Ben Young, MD
University of Michigan
Longitudinal Choroidal Development in Preterm Infants
Dr. Suzanne Michalak was awarded the prestigious Raymond R. Margherio Award for her project describing choroidal development in preterm infants. While the choroid is a critical part of the vascular supply for the outer retina, little is known about how it develops in preterm infants. Dr Michalak explained that it is limited to date to post-mortem histology studies, which are limited by ex-vivo vascular collapse. She also pointed out that while indocyanine green angiography could be used, it is limited in quantification of 3D structural growth.
Improvements in hand-held OCT, however, allow us to practically visualize the choroidal-scleral junction, and choroidal thickness, in preterm infants. She showed that in earlier work, at 36 weeks postmenstrual age (PMA), 94% of eyes had a measurable choroidal thickness with the devices available at the Duke Eye Center. They’ve also previously found associations with thinner choroid to oxygen supplementation requirements and pre-plus/plus disease status.
However, until now, the growth behavior of the choroid in prematurity over time has been unknown. Dr. Michalak pointed out that this information will be critical to interpreting choroidal thickness in future studies, so her aim in this project was to characterize the developmental trajectory of the choroid.
Preterm infants were imaged with OCT at time of regular screening, then the central 1mm average choroidal thickness was measured by two graders. Growth was modeled by a segmented mixed effects model. They were able to image 79 patients with a mean gestational age (GA) of 27 weeks from 4 or more time points from 30-60 weeks PMA.
Using their segmented mixed model, they found infants’ choroid grew 15 microns in thickness per week from 30 weeks PMA until a transition point at age 38 weeks, where growth virtually stops, which follows similar patterns as axial length, RNFL thickness and retinal vasculature. Using this normative dataset, she then compared these relatively normal infants to those with low birth weight, or very early GA, who both had slower initial growth rates, and a later transition point. Dr Michalak concluded that this interesting finding opens the gateway to the possibility that choroidal growth rate could be used as a biomarker for screening for ROP, specifically noting that in future studies they will investigate whether treatment-requiring ROP changes the growth rate of the choroid.