The emergent angle of the temporal retinal vessels and its relationship to prematurity

Abstract

Abstract: : Purpose: To investigate in preterm infants the angle between the major temporal retinal blood vessels as they emerge from the optic disc and to determine: interocular symmetry, and whether the major temporal angle is affected by the degree of prematurity (gestational age [GA]) and retinopathy of prematurity (ROP). Methods: Digital images from 51 babies of between 36 and 44 weeks post menstrual age were obtained with a Retcam 120 (Massie Labs, Dublin, CA). They were categorised by GA at birth. Group 1 comprised babies from 24–27 weeks GA (n=18), Group 2 28–31 weeks (n=17) and Group 3 ≥32 weeks GA (n=16). Image analysis was carried out using Paintshop Pro. (www.jasc.com). Stage of ROP was recorded clinically. The centre of the optic disc and fovea were identified by 2 observers. The image was rotated to align disc and fovea on a horizontal meridian and a perpendicular line drawn through the fovea to the inferior and superior temporal retinal vascular arcades. The angles from the optic disc to the points of intersection of the superior (&#952s) and the inferior (&#952i) vessels with foveal vertex were calculated. Results: The mean angle between the temporal retinal vessels was 82.0°OS and 83.5°OD with range 40.0°OS and 37.6°OD. &#952s (mean OS 42.8°, OD 42.2°) proved to be significantly greater than &#952i (mean OS 39.2°, OD 40.3°) in both left and right eyes (p<0.001 OS, p=0.01 OD). &#952s+&#952i (mean group 1 79.9° OS, 79.9° OD; group 2 81.0° OS, 83.6° OD; group 3 85.5° OS, 87.5° OD) increased significantly between GA groups 1 and 2 (p=0.025 OS, p<0.001 OD) and GA groups 2 and 3 (p<0.001 OS & OD). There were no significant differences in &#952s, &#952i, and &#952s+&#952i between the left and right eyes and no correlation with ROP stage. Conclusion: In preterm infants temporal vessel angle increases with increasing time in utero (ie increasing GA), independent of ROP stage. While there is no interocular asymmetry of this angle the superior and inferior vessels are asymmetric to the fovea.. Shortening of the gestational period affects retinovascular development and as the morphology of the major vessels reflects the underlying microvasculature this merits further study.

Keywords: retinal development • retinopathy of prematurity • retina