Ischemic Optic Neuropathy
GENERAL INFORMATION PRIMARILY FOR PATIENTS AND LAY PEOPLE
By S. S. Hayreh and P.A. Podhajsky
This web page is intended to give basic information about ischemic optic neuropathy, which is sometimes called "stroke of the optic nerve" in lay persons’ term. Ischemic optic neuropathy is one of the most common causes of loss of vision in persons past middle age. However, it does occur less commonly, in younger persons. Knowledge about this disease will enable patients and their doctors to work together to understand the disease. Early diagnosis, recognition of various risk factors, and carrying out the treatment and follow-up visits as recommended, are the most important aspects of care for persons with ischemic optic neuropathy. The following description of ischemic optic neuropathy is based on our basic, experimental and clinical studies published in the peer reviewed journals. [1-77]
The Eye
The eye is often compared to a camera. Light comes in through the cornea, pupil, and lens at the front of the eye just as the lens of the camera lets in light to the film. This light is then focused on the inside wall of the eye called the retina (as on the film in a camera). This picture is then sent to the brain along the optic nerve, which connects the eye to the brain. We see properly when all of these parts of the eye and brain are working togetherThe Optic Nerve
The optic nerve is unique because it is the only nerve in the body that a physician is able to see directly (without surgery) as it begins at the back of eye. The optic nerve is made up of a million tiny, delicate nerve fibers that are like wires. Many blood vessels nourish the optic nerve with blood rich in oxygen and nutrition. Vision actually takes place in the brain when the messages from the eye travel to the brain along the optic nerve; however, the nerve has to be healthy to transmit these messages. The whole situation may be compared to a video camera (i.e. the eye) taking the picture and transmitting along the cable (the optic nerve) to the television (the brain); if the cable is damaged for any reason, although the video camera and the television may be perfectly normal, a distorted picture or no picture is seen on the television.
While explaining this disease, a doctor may say that there has been a "stroke at the back of the eye", "blocked blood vessel", or "broken blood vessel at the back of the eye". A "stroke" is an interruption of the blood supply to the brain or a nerve in the body. When a person has a major "stroke" in the brain, the blood supply to a part of the brain that controls speech or movement of the arms and legs is often affected. With a "stroke at the back of the eye" a loss of vision develops because the retina or the optic nerve may have its circulation interrupted. How much vision is lost depends on how much the retina or the optic nerve is affected. In this website we are discussing only the stroke of the optic nerve and NOT that of the retina.
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