Uremic Optic Neuropathy - Symptoms, Causes, and Treatment

Introduction

Uremic optic neuropathy is a rare disorder in patients with chronic kidney diseases. It causes loss of vision in these patients. It is common in individuals with undiagnosed renal disease. Uremia with superimposed anemia, malnutrition, and hypertension contributes to optic neuropathy. The vision loss is reversible if the condition is diagnosed early and the treatment is initiated.

What Is Uremia?

Urea is one of the components of urine. Uremia is a condition in which high levels of urea are present in the blood. It occurs in renal dysfunction, where the kidneys fail to filter the toxic products and excrete them in urine. Uremia is seen in chronic kidney diseases. It results in complications like fluid accumulation, electrolyte imbalance, and hormonal and metabolic problems. Dialysis is performed in such cases to remove the toxic products in the blood.

What Causes Uremia?

Uremia can be caused by prerenal, renal, and postrenal causes. It includes the following:

• Prerenal azotemia caused by a decrease in the blood flow through the kidneys results in uremia. It is due to low blood pressure, congestive heart failure, bleeding, shock, and dehydration, or due to an increase in urea production in the liver as a result of a high purine diet.

• Renal causes of uremia include renal dysfunction in conditions such as acute and chronic kidney failure, tubular necrosis, acute and chronic glomerulonephritis, and other kidney diseases.

• Post-renal causes of uremia include decreased elimination of urea due to urine outflow obstruction by calculi, presence of tumors in the bladder or prostate, or infections.

What Are the Signs and Symptoms of Uremia?

Uremia is associated with classical signs such as loss of appetite, muscle atrophy, shallow respiration, metabolic acidosis, and abnormal mental function. It also causes hypertension, anemia, nervous system abnormalities, and various other abnormalities, and It affects various systems in the body. It decreases the glomerular filtration rate. It causes seizures and coma if left untreated.

What Is Optic Neuropathy?

Optic neuropathy is the common cause of loss of vision. It refers to damage to the optic nerve due to various causes. The optic nerve is composed of millions of fibers in the retina, which sends visual signals to the brain. Damage to the nerve cells of the optic nerve leads to vision loss. Damage to the optic nerve can be due to diseases, chronic illness, tumors, malnutrition, chronic inflammation, injury, aneurysms or strokes, and exposure to toxins in the environment.

What Is Uremic Optic Neuropathy?

Uremic optic neuropathy refers to loss of vision in patients with chronic kidney disease. It causes sudden vision loss and involves focal edema of the optic nerve head. It is a rare condition because patients with chronic kidney disease undergo dialysis, and the possibility of the occurrence of vision loss is limited. It is a potentially reversible condition that remains underdiagnosed. Optic neuropathy in uremia is categorized into five groups, which includes the following:

• Uremic optic neuropathy (UON).

• Ischemic optic neuropathy.

• Optic neuropathy due to adverse drug reactions.

• Optic neuropathy due to increased intracranial pressure.

• Optic neuropathy due to cerebral infection.

Ischemic optic neuropathy is characterized by optic disc edema, sudden painless vision loss, and an altitudinal visual field defect. The visual field defect does not improve with dialysis. Intracranial hypertension is rare in patients with chronic kidney disease. Similarly, patients with chronic kidney disease do not present with cerebral infections, encephalopathy, or seizures. Hence, if all these conditions are ruled out, uremic optic neuropathy is diagnosed.

What Are the Signs and Symptoms of Uremic Optic Neuropathy?

Uremic optic neuropathy occurs as a manifestation of renal failure and end-stage renal disease.

Patients with uremic optic neuropathy present with features such as;

• Progressive vision loss.

• Reduced pupil reactions to light.

• Inflamed optic nerve.

• Flashing or flickering lights while moving the eyes.

• Colors may appear vivid, and vision loss develops fully or partially and progresses. It may also cause pain in the face, eye socket, and pain in eyes.

• Uremic optic neuropathy causes sudden vision loss and involves focal edema of the optic nerve head. It also causes other disorders like swelling of the optic nerve heads and blurring of the margins of the optic disks.

How Does Uremic Optic Neuropathy Occur?

The exact mechanism for uremic optic neuropathy has not been established. Nerve conduction studies have demonstrated visual defects in uremic patients and the improvement in visual system dysfunction after dialysis. It is believed that uremia results in the build-up of toxic compounds like guanidino compounds, Myo-inositol, and a few other middle molecules. These compounds may inactivate transketolase, a vitamin-B-dependent enzyme resulting in optic nerve dysfunction and vision loss. A deficiency in vitamin B can cause damage to the optic nerve resulting in blurred vision or loss of vision.

How Is Uremic Optic Neuropathy Diagnosed?

The diagnosis is based on history, clinical examination, and other laboratory tests. Patients with vision loss are examined with an ophthalmoscope. Laboratory tests like blood tests are performed to diagnose uremia and to evaluate the glomerular filtration rate. Urine tests are performed to determine creatinine clearance. Uremicoptic neuropathy is diagnosed if vision loss is present in patients with chronic kidney disease with uremia.

How Is Uremic Optic Neuropathy Treated?

Uremic optic neuropathy is a reversible condition in which vision loss reverses if uremia is treated. Hemodialysis is performed to remove the toxins in the blood. It removes the uremic toxins in the blood. Dialysis reduces optic disc edema by reducing volume overload and uremic toxins. Steroids are also given to reduce optic disc edema. Dialysis and steroids help in the reversal of optic nerve damage and vision loss with progressive dialysis sessions.

Conclusion

Uremic optic neuropathy is a rare disorder in patients with chronic kidney disease. Vision loss in such patients should be considered an emergency and managed immediately to prevent permanent nerve damage and permanent loss of vision. Timing of initiation of treatment is vital, as the outcomes of the treatment depend on it. The vision loss is reversible if the condition is diagnosed early and the treatment is initiated. Hence, early diagnosis and treatment are crucial to managing this condition.