When the optic nerve stops working, it undergoes degeneration, called optic atrophy.
Here is a cross section through the back of the eye where the optic nerve has atrophied (thanks to www.mrcophth.com/ for this image). You can clearly see a dip where there should be nerve tissue. This is due to the shrivelling up of a bundle of nerve fibers from the optic nerve. This eye would have been completely blind.
Signs and Symptoms
Depending on what the underlying pathological process is, the symptoms can be quite different. For instance, in a multiple sclerosis patient it may take a number of months or years before a complete optic atrophy develops. Long before the progressive optic atrophy develops, there may have been double vision first because of weakness in the eye muscle coordination.
On the other end of the scale there might be a sudden loss of vision because of a brain tumor that puts pressure from behind the eye onto the optic nerve leading to a sudden reversible optic atrophy. If the tumor is benign and can be neurosurgically removed, part or all of the vision can be recovered provided the neurosurgeons is consulted in time.
When the physician looks through the ophthalmoscope or examines the eye with the help of the slit lamp, this picture of the fundus with optic atrophy would be seen. This was found in a patient who was blind on that eye from multiple sclerosis.
With a condition like multiple sclerosis optimal treatment including immunotherapy can arrest the disease process thus stopping or preventing the development of optic atrophy. Unfortunately, if optic atrophy has taken place and the nerve tissue is lost, nothing can be done to help this patient. However, in an acute optic atrophy case with increased eye pressure (e.g. glaucoma), the eye pressure can be quickly lowered and the patient may recover some or all of the vision. Similarly, as already pointed out in the case where a benign tumor puts pressure from behind onto the eye, removal of the tumor can often restore most, if not all of the vision.
1. The Merck Manual ( thanks to www.merckmanuals.com for this link): optic neuritis, which leads to optic atrophy
2. Ferri: Ferri’s Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.
3. Rakel: Conn’s Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier