Characteristics of retinal vascularization in premature infants

Objective To determine the characteristics of retinal vascularization in premature infants. Methods A prospective study was carried out which included all premature infants with birth weight〈2 000 g, who were hospitalized in Guangdong Women and Children＇s Hospital from September 1, 2009 to August 31, 2010. Close retinal screening and follow-up were carried out in order to record retinal vascularization at different postconceptional ages. Spearman correlation analysis was performed for statistical analysis. Results A total of 231 infants were enrolled, and follow-up was completed in 212 infants giving a follow-up rate of 91.8%. Twentyeight infants developed retinopathy of prematurity （ROP） resulting in a ROP morbidity of 13.2%, and 184 cases had full retinal vascularization. The median birth weight was 1 600 g （1 000-1 900 g） and the median gestational age was 32.4 weeks （27.0-35.5 weeks）. In the 32-week postconceptional age group, the proportion with full vascularization in ZoneⅠ,ⅡandⅢwas 87.1%（81/93）, 7.5%（7/93） and 0.0%（0/93）,＆amp;nbsp;respectively. In the 36-week postconceptional age group, full vascularization was observed in ZoneⅠ, and the proportion with full vascularization in ZoneⅡandⅢrose sharply at 38-week and 40-week postconceptional age, respectively. The proportion with full vascularization in ZoneⅢwas 100.0%（24/24） at 43-week postconceptional age. According to Spearman correlation analysis, there was a positive correlation between ZoneⅡand Zone Ⅲ retinal vascularization progression and postconceptional age （r=0.690 and 0.720;P=0.000）. In premature infants, full retinal vascularization in ZoneⅠoccurred at 36-week postconceptional age. The median gestational age for ZoneⅡand ZoneⅢretinal vascularization was 38 weeks （32.2-40.4 weeks） and 41 weeks （36.0-42.6 weeks）, respectively. Therefore, a further 2-3 weeks were required for full retinal vascularization in ZoneⅡand ZoneⅢ. The time differences for undervascularization in ZoneⅡandⅢwere 8 to 10 weeks, and the time differences for full vascularization in ZoneⅡandⅢwere 8 weeks and 6 weeks, respectively. Conclusion Retinal vascularization varies in premature infants. Almost all premature infants complete vascularization by term gestational age and the majority of infants need to be followed up to 41 weeks. It is essential to focus on the different retinal regions during maturation. Key words: Retinopathy of prematurity; Retinal neovascularization; Fundus oculi