According to Islamic rules, is it required for a woman to wear the headscarf in the presence of a non-Mahram blind man?
"Once a blind man asked for permission to enter Fatima's (Her Holiness) house but she kept a veil between them. The Messenger of Allah (SAWS) noticed her (Our Lady Fatimah (SWT)) actions and asked: Why did you (Her Holiness (SWT)) keep a veil between you (Her Holiness (SWT)) when he cannot see you?" Her Holiness Fatimah (SWT) answered: Messanger of Allah, it is true that he cannot see me (Her Holiness (SWT)), but I (Her Holiness (SWT)) can see him and he can smell my (Her Holiness (SWT)) fragrance.' At this, the Prophet (SAWS) said: "I bear witness that you are part of me". (Book `Fatimah the Gracious' Pg 187)
Umm Salamah (radiallahu anhaa), the mother of the believers (wife of Rasulullah), narrates (emphasis mine):
I was with the Messenger of Allah (salallahu alayhi wa sallam) along with Maimunah (May Allah be pleased with him) when Ibn Umm Maktum (May Allah be pleased with him) (who was blind) came to visit him. (This incident took place after the order of Hijab). The Prophet (salallahu alayhi wa sallam) told us to hide ourselves from him (i.e., observe Hijab). We said: "O Messenger of Allah (salallahu alayhi wa sallam), he is blind and is unable to see us, nor does he know us." He replied; "Are you also blind and unable to see him?" (Riyad As-Saliheen; from Abu Dawud and At-Tirmidhi's collections)
In this hadith, Abdullah Ibn Umm Maktoom (radiallahu anhu) came to visit Rasulullah. Abdullah ibn Umm Maktoom is none other than the same sahabi mentioned in Surah Abasa. From the tafseer of that great surah, we know that he was a3maa, or blind from birth.
In this case, the wives of the Prophet (may Allah be pleased with them) did not wear hijab at this time. The hadith mentions that
this took place after the order of Hijab. And in this case, Rasulullah rebuked them for not wearing hijab in front of him, although he was blind.
From this hadith, and other proofs, scholars mention that it is absolutely required for a woman to wear hijab in front of a non-mahram, even if he is blind.
And Allah knows best.
She doesn't need to but she may. An example exists in the history of Islam when a blind person came to the Prophet (S.A.)'s or Hazrat Fatimeh (S.A.)'s house and she left the room or wore her Hijab (sorry, I have read that some years ago and don't remember the exact details), that's the place the Prophet (S.A.) says about her that she is a part of me, who bothers her has bothered me and who bothers me has bothered Allah, if my memory helps.