Geordie's swirling rainbow crap vision is because part of his brain is missing. (Not a joke) It was never a tech problem. Either they couldn't add more brain to what brain he had or they were not allowed to for ethical or legal reasons. Eugenics ban? If Geordie had left the federation and alien doctors had got a look at him, who did not care about the Eugenics ban, they could have grown him more brain, and he would have had normal vision, despite being a criminal deserving incarceration.