I only know of idiopathic because a doctor friend of mine once told me that I had a strange dark patch on my eyeball. He examined my other eye and found it there too. We worried and fretted about it for a few minutes before he calmly concluded that I had idiopathic eyes and left it at that. I started to feel Miltonic and Homeric and considered morosely that my light was spent. Later I remembered that I wear contact lenses.