Abstract
Purpose: :
The C57BL/6 mouse is commonly used in ophthalmic research and the central corneal thickness (CCT) is often one of the parameters of interest. However, there is a large discrepancy in values reported, many of which were determined from histological specimens, and minimal details provided for the early postnatal period. The purpose of this study was to determine changes in postnatal murine CCT using, for the first time, spectral domain optical coherence tomography (SD-OCT), thereby avoiding tissue fixation effects, and to compare these results to those from histological sections.
Methods: :
Spectralis, a spectral domain OCT instrument, was optically modified to obtain high resolution images of the mouse anterior segment and was calibrated for accurate axial measurements. Thirty mice (C57BL/6) from P0-P42 and thirty-two mice greater than P42were euthanized, weighed, and scanned with SD-OCT. Eyes were collected and processed for histological sections. ImageJ software was used to measure the CCT in the OCT scanned images as well as the histological micrographs.
Results: :
Both methods of measurement showed a linear, rapid increase in CCT for the first 42 postnatal days before leveling off. Compared to SD-OCT , histology measurements followed a steeper slope and resulted in a final value nearly 25% thicker. SD-OCT produced the highest coefficient of determination (r2=0.86) and showed an increase in CCT from approximately 58µm at P0 to 126µm at P42. Bland-Altman analysis of right and left eye measures was used as an indication of instrument reliability where SD-OCT clearly showed greater agreement.
Conclusions: :
The first 6 weeks postnatal is a time of continued development and rapid maturation in the mouse, as evidenced by changes in CCT. However, preparation of histological sections results in variable CCT values. SD-OCT avoids the harsh effects of tissue fixatives and provides a reliable measure of CCT, as well as high resolution images of the entire cornea. In addition, SD-OCT provides the means to assess in vivo morphology in the murine anterior segment and follow it over time. Perhaps SD-OCT should be considered as a benchmark for histological specimen preparation and for other methods of CCT measurement.
Keywords: cornea: basic science • development • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)