Retinopathy of prematurity: incidence and risk factors

OBJECTIVE: To determine the incidence of Retinopathy of Prematurity (ROP) in high risk babies admitted to the neonatal unit and to study risk factors for it's development. DESIGN: Prospective cohort study. SETTING: Level II Neonatal Intensive Care Unit. SUBJECTS: 100 babies admitted to the neonatal unit during a 4 year period who were below 1500 g or whose gestation was < or = 34 weeks. METHODS: Examination of the eye was done in the neonatal unit or in the neonatal follow up clinic by an Ophthalmologist by indirect Ophthalmoscopy at 4-6 weeks postnatal age. RESULTS: The incidence of ROP was 46%. Of the 100 babies screened, 21 had stage I, 14 had stage II, 8 had stage III and 3 had stages IV and V. The incidence of ROP was 73.3% among < 1000 g babies and 47.3% among < 1500 g babies. The incidence of ROP among 28-29 weeks, 30-31 weeks and 32-33 weeks babies was 83%, 60% and 50%, respectively. The maximum stage of ROP developed between 37-42 weeks post conceptional age in 69% subjects. On univariate analysis, gestation < or = 32 weeks, anemia, Blood transfusions, apnea and exposure to oxygen significantly increased the risk of developing ROP. On multivariate logistic regression analysis, anemia and duration of oxygen therapy were the significant independent predictors of development of ROP. Nine of the 46 babies underwent cryotherapy for threshold ROP. CONCLUSION: The incidence of ROP among high risk babies is significant and duration of oxygen therapy and anemia are independent factors predicting the development of ROP. All high risk babies should be screened for ROP. Cryotherapy is a relatively simple procedure which can be done in the neonatal unit.