One of the readers submitted the following question:
I came across your name while looking for information related to optic nerve repair – I was also trying to locate the email address of Dr. Neil Miller, which I couldn’t find – then I came across your blog, and hence this email. This subject has been of profound personal interest to me – my sister, who is now 46, and lives in India, lost her eye-sight completely in 1991. She had undergone three brain surgeries over a 14 year period – the surgeries were done to remove a persistent brain tumor that occurred in the vicinity of the optic nerve. While the initial surgeries were successful, the final surgery in 1991 left her with complete blindness after the tumor was removed. The tumor has not returned since 1991, and neither has her vision.
I’ve been in the US for the last 14 years, and have been reading articles on this subject - perhaps neurosurgery would advance to the level that could result in a cure for my sister. I’d very much appreciate hearing your views on this. I am happy to bring her to the US for treatment, even if there were a slim chance of success.
Several components of the human visual system must work together for an image to be detected, transmitted, and then processed by the brain. A simple model for the complex visual system can be represented by a video camera, wires, and computer. The eye is similar to a video camera with sensors that detect colors, shapes, and motion. The optic nerve is the wire that connects the eye (i.e. video camera) to the brain (i.e. computer) for processing of visual information. The average human optic nerve is about 1.5-2.0 mm in diameter (less than one tenth of an inch) and contains 1.2 million nerve fibers.
The ganglion cells in the eye give rise to the nerve fiber layer which aggregate and form connections with the brain via the optic nerve. Disruptions along the path of the optic nerve result in visual loss. In the situation of a brain tumor, the tumor can compress the optic nerve and cause visual loss. When there are surgeries around the optic nerve, parts of the optic nerve may be damaged resulting in visual loss. Sometimes, during tumor removal surgery, the entire optic nerve can be cut.
When the entire optic nerve is cut, all 1.2 million nerve fibers within the nerve are also cut. Current research is focused on growth factors that guide the growth of a damaged optic nerve and assist the connection of the nerve with the proper areas in the brain [
review article]. The problem is that 1.2 million nerve fibers must be reconnected properly for the visual system to function correctly. At the present time, we do not have the medical technology to repair damaged optic nerves in humans.
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