The evidence on this (scant, but exists) is not fully conclusive, but it is interesting.

Congenital (born with) or Early Childhood blindness is indeed something that have not been found together with schizophrenia.

Ref: https://www.researchgate.net/publication/355251682_Corrigendum_Base_Rates_Blindness_and_Schizophrenia

However, as the joint probability is low, that doesn't mean it does not or can not exist.

But it does open up interesting questions. So, let's assume C/E blindness is protective.

Ponderings:

1. IF much (all?) of schizophrenia is a result of spiritual disturbances (you can call the demonic, possession, spirit influence, walking two worlds <- it's all in the same continuum) *1

AND

2. IF the old world lore of possession happening (and being visible) through eyes (or looking into something) and via the optic nerve through your spiritual defences, AND how just "not looking at" sources of possession can actually protect you,

THEN does the lack of physical seeing (and maybe associated lack of spiritual entry into a person) indeed protect from spirit possession -> protects from the DSM -classification known as schizophrenia.

To me Schizophrenia is NOT a well known/understood mental disease (so DSM classification is incorrect) : it is a somewhat identifiable cluster of symptoms (like "hearing voices"), but the actual cause, mechanisms, full effects and treatment cures are unknown in modern medicine. *1

*1 Except for fact that spirit de-posesssion, exorcism, spirit banishing (<- again, many names, similar mechanisms), all of which have provenly instantly "cured" completely treatment resistant schizophrenia which have sometimes lasted for decades.

The literature on the latter is actually quite wide, if one is willing to search and read a bit:

• Glimpses of the Devil A Psychiatrist's Personal Accounts of Possession, Exorcism, and Redemption; M. Scott Peck, MD (2005)

• People of the Lie The Hope for Healing Human Evil; Morgan Scott Peck (2015)

• How To Become a Schizophrenic The Case Against Biological Psychiatry; John Modrow (2003)

• Presence of Spirits in Madness;Wilson Miles Van Dusen (1983)

• Possession - Interdisciplinary Roots ; D.A. Begelman, PhD (1991)

• Practicing exorcism in schizophrenia ; Kazuhiro Tajima-Pozo (BMJ, 2011)

• Is It Schizophrenia or Spirit Possession Miriam Azaunce (1995).pdf

• Spirit Possession and Trance - New Interdisciplinary Perspective; Schmidt (2010)

• Schizophrenia or Spirit Possession; Mike Williamson (2014)

Interesting question by OP, got me thinking about this again. Thanks.

Addition: The conspiracy angle. The idea that schizophrenia could have anything to do with spiritual issues is actively discouraged, laughed at, censored (hard to get medically published) and fought. The drugs don't cure schizophrenia and spirit possession is a big (otherwordly) trade area (read: The Light of Darkness A Warrior's Tale for Our Time; Robert Wiegand, Bruce MacDonald (2020) on that). That's the conspiracy part.

The evidence on this (scant, but exists) is not fully conclusive, but it is interesting.

Congenital (born with) or Early Childhood blindness is indeed something that have not been found together with schizophrenia.

Ref: https://www.researchgate.net/publication/355251682_Corrigendum_Base_Rates_Blindness_and_Schizophrenia

However, as the joint probability is low, that doesn't mean it does not or can not exist.

But it does open up interesting questions. So, let's assume C/E blindness is protective.

Ponderings:

1. IF much (all?) of schizophrenia is a result of spiritual disturbances (you can call the demonic, possession, spirit influence, walking two worlds <- it's all in the same continuum) *1

AND

2. IF the old world lore of possession happening (and being visible) through eyes (or looking into something) and via the optic nerve through your spiritual defences, AND how just "not looking at" sources of possession can actually protect you,

THEN does the lack of physical seeing (and maybe associated lack of spiritual entry into a person) indeed protect from spirit possession -> protects from the DSM -classification known as schizophrenia.

To me Schizophrenia is NOT a well known/understood mental disease (so DSM classification is incorrect) : it is a somewhat identifiable cluster of symptoms (like "hearing voices"), but the actual cause, mechanisms, full effects and treatment cures are unknown in modern medicine. *1

*1 Except for fact that spirit de-posesssion, exorcism, spirit banishing (<- again, many names, similar mechanisms), all of which have provenly instantly "cured" completely treatment resistant schizophrenia which have sometimes lasted for decades.

The literature on the latter is actually quite wide, if one is willing to search and read a bit:

• Glimpses of the Devil A Psychiatrist's Personal Accounts of Possession, Exorcism, and Redemption; M. Scott Peck, MD (2005)

• People of the Lie The Hope for Healing Human Evil; Morgan Scott Peck (2015)

• How To Become a Schizophrenic The Case Against Biological Psychiatry; John Modrow (2003)

• Presence of Spirits in Madness;Wilson Miles Van Dusen (1983)

• Possession - Interdisciplinary Roots ; D.A. Begelman, PhD (1991)

• Practicing exorcism in schizophrenia ; Kazuhiro Tajima-Pozo (BMJ, 2011)

• Is It Schizophrenia or Spirit Possession Miriam Azaunce (1995).pdf

• Spirit Possession and Trance - New Interdisciplinary Perspective; Schmidt (2010)

• Schizophrenia or Spirit Possession; Mike Williamson (2014)

Interesting question by OP, got me thinking about this again. Thanks.