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Optha review

Optha review . Anatomy . Number of bones in bone orbit = 7 bones Bones making up the Rim = Frontal, Maxillary, Zygomatic Close relation to cranial cavity = orbital roof Nasolacrimal fossa = Roof Weakest point of bony orbit = Ethmoidal bone , even infection can break it

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Optha review

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  1. Optha review

  2. Anatomy • Number of bones in bone orbit = 7 bones • Bones making up the Rim = Frontal, Maxillary, Zygomatic • Close relation to cranial cavity = orbital roof • Nasolacrimalfossa = Roof • Weakest point of bony orbit = Ethmoidal bone , even infection can break it • Sinusitis (Mucocele) can cause = orbital cellulitis

  3. Strongest wall of orbit = lateral wall usually fractured in RTA • Floor is strong but fractures are common • If we have muscle entrapment >> fixed eye + Diplopia maybe • Smallest = palatine , can’t be seen

  4. Optic foramen and superior ophthalmic fissure • Optic foramen: within lesser wing of sphenoid. • Contents: • Optic nerve • Opthalmic artery (internal carotid) • Sympathetic plexus

  5. Superior orbital fissure : Annulus of zinn • Most of rectus muscle. • Inside the Annulus: • Optic foramen (canal) • Abducent nerve • Oculomotor (Sup. & Inf. Division) • Nasociliary nerve

  6. Superior orbital fissure : Annulus of zinn • Outside the Annulus: • Trochlear nerve • Lacrimal nerve • Frontal nerve • Opthalmic veins • Recurrent meningeal branch of opthalmic artery

  7. Extraocular muscles • All by 3rd CN (Oculomotor) • Exception is : • SO 4 : superior oblique by 4thTrochlear • LR 6 : lateral rectus by 6thAbducent • Must know the function of each • Superior oblique = depression, intortion • Inferior oblique = elevation , extortion

  8. Levatorpalpebrasuperioris • Can raise upper eye lid by 15 mm • Palsy >> Ptosis (CN 3) • Muscle that give you the eye Crease • Inserts little anterior to Tarsal plate • Inside it >> Mebomian gland (sebum) • Sebum >> part of the tear film

  9. Conjunctiva • Mucus membrane , Goblet cells (produce mucin) • non keratinized epithelium • lubrication, tears (mucin) , immunity • Palpebral conjunctiva Lines the eyelids. • Bulbaror ocular conjunctiva Covers the eyeball. • FornixconjunctivaForms the junction between the bulbar and palpebral conjunctivas. • Terminates at the Limbus

  10. Arterial blood supply of EYE LID • Superficial: • Facial ( external carotid) • Deep: • Opthalmic ( internal carotid)

  11. Venous drainage of EYE LID • Superficial: • drains into the internal and external jugular veins. • Deep: • Vortex >> which flows into the cavernous sinus.

  12. LYMPHATICS • Only found in eye lid & conjunctiva • Spread of systemic infection to the eye is not easy because of this. • Lymphadenopathy ? >> external eye infection • Adenovirus conjunctivitis >> lymphadenopathy in the neck

  13. Lacrimal gland • Located in nasolacrimalfossa (ROOF) • Divided into 2 parts: • Palpebral • Orbital • Smaller, palpebral part can be seen in the superolateralconjunctivalfornix, when you ever the eye lid.

  14. Eye globe • Vitreous >> Sodium hyaluronate • Anterior & posterior chambers >> aqueous fluid (ciliary body).

  15. Arterial blood Supply of the Orbit • First you have to know : Uveal tract = Iris , Choroid , ciliary body vascular pigmented middle layer of the eye. • Posterior ciliaryvessels >> uveal tract. • Cilioretinal arteries >> the sclera, cornea, conjunctiva. • The anterior ciliary arteries >> rectus muscles.

  16. Venous drainage • The vortex veins drain >> Uveal tract • Superior and inferior ophthalmic veins>> Orbit.

  17. Cornea • Layers : • Tear film • Epithelium >> regrows in 7 days • Bowman’s membrane >> Scar if injured • Stroma >> keratocytes , collagen • Decemet’s membrane • Endothelium >> single cells , if you lose it its gone.

  18. Tear film • From outer most to inner : • Lipid >> mebomian gland • Aqueous >> lacrimal gland • Mucus >> goblet cells in conjunctiva

  19. Sclera • Opaque, fibrous, protective, containing collagen and elastic fiber.

  20. Retina • Neurosensory • 10 layers • Fovea >> sharpest image (all cons) • Ganglion cells layer axons >> optic nerve

  21. Lens • Outer most part >> capsule • Epithelium keeps migrating • Zonules >> for accomodation

  22. Optic nerve • Formed by axons of ganglion cells • Optic nerve is surrounded by meninges. • The central retinal artery and vein enter the eye in the center of the optic nerve.

  23. Embryology • End of 4th week of pregnancy • Forebrain • Neuroectoderm: A pair of optic vesicles evaginate ( gives optic stalk too) it is • Invagination of optic vesicle >> optic cup • Invagination of Surface ectoderm >> lens placode >> lens pit >> lens vesicle. • Full development by 8 weeks.

  24. For reading • Neuroectoderm gives rise to the following compartments of the eye: • Retina • Epithelial lining of Ciliarybody and Iris • Optic nerves • Vitreous • Retina Develops from the walls of the optic cup

  25. Difference between Sclera & Cornea ?? Arrangement of the Stromal contents ! • Choroid is very highly vascularised any problem like autoimmune or infection is the job of choroid to deal with.

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