Investigating animal models of optic neuropathy: An accurate method for optic nerve and chiasm dissection in mice

Numerous disorders affecting the optic nerve require histological examination of whole length optic nerves and chiasm. Most methods employed to study the histopathology of the optic nerves in animal models of human diseases involve resection of a short retrobulbar section after eye globe exenteration, commonly obtained in mice. This approach might affect the morphology of the optic nerve, thus limiting accurate identification of pathological changes in the tissue. Some histological studies were performed on longer or more posterior parts of the anterior visual pathway included the chiasm. However, an accurate replicable protocol for such whole length (eye globe to chiasm) dissection is currently unavailable in published literature. Here we describe a protocol for dissecting the whole length of the optic nerves and chiasm through a craniotomy incision. We describe in detail the stages necessary for exposing the optic nerves, the chiasm and the optic tracts, and for detaching them with minimal traction. The existing replicable method provide only a sample of the retrobulbar optic nerve and the sample might be affected by traction. Our protocol provides a whole length specimen of the optic nerve and chiasm without concern of traction artifacts. We present a simple and straightforward approach to isolate the complete anterior visual pathway in the mouse for histopathological evaluation.