Prolonged Surgery: Studies have shown a significant increase in postoperative visual loss incidence when surgery duration exceeds 6 hours. This is because long periods of low perfusion pressure and high intraoperative fluid shifts lead to tissue edema, including in the optic nerve.
Blood Loss (more than 1 liter): Surgeries with blood loss of more than 1 liter, such as cardiac and spinal fusion surgeries, increase ischemic conditions that cause visual impairment. Blood loss is related to ischemic optic neuropathies, as it reduces oxygen delivery to the optic nerve. Aggressive blood loss management is important to reduce the risk of postoperative visual loss.
Prone Position during Surgery: Spine surgeries often require patients to be in a prone position. Pressure on the abdomen in the prone position increases venous congestion, elevates intraocular pressure, and reduces optic nerve perfusion.
Spinal Instrumentation: Complex spine surgeries, especially those involving long-segment fusion or instrumentation, are associated with high risks of prolonged anesthesia, increased blood loss, and greater chances of optic nerve ischemia.
Use of the Wilson Frame: The Wilson frame arches the patient so the head lies below the heart, increasing venous congestion and periocular edema; its use was one of the six independent ION risk factors in the ASA registry case-control analysis (with male sex, obesity, longer anesthetic duration, greater blood loss, and a lower colloid proportion). A Jackson table, which keeps the head level with the heart and the abdomen hanging free, is the preferred alternative.
| Item | Recommendation | Rationale |
|---|---|---|
| Horseshoe headrest | Avoid | Compresses the eyes in the prone position and can cause anterior ischemic damage |
| Mayfield pins or tongs | Substitute for the horseshoe headrest | Prevents direct eye pressure and reduces the incidence of anterior ischemic optic neuropathy |
| T-pillow | Substitute for the horseshoe headrest | Prevents direct eye pressure and reduces the incidence of anterior ischemic optic neuropathy |
| Three-pin head holder | Appropriate headrest choice | Minimizes pressure on the globe and optic nerve |
| Jackson table or Wilson frame | Position the head level or slightly elevated; avoid excessive head-down positioning | Head-level or slightly elevated positioning on the Jackson table reduces venous congestion; the surgical table and positioning frames used in spine surgery can increase the risk of venous stasis and ocular compression, compromising optic nerve blood flow |
| Eye tape or ointment | Keep the eyes closed throughout | Prevents corneal abrasion; avoiding external pressure on the eyes also reduces the risk of central retinal artery occlusion |
