Optic Atrophy

OPTIC ATROPHY

• Refers to optic nerve shrinkage from any cause which produces degeneration of axons in the anterior visual system.
• Optic atrophy is the end result of any pathological process.
• That damage axons b/w retinal ganglionic cells to lateral geniculate body (LGB).

OPHTHALMOSCOPIC CLASSIFICATION:

1. Primary (simple) optic atrophy

• Results from the lesions proximal to the disc without antecedent papilloedema.
• Lesions of optic nerve, optic chiasma, optic tract & LGB cause primary optic atrophy.

Its common cause are:

1. trauma to the optic nerve or chiasma
2. demyelinating disorders like multiple sclerosis 
3. Leber’s hereditary neuritis
4. toxic amblyopia
5. tabes dorsalis (Syphilis)
6. Vitamin B deficiency

• Optic disc is greyish-white or white (chalky white) with clear margin.
• Shallow, saucer-shaped atrophic cupping due to degeneration of nerve fibres.
• Surrounding retina & retinal vessels are normal as the disease process is proximal (behind) the optic disc.

2. Consecutive optic atrophy

• Occurs following destruction of ganglionic cells secondary to degenerative or inflammatory lesions of choroid or retina.

Its common cause sre:

1. retinitis pigmentosa
2. diffuse chorioretinitis
3. pathological myopia
4. CRAO
5. Glaucoma

• Disc is yellow-waxy in colour & the retinal vessels are attenuated.

3. Secondary optic atrophy

• Occurs after disc edema.
• Also c/d postpapilledematous optic atrophy

Its causes are:

1. Papilloedema
2. Optic neuritis (papillitis)
3. Neuroretinitis
4. Ischemic optic neuropathy

• Characterised by disappearance of vascularity of disc which causes increase in pallor of disc.
• Post-neuritic optic atrophy is a secondary optic atrophy which develops as a sequel to long standing papilloedema or papillitis.

4. Glaucomatous optic atrophy

• Occur in long stannding glaucoma i.e chronic open angle or closed angle glaucoma.
• There is glaucomatous cupping of optic disc.
• Abrupt margins of optic disc & normal retinal appearance.

5. Ischemic optic atrophy

• Due to disc ischemia caused by giant cell arteries, severe hemorrhage, severe anemia.
• Disc is pale with obliteration of retinal vessels.

6. Toxic optic atrophy

• Due to chronic retrobulbar neuritis secondary to toxic agents (toxic amblyopia)

Common causes are:

1. tobacco
2. ethyl alcohol
3. methyl alcohol
4. lead quinine
5. chloroquinine

1. Ascending atrophy:

• Acsending optic atrophy (Wallerian degeneration) follows damage at retinal ganglion cell level.
• Nerve fiber degeneration progress (ascends) from the eye-ball towards the lateral geniculate body.
• So, consecutive optic atrophy is a type of ascending atrophy.

2. Descending atrophy:

• Descending (retrograde) atrophy.
• Occurs when degeneration proceeds from the region of optic tract, chiasma or retrobulbar portion of optic nerve towards optic disc.
• So, primary optic atrophy is a type of descending atrophy.

3. Cavernous (Schnable’s) optic atrophy:

• Mucoid degeneration of glia occurs.

Seen in:

1. chronic simple glaucoma 
2. methyl alcohol poisoning
3. high myopia

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