optic nerve

Question 1

Q1: What is the optic nerve and what is its function?

Answer 1

A1: The optic nerve is the second cranial nerve and consists of the axons of ganglion cells in the retina. It transmits signals that serve vision and the papillary light reflex.

Question 2

Q2: How is the optic nerve surrounded and protected?

Answer 2

A2: The optic nerve is surrounded by the three meninges (dura, arachnoid, and pia matter) and cerebrospinal fluid (CSF), similar to the brain.

Question 3

Q3: What structures pierce the optic nerve?

Answer 3

A3: The optic nerve is pierced by the central retinal artery and the central retinal vein.

Question 4

Q4: Where do the visual fibers from ganglion cells and pupillary fibers go?

Answer 4

A4: Visual fibers (80%) from ganglion cells go to the lateral geniculate body, while pupillary fibers (20%) go to the pretectal area.

Question 5

Q5: How does the optic nerve leave the eye and enter the orbit?

Answer 5

A5: The optic nerve fibers leave the eye by passing through the lamina cribrosa of the sclera to enter the orbit.

Question 6

Q6: What happens to the optic nerve fibers in the orbit?

Answer 6

A6: In the orbit, the optic nerve fibers become myelinated and are covered by meninges.

Question 7

Q: What is Visual acuity?

Answer 7

A: Visual acuity is a test that measures the sharpness and clarity of vision.

Question 8

Q: What is Color vision?

Answer 8

A: Color vision is a test that assesses the ability to perceive and distinguish different colors.

Question 9

Q: What is Pupillary light reflex?

Answer 9

A: Pupillary light reflex is a test that evaluates the response of the pupil to light stimulation, which helps assess the function of the optic nerve.

Question 10

Q: What is Visual field assessment?

Answer 10

A: Visual field assessment is a test that measures the extent and quality of a person’s peripheral vision.

Question 11

Q: What is Visual evoked potential?

Answer 11

A: Visual evoked potential is a test that measures the electrical activity of the brain in response to visual stimuli, providing information about the functioning of the optic nerve.

Question 12

Q: What are the two categories of optic neuritis?

Answer 12

A: Optic neuritis can be categorized into two groups: non-infective and infective.

Question 13

Q: What are some examples of non-infective optic neuritis?

Answer 13

A: Non-infective optic neuritis can be associated with demyelinating diseases such as multiple sclerosis (MS), idiopathic causes, toxic exposure to substances like tobacco or certain drugs, and ischemic conditions related to diabetes, hypertension, and atherosclerosis.

Question 13

Q: What are some examples of infective optic neuritis?

Answer 13

A: Infective optic neuritis can be caused by viral infections (e.g., influenza, chickenpox, measles, mumps) or as an extension of infections from sinuses, orbit, or meninges. Granulomatous causes, such as sarcoidosis, tuberculosis, and syphilis, are rare but possible.

Question 14

Q: What is demyelination in relation to the optic nerve?

Answer 14

A: Demyelination refers to a pathological process where the myelin layer surrounding nerve fibers is lost. In demyelinating diseases, such as multiple sclerosis, the white matter tracts of the brain, brainstem, and spinal cord are affected. However, peripheral nerves are not involved.

Question 15

Q: What are some symptoms of optic neuritis?

Answer 15

A: Symptoms of optic neuritis can include rapid and significant deterioration of vision (usually painless in papillitis), defective color vision (colors appearing “washed out”), and pain around the eye, especially with eye movements or pressure.

Question 16

Q: What are the clinical features of optic neuritis with papillitis?

Answer 16

A: Clinical features of optic neuritis with papillitis include:

Unilateral involvement
Early decrease in vision
Less congested veins
Afferent pupillary defect
Field defects: central scotoma relative for red and green
Vitreous: dust-like opacities
No symptoms of increased intracranial pressure (ICT)
Affected visual evoked potentials (VEP)

Question 17

Q: Q: What are the clinical features of optic neuritis with bilateral involvement?

Answer 17

A: Clinical features of optic neuritis with bilateral involvement include:

Normal vision early on
More congested veins
Normal pupillary reaction
Field defect: increased blind spot
Normal vitreous
Symptoms of increased intracranial pressure (ICT)
Normal visual evoked potentials (VEP)

Question 18

Q: Q: What is the recommended treatment for idiopathic intracranial hypertension (IIH) causing optic neuritis?

Answer 18

A: In cases of idiopathic intracranial hypertension (IIH) causing optic neuritis, treatment options may include:

Acetazolamide to decrease the production of cerebrospinal fluid (CSF)
Encouraging weight loss
Ventriculoperitoneal shunts if necessary

Question 19

Q: Q: How should follow-up be conducted for optic neuritis?

Answer 19

: Follow-up for optic neuritis should involve:

Visual acuity (VA) assessment
Fundus examination
Visual field testing (VF)

Question 20

Q: Q: What is primary optic atrophy?

Answer 20

A: A: Primary optic atrophy refers to the atrophy of the optic disc without previous optic disc edema. It can be congenital, toxic, or related to retrobulbar pathology.

Question 21

Q: Q: What is secondary optic atrophy?

Answer 21

A: A: Secondary optic atrophy occurs after optic disc edema, which can be caused by conditions such as papillitis or papilledema.

Question 22

Q: Q: What is consecutive optic atrophy?

Answer 22

A: A: Consecutive optic atrophy is optic atrophy that occurs due to the presence of retinal disease, such as retinitis pigmentosa or central retinal artery occlusion.

Question 23

Q: Q: What is post-glaucomatous optic atrophy?

Answer 23

A: A: Post-glaucomatous optic atrophy refers to optic atrophy that occurs in the end stages of glaucoma.

Question 24

Q: Q: What are the differences between primary optic atrophy and secondary optic atrophy?

Answer 24

A: A: The differences between primary optic atrophy and secondary optic atrophy are as follows:Color: Primary optic atrophy appears milky white, while secondary optic atrophy appears grayish white.
Edges: The edges of primary optic atrophy are well-defined, whereas the edges of secondary optic atrophy are ill-defined.
Cup: Primary optic atrophy has an atrophic, shallow cup, while secondary optic atrophy may be filled by fibrous tissue or have a deep cup.
Lamina: The lamina is well seen in primary optic atrophy but not seen in secondary optic atrophy.
Vessels: In primary optic atrophy, the vessels are slightly attenuated, while in secondary optic atrophy, the vessels are attenuated or sheathed.
Nasal shift: The retina is normal in primary optic atrophy, but in secondary optic atrophy, there may be a nasal shift.