As far as I recall, various people were not familiar with the VISOR when they first encounter Geordi. Yet he was apparently fitted with it when he was five.
Is the VISOR extremely rare or unique? Is it experimental? Did we ever encounter another instance of similar technology?
Based on Geordi's conversations with Doctors Crusher and Pulaski in TNG: Encounter at Farpoint, Part I and TNG: Loud As A Whisper it would seem that the use of this technology is vanishingly rare. Sufficiently so that a Starfleet doctor with two decades of medical experience hasn't even seen one in real life and a renowned specialist in surgical research has only encountered a few similar cases in all of her years of practice.
CRUSHER: Naturally I've heard of your case. The visor implants you wear ...
LAFORGE: Is a remarkable piece of bio-electronic engineering by which I quote see much of the EM spectrum ranging from simple heat and infrared through radio waves et cetera, et cetera, and forgive me if I've said and listened to this a thousand times before.
and
PULASKI: It's possible to install optical devices which look like normal eyes, and would still give you about the same visual range as the visor.
LAFORGE: Done? You say almost. How much reduction?
PULASKI: Twenty percent. There is another option. I can attempt to regenerate your optic nerve, and, with the help of the replicator, fashion normal eyes. You would see like everyone else.
LAFORGE: Wait a minute. I was told that was impossible.
PULASKI: I've done it twice, in situations somewhat similar to yours. Geordi, it would eliminate the constant pain you are under. Why are you hesitating?
That all being said, we see other Starfleet personnel wearing VISORs in 2380, in LD: Room for Growth and LD: Second Contact. It's possible that Geordi made them fashionable given how famous the Enterprise crew are.
