Image transmission
The luminous visual information that we perceive enters the eye through the cornea and the lens. Arrived at the level of the retina, the many cones and rods present transform the luminous flux into a nerve impulse, which is then transmitted to the optic nerve. The latter is made up of approximately 1.2 million axons (fibers of neurons) from the ganglion cells of the retina and which converge in a bouquet at the back of the eyeball. Then it’s off on an express trip to the brain!
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Through the eye… The retina’s photoreceptor cells (cones and rods) pick up light and encode its characteristics in the form of electrical signals. The image is then inverted.
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…along the optic nerve These electrical signals are sent along each of the fibers of the optic nerve, which join at the level of the optic chiasm.
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… to the brain Information from both eyes is assembled at the level of the chiasma. After passing through relay zones (synapses), they are transmitted to the visual cortex which reconstructs the image correctly.
A fragile nerve
Certain pathologies of the eye can affect the optic nerve. The best known is glaucoma. But inflammation (optic neuritis), tumor (meningioma), infection (herpes) or systemic diseases (sarcoidosis, tuberculosis, etc.) also sometimes impact its functioning. This can result in visual disturbances, perception of the visual field, colors or contrasts.
Trauma, dietary deficiency (particularly vitamin B12), toxic neuropathies due to alcohol or taking certain medications can also cause damage to the fibers of the optic nerve, which cannot be regenerated.
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