Morphology of the murine optic nerve

Area of Science:

• Ophthalmology
• Neuroscience
• Comparative Anatomy

Background:

• The optic nerve (ON) transmits visual information from the retina to the brain.
• Understanding the structural and vascular anatomy of the ON is crucial for studying optic neuropathies like glaucoma.

Purpose of the Study:

• To investigate the detailed morphology of the murine optic nerve.
• To characterize the vascular supply and glial composition of the mouse ON.

Main Methods:

• Light and electron microscopy were used to examine C57/Bl6 and BalbC mouse eyes.
• Microvascular casting and scanning electron microscopy visualized the ON vasculature.
• Immunohistochemistry identified glial fibrillary acidic protein (GFAP), connexin 43, carbonic anhydrase II, and collagen types I and III.

Main Results:

• The transition from nonmyelinated to myelinated ON occurred 0.6 mm behind the globe.
• A lamina cribrosa was absent; axons passed through a scleral hole with collagenous support.
• Elongated astrocytes, positive for GFAP, formed layers within the ON, replacing connective tissue beams.
• The nonmyelinated ON received arterial supply from the central retinal artery, with no contribution from choroidal vessels.

Conclusions:

• The mouse ON head exhibits unique features, notably the absence of a lamina cribrosa and choroidal vascular supply.
• These distinct anatomical characteristics in mice may impact the relevance of glaucoma models.
• Further research in glaucomatous mice is needed to ascertain the roles of the lamina cribrosa and choroidal vasculature in optic nerve damage.