Postoperative blindness is a serious condition with risk factors including intraoperative hypotension, prone position, and anemia. Immediate consultation with an ophthalmologist is necessary. The etiology of postoperative blindness can include ischemic optic neuropathy and/or retinal vessel occlusion.
Ischemic Optic Neuropathy
Ischemic optic neuropathy is caused by inadequate blood supply to the optic nerve. This condition can be triggered by various factors, including intraoperative hypotension (low blood pressure during surgery), blood loss leading to anemia, and prolonged surgery, especially in the prone position. These factors can lead to reduced perfusion of the optic nerve, resulting in ischemia and subsequent optic nerve damage. There are two types of ischemic optic neuropathy: anterior, which affects the front part of the optic nerve and can present with optic disc edema, and posterior, which affects the back part of the optic nerve and may initially show a normal fundoscopic exam but later present with delayed optic disc edema. Both types can lead to significant and often permanent vision loss.
Retinal Artery or Vein Occlusion
Retinal artery or vein occlusion usually causes unilateral vision loss. Examination may reveal a cherry red spot with retinal edema. Retinal artery or vein occlusion during surgery can be caused by several factors related to the surgical procedure and the patient's condition:
- Intraoperative Hypotension: Low blood pressure during surgery can reduce blood flow to the retina, increasing the risk of vessel occlusion.
- Prolonged Prone Position: Being in a prone position for an extended period can increase venous pressure and reduce arterial perfusion to the eyes, leading to occlusion.
- Blood Loss and Anemia: Significant blood loss and resulting anemia can decrease oxygen delivery to the retina, making the retinal vessels more susceptible to occlusion.
- Direct Pressure on the Eyes: Improper positioning or padding can result in direct pressure on the eyes, leading to compression of retinal vessels and subsequent occlusion.
- Embolism: Air or particulate emboli can be introduced during surgery, which can travel to the retinal vessels and cause blockage.
- Systemic Conditions: Underlying systemic conditions such as hypertension, diabetes, or cardiovascular disease can predispose patients to retinal vessel occlusion, which may be exacerbated by the stress of surgery.
- Vascular Spasm: Surgical stress and anesthesia can lead to vascular spasm, reducing blood flow to the retina and increasing the risk of occlusion.
