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Brittany Coats, Matthew Byrne; Morphological Analysis of Ovine Retinal Vasculature to Assess Risk for Retinal Hemorrhage as a Function of Age. Invest. Ophthalmol. Vis. Sci. 2018;59(9):6178.
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© ARVO (1962-2015); The Authors (2016-present)
Pediatric retinal hemorrhages are commonly associated with abusive head trauma. However, little is known about the biomechanics of pediatric retinal vasculature. Our long-term research goal is to understand the microstructural and mechanical characteristics of the immature retina to better identify retinal injury thresholds in infants. The objective of this study was to quantify differences in regional morphology between mature and immature vasculature at different depths within the retina.
Mature (n=9) and immature (n=4, 132 days gestation) ovine eyes were enucleated 4 hrs post-mortem and fixed in 4% paraformaldehyde. The retina was extracted from the eye and placed in a block buffer (5% BSA and 0.5% Triton X-100). Buffered retinas were washed with PBlec, stained with Alexa Fluor 488 and imaged on an A1R+ confocal microscope, beginning at the vitreous and increasing in depth towards the optic nerve layer. Image processing was used to quantify 6 morphological properties at 3 retinal depths. Two-way ANOVAs were used to evaluated the effects of age/depth and depth/region on morphology (p<0.05).
Average vessel length was significantly affected by age and depth (p<0.003), with longer vessels seen in mature retina, and vessel lengths decreasing with retinal depths in both ages (p<0.05). Vessel diameter also significantly decreased with depth, but only for mature retina (p<0.05). Vessel tortuosity was not different between mature and immature retina, and significantly increased with retinal depth (p<0.05). Immature retina had a significantly greater number of branch points compared to mature retina (p<0.001), and the number of branch points increased with retinal depth. No significant effects were seen for angular asymmetry.
Decreased lengths and branch points in the immature retina suggest a potential increased risk of retinal hemorrhage compared to adults. Immature retinal vessel diameters are smaller than adult diameters, which also suggests an increased risk. Further, mature retinal vessel diameters significantly decrease with retinal depth while immature vessel diameters are constant with depth. This may explain why traumatic retinal hemorrhage in children are often multilayered, and will be a focus of future computational investigations.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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