All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad (saw) is His slave and Messenger. It is permissible for a woman to take off her Hijab in front of a blind man provided she is sure that no one else may see her; the evidence is the narration which you mentioned in the question and which was reported by Imaams Muslim and Ahmad .As regards the narration in which the Prophet (saw) ordered Umm Salamah and Maymoonah to observe Hijab in front of Ibn Umm Maktoom then a group of scholars classified this narration as weak.However, some scholars provided this narration as evidence proving that a woman is prohibited from looking at a non-Mahram man, as the Prophet (saw) said to them: "Are both of your blind?" Therefore, the order to wear Hijab in this narration is for this purpose (i.e. forbidding women from looking at non-Mahram men).As regards the issue of staying in seclusion with a man, then it is not permissible for a woman to stay in seclusion with a non-Mahram man even if he is blind because it is not safe for the woman to be sexually attracted by him and vice-versa, and because there are authentic Prophetic narrations which absolutely forbid a man from staying in seclusion with a non-Mahram woman. Allaah Knows best. (Source: islam_web) Classified in Women and Family > Fiqh of Women