Retinopathy of prematurity is a multifactorial disease with disturbed retinal vasculogenesis which may lead to severe impairment of normal vision. Very few studies have been done to investigate the effects of light on the development of the retina, and on the incidence of ROP. There is some evidence from animal studies that free radicals formation may be induced by light exposure. The objective of this study is to investigate the role of ambient light on the development of ROP. Since June, 1995, all infants born with less than 32 weeks gestation and or < 1600 gr birth weight from two NICU were randomly allocated into two groups: Group I followed the normal routine of the nursery, with normal ambient light exposure. Group II had the eyes occluded from birth to 35 weeks corrected age. Ambient light was monitored with a Luximeter (ICEL LA-500). A indirect oftalmoscopy was performed at 2 weeks of age and every four weeks, or at shorter intervals according to clinical decision. ROP was graded according to the International ROP classification - 1987.

We admited a total of 184 infants in the study until november 1996. A total of 35 infants were excluded (deaths or transfers) and 149 were allocated in the two groups- Group 1-74 Group II-75. We observed no diference in birth weight (1261 vs 1211g) gestacional age (30.0 vs 30.5), severity of the respiratory disease, days on oxygen, incidence of sepsis, PDA, BPD in both groups. Ambient light in both NICU varied betwee 188 and 540 Lux. The overall incidence of ROP (all grades) was not different in the two groups 37.8: vs 37.3% p>0.05.

Retinopathy grade III or more was observed in 5 infants, 4 in group I and 1 in group II (eyes ocluded). Two infants required cryotherapy, both in group I. These differences were not statistically significant (p>0.05).

Our data show that ambient light does not have influence on overall incidence of ROP, but can not rule out an effect on grade III or more retinopathy.(CNPq)