Abstract
Purpose :
While the average length of the adult human optic nerve (ON) is known, no data actually exists on the length of the living neonatal ON, nor its postnatal speed of anteroposterior (AP) growth. We wanted to evaluate the length of the neonatal ON, as well as the speed of growth from birth to maturity.
Methods :
We utilized T1 and T2 axial magnetic resonance image (MRI) images from the Infant Brain Imaging Study (IBIS) network database (www.IBIS.org), which contains brain images from 15 normal infants scanned at birth and at one year. We evaluated average ON length from 5 additional Caucasian age cohorts (14 subjects/cohort): 3, 5, 10, 15 and 20y. Male:female ratios were equal, except for the 10y (46.7%; n=15) and 15y (42.9%; n=14) groups. Individuals were excluded if they presented with any visual complaints, growth anomalies or intracranial mass lesions. ONs were measured bilaterally from the posterior of the globe to the middle of the optic chiasm on both using the Siemens Leonardo workstation. Results were averaged. ON size was averaged for both sides from all individuals, with mean length in mm +/- SD reported.
Results :
The mean newborn ON is 25.3+/-mm in length, reaching 45.3mm (adult) by 20 years of age. This is an increase of 80%. Human optic nerve growth is linear in the first three years of life, reaching 86% of the total adult length by this time (Fig 1; area indicated by (1): slope y=4.55x+24.214; r2=0.9991). The ON continues slow growth, until ~15 y/o (Fig 1; area indicated by (2): slope y=0.52x + 36.7; r2=0.8214). AP ON length is stable thereafter through 20y (Fig).
Conclusions :
This is the first neuroradiological survey of in vivo total ON growth from birth to maturity. Our data reveal that the human ON grows by 80% after birth, with the greatest linear growth occurring within the first three years of postnatal life. ON growth continues at a slower rate from 5-15 years and then stops. This growth pattern likely corresponds to the increase in skull size around the age of puberty, and final skull growth. This data has relevance both to early antimetabolic treatments for cancer, as well as pinpointing the enhanced growth capacity of the juvenile ON, compared with adult ON.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.