I am having trouble believing that she had an "eyesight" problem due to aging in 1911. She would have been only 39 years old.
39 is not an unusual age to need reading glasses. People's eye sights start to deteriorate due to old age at about the age of 40 years, and nowadays many people start wearing reading glasses somewhere in their early forties. If Alexandra had read and written by poor lamplight a lot, it may very well be that she had difficulty focusing, especially when she was tired.
I just received "Purple Secret" as a Christmas gift which is a book about the genetic illnesses in the British Royal family. It presents a strong case for the existence of porphyria in many of the descendants of King George III which would include Alexandra. I stand by my previous statement, that I think she had porphyria. ...
"Purple Secret" mentions the DNA tests performed to identify the remains found in Siberia, but does not provide any evidence that Alexandra suffered from porphyria; I think it does not even discuss the question whether her various health problems might have been caused by porphyria. And for good reasons, I think: Alexandra suffered from back problems, headaches, fatigue, anxiety at public functions, and an 'enlarged heart' (cardiomegaly?), but not from symptoms common in porphyria patients such as abdominal pains, vomiting, seizures, hallucinations, paranoia, depression, etc.; the clinical picture of her health problems does not seem to fit that of porphyria.