Imaging of Retinal Ganglion Cells and The Ganglion Cell Layer in GLAST knockout mice by using Short-wave-length Confocal Scanning Laser Ophthalmoscope and Speckle Noise-reduced Spectral-domain Optical Coherence Tomography

Abstract

Purpose: : It has been reported that glutamate/aspartate transporter (GLAST)-deficient mice demonstrate spontaneous retinal ganglion cell (RGC) and optic nerve degeneration without elevated intraocular pressure. ¹⁾ The purpose of this study was to visualize and assess changes in RGCs and the ganglion cell layer (GCL) in the eyes of GLAST knockout mice by using a custom-made system that combines an eye-tracking system (Heidelberg Engineering) with short-wave-length confocal scanning laser ophthalmoscope (scSLO) and speckle noise-reduced spectral-domain optical coherence tomography (SD-OCT).

Methods: : Simultaneous scSLO and SD-OCT examinations were performed at 21, 28, 35, 49, and 90 days of age in GLAST -/-: Thy1-CFP Tg and GLAST +/+: Thy1-CFP Tg mice (n = 6 each). RGCs labeled with cyan fluorescent protein were visualized by scanning with 445-nm laser diodes. The number of RGCs was counted within 4 squares of area 310 × 310 µm at a distance of approximately 830 µm from the optic nerve head, and the results were averaged. A circular scan around the optic disc was acquired using speckle noise-reduced SD-OCT, and the thickness of the ganglion cell complex (GCC), which includes the retinal nerve fiber layer (RNFL), GCL, and inner plexiform layer (IPL), was measured manually. The number of RGCs and the thickness of the GCC were compared between groups.

Results: : The mean number of RGCs in 21-day-old GLAST -/- mice (35.0 [3.5]) was <30% of that in GLAST +/+ mice; however, the GCC thickness (76.0 [2.8] µm) was approximately the same in the 2 groups. In GLAST -/- mice, the number of RGCs further decreased through 49 to 90 days of age. In contrast, the GCC thickness dramatically decreased through day 28 (74.0 [2.8] µm) to 35 (60.0 [2.9] µm). At 90 days of age, the GCC thickness in 90-day-old GLAST -/- mice was 54.3 (1.2) µm and thinner than that in 90-day-old GLAST +/+ mice. In addition, there was almost no difference in the GCC thickness and the number of RGCs in the GLAST +/- and GLAST +/+mice.

Conclusions: : Simultaneous visualization and follow-up of damage in the RGCs and GCL in GLAST -/-: Thy1-CFP Tg mice was possible with scSLO and speckle noise-reduced SD-OCT combined with an eye-tracking system.Ref 1) : Harada T et al. J.Clin.Invest, 2007

Keywords: ganglion cells • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer