Even if that was a credible source, both the number of people born blind and the percentage of the population with schizophrenia must be tiny. So the expected number of cases could well be below 1 for that tiny fraction of a tiny fraction. Or it might just be undiagnosed, or someone affected by both might have died very young, or hasn’t got a standard if living that even makes a diagnosis reasonable/likely, or a myriad of other reasons. Also causation vs. correlation and all that…