What Is Optic Nerve Cupping?
The optic nerve is made of a bundle of millions of nerve fibers. It is responsible for carrying visual images. Any damage caused to the nerve can lead to vision impairment or blindness. Optic nerve cupping or disc cupping is a vision-threatening severe condition characterized by the death of small nerves surrounding the optic nerve. The death of the small nerve results in an illusion of a cup around the nerve. The death of the small nerves causes the risk of destruction of the primary nerve. Cupping is defined as the increase in the optic disc-to-cup ratio. In optic nerve cupping, the balance of the disc to the cup gets altered. Optic nerve cupping occurs with or without glaucoma. Around ten to fifty percent of patients with glaucoma also suffer from optic nerve cupping.
What Happens in Optic Nerve Cupping?
The optic nerve can be described as an electric cord that connects the eye with the brain. Various meshes and a network of nerve fibers surround the optic nerve. Damage to the nerve is linked to primary nerve damage. Patients with secondary glaucoma (an eye condition leading to vision loss and temporary blindness) have a higher chance of optic nerve cupping.
The optic nerve carries the sensory functions of the eye to the brain. The optic nerve consists of millions of smaller nerve cells. The nerve bundles enter the brain through the optic disc at the back of the eye. The centermost part of the optic disc is the cup. Due to various optical conditions like glaucoma, these small nerve cells die. The loss of the smaller nerves ultimately results in the primary nerve damage and widening of the optic cup compared to the disc.
What Causes Optic Nerve Cupping?
The two major causes of optic nerve cupping are trauma caused to the optic nerve or other underlying medical conditions, such as:
-
Glaucoma.
-
Optic neuritis (inflammation of the optic nerve).
-
Atrophy of the optic nerve (deterioration of the optic nerve).
-
Optic nerve head drusen (benign calcifications within the optic nerve head).
What Are the Various Types of Optic Disc Cupping?
Optic disc cupping, based on its association with glaucoma, is of two types:
-
Glaucoma-Associated Cupping: Glaucoma remains one of the major causes for causing cupping.
-
Non-Glaucoma-Associated Cupping: Optic nerve cupping without glaucoma as the cause is non-glaucoma-associated cupping.
Based on the cause, optic nerve cupping can be of the following types:
-
Congenital Cupping: Congenital cupping can be due to incomplete closure of the embryonic fissures, oblique insertion of the optic nerve, and a tilted optic disc.
-
Acquired Cupping: Acquired cupping can occur due to various other causes acquired by a patient during his lifetime.
What Are the Signs and Symptoms of Optic Nerve Cupping?
The symptoms of optic nerve cupping depend on the underlying cause.
-
Reduction in sharpness of the vision.
-
Difficulty in peripheral vision.
-
The blurring of vision.
-
Defect in sharpness.
-
Color blindness or color vision deficiency (decreased or altered ability to differentiate specific colors).
-
There is a loss of visual acuity.
-
Unilateral damage to the nerve with associated systemic symptoms like headache, etc., indicates a non-glaucomatous optic nerve cupping.
-
The relative afferent pupillary defect is also observed in patients with optic nerve cupping.
How Are Patients With Optic Disc Cupping Diagnosed?
The naked eye cannot detect optic nerve cupping. An ophthalmoscopy test detects the condition. An ophthalmologist tests the optic disc-to-cup ratio. If the balance of the cup to that of the disc is more remarkable than six-tenths, then the cupping is caused due to glaucoma. Cupping is more deep or severe in glaucomatous patients compared to others. Magnetic resonance imaging (MRI) with contrast for evaluating the orbit is preferred in severe cases.
A trained optometrist or an ophthalmologist performs the ophthalmoscopy test. Before the examination, the pupils of the eye get dilated. Post-dilation of the pupils, the rooms are darkened, and the patient is asked to push his head back to examine the eyes.
How Are Patients With Optic Disc Cupping Managed?
There is no one particular treatment for resolving optic nerve cupping. Instead, the management procedures aim to determine the condition's underlying causes.
-
Glaucoma is treated with eye drops and laser surgery. Laser trabeculectomy helps lower the intraocular pressure, which further helps reduce the damage caused to the optic nerve.
-
Optical drusen are treated with an intraocular pressure lowering device.
-
Oral pills can be prescribed to reduce the fluid production inside the eyes.
-
Steroids are prescribed for patients suffering from optic neuritis.
-
Conventional surgeries can be performed to reduce eye pressure.
Optic nerve cupping is a severe vision-threatening condition with no particular cure. Patients suffering from optic nerve cupping along with glaucoma are prone to vision loss at an early stage.
What Are the Conditions That Mimic Optic Disc Cupping?
Conditions that are to be considered before forming a confirmative diagnosis of optic nerve cupping are:
-
Compressive optic neuropathies like pituitary adenomas (anterior pituitary tumor), aneurysms (abnormal swelling or bulge in the blood vessel), and meningiomas (central nervous system or CNS tumor).
-
Optic neuropathies can occur due to various reasons. Neuropathies can occur due to nutritional, hereditary, or toxic factors. Dominant optic neuropathy is the most common neuropathy. Nutritional deficiencies can lead to optic neuropathies.
Conclusion:
Optic nerve cupping is an optical condition characterized by the destruction of the small nerve fibers surrounding the optic nerve. This destruction damages the primary nerve and causes loss of visual acuity. Glaucoma remains the major causative factor for optic nerve cupping. Other hereditary and acquired causes can also lead to optic nerve cupping. Based on its association with glaucoma, the disease can be classified as glaucomatous or non-glaucomatous. Patients present with signs and symptoms that are characteristic of the underlying disease. The condition cannot be diagnosed with the naked eye and is detected with the help of an MRI or ophthalmoscope. Situation management aims to control the underlying vision problem and prevent further disease worsening. Early detection of the state helps in controlling the progression of the disease.
