(Table 48-8: Postoperative Ocular Complications).
The incidence of eye injuries associated with nonocular surgery is very low (0.056%). Certain types of surgery, including complex spinal surgery in the prone position, operations involving extracorporeal circulation, and nasal or sinus surgery, may increase the risk of serious postoperative visual complications. Injuries associated with regional anesthesia for ophthalmic surgery are typically permanent and related to the block technique.
- Corneal abrasion is the most common ocular complication after general anesthesia (incidence of 0.15–0.17% when the eyes are protected). Patients complain of pain and a foreign body sensation that is exacerbated by blinking. An ophthalmology consultation is appropriate, and treatment is prophylactic topical application of antibiotic ointment and patching of the injured eye. Healing usually occurs within 24 to 48 hours.
- Retinal ischemia may result from external pressure on the globe (causing central retinal artery occlusion) as during surgery in the prone position. (It is critically important to monitor external pressure on the eye in the prone position.)
- Pathognomonic findings of central retinal artery occlusion on funduscopic examination reveal a pale, edematous retina and a cherry red spot.
- Embolic or arteritic causes of central retinal artery occlusion may be discovered via echocardiography, carotid ultrasonography, and temporal artery biopsy.
- Ischemia optic neuropathy (ION) is the most common cause of visual loss in patients older than 50 years of age. The incidence of postoperative vision loss after spine surgery performed in the prone position may be as high as 0.1%. (It is prudent to discuss this potential complication before surgery as part of the informed consent process.)
- Anterior ischemic optic neuropathy is thought to reflect temporary hypoperfusion or nonperfusion of the vessels supplying the anterior portion of the optic nerve. Patients typically experience painless visual loss in the early postoperative period that is associated with an afferent pupillary defect and optic disc edema or pallor. Magnetic resonance imaging initially shows enlargement of the optic nerve followed by optic atrophy. Visual loss is usually permanent.
- Posterior ischemic optic neuropathy is produced by decreased oxygen delivery to the retrolaminar part of the optic nerve. (Posterior optic nerve has a less luxuriant blood supply than the anterior optic nerve.) Most cases of perioperative ION associated with spine surgery occur in the posterior optic nerve.
- The etiology of ION may be more influenced by intraoperative factors than by any known pre-existing comorbidities or vasculopathy (Table 48-9: Etiology of Ischemic Optic Neuropathy Following Spine Surgery).
- At least half the risk factors support the speculation that acute venous congestion of the optic canal is a potential contributor to perioperative ION.