optic canal

Examples of optic canal in the following topics:

• Orbits

  • To the rear of the orbit, the optic foramen opens into the optical canal through which the optic nerve and ophthalmic artery pass.
  • The lacrimal and ethmoid bones contribute to the medial wall of the orbit and also to the medial wall of the orbital canal.
  • Finally, the sphenoid bone forms the posterior wall of the orbit and also contributes to the formation of the optic canal.

• Optic (II) Nerve

  • The optic nerve is also known as cranial nerve II.
  • The optic nerve is the second of twelve paired cranial nerves.
  • As a consequence, optic nerve damage produces irreversible blindness.
  • The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running posteromedially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.
  • An illustration of the brain highlighting the optic nerve and optic tract.

• Foramina

  • Optic foramen: Located in the sphenoid, it allows the passage of the ophthalmic artery and nerve from the optic canal into the orbit.

• The Vestibular System

  • The base of each canal has a swelling that contains a cluster of hair cells.
  • One canal lies horizontally, while the other two lie at about 45 degree angles to the horizontal axis.
  • Upon cessation of acceleration or deceleration, the movement of the fluid within the canals slows or stops.
  • Note that the canals are not sensitive to velocity itself, but to changes in velocity.
  • Finally, the vestibular signals project to certain optic muscles to coordinate eye and head movements.

• Canals

• Vision: The Visual System, the Eye, and Color Vision

  • The image is transduced into neural impulses and then transferred through the optic nerve to the rest of the brain for processing.
  • The optic chiasm is a complicated crossover of optic nerve fibers behind the eyes at the bottom of the brain, allowing the right eye to "wire" to the left neural hemisphere and the left eye to "wire" to the right hemisphere.
  • These cues range from the convergence of our eyes and accommodation of the lens to optical flow and motion.
  • Clockwise from left: Optic nerve, optic disc, sclera, choroid, retina, zonular fibers, posterior chamber, iris, pupil, cornea, aqueous humor, ciliary muscle, suspensory ligament, fovea, retinal blood vessels.
  • In center: Vitreous humour, hyaloid canal, lens.

• Development of Vision

  • Development of the optic vesicles starts in the three-week embryo from a progressively deepening groove in the neural plate called the optic sulcus.
  • As this expands, the rostral neuropore (the exit of the brain cavity out of the embryo) closes and the optic sulcus and the neural plate becomes the optic vesicle.
  • The lens then acts as an inducer back to the optic vesicle to transform it into the optic cup and back to the epidermis to transform it into the cornea.
  • Iris is formed from the optic cup cells.
  • After the closure of the tube they are known as the optic vesicles.

• Brain Tumors

  • A brain tumor is an intracranial solid neoplasm—a tumor (defined as an abnormal growth of cells)—within the brain or the central spinal canal.
  • Brain tumors include all tumors inside the cranium or in the central spinal canal.
  • Consequences of intracranial hypertension: Large tumors or tumors with extensive perifocal swelling (edema) inevitably lead to elevated intracranial pressure (intracranial hypertension), which translates clinically into headaches, vomiting (sometimes without nausea), altered state of consciousness (somnolence, coma), dilation of the pupil on the side of the lesion (anisocoria), papilledema (prominent optic disc at the funduscopic eye examination).

• Embryonic Development of the Brain

  • The hollow interior is called the neural canal.
  • The optical vesicle (which will eventually become the optic nerve, retina and iris) forms at the basal plate of the prosencephalon.

• Lasers

  • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback.
  • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback (usually an optical cavity).
  • When a gain medium is placed in an optical cavity, a laser can then produce a coherent beam of photons.
  • The gain medium is where the optical amplification process occurs.
  • The most common type of laser uses feedback from an optical cavity--a pair of highly reflective mirrors on either end of the gain medium.