Risk Factors Evaluation of Threshold Retinopathy of Prematurity

This study aimed at the evaluation of risk factors associated with threshold retinopathy of prematurity (ROP) in infants stricken with ROP referred to Farabi Eye Hospital during years 2008-2009. Since blindness and adverse impairments will occur in a high percentage of infants stricken with threshold retinopathy, we did intend to examine relation between demographic factors with threshold retinopathy in Farabi Eye Hospital, which, as a tertiary center, represents an appropriate sample of Iran’s population. In this retrospective case-control study, sample consisted of infants less than 36 weeks and birth weight under 2,500 grams that were referred to Farabi Eye Hospital in order to screen threshold retinopathy of prematurity. They were checked up and a questionnaire was filled out for each infant. Based on the gathered data, the relation between risk factors and threshold ROP was examined. Out of 1,718 eyes participated in this study, 791 eyes had retinopathy. The incidence of threshold retinopathy in this study was 7.4% percent. Using independent sample t-test between two groups (infants with threshold retinopathy and infants without it) showed significant relationships between gestational age, birth weight, oxygen supplementation, duration of ventilation, blood transfusion, respiratory distress syndrome (RDS), post-conceptual age and chronic respiratory disease with threshold ROP. Cross-tab test revealed a significant relation between threshold retinopathy and sepsis (P=0.006), oxygen supplementation (P=0.000), blood transfusion (P=0.004), RDS (P=0.000), weight (P=0.000) age at first examination (P=0.000), and duration of ventilation. Logistic regression showed that sepsis and the age more than 40 weeks at the time of examination are the predicting factors of threshold retinopathy. Threshold ROP was seen in patients with birth weight more than 1,500 gram so screening criteria in developing country is not appropriate for us. The most important risk factors of threshold ROP are low gestational age, low birth weight and the delayed initial examination and the duration of oxygen therapy.