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 Sinusitis (Mucocele) can cause = orbital

cellulitis

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

Optic foramen and superior ophthalmic fissure Optic foramen: within lesser wing of

sphenoid. Contents:1. Optic nerve 2. Opthalmic artery (internal carotid)3. Sympathetic plexus

Superior orbital fissure : Annulus of zinn

Most of rectus muscle. Inside the Annulus:1. Optic foramen (canal)2. Abducent nerve3. Oculomotor (Sup. & Inf. Division)4. Nasociliary nerve

Superior orbital fissure : Annulus of zinn Outside the Annulus:1. Trochlear nerve 2. Lacrimal nerve 3. Frontal nerve4. Opthalmic veins5. Recurrent meningeal branch of

opthalmic artery

Extraocular muscles

All by 3rd CN (Oculomotor) Exception is :1. SO 4 : superior oblique by 4th

Trochlear 2. LR 6 : lateral rectus by 6th Abducent

Must know the function of each Superior oblique = depression,

intortion Inferior oblique = elevation ,

extortion

Levator palpebra superioris 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

Conjunctiva Mucus membrane , Goblet cells (produce mucin) non keratinized epithelium lubrication, tears (mucin) , immunity

Palpebral conjunctiva Lines the eyelids.

Bulbar or ocular conjunctiva Covers the eyeball.

Fornix conjunctivaForms the junction between the bulbar and palpebral conjunctivas.

Terminates at the Limbus

Arterial blood supply of EYE LID Superficial:1. Facial ( external carotid)

Deep:1. Opthalmic ( internal carotid)

Venous drainage of EYE LID Superficial:1. drains into the internal and external

jugular veins. Deep:1. Vortex >> which flows into the

cavernous sinus.

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

Lacrimal gland

Located in nasolacrimal fossa (ROOF)

Divided into 2 parts: 1. Palpebral2. Orbital

Smaller, palpebral part can be seen in the superolateral conjunctival fornix, when you ever the eye lid.

Eye globe

Vitreous >> Sodium hyaluronate

Anterior & posterior chambers >> aqueous fluid (ciliary body).

Arterial blood Supply of the Orbit First you have to know : Uveal tract = Iris , Choroid , ciliary bodyvascular pigmented middle layer of the eye.

Posterior ciliary vessels >> uveal tract.

Cilioretinal arteries >> the sclera, cornea, conjunctiva.

The anterior ciliary arteries >> rectus muscles.

Venous drainage

The vortex veins drain >> Uveal tract

Superior and inferior ophthalmic veins>> Orbit.

Cornea

Layers :1. Tear film 2. Epithelium >> regrows in 7 days 3. Bowman’s membrane >> Scar if

injured4. Stroma >> keratocytes , collagen5. Decemet’s membrane 6. Endothelium >> single cells , if you

lose it its gone.

Tear film

From outer most to inner :

1. Lipid >> mebomian gland2. Aqueous >> lacrimal gland 3. Mucus >> goblet cells in

conjunctiva

Sclera

Opaque, fibrous, protective, containing collagen and elastic fiber.

Retina

Neurosensory 10 layers Fovea >> sharpest image (all cons) Ganglion cells layer axons >> optic

nerve

Lens

Outer most part >> capsule Epithelium keeps migrating Zonules >> for accomodation

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.

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.

For reading

Neuroectoderm gives rise to the following compartments of the eye:

Retina Epithelial lining of Ciliary body and Iris Optic nerves Vitreous

Retina Develops from the walls of the optic cup

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.