Abstract
Purpose: :
To visualize the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) in DBA/2J mice by using spectral-domain optical coherence tomography (SD-OCT) with speckle noise reduction and to compare the thickness of the ganglion cell layer complex (GCC) and RNFL among mice of different ages.
Methods: :
An eye-tracking SD-OCT system for animals (Multiline OCT; Heidelberg Engineering) was used to scan the eyes of 2- to 7-month-old DBA/2J mice (n = 10), which are a mouse model of secondary angle-closure glaucoma. Each retinal layer, including the RNFL, GCL, and inner plexiform layer (IPL), was visualized; for the procedure, the speckle noise was reduced by averaging 100 B-scans at each identical location of interest. Twelve radial scans through the optic disc and 1 circular scan around the optic disc were performed. We manually measured the thickness of the GCC (RNFL + GCL + IPL) and RNFL in each of the 4 segments (superior, inferior, nasal, and temporal segments) and compared the thickness of these layers among the 4 segments. The thickness was also compared among the mice of different ages. The intraocular pressure (IOP) of each mouse was measured using a tonometer (TonoLab; Tiolat).
Results: :
The mean IOP in the 7-month-old mice was higher than that in the 2-month-old mice (20.6 mmHg and 10.4 mmHg, respectively). In the 2-month-old mice, the mean thickness of the GCC was 69.2 µm, 71.4 µm, 68.3 µm, and 67.7 µm in the superior, inferior, nasal, and temporal segments, respectively. The mean (SD) thickness across all segments of the GCC in the 7- and 2-month-old DBA/2J mice was 67.6 (3.7) µm and 69.1 (3.4) µm, respectively (p = 0.1, t test). In contrast, the mean RNFL thickness in the 7-month-old mice was significantly lesser than that in the 2-month-old mice (27.6 (1.4) µm and 29.7 (1.5) µm, respectively; p = 0.0025, t test).
Conclusions: :
The RNFL and GCL in DBA/2J mice could be clearly visualized using SD-OCT. The RNFL was thinner in older mice that had a higher ocular pressure than in younger mice that had a lower ocular pressure. Imaging of the RNFL and inner retinal layer by using SD-OCT is an excellent noninvasive approach to assess changes in a mouse glaucoma model.
Keywords: nerve fiber layer • ganglion cells • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)