Optic radiation (lesions)

Lesions within the part of the optic radiation passing straight to the occipital cortex tend to produce homonymous hemianopia - loss of the contralateral visual field in both eyes.

Lesions of Meyer's Loop of the optic radiation on one side produces a loss of the upper, outer quadrant of vision on the same side in both eyes - homonymous superior quadrantanopia. This defect may be the first sign of temporal lobe lesions, or indeed, it may be the residual effect of a temporal lobectomy.