Abstract
Purpose: :
To describe foveal morphological characteristics in preterm neonates without severe retinopathy of prematurity (ROP) using spectral domain optical coherence tomography (SD OCT).
Methods: :
Twenty-two preterm neonates, 31-41 weeks post-menstrual-age (PMA) were enrolled with parental consent in this IRB approved study. After routine dilated fundus examination in the neonatal intensive care unit (NICU), SD OCT imaging of the macula was performed using an FDA approved portable handheld system (Bioptigen Inc., RTP, NC). Five children and two adults imaged with the same system served as comparison groups. Images from one eye of each subject were graded using OSIRIX medical imaging software (OSIRIX Foundation, Geneva, Switzerland). Photoreceptor layer (PRL) thickness was measured semi-automatically using DOCTRAP software (Duke University, NC). Foveal slope was calculated using a previously described method.1 Subjects requiring laser or with any ROP worse than stage 2 were excluded. Kruskal-Wallis and Wilcoxon tests were used to compare findings between groups.
Results: :
Ten preterm neonates met inclusion criteria. Images revealed the presence of inner retinal layers at the foveal center in all 10 eyes. Preterm neonates had a shallower foveal pit than children and adults (mean slopes 5.6° vs. 8.7° and 10.2°, respectively, p for trend=0.034), and the PRL was thinner at the foveal center than in children and adults (mean thickness 31.6 vs 122.9 and 159.9 microns, respectively, p for trend=0.003). Other signs of immaturity noted in the preterm neonates group were the absence at the foveal center of retinal layers normally present on OCT in the adult fovea, such as inner segment-outer segment junction and external limiting membrane. These layers first appeared 3 mm from the fovea in preterm neonatal eyes at 41 weeks PMA.
Conclusions: :
Early photoreceptor development can be observed in neonates imaged with SD OCT in the NICU. Several morphological changes in the human fovea occur after birth in preterm neonates without severe ROP, highlighting the importance of this period in the development of a normal human fovea. ROP and other diseases such as albinism may affect normal foveal development during this period.1 Dubis A, McAllister J, Carroll J. BJO. 93:1223-7 (2009).
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retinal development • retinopathy of prematurity