Postoperative Vision Loss

Applied Anatomy of Visual Pathway

The visual pathway is the pathway over which a visual sensation is transmitted from the retina to the brain. This includes a cornea and lens that focuses images on the retina, and nerve fibers that carry the visual sensations from the retina through the optic nerve. Optic nerve fibers travel through the optic chiasma to the lateral geniculate body of the thalamus, and optic radiations terminate in an occipital lobe ( Figure 1 ). Each optic nerve carries the fibers from only the ipsilateral retina, while the optic chiasma contains fibers from both the eyes. These fibers pass through the lateral geniculate body on the same side of the brain then reach the occipital lobe through optic radiations.

Interruptions anywhere in the visual pathway can lead to the blindness.

Arterial Supply of the Optic Nerve

The predominant blood supply of the eye is by the ophthalmic artery (OA), which is the first intracranial branch of the internal carotid artery ( Figure 2 ). The OA gives the posterior ciliary arteries, the central artery of retina, and pial arteries along the optic nerve. The anterior portion of the optic nerve is profusely supplied by various sources, including posterior ciliary arteries and Circle of Zinn–Haller formed by choroidal, posterior ciliary arteries. The posterior segment receives blood supply from the adjacent carotid and hypophyseal arteries. The middle segment of the optic nerve is supplied only by small pial arteries, which are less dense in the middle segment as compared to retrobulbar segment, putting it at risk of ischemia.

Causes of POVL

Vision loss after spinal surgery can be categorized into five groups:

• 1.

  External ocular injury (corneal abrasion or sclera injury)

• 2.

  Retinal ischemia

• 3.

  Ischemic optic neuropathy (INO)

• 4.

  Cortical blindness

• 5.

  Acute glaucoma

• 6.

  Posterior reversible encephalopathy syndrome (PRES)