1. Optic nerve and visual pathway

2. Optic nerve
The optic nerve is the second cranial nerve situated in the posterior part of the globe
It transmits visual impulses from the retina to the brain
The head of the optic nerve is called optic disc

3. Visual pathway Retinal fibers leave half of the image in opposite side
Mutual crossing is known as optic chiasm
Nasal fibers mix with uncrossed temporal sector to form optic tract
Cell station in brain lateral geniculate body (relay station)
Fibers spread out to reach their final destination the visual cortex

4. Symptoms of optic nerve disease
Loss of vision
Scotomata
Disturbances in color vision
Pain is conspicuously absent, except (retrobulbar)

5. Signs of optic nerve disease
Relative afferent pupillary defect (RAPD)
Margins, surface, color of the disc
Pulsation of the central retinal vein
Shape and size of the physiological disc

6. Diseases of optic nerves
Optic neuritis
Neuroretintis
Retrobulbar neuritis
Anterior Ischaemic optic neuropathies (AION)
Papillitis
Optic atrophy

7. Abnormalities Drusen : Two kinds of drusen occur in the optic nerve
Common drusen - Disc margins blurred appearance, visual field defect
Giant drusen - Astrocytic hamartomas, that occur with tuberous sclerosis
Conus: It is congenital cresent, choroid and retinal pigment epithelium do not extend upto the optic disc.
Defective vision, hypermetropic astigmatism and visual fields defect
Coloboma : Incomplete closure of the embroynic fissure causes optic nerve defects ranging from a deep physiological cup to a pit in the optic disc

8. AION
It is a segmental infarction of the anterior part of the optic nerve, caused by the occlusion of short posterior ciliary arteries.
Symptoms : Headache, scalp tenderness, jaw claudication, pain and stiffness of the proximal muscles.
Investigation : Fields, ESR, C-reactive protein
Treatment : High dose of oral steroids (tapering dose)

9. Papillodema
Papillodema is the bilateral non inflammatory passive swelling of the optic disc, produced by raised intracranial tension.
Symptoms: Headache, vomiting without nausea, focal neurological deficit

10. Optic atrophy
Optic atrophy is the degeneration of optic nerve fibers with loss of their myelin sheaths and characterised by the pallor of the optic disc.
Symptoms :
sudden or gradual loss of field vision
color vision impaired
RAPD
Investigations :
Central field
FFA
X-ray skull
CT scan brain

11. Thank you