Why did Geordi have his visor replaced with ocular implants between Generations and First Contact?

Question

In First Contact, Geordi is not wearing his VISOR and instead has ocular implants. In the previous movie, Generations, Geordi still has his VISOR for the whole movie. Why did he change?

Answer 1

Katherine Pulaski offered Geordi the options of ocular implants or the regeneration of his optic nerve all the way back in TNG season 2. At the time, he didn't seem keen on the ocular implants, as they would've reduced his visual range by twenty percent.

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?

LAFORGE: Well, when I came to see you, it was to talk about modifying this. And now you're saying it could be possible for me to have normal vision?

PULASKI: Yes.

LAFORGE: I don't know. I'd be giving up a lot.

PULASKI: There's something else you must know. This is a one shot. If you decide to change your mind, there's no going back. And there are risks. I can offer choices, not guarantees.

LAFORGE: Well, this is a lot to think about. I'll get back to you, Doctor. Thank you.

_{Star Trek: The Next Generation - S02E05 - "Loud As A Whisper"}

Evidently, Geordi stuck with the VISOR until some time between Star Trek: Generations and Star Trek: First Contact -- so, between six and eight years later, in-universe -- at which point, he chose to go with ocular implants. I don't believe any official source has ever explained why he went with the ocular implants at that specific point in time, although, given that six-plus years had passed since he was first offered them, it's possible that the technology had improved, making them a more attractive option.

It's also worth noting that in Star Trek: Generations, Geordi was captured by Tolian Soran and some rogue Klingons, including the Duras sisters, Lursa and B'Etor. They modified his VISOR to transmit a video signal to the main viewscreen on the bridge of their Bird-of-Prey, through which they ascertained the Enterprise-D's shield modulation, enabling them to bypass its shields and ultimately destroy it.

LURSA: That's it! Replay from time index nine two four. ...Magnify this section and enhance. ...Their shields are operating on a modulation of two five seven point four.

B'ETOR: Adjust our torpedo frequency to match two five seven point four!

_{Star Trek: Generations (1994)}

While we lack official confirmation that the VISOR's role in the destruction of the Enterprise-D influenced Geordi's decision to replace it with ocular implants, the relative timing of those events fits nicely with that theory, and it's hard to believe that he and Starfleet wouldn't have started to view the VISOR as a liability after such a catastrophic security breach.

Answer 2

I'm not sure it has ever been spelled out in universe, but out of universe LeVar Burton explained in an interview:

It was time. Eighty percent of my vision was cut off when I wore that thing, and it physically hurt, which was one of the more important reasons I wanted to get out from underneath it. We held on to it for so long, because, as Rick says, it was one of the ways that we established in the minds of the audience the technology of the twenty-fourth century.

On the series it became problematic because it was cost prohibitive. We were never able to show the audience what Geordi saw, because it was too expensive and we were on a tight budget. So it became a barrier to storytelling, physically painful for me, and on a spiritual level, it’s really just a sin to cover an actor’s eyes.

I wasn’t really aware of how much of a barrier it had become until we shot this movie, and in the absence of the VISOR, I noticed that the other actors were relating to me very differently. They were engaging me in a way that they never did in scenes. So the visor is dead; long live the visor!

Answer 3

In-universe, Geordi's VISOR causes him constant pain.

From "Encounter at Farpoint":

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.

(Without the Visor, Geordi La Forge's eyes are white sightless orbs, and he has flashing red lights at his temples)

CRUSHER: You've been blind all your life?

LAFORGE: I was born this way.

CRUSHER: And you've felt pain all the years that you've used this?

LAFORGE: They say it's because I use my natural sensors in different ways.

So as soon as an alternative was possible, Geordi would have a strong reason to switch as soon as possible.

Geordi had been offered some means of eliminating the pain, but they are risky and/or would interfere with vision. From the same episode:

CRUSHER: Well, I see two choices. The first is painkillers.

LAFORGE: Which would affect how this works. No. Choice number two?

CRUSHER: Exploratory surgery. Desensitise the brain areas troubling you.

LAFORGE: Same difference. No, thank you, Doctor.

CRUSHER: I understand.

Answer 4

In the deuterocanonical Trek Litverse (specifically The Insolence of Office) it was because of security concerns following the events of Generations in which his VISOR was hacked and used to aid in the destruction of the Enterprise-D, and coupled with the previous incident of VISOR-based brainwashing in The Mind's Eye.

La Forge was ordered by Admiral Hayes (of various screen appearances) to replace his VISOR as a security risk or be reassigned to a less-sensitive post.

La Forge was tempted to tell the admiral that, no, he wouldn’t pardon the expression. But he restrained himself, and said instead, “Sir, I have had this VISOR for over thirty years. It’s a part of who I am. You can’t force me to give it up.” “No, Mr. La Forge, I can’t force you,” Hayes said. “However, should you elect not to comply with Starfleet’s current security standards, you would not be able to continue to serve aboard the Enterprise.”