Purpose  To investigate the influence of myopia and blood vessel location on retinal nerve fiber layer thickness profile measured with spectral-domain optical coherence tomography (Cirrus HD OCT) in normal subjects.
Methods  A total of 105 eyes from 105 healthy subjects were included. The peripapillary retinal nerve fiber layer in each eye was imaged with Cirrus HD OCT (Carl Zeiss Meditec, Dublin, CA). The midpoints between the major superior temporal vein and artery and the major inferior temporal vein and artery were determined and converted to degrees at the location where the vessels cross the 3.46 mm circle. The angles of the superior and inferior peaks in the RNFL thickness profile were recorded. Based on the internal normative database, abnormal red superpixels in the deviation map were calculated with automatic software developed from Matlab. The associations of the angles of the peaks in the RNFL thickness profile with the axial length and blood vessel location were analyzed by Pearson correlation analysis. Multivariate regression analyse was used to investigate the association between age, axial length, blood vessel angle and abnormal red superpixels.
Results The mean age and axial length were 22.64± 3.92 years (range, 18–40) and 25.55 ±1.11 mm (range, 22.52–28.77mm). Significant interindividual variations were found in the blood vessel locations and angles of the peaks in the RNFL thickness profile. The angles of RNFL thickness peak correlated significantly with the axial length and blood vessel angles (r=-0.32 and 0.69, all with p<0.01). Both axial length and blood vessel angle were independently associated with abnormal red superpixels.
Conclusions Axial length and blood vessel location significantly affected the RNFL profile. Eyes with long axial length and horizontally deviated blood vessels differ considerably from the normative data provided with the HD-OCT system. The myopia status and blood vessel location should be taken into account when interpet the results of the RNFL thickness measured with OCT .