Etiology of secondary atrophy of the optic nerve

The most important causes are as follows:

❖ Anterior ischemic optic neuropathy.

H The etiology of any atrophy of the optic nerve should be determined to exclude possible life-threatening intracerebral causes such as a tumor.

Symptoms: The spectrum of functional defects in optic atrophy is broad. These range from small peripheral visual field defects in partial optic atrophy to severe concentric visual field defects or blindness in total optic atrophy.

Diagnostic considerations: The most important examinations are a detailed history, ophthalmoscopy, and perimetry testing. Color vision testing and visual evoked potential may be useful as follow-up examinations in beginning optic atrophy.

Primary atrophy of the optic nerve. Ophthalmoscopy will reveal a well defined, pale optic disk (Fig. 13.14). The pallor can cover the entire optic disk (it will appear chalk white in total optic atrophy), or it may be partial or segmental. The neuroretinal rim is atrophied, which causes the optic disk to flatten out. The diameter of the retinal vessels will be decreased.

Secondary atrophy of the optic nerve. Ophthalmoscopy will reveal a pale optic disk. The disk is slightly elevated due to proliferation of astrocytes, and the margin is blurred (Fig. 13.15). The optic cup will be partially or completely obscured. The retinal vessels will be constricted.

Treatment: The disorder involves irreversible damage to the nerve fibers. As a result, no effective treatment is available.

Prognosis: Early identification and timely management of a treatable cause such as a tumor or pernicious anemia can arrest the progression of the disorder. Where this is not the case, the prognosis for vision is poor.

382 13 Optic Nerve Primary atrophy of the optic nerve.

Fig. 13.14 The optic disk is well defined and pale. The neuroretinal rim is atrophied resulting in a flattened optic disk.

— Secondary atrophy of the optic nerve.

Fig. 13.15 The optic disk is elevated and pale due to proliferation of astro-cytes.

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