Optic Nerve Abnormalities - Causes, Symptoms, Diagnosis, and Treatment

What Is the Optic Nerve?

The optic nerve is the nerve that starts from the brain and supplies the eyes. Both eyes have an optic nerve of their own. Since they originate from the brain, they are known as cranial nerves. The optic nerve is the second cranial nerve. The optic nerve contains millions of nerve fibers that carry electrical impulses to the brain that get interpreted as the vision that humans see.

• Optic Nerve Anatomy: Optic nerve leaves the eye from the optic disc after collecting visual information from the retinal cells. It travels through the cranial bone through an opening called the optic canal. After leaving the optic canal, both optic nerves cross each other. This is called optic chiasma. These nerves then reach the visual cortex. The visual cortex is a part of the brain that interprets signals from the brain and processes it as sight.

What Are Optic Nerve Abnormalities?

Optic nerve abnormalities can be classified as inborn or obtained. Optic nerve abnormalities that are present since birth have irregularities in the size and shape of the optic disc and its surrounding structures. These irregularities are characterized by anomalies of optic disc size or compliance and by the presence of unusual tissue at the nerve head (pseudo swelling). Acquired irregularities of the optic nerve are grouped by the response of the optic nerve to various stimuli.

What Are the Symptoms of Optic Nerve Abnormalities?

Any abnormalities of the optic nerve may present with various symptoms. Each condition may have a characteristic feature of its own. It is advisable to obtain a medical opinion as soon as one notices some vision changes. Some of the most common features of optic nerve abnormalities may include:

1. Pain in the eyes.

2. The blurring of vision.

3. Recurrent headaches.

4. Decrease in the visual field.

5. Reduction of visual acuity.

6. Color blindness.

7. Loss of vision.

8. Presence of flickering or floating in the eyes.

What Are the Congenital Abnormalities of Optic Nerve?

Congenital abnormalities of the optic nerve are those defects that may be present since birth. It includes the abnormalities of the disc size and the disc formations. The various congenital abnormalities of the optic nerve include:

Congenital Abnormalities of the Disc Size: A normal optic disc is around 1.5 millimeters in diameter.The abnormalities of the disc size may include aplasia (missing optic disc) or a smaller optic disc.

1. Aplasia: It is a rare disorder of the optic disc, where the entire optic disc contents (optic nerve, optic vessels, and retinal cells) might be missing.

2. Hypoplasia of the Optic Disc: The optic disc may be hypoplastic or smaller in size. In this condition, the optic nerve may be underdeveloped due to various factors. It may affect one or both of the eyes.

3. Megalopapilla: Megalopapilla is an inherent condition of the optic nerve that is caused due to various congenital factors. In this condition, the optic nerve head is enlarged in size. The other components may or may not be affected.

Congenital Abnormalities of the Disc Formations: The disc and cup ratio of the eye is fixed around a certain range of values. At times this disc cup ratio may have extreme differences, leading to congenital abnormalities of the disc cup ratio. Some of the congenital disc abnormalities include:

1. Tilted Disc: Tilted optic disc is a common optical finding. In this condition, the optical disc may be tilted or rotated from its normal position.

2. Morning Glory Optic Disc: The morning glory optic disc is a rare congenital condition of the optic disc. This condition occurs when the optic disc fails to form completely in-utero. The optic disc may be in a funnel shape in this condition. This condition usually occurs only in one eye.

3. Optic Disc Coloboma: This is a very rare condition of the optic disc. In this congenital condition, there is a fissure that may be formed in the optic disc. It may occur along with other colobomas of the eye, such as coloboma of the iris or eyelid.

4. Optic Pit: Optic pit is a rare condition of the eye where there is an incomplete formation of the optic disc.

5. Peripapillary Staphyloma: It is a condition of the optic disc that may be present since birth. The optic disc may be surrounded by a deep fundus.

Pseudo Swelling of the Optic Disc: This denotes the swelling of the optic disc without edema or any fibrous layer on the optic nerve. The following conditions may denote false swelling of the optic disc:

1. Hyperopia: Hyperopia may also be known as farsightedness. This condition may be associated with false swelling of the optic disc.

2. Myelinated Fibers: The myelinated nerve fiber layers of the optic nerve may fail to shed after birth.

3. Optic Disc Drusen: In this condition, there is fatty deposits at the back of the eyes. Fatty proteins and calcium make up these deposits.

4. Bergmeister Papilla: This condition signifies the remnants of fetal tissues (fetal hyaloid artery) that were supposed to cease to exist after birth. In Bergmeister papilla, the central optic disc may appear as a tuft.

What Are the Acquired Abnormalities of Optic Disc?

Acquired abnormalities of the optic disc are those abnormalities that occur throughout life. It may or may not be due to any underlying condition. It may be a permanent condition or may resolve upon giving treatment. The various acquired abnormalities of the optic disc are:

• Cupping Abnormalities: Optic disc cupping is a condition that develops over a period of time. In this condition, the optic disc may be cup-shaped. A normal optic disc may be more closely packed and of a smaller diameter.

• Swelling of the Optic Disc: Optic disc swelling may be caused due to various factors. This could be transient or permanent. It may affect only one or both eyes. The various conditions that may cause the swelling of the optic disc are:

  • Papilledema: This condition refers to the swelling of the optic disc that may be caused by an increase in intracranial pressure. This increase in intracranial pressure can be due to various reasons.
  • Eye Infection: Swelling of the optic disc can be caused due to various bacterial or viral infections In such types of infective swellings, the condition resolves on its own after the resolution of the infection.
  • Ischemia: There may be a swelling of the optic disc following an ischemic condition of the eye. This is a very serious condition as it may even lead to vision loss.
  • Compression: Compressions of the optic nerve may occur not necessarily due to swelling in the optic disc. There may be compression of the optic nerve due to any tumor or any other pathology of the brain.
  • Infiltration: This is a condition in which neutrophils, which are a form of immune cells; accumulate in the optic disc. This may give a swollen appearance to the optic disc.

• Atrophy of the Optic Disc: It is a deteriorative condition of the optic disc. It may be associated with a disease or may even be due to the aging-related process. This atrophy may occur in bits and will be referred to as diffuse atrophy. Sometimes an entire segment of the optic nerve may undergo degeneration or aging which may be known as segmental atrophy.

Conclusion

Optic disc abnormalities may be caused due to various factors. Some of these factors may be present since birth, and other abnormalities may develop due to factors such as aging, infection, or many other features. Some of these conditions may present with symptoms, and some may be asymptomatic. In case of any symptoms, it is advisable to obtain medical attention at the earliest. Even in the absence of any symptoms, a periodic eye check-up can prevent a lot of diseases and complications and at the same time, promote optimal vision.