how does the first symptom effect the vision?
A "visual hallucination" is "the perception of an external visual stimulus where none exists".
Hallucination
A "visual hallucination" is "the perception of an external visual stimulus where none exists". A separate but related phenomenon is a "visual illusion", which is a distortion of a real external stimulus. Visual hallucinations are classified as simple or complex:

For example, one may report hallucinating a giraffe. A simple visual hallucination is an amorphous figure that may have a similar shape or color to a giraffe ("looks like" a giraffe), while a complex visual hallucination is a discrete, lifelike image that "is", unmistakably, a giraffe.
who is most likely to be diagnosed with schizophrenia Males are more often affected and on average have an earlier onset. what are some of its symptoms? hallucinations, delusions, disorganized thinking, social withdrawal, decreased emotional expression, apathy. what causes it? Genetic ; Environmental factors such as being raised in a city, cannabis use during adolescence, infections, the ages of a person's mother or father, and poor nutrition during pregnancy.
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Hallucination [SEP] Visual
A "visual hallucination" is "the perception of an external visual stimulus where none exists". A separate but related phenomenon is a "visual illusion", which is a distortion of a real external stimulus. Visual hallucinations are classified as simple or complex: For example, one may report hallucinating a giraffe. A simple visual hallucination is an amorphous figure that may have a similar shape or color to a giraffe ("looks like" a giraffe), while a complex visual hallucination is a discrete, lifelike image that "is", unmistakably, a giraffe.