Junior Blind of America

 

Definition:
Optic Nerve Atrophy (ONA) is a permanent visual impairment caused by damage to the optic nerve. The optic nerve functions like a cable carrying information from the eye to be processed by the brain. The optic nerve is comprised of over a million small nerve fibers (axons). When some of these nerve fibers are damaged through disease, the brain doesn’t receive complete vision information and sight becomes blurred. A person’s ability to see clearly (visual acuity) is affected due to nerve damage that occurs in the central part of the retina responsible for detail and color vision (macula). These areas of the eye are more vulnerable to the effects of atrophy. ONA is the end result of damage to the optic nerve. It can affect one or both eyes. It may also be progressive, depending on the cause.

Cause:
There are many unrelated causes of optic atrophy. The most common cause is poor blood flow, called ischemic (optic neuropathy, which most often affects the elderly. The optic nerve can also be damaged by shock, various toxic substances, radiation, and trauma.Various eye diseases, most commonly glaucoma, can also cause ONA. In addition, the condition can be caused by diseases of the brain and central nervous system, such as cranial arteritis (sometimes called temporal arteritis), multiple sclerosis, brain tumor, and stroke.The causes can range from trauma to systemic disorders. Some additional possible causes of ONA include:

• Optic neuritis. Optic neuritis is an inflammation of the optic nerve. It may be associated with eye pain worsened by eye movement. It is more common in young to middle-aged women. Some patients with optic neuritis may develop multiple sclerosis later on in life.
• Leber’s hereditary optic neuropathy. This is a disease of young men (late teens, early 20s), characterized by an onset over a few weeks of painless, severe, central visual loss in one eye, followed weeks or months later by the same process in the other eye. At first optic disc may be slightly swollen, but eventually there is optic atrophy.
• Toxic optic neuropathy. Nutritional deficiencies and poisons can be associated with gradual vision loss and optic atrophy, or with sudden vision loss and optic disc swelling.
• Glaucoma. Glaucoma may be caused by an increase of pressure inside the eye. This increased pressure may eventually affect the optic nerve if left untreated.
• Syphilis. Left untreated, this disease may result in optic atrophy.

 

Characteristics:
Although there are several types of ONA, the following characteristics are common to most:

• Central vision is affected
• Color vision deficits may be evident
• It may be difficult for children with ONA to discriminate contrast, due to damage in the area of the eye responsible for detailed vision (macula)
• A wide range of acuity loss exists in this population
• Onset of ONA may be gradual or sudden depending on the cause
• A general decrease of sensitivity in all visual fields (depressed visual fields) may occur, also dependent on the cause of ONA
• Many children with ONA have additional neurologic problems, such as seizures, developmental delays or motor problems, and Cortical Visual Impairment (CVI). When CVI coexists with ONA, it may be difficult to determine which diagnosis is responsible for specific visual problems).

 

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