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ORBIT II

ORBIT II. Dr. Mujahid Khan. Blood Supply. Ophthalmic Artery: It is a branch of Internal Carotid Artery Emerges from cavernous sinus Runs forward lateral to the optic nerve Reaches the medial wall of the orbit Gives away several branches. Central Artery of Retina. Is a small branch

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ORBIT II

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  1. ORBIT II Dr. Mujahid Khan

  2. Blood Supply Ophthalmic Artery: • It is a branch of Internal Carotid Artery • Emerges from cavernous sinus • Runs forward lateral to the optic nerve • Reaches the medial wall of the orbit • Gives away several branches

  3. Central Artery of Retina • Is a small branch • Pierces the meningeal sheath of optic nerve & gain entrance to the nerve • Enters the eyeball at the centre of optic disc • Divides into 2 branches called end arteries

  4. Ciliary Arteries • Can be divided in two groups • Anterior group enters the eyeball near the corneoscleral junction • Posterior group enters the eyeball near the optic nerve

  5. Lacrimal Artery • It supplies the lacrimal gland

  6. Supratrochlear & Supra orbital Arteries • Are distributed to the skin of the forehead

  7. Ophthalmic Veins • Superior ophtalmic vein communicates in front with the facial vein • Inferior ophthalmic vein communicates with the pterygoid plexus through the inferior orbital fissure • Both the veins pass backward through superior orbital fissure & drain into cavernous sinus

  8. Lymph vessels • No lymph nodes or vessels are present in the orbital cavity

  9. The Eye • Eyeball consists of 3 coats: • The fibrous coat • The vascular pigmented coat • The nervous coat

  10. Fibrous Coat • Made up of posterior opaque part, the sclera & anterior tranparent part cornea

  11. Sclera • Composed of dense fibrous tissue • Pierced by optic nerve posteriorly and is fused with the dural sheath of the nerve • Lamina Cribrosa is the area of sclera that is pierced by optic nerve fibers • Also pierced by ciliary arteries & nerves • Is continuous in front with the cornea

  12. Cornea • Is transparent • Responsible for refraction of light entering the eye • It is in contact with the aqueous humor posteriorly

  13. Vascular Pigmented Coat • Consists from behind forward: • Choroid • Ciliary body • Iris

  14. Choroid • Is composed of an outer pigmented layer and an inner highly vascular layer

  15. Ciliary Body • Is continuous posteriorly with choroid • Anteriorly lies behind the peripheral margin of iris • Composed of: • Ciliary ring • Ciliary process • Ciliary muscle

  16. Ciliary ring is the posterior part of the body, has shallow grooves, Ciliary striae • Ciliary processes are radially arranged folds connects the suspensory ligaments of the lens • Ciliary muscle is composed of meridianal and circular fibers of smooth muscles

  17. Iris • Is a thin, contractile, pigmented diaphragm • Has central aperture called pupil • Is suspended in the aqueous humor between the cornea and lens • Its periphery is attached to the anterior surface of the ciliary body • Divides the space between cornea and lens into anterior & posterior chambers

  18. Nervous Coat or Retina • Consists of an outer pigmented layer & inner nervous layer • Its outer surface is in contact with choroid • Inner layer in contact with the vitreous body • Posterior three-fourths is the receptor organ • Macula lutea is the oval yellowish area in the center of the posterior part • Fovea centralis is the central depression

  19. Retina • Optic nerve leaves the retina to medial side of macula lutea by the optic disc • Optic disc is depressed at its center, where it is pierced by central artery • Optic disc is insensitive to light and referred as blind spot • Optic disc is seen to be pale pink with ophthalmoscope examination

  20. Optic Nerve • Enters the orbit from middle cranial fossa by passing through the optic canal • Accompanied by ophthalmic artery • It is surrounded by sheaths of pia, arachnoid and dura maters • It runs forward and laterally within the cone of the recti muscles

  21. Optic Nerve • Pierces the sclera at a point medial to the posterior pole • The meninges fuse with the sclera • The subarachnoid space extends forward as far as the eyeball • A rise in pressure of the CSF within the cranial cavity is transmitted to the back of the eyeball

  22. Nasociliary Nerve • Arises from the ophthalmic division of the trigeminal nerve in the lateral wall of the cavernous sinus • Enters the orbit through the lower part of the superior orbital fissure • Crosses above the optic nerve with the ophthalmic artery • Ends by dividing into the anterior ethmoidal and infratrochlear nerves

  23. Branches of Nasociliary Nerve • Communicating branch to the ciliary ganglion • The long ciliary nerves (2-3 in number) • Posterior ethmoidal nerve • Infratrochlear nerve • Anterior ethmoidal nerve • External nasal nerve

  24. Ciliary Ganglion • It is about the size of a pinhead • It is a parasympathetic ganglion • Situated in the posterior part of the orbit on the lateral side of the optic nerve • Receives its preganglionic parasympathetic fibers from the oculomotor nerve via nerve to inferior oblique • The postganglionic fibers leave the ganglion in the short ciliary nerves

  25. Contents of the Eyeball • Aqueous Humor • Vitreous body • lens

  26. Aqueous Humor • Clear fluid fills the ant. & post. Chambers • Is a secretion from ciliary processes • Drained away through canal of Shlemm • Obstruction to its draining results in glaucoma • Glaucoma causes degenerative changes in the retina

  27. Aqueous Humor • Supports the wall of the eyeball • Maintains its optical shape • Nourishes the cornea and lens • Removes the products of metabolism

  28. Vitreous Body • Is a tranparent gel • Fills the eyeball behind the lens • Hyaloid canal is a narrow channel runs through it extends from optic disc to posterior surface of the lens • Canal is filled with hyaloid artery in fetus • Contribute in the magnifying power of eye • Supports posterior surface of lens

  29. Lens • Is a transparent, biconvex structure • Enclosed in a transparent capsule • Situated behind the iris & in front of vitreous • Encircled by ciliary process • Assumes globular shape due to tense elastic capsule • Its circumference attached to the ciliary process by suspensory ligament

  30. Lens • Suspensory ligament keeps the elastic lens flattened • Ciliary muscle contracts to accommodate the eye for close objects • Lens becomes dense & less elastic in advance age resulting in presbyopia • Glasses are used to overcome presbyopia

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