Affiliation:
1. The Hong Kong Polytechnic University
Abstract
Abstract
Background
Myopia is the leading cause of distance refractive error, in which objects form in front of the retina rather than on the retina itself during emmetropization. Mice is an emerging model for experimental myopia. This study aims to compare ocular biometric measurements with Purkinje image-based and optic nerve head alignment methods of normal eyes in C57BL/6J mice.
Methods
Ocular dimensions and refractive development were measured on postnatal days P21 (n = 10), P28 (n = 15), and P35 (n = 8). The Purkinje image-based alignment (P1) was determined by a photorefractor and aligned perpendicular to the corneal apex using spectral domain optical coherence tomography (SD-OCT). In comparison to the optic nerve head (ONH) alignment due to the lack of fovea in mice retina. Variance analysis, regression analysis and Bland‒Altman analysis were performed to compare differences between alignment methods and replication by another operator.
Results
Mice developed hyperopic ametropia under normal visual conditions. The photorefractor measured a technical variation of 3.9 D (95% CI, n = 170, triplicates). Bland-Altman analysis revealed a shorter (mean ± SD) axial length (-26.4 ± 18.1 µm) and vitreous chamber depth (-39.9 ± 25.4 µm) in Purkinje image-based alignment. Significant difference in the relative growing trend in VCD (linear regression, p = 0.02), relatively stable and shortening when measured with ONH alignment from postnatal age 21 to 35 days.
Conclusions
SD-OCT allowed precise in-vivo ocular dimension measurement and segmentation. A significantly shorter AL and VCD were observed in Purkinje image based (P1) alignment compared to ONH method, highlighting the importance of alignment methods in optical based technique that may introduce false positive axial elongation in myopia research. Axial length has better consistency over VCD for the evaluation of axial elongation.
Publisher
Research Square Platform LLC