Purpose: To investigate the baseline position of the central vascular trunk (CVT) and the characteristics of the optic nerve head (ONH) in newborns.
Methods: CVT position was evaluated based on fundus images obtained from newborns who had undergone eye-screening examinations. It was then graded according to the optic disc area as follows: grade 1, within central 4%; grade 2, within central 9%; grade 3, within central 16%; grade 4, within central 25%; grade 5, outside central 25% of optic disc area. The direction of the CVT position was determined in cases of grade 2 or more as superior, inferior, nasal, and temporal, relative to the optic disc center. The ovality index and the vertical cup-to-disc ratio were determined as well.
Results: In 1000 fundus images from 1000 newborns, 87.1% showed grade 1 (95% confidence interval 84.7-88.8), and 10.7% showed grade 2. The most common CVT direction was central (87.1%, grade 1), followed by nasal (11.0%) and inferior (1.2%). The ovality index was 1.28 ± 0.09 (range, 1.01-1.61). The ONH shape was vertically oval and highly uniform. The average vertical cup-to-disc ratio was 0.29 ± 0.13 (range, 0.00-0.67).
Conclusions: The CVT of newborns was located in the central area of the ONH in most cases. The shape of the optic disc was vertically oval, and very similar among the newborns. Considering the high variability of ONH morphology and the diverse location of the CVT in adults, our result suggests that the shape of the ONH and the CVT position might change during eyeball growth.