Ophthalmic artery occlusion: a cause of unilateral visual loss following spine surgery.

Dear Editor,

Blindness can be a complication with far-reaching medicolegal implications in anesthesia practice. Alterations in vision and blindness after anesthesia for major surgical procedures, particularly cardiopulmonary bypass or spine surgery, are well-documented, with an incidence varying between 0.05% and 1%.1 A review of eye injuries after nonocular surgeries published twice as, The Practice advisory by the American Society of Anesthesiologists have listed various causes of perioperative visual loss after nonocular surgeries.2,3

We believe ophthalmic artery occlusion should be included in this list and appropriate measures should be taken to prevent this complication. The following case is instructive.

A nine-year-old boy underwent ′uneventful′ corrective spinal surgery for atlanto-axial subluxation following rheumatic fever. The surgery was performed in a prone position lasting six hours and 30 min. The blood loss was 150-200 ml. The child was hemodynamically stable throughout the procedure. Preoperative hemoglobin level was 12.5 gm/dl. The child complained of total blindness in the left eye immediate postoperatively. Ophthalmic reference was sought after two weeks.

The right eye was normal. The vision in the left eye was no light perception with relative afferent pupillary defect. Intraocular pressure in the right eye was 17 mmHg and in the left eye was 12 mmHg. Fundus examination in the left eye showed diffuse disc pallor, severe attenuation of retinal vessels (arteries as well as veins), diffuse opacification of the retina with a ′featureless′ appearance [Fig. 1]. An optical coherence tomography (OCT) of the retina [Fig. 2] showed hyper-reflectivity of the retinal layers with normal retinal thickness in the left eye.

Figure 1

50° fundus photograph showing normal right eye picture (A) and disc pallor, vascular attenuation and featureless retina of the left eye (B)

Figure 2

Optical coherence tomography picture showing normal right eye (A) and hyper-reflectivity of the retinal layers in the absence of retinal thickening of the left eye (B)

Color Doppler imaging of orbital vessels could not be done due to financial constraints. Nevertheless, typical clinical features and OCT picture confirmed the diagnosis of ophthalmic artery occlusion on the left side.

The neurosurgeon believed that inadvertent prolonged compression of the left eye in prone position was the cause of this complication. Prolonged ocular compression is a recognized cause of ophthalmic artery occlusion.4,5 Other potential causes of visual loss after nonocular surgeries under general anesthesia are acute blood loss, anemia, hypotension, hypoxia and circulatory shock. Prone and Trendelenburg positions can lead to visual loss related to decreased venous return from the head.6 Visual impairment may also result from increased intracranial pressure, which contributes to undue pressure on the optic nerve. Cerebral embolism is rare but can be associated with occipital cortical infarct or cortical blindness. The prognosis for visual recovery from ischemic neuropathy and retinal artery occlusion is poor. Cortical blindness usually improves to varying degrees. Effective treatment of perioperative amaurosis is lacking and usually ineffective, making prevention the cornerstone of management. Unacceptable hemoglobin and hematocrit values should be corrected preoperatively and levels monitored during the surgery to avoid intraoperative anemia in at-risk patients. The blood pressure of patients with predisposing diseases should be kept within normal limits. To avoid this devastating complication, it is imperative that anesthesia providers understand contributing factors and prevention strategies.

Anesthesiologists should be aware of ophthalmic artery occlusion as a possible cause of perioperative visual loss. Understanding of possible mechanisms and taking preventive measures can avert this complication.