Scotoma (came from the Greek word for darkness: skotos): a blind spot or area of reduced vision surrounded by a normal visual field.
i.e.: A person can see normally except where the scotoma is.
Scotomas may affect one or both eyes.
 They can be either absolute, where the person can see nothing within the scotoma, or relative, where the person can see something within the scotoma, but less than usual.

Negative scotoma: an area of partial or total blindness.
 Usually it is followed by a scintillating scotoma, but the negative scotoma may be surrounded by a scintillating scotoma.
A negative scotoma may be either be an absolute scotoma and may seem like a blank spot where the person can not see any light, or a relative scotoma in which some light may be seen but less than normal, the scotoma  may be blurry as if looking through thick plastic.
Negative scotomas are usually not noticed by a person and are found by an eye or ophthalmic examination.

Positive scotoma: an area of vision loss or blockage that may be seen as a dark or black spot or the blockage of vision may be what seem to be various shapes or lines that may change in brightness i.e they may get darker and lighter so it seems like a flickering light.

Fortification scotoma (AKA:teichopsia): seeing lines that look like the lines of a fort.
The lines may be gray or colored and the brightness may change from darker to lighter so that they appear to be flickering then the fortification scotoma may be called a scintillating scotoma.

Scintillating scotoma: is the progression of a fortification scotoma i.e When the lines seen in a fortificatin scotoma change in brightness rapidly so they look like flickering lights.
This is one of the most common scotomas a person who has a migraine with aura may see.
It usually starts as a spot of flickering lights in the center of a person's visual field it then gets larger.
Scotoma (came from the Greek word for darkness: skotos): a blind spot or area of reduced vision surrounded by a normal visual field. i.e.: A person can see normally except where the scotoma is. Scotomas may affect one or both eyes.  They can be either absolute, where the person can see nothing within the scotoma, or relative, where the person can see something within the scotoma, but less than usual.
Negative scotoma: an area of partial or total blindness.  Usually it is followed by a scintillating scotoma, but the negative scotoma may be surrounded by a scintillating scotoma. A negative scotoma may be either be an absolute scotoma and may seem like a blank spot where the person can not see any light, or a relative scotoma in which some light may be seen but less than normal, the scotoma  may be blurry as if looking through thick plastic. Negative scotomas are usually not noticed by a person and are found by an eye or ophthalmic examination.
Positive scotoma: an area of vision loss or blockage that may be seen as a dark or black spot or the blockage of vision may be what seem to be various shapes or lines that may change in brightness i.e they may get darker and lighter so it seems like a flickering light.
Fortification scotoma (AKA:teichopsia): seeing lines that look like the lines of a fort. The lines may be gray or colored and the brightness may change from darker to lighter so that they appear to be flickering then the fortification scotoma may be called a scintillating scotoma.
Scintillating scotoma: is the progression of a fortification scotoma i.e When the lines seen in a fortificatin scotoma change in brightness rapidly so they look like flickering lights. This is one of the most common scotomas a person who has a migraine with aura may see. It usually starts as a spot of flickering lights in the center of a person's visual field it then gets larger.
Aura (symptom)