What Is the Optic Nerve Sheath?
Optic canal (OC) is an important channel for cranial-orbital communication, and the intracranial optic nerve (Opticnerve, ON) and ophthalmic artery enter the orbit. The optic canal has two mouths, four walls, and a narrow part, that is, the craniotomy, orbital mouth, upper wall, lower wall, inner wall, outer wall, and narrow part of the optic nerve tube.
- Chinese name
- Optic canal
- Foreign name
- Optic canal
- Short name
- OC
- Meaning
- An important channel for cranial-orbital communication
- Optic canal (OC) is an important channel for cranial-orbital communication, and the intracranial optic nerve (Opticnerve, ON) and ophthalmic artery enter the orbit. The optic canal has two mouths, four walls, and a narrow part, that is, the craniotomy, orbital mouth, upper wall, lower wall, inner wall, outer wall, and narrow part of the optic nerve tube.
Optic tube overview
- The craniotomy is a horizontal oval, the base of the outer sphenoid winglet and the base of the anterior bed process, and the upper part of the internal carotid bed process is inferior. It becomes narrower when entering the orbit, and the distal end of the medial wall becomes thicker than the proximal end. This thickened part is called the optic canal ring (Opticring), which separates the sphenoid ethmoid sinus by the bony structure.
Optic tube physiology
- The average thickness of the central tube wall of the optic nerve tube is 0.21mm, and the average thickness of the ring section is 0.57mm. In this way, the distal end of the optic tube includes the narrowest and thickest part. Diagonally forward and outward. The posterior mouth opens at both ends of the optic crisscross groove; the anterior mouth is the optic nerve foramen of the orbital apex. Through this tube, there are mainly optic nerves, and birds form the optic nerve holes directly. The tube is about 4-9mm long, with optic nerve and its three layers of sheath, ophthalmic artery and small branches of sympathetic nerve in the tube.
Optic neural tube physiological significance
- The optic canal craniotomy is a horizontal oval shape; the orbital mouth is a vertical oval shape. It becomes narrower when entering the orbit, and the distal end of the medial wall becomes thicker than the proximal end. This thickened part is called the optic canal ring (Opticring), which separates the sphenoid ethmoid sinus by the bony structure. The average thickness of the central tube wall of the optic nerve tube is 0.21mm, and the average thickness of the ring section is 0.57mm. In this way, the distal end of the optic tube includes the narrowest and thickest part. When performing OC decompression, the narrowest and thickest part of the distal end must be removed, and the optic canal sheath must be opened. However, there is still controversy about opening the ON sheath, and it is believed that when the sheath is opened, the blood supply of the ON will be damaged and the vision will be damaged.
Optic tube anatomy
- The optic canal is a tubular channel that runs between the orbital cavity and the cranial cavity. It is surrounded by the superior and inferior roots of the sphenoid winglets, the outer side of the sphenoid body and the outer ethmoid sinus bone wall. The continuum covered by the falciform fold in the rear is called the optic canal membrane. Radiologically, this tube is called the optic nerve foramen, which is only suitable for X-ray films. Optic tube decompression and open surgery is one of the basic surgical methods of skull base surgery, and its applied anatomy knowledge is very important for ophthalmology, otolaryngology and neurosurgeons.
Optic nerve tube decompression
- In the treatment of the optic nerve tube trauma, in the early post-injury period, in order to prevent vasoconstriction, a vasodilator should be injected after the ball. When there is spasm or thrombosis in the central retinal artery, anti-spasmodic drugs should be used in time. In order to reduce the oppression of the optic nerve itself and its nutritional vessels due to edema, large doses of glucocorticoids and fibrinolytic enzymes can be used appropriately. Optic nerve decompression is generally used in surgery for the purpose of decompressing the optic nerve tube or removing arachnoid adhesions.