This anomaly helps eye healthcare professionals in the assessment of the site of the lesion along the visual pathway, which produces well-described visual field defects, also known as hemianopias, posterior, or at the chiasm.īeyond the chiasm, the pathway continues as two distinct tracts, each carrying the temporal fibers from the other eye. Here more than half of the nasal fibers from the left eye decussate to join the temporal fibers of the right eye and form the right optic tract and vice versa. This continues till the two optic nerves join together to form the optic chiasm directly behind and above the pituitary stalk. It exits into the middle cranial fossa to form the intracranial part of the optic nerve. It then enters the optic canal, a bone-encased tunnel intended to protect the nerve. The axons exit the orbit through the orbital foramen, simultaneously with the ophthalmic artery and sympathetic fibers. The nerve is surrounded by the dura, which is in continuation of that of the brain, allowing free movement of CSF between the eye and the intracranial vault. These fibers join together at the optic disc and are redirected posteriorly out of the eye to form the orbital part of the optic nerve. It consists of two types of fibers, namely temporal and nasal fibers, which control the nasal and temporal parts of the visual field, respectively. The ganglion cell layer and nerve fiber layer serve as the foundation of the optic nerve the former contains the cell bodies, and the latter contains the axons as they stream across the retina. The photoreceptor layers consist of the rods and cones, which generate action potentials with the help of rhodopsin through photosensitive cycles. The optic pathway begins in the retina, which is a complex structure made up of ten different layers. The visual system consists of two primary parallel pathways: an optic pathway and a pupillary reflex pathway.
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