The most rigorous evidence comes from a 2018 whole-population study tracking nearly half a million children born in Western Australia between 1980 and 2001. Of those, 1,870 developed schizophrenia, but not one of the 66 children with cortical blindness did.
1,870 / 500,000 = 0.374% of people in the general population
1,870 / 500,000 = 0.374% of people in the general population
0.374% * 66 = 0.25
Not particularly rigorous.