Earlier tonight my mother informed me that she could not focus on text that is on a piece of paper while it is held straight out(vertical) but she can in fact read it fine while the page is held horizontally. My mother has always had 20/20 vision, she has normal color vision (I, her male son, have slight red green color blindness). I have read on as many causes for blurred vision as I can find and have been unable to find anything that would pertain to this case. We conducted an Amsler grid test and she said that she did not see any breaks or gaps in the grid, Although she said that it was blurry while looking at it with her right eye. She says that this problem has been going on for the last 3-4 months, 6 at the most. She also had a problem not too long ago where her right eye became red and swollen. She went to the doctor and they said that she was probably having an allergic reaction. I am fairly certain that the blurry vision is not caused by an allergic reaction because it would most likely effect both eyes not just one. If anyone has any info they can provide it would be greatly appreciated.