A Dark World
It is beyond dark, it is pitch black. No motes of light, to glittering beams, no nothing. You blink and cannot tell if you did just blink or not. Away in the distance a humming begins. You hear it, and turn towards it. It is coming from your left, and down a ways. Beyond that you cannot tell. Reaching out, you grasp at empty air. The fear rises as you reach out for something, anything to grasp on, and through some flailing, you find a smooth wall.
Edging over to it, you follow the wall, letting it guide you towards the sound. Without warning the floor suddenly falls away. Your foot swings over empty air and down. Scrambling for purchase, your heart in your throat, you plummet after it.
Fortunately the hole is not deep, and you kneel at the bottom unhurt, just shaken. An unpleasant aroma fills the air here, but it is still utterly pitch black.
Sight. Most of us take it for granted. It is the sense which gives us most of our spatial awareness of the world around us. Take it away, and even if all the other senses are still present, it is a massive blow to the minds of those used to seeing.
Try it sometime. Blindfold your eyes, and try to carry out your daily tasks - make a drink of squash (nothing hot), or collect the morning post, or even navigate from one room to another. It can be an eye-opener (pun intended) just how difficult these simple tasks become. Without sight, the world suddenly becomes a strange, foreign, inhospitable place. It is by far the most important navigational sense we have.
VR Without Sight
Virtual worlds without the sense of sight do exist. They exist because people without the sense of sight exist. They rely on sound generation, tactile feedback, rarely smell, to replace the eyes, and convey the same information about the world the eyes would.
This means sounds and other sensory information has to be extremely distinctive so you can easily tell where you are. Different surfaces sound different to move on - grass, wood planking, mud, water, et al. This has to be made crystal clear in VR without the sense of sight, or else you become disorientated. This radically scales down the possible complexity of the VR.
Differing ambient music is often used to indicate the gradient of the land, and whether there is a sheer cliff or sudden fall nearby. Occasionally a smell stick may be used for the same purpose. Differences in the difficultyo f the terrain conveyed by force feedback and physical resistance.
If there is no sense of sight, every other sense must be present and utilised, to make up for the deficit. Without these, it is extremely difficult to receive enough sensory feedback to move around, to navigate.
Of course, there is no reason why sight could not be replaced with another, newer sense. Sonar or heat vision for example are not normal human senses, but could be overlaid on the mind via the normal sensory channel of sight, providing some form of echo location or heat trail.
In these cases, sight is still utilised, but overlaid with a different type of location based navigation.