Optic atrophy, a result of optic nerve damage may cause low vision, blindness

Optic atrophy (optic neuropathy) is a term used to refer to the end stage of a number of conditions that can cause optic nerve damage. The optic nerve is composed of a bundle of nerve fibers, each of which transports visual information from the retina to the visual processing centers of the brain. Significant damage or degeneration of the optic nerve due to any cause can result in vision loss.

Those suffering from poor blood supply to the optic nerve (ischemic optic neuropathy) are the most at risk for optic atrophy, with the elderly being the most common demographic affected. However, optic atrophy may also be caused by shock, radiation, toxic substances, or trauma. Disease of the brain or central nervous system, stroke, brain tumor, as well as eye diseases such as glaucoma may also lead to the condition.

In the United States, the prevalence of blindness attributable to optic atrophy is about 0.8 percent. However, other sources have found this number to be as high as 0.12 percent. Optic atrophy is not a disease, but a sign of many disease processes.

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What are the causes and symptoms of optic atrophy?

The term “optic atrophy” implies the wasting away of optic nerve cells due to underuse or neglect, which is not a completely accurate description of the condition, as damage to the optic nerve is a causative factor. Any disease that can compromise ganglion cell function (a type of neuron found near the inner surface of the retina) can lead to the development of optic atrophy over time.

The following are some of the most commonly recognized optic atrophy causes:

Glaucoma

A progressive condition that causes pressure build-up within the eyes, which can lead to optic nerve damage. Intraocular pressure – the pressure within the eye – damages the optic nerve, which is responsible for sending the images you see to the brain to be interpreted.

When this nerve becomes damaged, it can lead to significant sight impairment or even blindness in just a few years. One of the most troubling aspects of glaucoma is that in its initial phases, it may not present with any symptoms, and it is not until you start to notice problems with your vision that glaucoma cases are diagnosed.

It is recommended that those over 40 years old who have a family history of glaucoma have a complete eye exam from an eye doctor every one to two years. This is especially important if you suffer from a health condition such as diabetes or high blood pressure, as these may also affect eye health.

Also read: Ocular hypertension may cause glaucoma and permanent vision loss if left untreated

Retrobulbar neuritis

A form of optic neuritis or inflammation of the optic nerve. Inflammation is a normal immune process, but it can still attack and damage healthy tissue in autoimmune conditions or other pathologies. Because the optic nerve is an important player in visual signaling to the brain, inflammation of it is often impaired. Inflammation of the optic nerve can be seen in conditions such as multiple sclerosis, diabetes mellitus, low phosphorus levels, or hyperkalemia.

Traumatic optic neuropathy

Occurs due to indirect injury to the optic nerve that is thought to be the result of transmitted shock from impact created to the intracanalicular portion of the optic nerve. This may occur from penetrating injury or from bony fragments in the optic canal or orbit that pierce the optic nerve. Significant trauma leading to orbital hemorrhage and optic nerve sheath hematoma can lead to optic neuropathy as well.

Central retinal vein occlusion (CRVO)

A condition characterized by blockage of a vein of the eye that normally funnels deoxygenated blood away from the eye. As a result, blood begins to back up within the eye, spilling out into the retina. This leads to swelling of the macula (a small but important area in the center of the retina needed to see details of objects clearly) affecting central vision. If this blood supply abnormality is not corrected, nerve cells within the eye can die, leading to a loss of vision.

Other causes:

• Giant cell arteritis (arthritic ischemic optic neuropathy)
• Chronic papilledema
• Chronic optic neuritis
• Leber’s optic neuropathy
• Methanol toxicity
• Retinitis pigmentosa (retinal degeneration)
• Tay-Sachs disease (retinal storage disease)
• Radiation neuropathy
• Syphilis
• Kjer-type optic atrophy (Juvenile optic atrophy)
• Drug toxicity
  • Disulfiram
  • Halogenated hydro-quinolones (amebicides)
  • Ethambutol
  • Isoniazid
  • Chloramphenicol
  • Vincristine
  • Ciclosporin
  • Cimetidine

Symptoms

Optic nerve atrophy symptoms will ultimately depend on the underlying condition but typically include the following:

• Blurred vision
• Difficulties with peripheral vision
• Difficulties with central vision
• Difficulties with color vision or contrast
• Reduction in vision sharpness

Types of optic atrophy

Pathologic optic atrophy

• Anterograde degeneration (Wallerian degeneration): Degeneration beginning in the retina and proceeding toward the lateral geniculate body (a relay center in the thalamus for the visual pathway). Larger axons of nerves disintegrate more rapidly than smaller axons. This type is characteristic of toxic retinopathy and chronic simple glaucoma.
• Retrograde degeneration: Degeneration that begins from the proximal portion of the axon, proceeding towards the optic disc. This form can be caused by intracranial tumors.
• Trans-synaptic degeneration: Refers to a neuronal degeneration that occurs on one side as a consequence of a neuron loss on the other side. This type is often appreciated in individuals with occipital damage that had occurred either in utero or during early infancy.

Ophthalmoscopic optic atrophy

• Primary optic atrophy: The degeneration of optic nerve fibers in an orderly manner that is replaced by columns of glial cells (the cells that normally surround neurons). This can occur in conditions such as pituitary tumors, optic nerve tumors, traumatic optic neuropathy, or multiple sclerosis.
• Secondary optic atrophy: Marked degeneration of nerve tissue, with excessive proliferation of glial cells that occur as a result of conditions that indirectly affects the optic nerve. This condition may include papilledema or papillitis.
• Consecutive optic atrophy: Characterized by a waxy pale optic disc with normal disc margins. Also, arteries located here are markedly diminished. This type can be seen with retinitis pigmentosa, myopia, or central retinal artery occlusion.
• Glaucomatous optic atrophy: Characterized by microscopic findings of vertical enlargement of cups, visibility of the laminar pores (laminar dot sign), backward bowing of the lamina cribrosa, bayoneting and nasal shifting of the retinal vessels, and peripapillary halo and atrophy.
• Temporal pallor: Characterized by a pale optic disc with clear, demarcated margins and normal vessels. This is often seen in patients suffering from multiple sclerosis, particularly ones with optic neuritis.

Etiologic optic atrophy

• Hereditary atrophy: Includes autosomal-dominant optic atrophy type 1, X-linked optic atrophy type 1, as well as hereditary optic atrophy type 3.
• Consecutive atrophy: An ascending type of atrophy that includes the likes of chorioretinitis, pigmentary retinal dystrophy, and cerebromacular degeneration.
• Circulatory atrophy (vascular): A type of ischemic optic neuropathy that is caused when perfusion pressure of the ciliary body falls below the intraocular pressure. This often can be appreciated in conditions such as central retinal artery occlusion, carotid artery occlusion, and cranial arteritis.
• Metabolic atrophy: Can be seen as a result of disorders like thyroid ophthalmopathy, juvenile diabetes mellitus, nutritional amblyopia, toxic amblyopia, tobacco, methyl alcohol, and drugs.
• Demyelinating atrophy: Can be seen in diseases such as multiple sclerosis and Devic disease.
• Pressure or traction atrophy: Seen in diseases like papilledema and glaucoma
• Post-inflammatory atrophy: Seen in diseases like optic neuritis, perineuritis secondary to inflammation of the meninges, and sinus and orbital cellulitis.
• Traumatic optic neuropathy: While poorly understood, this type is highlighted by optic nerve impingement from a penetrating foreign body or bony fragment.

How to diagnose optic atrophy

The diagnosis of virtually any eye condition will be done by an ophthalmologist, as they are skilled at identifying and assessing various forms of vision loss and eye pathology. If your ophthalmologist suspects you may be suffering from optic atrophy, the first thing they will do is get a direct close up look at the eye with a tool called an ophthalmoscope. This tool will allow your doctor to look at the optic disc (the point where the optic nerve enters). Depending on the color of this disc, change in blood flow to the eye can be suspected. A pale optic disc would indicate decreased blood flow, for example.

Other tests may also be done depending on the suspected cause of optic atrophy. If your doctor suspects that a tumor is the most likely cause of your changes in vision, imaging studies will be ordered, such as a magnetic resonance imaging (MRI) test. Ancillary tests to measure your vision and peripheral and color vision will also be done.

Prevention and prognosis of optic atrophy

While it may not always be possible to prevent optic nerve atrophy, taking the following steps is considered the most effective method of prevention:

• Careful management of blood pressure, especially in older individuals
• Prevent injury to the face when in situations that may lead to injury, as this will help protect the eye area
• Make it a point to get annual eye exams to check for glaucoma
• Avoid the consumption of home-brewed alcohol and forms of alcohol not intended for consumption, as they may contain methanol.

The prognosis of optic atrophy will depend on the severity of the underlying condition causing the problem. Some causes, such as inflammation of the optic nerve (optic neuritis), may resolve any vision problems once the inflammation has cleared up, but other causes may not see any improvement in vision at all. The most proactive thing to do is to have any potential eye condition diagnosed early by maintaining routinely scheduled doctors visits.

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