A new laser induced traumatic optic neuropathy model

Abstract

Purpose: Current models of traumatic ocular neuropathy rely on blunt force trauma delivered by direct weight contact or compressed air to the eye. These models generate gross generalized damage that can often very severe and not mimic what is observed with humans. We have developed a novel retinal injury animal model using a Nd:YAG laser generating a photodisruptive force above the retina to focus injury of a determined magnitude reliably into the rodent eye which is reproducible, can be followed longitudinally in vivo, is limited to the eye and does not result in mortality, and which more closely mimics the types of retinal injury and structural damage observed with human traumatic optic neuropathy.

Methods: A Nd: YAG l laser was used to generate a photodisruptive blast injury with 0.4 mJ of energy above the level of the retina and behind the lens in the peripapillary region in Thy1-ChR2/EYFP murine eyes (n=45). Eyes were imaged using spectral domain optical coherence tomography (SD-OCT) and a confocal scanning laser ophthalmoscope (CLSO) before laser treatment and up to 20 weeks after treatment along with IOP measurements. Mice were sacrificed at various time points and perfused transcardially with paraformaldehyde. Histology of whole mount retina and retinal sections was determined with hematoxylin/eosin (HE) and immunostaining with RGCs markers, such as brn3b and thy-1.

Results: After one week, the retina ganglion cells (RGCS) were observed to be significantly diminished in number in a wedge shape origination from the circumpapillary region of laser treatment as measured by CSLO (HRT). By 20 weeks, a similar pattern of ganglion cell layer loss was measured using SD-OCT. IOP was not statistically different at all measured time points. Histologically, HE staining demonstrated a significant loss of RGCS and nerve fiber layer, consistent with the imaging results from SD-OCT and CSLO only in laser associated regions. Similarly, immunohistological staining for RGC markers confirmed RGC loss in the regions of laser treatment compared to adjacent non-lasered regions of the retina.

Conclusions: We developed a new model using a photodisruptive force generated by a Nd:YAG laser to reliably deliver blunt trauma to the retina and cause loss of RGCs and nerve fibers similar to that observed in traumatic optic neuropathy that is amenable to study of neuroprotective strategies in vivo.

Keywords: 695 retinal degenerations: cell biology • 742 trauma • 531 ganglion cells