Optic Nerve Crushed Mice Followed Longitudinally With Spectral Domain Optical Coherence Tomography (SD-OCT)

Abstract

 

Purpose:

 

To investigate the longitudinal effect of optic nerve crush injury on adult mice using SD-OCT and ganglion cells (RGC) quantification using flow cytometry.

 

Methods:

 

Five C57Bl/6 mice were anesthetized for volumetric baseline imaging of both eyes with SD-OCT (1.5x1.5x2.0 mm scan; Bioptigen, Durham, NC), centered on the optic nerve head (ONH). Optic nerves of one eye from each mouse were crushed under direct visualization for 3 seconds, 1 mm posterior to the globe. The ONHs of both eyes were imaged for up to 23 days post-injury using SD-OCT. Enface SD-OCT images were used to manually register all subsequent scans to the baseline enface image. Retinal thickness measurements from each day of follow-up were compared to baseline using custom software. Thickness measurements were taken along a sampling band with radii of 0.33-0.42 mm centered on the ONH. At 23 days, three mice were sacrificed, eyes were removed and then rendered into a single cell suspension by incubation in 1 mg/ml collagenase IV supplemented with 1% FBS. RGCs were enumerated by flow cytometric analysis using anti-CD45 and anti-CD90.2 (Thy1.2) antibodies.

 

Results:

 

Marked increase followed by a decrease in retinal thickness was seen in nerve-crushed eyes that may reflect an early inflammatory response (Figure b). The decrease in retinal thickness appears to stabilize 7-12 days post nerve crush. Control eyes showed and early decrease in retinal thickness that stabilizes at the same time as the experimental eye (Figure a). Experimental eyes had thinner retina than control eyes after one week (Figure c). Flow cytometry indicated an average reduction in RGC of 26.1±10.2%.

 

Conclusions:

 

An overall retinal thinning was seen in nerve-crushed eyes after an initial phase of thickening. SD-OCT can be used to quantitatively monitor changes in retinal thickness in mice over time.  

 

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