Abstract
Purpose: :
To visualize and assess changes in the retinal ganglion cells (RGCs) and ganglion cell layer (GCL) of eyes with acute retinal ganglion cell damage in Thy 1-CFP mice by using a custom-made system combining eye-tracking function (Heidelberg Engineering) with HRA (445 nm, 448 nm) and speckle-noise-reduced spectral-domain optical coherence tomography (SD-OCT).
Methods: :
N-methyl-D-aspartate (NMDA) (20 nmol/2 µl) was injected into the vitreous of the eye in Thy 1-CFP mice (n = 4). HRA and OCT examinations were performed simultaneously 4 and 7 days after the injection. The same volume of phosphate-buffered saline (PBS) was injected intravitreally into animals of different groups. RGCs were visualized by scanning with 445-nm laser diodes. The number of RGCs was counted within 6 squares of area 100 × 100 µm at a distance of approximately 200 µm from the optic nerve head and the results were averaged. Visualization of GCL and RNFL on SD-OCT scans was enhanced by reducing speckle noise, which was done by averaging 50 B-scans at each identical location of interest. In SD-OCT, 12 radial scans through the optic disc and circle scans around the optic disc were acquired, and the ganglion cell layer complex (GCC: RNFL+GCL+IPL) thickness was manually measured. The number of RGCs and the thickness of the GCC were compared between groups.
Results: :
Before NMDA injection, the mean number of RGCs was 39.8 (2.0) µm and the mean GCC thickness was 69.0 (3.2) µm. Four and seven days after the NMDA injection, the mean number of RGCs dramatically decreased to 8.7 (1.4) and 7.3 (1.5), respectively, but the mean GCC thickness gradually decreased to 54.8 (2.2) µm and 47.5 (3.8) µm, respectively.
Conclusions: :
Simultaneous visualization and follow-up of damage in the RGCs and GCL were possible with HRA and speckle-noise-reduced SD-OCT with an eye-tracking system.
Keywords: ganglion cells • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)