P317
Second degree polynomial approach of retinal nerve fiber trajectories and its
association with axial length in healthy eyes
Takehiro Yamashita, Taiji Sakamoto, Yuya Kii, Minoru Tanaka, Kumiko Nakao
Department of Ophthalmology, Kagoshima University Medical and Dental Hospital, Kagoshima - Japan
Purpose: To investigate the second degree polynomial approach of retinal nerve fiber (RNF) trajectories using
red free fundus photographs and its association with axial length in young Japanese healthy eyes.
Methods: A Prospective observational cross-sectional study comprised 109 right eyes of 109 healthy young
Japanese participants. All participants (mean age 25.6 ± 3.5) underwent comprehensive ophthalmologic
examination, including axial length, red free fundus photograph and optical coherence tomography (OCT)
peripapillary retinal nerve fiber layer (RNFL) thickness imaging. Supra and infra temporal peak RNFL thickness
positions were assessed using the Spectralis OCT RNFL circle scan images. The trajectory of the RNF passing
through the supra and infra temporal peal RNFL thickness position was plotted in red free fundus photograph
and was fitted to second degree polynomial (ax*x/100+bx+c) using Image J. The coefficient ‘a’ was used for the
degree of the RNF trajectory. Intraclass correlation coefficient was used as a measure of reliability within raters.
The relationship between the RNF trajectory and the axial length was investigated using linear regression analysis.
Results: The mean axial length was 25.5 ± 1.4 mm and the mean RNF trajectory was 0.472 ± 0.123. Intrarater and inter-rater correlation coefficients of the RNF trajectory were 0.954 and 0.881, respectively. The RNF
trajectory was significantly positively associated with the axial length (R = 0.34, p < 0.001).
Conclusions: In this second degree polynomial approach, the longer axial length made the RNF trajectory
appear more close to the fovea.