Model Introduction
Traumatic Optic Neuropathy (TON) is a nerve injury caused by direct or indirect trauma leading to ischemia, edema, inflammation, rupture, or atrophy of the optic nerve. This condition is a severe blinding eye disease, occurring in 0.5%–5% of patients with craniocerebral injury. It has a poor prognosis, often leaving permanent visual impairment, and is a major cause of disability from head trauma. There is currently no universally accepted effective treatment. Establishing stable, reproducible optic nerve injury animal models for intervention research is of great significance for elucidating injury mechanisms and exploring effective treatment strategies. Common experimental animals include mammals such as rats, rabbits, cats, and dogs. Among these, rats are the most commonly used small animal model due to their cost-effectiveness, ease of handling, deep retinal pigment layer, and the convenience of retinal flat-mounting.
Research Applications
Traumatic optic nerve injury animal models can be used to:
- Study mechanisms of optic nerve ischemia, edema, and inflammatory response;
- Observe nerve fiber rupture and degenerative changes;
- Analyze the progressive loss of retinal ganglion cells (RGCs);
- Evaluate functional impairment changes under different injury severities;
- Explore neuroprotective and regenerative intervention strategies.
Key Points of Experimental Design
I. Optic Nerve Transection Model The simplest model to establish with easily unified injury standards.
- Method: After anesthesia and fixation, the bulbar conjunctiva is incised under an operating microscope. The lateral rectus muscle is bluntly dissected, and the eyeball is retracted to expose the optic nerve, which is then transected behind the globe.
- Advantages: Consistent injury volume, simple operation, facilitates controlled studies.
- Limitations: Not conducive to repair and regeneration research.
II. Optic Nerve Crush Model Currently the most widely used method, closest to clinical optic nerve contusion; primarily used for incomplete injury research.
- Method: The optic nerve is exposed and crushed behind the globe using calibrated forceps, avoiding injury to the ophthalmic artery. Duration and force vary by design (e.g., using a force equivalent to 50g or 60g for 10–30 seconds).
- Validation: Optic nerve swelling, sparse and edematous nerve fibers, gradual reduction of RGCs.
- Advantages: Simple operation, no craniotomy required, intact optic nerve sheath, high survival rate, aligns with clinical contusion characteristics.
- Disadvantages: Lack of unified crushing standards, operator-dependent, difficult to quantify precisely.
III. Optic Nerve Impact Model An indirect injury model resembling clinical indirect optic nerve injury. Divided into closed and open types.
- Closed Impact: Animals are fixed in a helmet, and an accelerated impactor strikes the head to cause indirect injury.
- Open Impact: After exposing the orbital wall and optic nerve canal area, a Fluid Percussion Injury (FPI) device is used for quantitative impact.
- Manifestations: Gradual reduction of retinal cells, new axon formation (more in mild than severe groups), prolonged F-VEP latency, and reduced amplitude.
- Advantages: Maintains optic nerve integrity, quantifiable injury, good reproducibility (open model is closer to clinical cases).
- Disadvantages: Open surgery is complex with high equipment requirements; closed surgery has a low success rate and high mortality.
IV. Optic Nerve Traction Model
- Method: After anesthesia and conjunctival incision, the eyeball is pulled outward until the posterior pole is level with the orbital rim, then repositioned.
- Advantages: Strong clinical relevance, accurately quantifiable injury.
- Disadvantages: Complex device, many surgical steps, not suitable for large-scale implementation.
Key Detection Indicators
Histological Indicators:
- Optic nerve swelling and edema
- Nerve fiber density
- Retinal Ganglion Cell (RGC) count
- Axonal regeneration
Functional Indicators:
- Flash Visual Evoked Potential (F-VEP) latency
- F-VEP amplitude changes
- Injury severity grading
Model Evaluation Dimensions:
- Injury Types: Transection, Crush, Impact, Traction.
- Evaluation Criteria: Clinical relevance, Quantifiability, Reproducibility, Complexity, Survival rate.
