visual pathways

Visual Field

The entire area that can be seen when the eyes are fixed in a particular position.

Photoreceptors

Cells in the retina that respond to light; specifically rods and cones.

Bipolar Cell

The 1st order neuron in the visual pathway, connecting photoreceptors to ganglion cells.

Ganglion Cell

The 2nd order neuron in the visual pathway, whose axons form the optic nerve.

Optic Nerve

A bundle of axons that carry visual information from the retina to the brain.

Optic Chiasm

The point where the optic nerves partially cross, allowing visual information from both eyes to be combined.

Decussate

To cross from one side of the body to the other, as in the crossing of nasal retinal fibers at the optic chiasm.

Optic Tract

The continuation of the optic nerve after the optic chiasm, carrying information from the contralateral visual field.

Lateral Geniculate Nucleus (LGN)

A thalamic nucleus where axons from the optic tract synapse with 3rd order neurons.

Optic Radiations

Axons that carry information from the LGN to the visual cortex.

Primary Visual Cortex

The area of cortex surrounding the calcarine sulcus, where visual information is initially processed.

Homonymous Visual Field Loss

Loss of the same visual field area in both eyes.

Macula Sparing

Preservation of central vision despite visual field loss, typically resulting from lesions in the visual cortex supplied by the PCA.

Temporal Visual Field

The part of the visual field that is closer to the temples and projects onto the nasal retina.

Nasal Retina

The part of the retina closest to the nose.

Superior Colliculus

A midbrain structure involved in eye movement and visual processing.

Observer Pattern of Testing

A method of assessing visual field loss using two circles to represent the field of view of each eye.