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Describe optic atrophy with its types and causes.

Ophthalmology · 3rd Professional

Types of Optic Atrophy

Optic atrophy is degeneration of the optic nerve axons with loss of the capillaries and glial replacement, seen as pallor of the optic disc.
It is the end result of any optic neuropathy, not a diagnosis in itself.

Type	Appearance and causes
Primary	Atrophy without preceding disc swelling. The disc is chalky white with sharp, clearly defined margins, the lamina cribrosa is visible at the floor of the cup, and the vessels are normal or slightly narrowed. Causes: retrobulbar neuritis, compression (tumour, aneurysm, thyroid eye disease), trauma, hereditary disease (Leber, dominant optic atrophy), and toxic and nutritional neuropathies
Secondary (consecutive to swelling)	Atrophy following disc swelling. The disc is dirty grey or greyish-white with blurred, indistinct margins, the physiological cup is filled, and there is peripapillary sheathing of the vessels and gliosis. Causes: chronic papilloedema, papillitis, and ischaemic optic neuropathy
Consecutive (retinal)	Following retinal disease. The disc has a waxy yellow pallor with markedly attenuated arterioles. Causes: retinitis pigmentosa, central retinal artery occlusion, extensive chorioretinitis and panretinal photocoagulation
Glaucomatous	Progressive cupping with the pallor confined TO the cup and the remaining rim retaining its colour; with bayonetting of vessels and a laminar dot sign. Pallor exceeding the cupping is not glaucomatous and demands imaging
Band (bow-tie) atrophy	A horizontal band of pallor across the disc with relative preservation above and below, from loss of the nasal fibres. It indicates a chiasmal or optic tract lesion, and appears in the eye whose temporal field is lost — so it is a valuable localising sign
Temporal pallor	Loss of the papillomacular bundle; seen in toxic and nutritional neuropathies, dominant optic atrophy and after optic neuritis

Assessment — the pallor must be judged against the fellow disc and against the function. Pallor without functional loss should be doubted: many normal discs look pale, especially in myopes and in a large disc
The functional assessment is what confirms it — reduced acuity, impaired colour vision (which is affected out of proportion and is the most sensitive test), a relative afferent pupillary defect if unilateral, reduced contrast sensitivity, and a field defect
OCT of the retinal nerve fibre layer quantifies the axonal loss objectively, and distinguishes true atrophy from a pale-looking normal disc
The essential clinical task IS TO find the cause, since the atrophy itself cannot be treated and the cause may be progressive and treatable

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