Many great minds have wondered about this. Of course, so have many total prunepits, so don’t jump to any rash conclusions. While there may be exceptions, in general the dreams of the congenitally blind contain no visual elements and consist predominantly of sound plus smell, touch and the sense of movement.
Plotwise they tend to to be reality-based — e.g., a reprise of the events of the day — with less of the fantasy you find in the dreams of sighted people. There’s also more conversation. Persons who become blind after birth often see in their dreams, although it depends on (a) how old they were when they became blind and (b) how long it’s been since. If you’re blinded before the age of six or seven you generally see little or nothing in your dreams. Dreams of people who become blind when older are often indistinguishable from those of the sighted, but as time goes on many “see” less and less.
To some extent, I gather, the lack of visual elements in the dreams of the blind can be counteracted by force of imagination. Helen Keller, who became blind at the age of 19 months, claimed to have “visions of ineffable beauty.” These ran to things like pearls. To my mind this betrays a certain want of ambition. A man’s reach should exceed his grasp, right? So I’d want to see what I could work up along the lines of Jacqueline Bisset. But at least we know there’s hope.