Abstract
Purpose: :
The major temporal vessel angle is an indicator of the structural integrity of the posterior pole of the retina. It was previously measured manually. (BJO 2006;90:702-704) Advances in image analysis now permit vessel measurements to be undertaken automatically (IOVS 2008;49:3577-3585). This study quantifies semi- automatically the temporal retinal artery angle (TAA) and temporal retinal vein angle (TVA) in preterm infants over a range of birth weights (BW).
Methods: :
One RetCam II (Clarity Medical System, Pleasanton,Ca) image from each of 68 preterm infants with and without retinopathy of prematurity (ROP) born at 23-31 weeks gestational age (GA) acquired at 33-42 weeks postmenstrual age (PMA) was selected. Infants were grouped according to BW (<751g;751-1000g;1101-1250g;>1250g). TAA and TVA were measured by Computer Aided Image Analysis of the Retina (CAIAR - Imperial College London). Data was analysed using Kruskal Wallis One Way Analysis of Variance test.
Results: :
68 TVAs and 64 TAAs were measured. The mean TAA was 97.1° ( ± 28.4° SD) and TVA was 129.6° (± 19.8° SD). TAA increases significantly with BW (p=0.003), but TVA does not (p=0.386). Separate analysis of those infants with ROP compared with those without ROP showed a significantly lower TAA in infants with ROP (p=0.006, Mann Whitney U Test) but no significant difference was found in TVA between those with and without ROP (p=0.174, Mann Whitney U Test).
Conclusions: :
Advancing retinal image analysis techniques that permit the precise geometric mapping of blood vessels in preterm infants may help to quantify topological change with respect to birth weight and disease. In the future, it may be used as a basis to confirm or refute the fractal basis of the retinal vascular tree.
Keywords: retinopathy of prematurity • imaging/image analysis: clinical • retinal development