In case anyone was wondering:
My sons' (two of my sons') condition is called Leber's Hereditary Optic Neuropathy. Whew, what a long name. About a hundred years ago (more or less), I studied medical terminology. "Optic neuropathy" would mean there is something wrong with the nerve that sends signals from the eye to the brain. Of course, everyone knows that "hereditary" means you inherit it from a parent. So, what does all this mean about this condition, sometimes called LHON for short?
LHON is caused by a gene that is passed on to children, only from the mother. A man who has LHON cannot pass the gene to his offspring. It's hard to trace this gene back because it wasn't defined and named until 1988! Yet, in this short time they've been able to do some research and put together some statistics. One thing they know is that it is possible for all of the children in a large family to have the gene and yet for only one child in that same family to actually have vision loss. No one knows for sure what causes the vision loss in someone who has the gene, or why someone else can have the gene and not lose vision.
What kind of vision loss occurs? The onset is often sudden and may continue for a few weeks or possibly a few months. It often affects one eye first, and then the other. Much of the time it is painless (except emotionally). It is not known to cause total blindness nor "light perception only". In other words, the person with this condition can usually see, even when he has stopped losing vision...but it does usually cause legal blindness or worse.
Now there's another definition to consider. What is legal blindness? "Perfect" vision is 20/20. Legal blindness, in this country, means that someone has a vision of 20/200 or worse in the better eye, after any correction, such as glasses. In the case of LHON, glasses don't help, since it's the optic nerve. As a matter of fact, there is no treatment or cure for this condition, which affects primarily the central vision. The peripheral - or "out of the corner of the eye" - vision usually remains pretty effective.
(NOTE ADDED MONTHS LATER: The "unthinkable" can happen more than once. Although we were totally caught off guard when our son Peter became legally blind, we also never dreamed our son Paul would be an exception in this exceptional condition...and become nearly totally blind. However, he may not have sight but he has a vision...to paraphrase his campaign when he ran for senator of his student government association. He is active, confident and competent.)