Question

1. Interruption of visual pathways at any level will cause a defect in the appropriate part of the          

visual field.

Interruption of visual pathways at any level will cause a defect in the appropriate part of the visual field. For example, the tiny lesion in the retina would result in a blind spot (scotoma) in that eye, whereas a similar lesion in the striate cortex would produce corresponding scotomas in both eyes. Interruption of the optic nerve on one side produces blindness in that eye. Damage to the optic nerve fibers as they cross in the optic chiasm results in loss of vision in both temporal fields of vision; this condition is known as bitemporal hemianopsia and occurs because the crossing fibers originate from ganglion cells in the nasal halves of each retina. A lesion of the entire optic tract, visual radiation, or visual cortex on one side causes homonymous hemianopsia, which is loss of vision in the entire contralateral visual field.

Briefly describe the changes in the vision would occur if the lesion is partial in the occipital lobe affecting visual cortex areas in your own words.

Answer 1

The lesion in a different part of the occipital lobe affects differently everytime as given below:-

1. Lesion in the anterior portion of occipital lobe causes peripheral homonymous hemianopia but doesn't affect the central visual field.

2. Lesions in the posterior portion of occipital lobe causes incomplete central homonymous hemianopia.

3. Lesion in both anterior and posterior lobe of the medial area causes incomplete central homonymous hemianopia and peripheral homonymous hemianopia.

4. Tiny lesion on occipital tip causes complete central homonymous hemianopia or quadrantanopia.

5. Lesion in the bilateral occipital tip and lateral posterior portion causes bilateral peripheral visual field disturbances (but only slightly) with complete central homonymous hemianopia on both sides.