The 7 bones of the orbit:
<ul>
 <li>Frontal</li>
 <li>Zygoma</li>
 <li>Maxillary</li>
 <li>Sphenoid</li>
 <li>Ethmoid</li>
 <li>Palatine</li>
 <li>Lacrimal</li>
</ul>
<ul>
 <li>Volume: 30ml</li>
 <li>There are no lymphatic vessels or nodes in the orbit</li>
 <ul>
 <li>Medial periocular tissues: drain to submandibular lymph nodes</li>
 <li>Lateral periocular tissues: drain to superficial preauricular nodes</li>
 </ul>
</ul>
<ClinicalCorrelate>A blow-out fracture most commonly affects the orbital floor postero-medially, often breaking the ethmoid bone medially too.</ClinicalCorrelate>
## Osteology
<ul>
 <li>Pear-shaped</li>
 <li>Supraorbital margin formed by frontal bone</li>
 <ul>
 <li>
 Supraorbital ridge only extends over the medial &frac12; to ⅔ of the superior orbital rim
 </li>
 </ul>
 <li>Infraorbital margin formed by zygomatic and maxilla</li>
 <li>Lateral margin formed by frontal and zygomatic</li>
 <li>
 Medial margin formed by maxillary process of frontal and lacrimal crest of the frontal process
 of maxilla
 </li>
 <li>Roof: frontal and lesser wing of sphenoid</li>
 <li>Floor: zygomatic, maxilla, palatine</li>
 <li>Lateral wall (thickest): zygomatic, greater wing of sphenoid</li>
 <li>Medial wall: frontal process of maxilla, lacrimal, ethmoid, body of sphenoid</li>
 <ul>
 <li>The lamina papyracea of the ethmoid bone is the weakest part of the orbit</li>
 </ul>
</ul>
## Relations
<ul>
 <li>Nasal cavity, ethmoid air cells and sphenoid sinus medially</li>
 <li>Frontal air sinus, meninges and frontal lobe superiorly</li>
 <li>Maxillary air sinus inferiorly</li>
 <li>Temporalis muscle, middle cranial fossa and temporal lobe laterally</li>
</ul>
## Openings
Optic canal
<ul>
 <li>Optic canal within the lesser wing of the sphenoid only</li>
 <li>4-10mm long</li>
 <li>Connects to middle cranial fossa</li>
 <li>Contains optic nerve and ophthalmic artery (with surrounding sympathetic plexus)</li>
</ul>
Superior orbital fissure
<ul>
 <li>Superior orbital fissure lies between the greater and lesser wings of sphenoid</li>
 <li>Also connects to middle cranial fossa</li>
 <li>
 Common tendinous ring (formed by thickening of periorbita) overlies the medial end of the
 superior orbital fissure, attached to
 </li>
 <ul>
 <li>Lesser wing of sphenoid</li>
 <li>Greater wing of sphenoid</li>
 <li>Orbital plate of ethmoid</li>
 </ul>
 <li>
 SOF outside ring: lacrimal, frontal and trochlear nerves and superior ophthalmic vein. Inferior
 ophthalmic vein passes below ring (also outside)
 </li>
</ul>
<ClinicalCorrelate>The 4th cranial nerve (trochlear) is therefore not affected by retrobulbar anaesthesia leaving some intorsion possible.</ClinicalCorrelate>
<ul>
 <li>SOF within ring: both branches of oculomotor nerve, nasociliary and abducens nerves</li>
</ul>
Refresher note: the nasociliary, frontal and lacrimal nerves are the three branches of the first (ophthalmic) division of the trigeminal nerve

Inferior orbital fissure
<ul>
 <li>Inferior orbital fissure lies between greater wing of sphenoid and maxilla</li>
 <ul>
 <li>Connects to</li>
 <ul>
 <li>Pterygopalatine fossa</li>
 <li>Infratemporal fossa</li>
 </ul>
 <li>Contains</li>
 <ul>
 <li>Maxillary nerve which becomes infraorbital nerve on entering the orbit</li>
 <li>Zygomatic nerve (also a branch of V2)&nbsp;</li>
 <li>Inferior ophthalmic vein draining to pterygoid plexus</li>
 <li>Infraorbital artery and vein</li>
 <li>Branches of the pterygopalatine ganglion</li>
 </ul>
 <li>Covered by vestigial muscle of Muller (function unknown)</li>
 </ul>
</ul>
Ethmoidal foramina
<ul>
 <li>Found where the roof joins the medial wall</li>
 <ul>
 <li>Anterior ethmoid foramen at the junction of the frontal and ethmoid bones&nbsp;</li>
 <ul>
 <li>Connects to anterior cranial fossa&nbsp;</li>
 <li>Contains the anterior ethmoidal nerve and artery</li>
 </ul>
 <li>Posterior foramina</li>
 <ul>
 <li>Contains the posterior ethmoidal nerve and artery supplying ethmoidal sinuses</li>
 </ul>
 </ul>
</ul>
## Lateral tubercle of Whitnall
<ul>
 <li>Insertions of:</li>
 <ul>
 <li>Check ligament of eyeball</li>
 <li>Suspensory ligament of eyeball</li>
 <li>Lateral canthal tendon</li>
 <li>Aponeurosis of levator</li>
 </ul>
</ul>
## Suspensory ligament (of Lockwood)
<ul>
 <li>Thickening of the inferior part of the fascial sheath of the eyeball (Tenon&rsquo;s)</li>
 <li>Receives fascial contributions from the inferior rectus and oblique muscles</li>
 <li>Attached medially to the lacrimal bone</li>
 <li>Attached laterally to the zygomatic bone (at the tubercle of Whitnall)</li>
</ul>

<HotTopic>There are no lymphatics in the orbit! Lymphatics from the conjunctivae and lids drain medially the submandibular glands and laterally to the superficial preauricular nodes.</HotTopic>

Orbit and ocular adnexae

Orbit

Intro

FRCOphth Part 2 Study Notes

Tumours, masses and neoplasia

Tumours overview

Uveitis

Uveitis background

Anterior uveitis

Intermediate uveitis

Uveitis in JIA

Uveitis with JIA

Retinal vasculitis

Sarcoidosis

Behcet's disease

Toxoplasmosis

Strabismus

Overview

Viral uveitis

Esotropia

Fungal uveitis

Mycobacterial uveitis

Adnexal masses

Exotropia

Spirochaetal uveitis (including Syphilis)

Melanoma

Nematode uveitis

Retinoblastoma

Retinoblastoma (for Part 2)

Incomitent

Voyt-Koyanagi-Harada syndrome

Conjunctival intraepithelial neoplasia

Vertical deviations

Sympathetic ophthalmia

AV Malformations and hamartomas

Arteriovenous malformations and hamartomas

Restriction syndromes

Paediatrics

Leucocoria

Congenital Cataract

Paediatric Glaucoma

Retinopathy of prematurity

Retinopathy of Prematurity

ROP-like disorders

Congenital nasolacrimal duct obstruction

White dot syndromes

Aniridia: Short Arm 11 Deletion (11p13)

Choristomas

Management Of Amblyopia

Alphabet patterns

Iris Nodules

Scleritis

Meningioma

Strabismus surgery

Optic nerve glioma

Lymphoma

Extraocular Muscles

Rhabdomyosarcoma

Idiopathic orbital inflammation

Orbital neuroblastoma

Anterior Persistent Foetal Vasculature

Lacrimal system

Metastatic lesions

Surgical Retina

Retinal Detachment

Vitreoretinal Interface And Macular Hole

Epiretinal Membrane

Medical Retina

Diabetic Eye Disease

Orbital Blood Vessels

Retinal Vascular Disease

Macular Degeneration

Central Serous Chorioretinopathy (CSCR)

Sickle Cell Retinopathy

Retinitis Pigmentosa

Albinism

Retinal Telangiectasias

Miscellaneous Retinopathies

Atropine And Myopia Progression

Pharmacology

Side Effects Of Systemic Drugs

Foetal Alcohol Syndrome

Neuro-ophthalmology

Optic Neuropathy

Papilloedema

Idiopathic Intracranial Hypertension

Chiasmal Disorders

Retrochiasmal Disorders

Migraine

Paranasal Sinuses

Supranuclear Motility Disorders

Third Nerve Palsies

Fourth Nerve Palsies

Sixth Nerve Palsies

Seventh Nerve Palsies

Anisocoria

Myasthenia Gravis

Myopathies

Blepharospasm

Functional Visual Loss

Lacrimal Glands

Phakomatoses

Developmental diseases

Tear Film

Eyelids

Blinking

Lid Malpositions

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Pigmented Conjunctival Lesions

Squamous Cell Carcinoma Of The Conjunctiva

Ocular Cicatricial Pemphigoid

Cornea

Corneal Structure And Development