tissue-damaging reactive oxygen may be a mechanism of retinal injury in retinopathy of prematurity (ROP). The purpose of this study is to determine an association between blood PP IX level and infant birth-weight and gestational age.
Methods: Erythrocyte PP IX levels were measured from the umbilical cord blood of 31 neonates, both full term and preterm. Birthweights and gestational ages were recorded.
Results: PP IX levels in infants weighing < 1000 grams (n = 7) average 200 micrograms/dl, which is significantly higher than PP IX levels in infants weighing > 1000 grams (125 micrograms/dl, n = 24; P < 0.02).
Conclusion: Elevated PP IX levels may place preterm neonates at increased risk for photosensitizing retinal injury.