As an "elderly" person myself, I am finding that taking self-defense classes is most helpful, and I highly recommend it. Take a real class from a certified school, whether it is karate, jiu-jitsu, or any other form of martial arts, and not a 'quickie' course from the recreation department in your town.
A lot of self defense is actually centered on awareness of one's surroundings, carrying yourself confidently, and looking people in the eye. A potential attacker wants to remain anonymous and retain the advantage of surprise.
Other aspects of self-defense include the use of surprise, yourself if you are attacked. Most attackers expect you to pull away from them, and are prepared for this. Instead, many self-defense moves have you move toward the attacker, with a move intended to put them off balance, both physically and psychologically, giving you the advantage.
Prior to my knee replacement surgery, I often used a cane; I was taught several ways for this to turn into a weapon of self defense.
I cannot offer insight for the blind and deaf, but those are my experiences and advice for the elderly. Best wishes on your article.