Perioperative Vision Loss

What is Perioperative Vision Loss?

Perioperative vision loss (POVL) means a person experiences complete or partial loss of vision after undergoing surgery that is not related to their eyes. It may show symptoms similar to different eye conditions. The first known case of POVL was reported in 1948 when a patient suffered a suspected optic globe injury (damage to the eyeball) due to too much pressure from an incorrect positioning on the headrest. It’s a rare, but very serious side effect that is usually realized when the patient is waking up from anesthesia, but they may also discover it shortly after their surgery.

What Causes Perioperative Vision Loss?

Postoperative Vision Loss (POVL), or unexpected loss of eyesight following surgery, has been found to occur most commonly with heart and spine operations. However, it can also happen after orthopedic surgeries (involving bones and muscles) that are not related to the spine, and surgeries in the abdomen.

The likelihood of experiencing POVL is estimated to be around 0.03% for spine fusion surgery, wherein parts of the spine are joined together, and 0.09% for heart surgeries. Among all types of surgeries, certain spine procedures may carry the highest risk of POVL. Specifically, surgeries for correcting scoliosis (a sideways curvature of the spine) and posterior lumbar fusion (joining together the lower part of the spine from the backside) pose a risk of POVL of about 0.28% and 0.14% respectively.

In operations focusing on the spine where the patient lies face-down, the most common type of POVL is Ischemic Optic Neuropathy (ION). ION happens when the blood supply to the eye’s optic nerve is blocked, potentially leading to vision loss. Projected occurrences of ION vary from 0.017% to 0.1%.

Other significant risk factors that might increase the chance of ION (besides the individual’s personal health traits) include using the Wilson frame (a special surgical table), the length of time under anesthesia (which often indicates how long the surgery lasts), the amount of blood loss during surgery, and getting more crystalloid (a type of fluid) than colloid (another type of fluid) in the fluids given to replace lost blood during the procedure.

Risk Factors and Frequency for Perioperative Vision Loss

People diagnosed with Postoperative Vision Loss (POVL) after spine surgery are often low-risk patients, according to the American Society of Anesthesiologists (ASA) grades I and II, meaning they have a minimal risk of complications related to anesthesia. POVL’s risk assessment strategies are therefore very different from the usual methods for assessing anesthesia risks.

There is some evidence to suggest that men are more likely to experience POVL, though it’s not yet clear why this is. POVL can affect people of all ages, but it’s rare in children under the age of 12. In general, Ischemic Optic Neuropathy (ION) is the most common reason for POVL. However, the risk factors can change with age. For children and teenagers (less than 18 years old), blindness caused by brain malfunction (cortical blindness) is the most common cause of POVL. In contrast, patients over 50 years old have a higher risk for Central Retinal Artery Occlusion (CRAO).

• POVL usually happens to low-risk patients with a minimal risk of complications from anesthesia.
• Men tend to get POVL more often than women, although the reasons aren’t entirely clear.
• POVL can happen at all ages, but it’s rare in kids under 12.
• In general, Ischemic Optic Neuropathy (ION) is the most common cause of POVL.
• The risk factors for POVL can change with age. For children and teenagers, brain-based blindness is the most common cause, while overt 50s are more at risk for blindness caused by blocked retina blood supply (CRAO).

The relationship between obesity and POVL is still under debate. One might assume that the increased pressure in the abdomen related to obesity may affect the blood flow to the eyes, increasing the risk of POVL. However, some studies found no significant impact of Body Mass Index (BMI) on the risk of POVL.

• The link between obesity and POVL is still unclear.
• Obesity could hypothetically increase the risk of POVL, since it can increase the pressure in the abdomen and affect the blood supply to the eyes.
• But, some studies have found obesity doesn’t necessarily increase POVL risk significantly.

Patients with peripheral vascular disease are twice as likely to get POVL. Other medical conditions like heart diseases, diabetes mellitus, prior stroke, high cholesterol, and kidney disease can increase the risk of POVL. However, studies regarding smoking and high blood pressure give inconsistent results. The association of pre-existing eye diseases with POVL remains uncertain and requires further research.

• People with peripheral vascular disease are twice as likely to get POVL.
• Other medical conditions, including heart diseases, diabetes mellitus, prior stroke, high cholesterol, and kidney disease may increase the risk of POVL.
• The results are inconsistent on whether pre-existing high blood pressure and smoking can increase your risk of POVL.
• Whether pre-existing eye diseases can increase the risk of POVL isn’t yet clear.

Signs and Symptoms of Perioperative Vision Loss

Anterior Ischemic Optic Neuropathy causes painless and progressive vision loss, which can be one or both eyes. Symptoms might only appear a few days after anesthesia. A noticeable sign is the abnormal pupil reflex; the eye may also show visual symptoms like blind spots, loss of light perception, or partial field of vision loss. On an early examination of the back of the eye, there is distinct swelling of the optic disc, thin blood vessels, and minor bleeding around the optic disc. At a later stage, the swelling lessens, blood vessels appear normal and no evidence of optic nerve discoloring is visible.

Posterior Ischemic Optic Neuropathy is very similar, but patients may experience vision loss right after waking up from anesthesia. Just like the previous condition, it presents an abnormal pupil reflex and similar visual complaints. However, upon early examination, the back of the eye looks normal, and only a late examination reveals discoloring of the optic nerve.

Orbital Compartment Syndrome causes painful visual loss immediately after anesthesia which can worsen within the next several days. Other symptoms include rapid swelling around the eye, along with swelling within the eyelid and abnormal protrusion of the eyeball.

Corneal Abrasion is a condition where patients may wake up from anesthesia with painful vision loss. This can be in one or both eyes and is often accompanied by tearing, a sensation of an alien object, and light sensitivity. Upon examination, an abrasion or foreign body might be seen with specific eye staining.

Central Retinal Artery Occlusion leads to patients experiencing vision loss in one eye immediately after waking up from anesthesia. There might be a slow or absent pupil reflex. An early eye exam may show a specific red spot in the optical macula against a background of an impacted, whitened retina. In a later examination, the optic nerve may look pale as the retina’s blood flow is restored.

Cortical Blindness might only involve vision loss directly after anesthesia. If one side of the brain is impacted, there might be partial side vision loss in the opposite eye, with or without loss of macular vision. If both sides of the brain are impacted, it results in complete vision loss, with or without certain areas of the macula being unaffected. Patients might present other symptoms such as agitation, confusion, or even unconsciousness, as well as nausea, vomiting, and seizures.

In Pituitary Apoplexy, vision loss might only show up after anesthesia. A common pattern is partial side vision loss or certain areas of vision blocking. Additionally, patients might experience headaches, nausea, vomiting, signs of meningitis, altered mental state, and paralysis of several eye muscles.

Testing for Perioperative Vision Loss

Preventing and quickly recognizing POVL (postoperative visual loss) is crucial. Most delays usually come from late recognition of the problem rather than worsening condition after the surgery. An eye specialist should be called right away if POVL is suspected to conduct a more thorough eye examination and identify where the issue along the vision pathway is located.

If there is a worry about cortical visual loss, a neurology specialist should also be consulted. The hospital should be alerted for a potential stroke, starting with a non-contrast CT scan of the head – this type of imaging helps rule out bleeding in the brain. The next step may involve a CT angiography of the head, a type of imaging that helps rule out a blockage in a large vessel in the brain. Ultimately, an MRI scan of the brain might be needed to determine the extent of a potential stroke.

Investigations are ongoing to test real-time flash visual evoked potentials (VEP) as a potentially useful tool for monitoring eyesight during spine surgery performed in a prone (face down) position. The type of anesthesia used during surgery can affect the stability of these VEP readings. A small study found that total intravenous anesthesia (TIVA) is associated with more prominent VEP readings and quicker response times than balanced anesthesia. This suggests that TIVA could be the most efficient anesthesia regimen when using VEP monitoring.

Treatment Options for Perioperative Vision Loss

Unfortunately, there are no treatments proven to work for conditions known as central retinal artery occlusion and ischemic optic neuropathy. These conditions happen when the blood supply to the eye’s retina or optic nerve is blocked. If vision loss is because of issues in the brain’s visual processing areas and imaging shows that a cerebral artery (an artery that supplies the brain) is blocked, it might be possible to restore the blood flow. This can be done with procedures to remove or break up the clot causing the blockage, as long as it’s performed within a specified time limit, usually 3-4 hours after the blockage has occurred.

But, the danger of vision loss during surgery is higher in cases where the operation lasts more than five or six hours. Therefore, not many people could be able to receive the clot-removing procedures within the prescribed 3-4 hour cutoff. Additionally, when a serious operation like spinal surgery is happening, the risk of severe bleeding from using clot-busting drugs to dissolve the blockage needs to be balanced with the risk of paralysis due to compression of the spinal cord—which could happen if there’s bleeding at the surgical site.

If vision loss is a result of a condition called ‘cortical vision loss secondary to PRES’, controlling seizures and high blood pressure, stopping any possible harmful medications and dealing with other contributing factors can help manage the condition. ‘PRES’ or ‘Posterior Reversible Encephalopathy Syndrome’ is a rare disorder in the brain, which leads to seizures, headaches, confusion, and visual loss.

If a condition called ‘pituitary apoplexy’ is found because of a brain scan, a specialist doctor called a neurosurgeon should be contacted immediately. This condition involves sudden bleeding into an important gland in the brain called the pituitary gland. Research suggests that removing the blood collection through surgery within 48 hours can often help improve vision.

Finally, if vision loss has occurred due to a ‘corneal abrasion’, which is essentially a scratch on the front surface of the eye, the object causing the scratch (if still present) will need to be removed. Also, further medical eye care would be needed to support the recovery process.

What else can Perioperative Vision Loss be?

When a patient experiences loss of vision during or after a surgery, there can be several possible reasons. These include:

• Ischemic optic neuropathy: This can either be of the ‘anterior’ or ‘posterior’ type and it occurs when the optic nerve head or the posterior part of the optic nerve, respectively, don’t get enough blood supply.
• Orbital compartment syndrome: Usually seen when the eye gets injured. Here, pressure builds up inside the eye socket, affecting the blood flow and potentially leading to damage.
• Corneal abrasion: This can happen if the eye is directly hurt during the surgery.
• Central retinal artery occlusion: Known as a retinal stroke, this is caused by an interruption in blood flow to the retina, often due to pressure on the eye. The extent of vision loss can greatly vary from patient to patient.
• Cortical blindness: This is a result of a stroke affecting the part of the brain involved in vision or swelling behind the eye. It can occur due to altered blood flow or a blockage. One suspected cause of this condition is damage to the thin layer of cells lining our blood vessels.
• Pituitary apoplexy: Though rare, this condition is an emergency when there is a blockage or bleeding into a pituitary tumor or the pituitary tissue. It has been reported in people having spine surgeries and it can be caused by changes in blood flow, blood thinning medications or the use of fluid replacement.

The doctor has to carefully review these possibilities and conduct tests in order to figure out the cause of the vision loss.

What to expect with Perioperative Vision Loss

Ischemic optic neuropathy, a type of vision loss called POVL, is unfortunately the most common subtype and most patients have not found an effective treatment, leading to poor outcomes. Because of this, the best approach is preventing it. Rarely, some patients may spontaneously and fully recover their vision.

However, other less common causes of POVL, such as pituitary apoplexy (a sudden hemorrhage into the pituitary gland at the base of the brain), cortical blindness due to PRES (a disorder in the brain named Posterior Reversible Encephalopathy Syndrome), and a corneal abrasion (a scratch on the eye’s cornea), tend to have better outcomes. Particularly, patients with pituitary apoplexy can improve their visual deficits if they have surgery within 48 hours.

The prognosis for cortical vision loss depends on the extent of the lack of blood supply to the brain. However, PRES, which is characterized by swelling beneath the cerebral cortex (the outer layer of the brain), is usually reversible since it does not involve extensive lack of blood supply, so most patients completely recover. The prognosis for a corneal abrasion is also promising, with early recognition and proper supportive care.

Possible Complications When Diagnosed with Perioperative Vision Loss

Vision loss after surgery (known as POVL) can cause more health issues for patients, particularly those who already suffer from back disorders. This additional health problem can reduce quality of life and even make it harder to recover, threatening a patient’s long-term wellbeing. More research is required to fully understand how POVL can affect patients’ health outcomes.

Understanding POVL:

• POVL may lead to more health problems, especially if you already have spine disorders
• This can limit your quality of life
• It could also make recovery more difficult
• More research is needed to measure the impact of POVL on patient recovery

Preventing Perioperative Vision Loss

Patients being considered for heart or back surgery should be informed about the risk of POVL (Postoperative Vision Loss), a rare but serious condition that could cause loss of sight after surgery. This warning is particularly important for persons who may be more susceptible to this risk. These include male patients, individuals with a pre-existing condition that affects blood flow to their arms and legs (known as peripheral vascular disease), and patients preparing for back surgery that involves the spinal cord’s rear portion. Additional risk factors are the use of a special support structure called a Wilson frame during surgery, surgeries that are expected to be lengthy, or procedures where significant blood loss is anticipated.