The orbit

THE ORBIT

By : Sinchana S Kumbar I yr 14O0027

The skull can be divided into two parts: the cranium and the face.

The Cranium 2 Parietal bones Occipital bone 2 temporal bones Ethmoid bone Sphenoid bone

The Face – Frontal 2 Maxillary bones 2 Nasal bones Vomer 2 Lacrimal bones Palatine bones 2 Zygomatic bones Mandible bone .

ORBIT:

Bony cavity Made of - 7 bones * Contains ocular contents in it -

Pear shaped , apex is directed post. , medially and slightly upwards

DIMENSIONS

Rim : horizontally - ~ 40 mm

vertically - ~35 mmDepth : Medially - ~42 mm

Laterally - ~ 50 mmInter orbital width - ~25 mm

Extra orbital width - ~100 mm

Volume – 30 ml

ORBITAL WALLS

It is comprised – •Roof•Floor•Medial wall•Lateral wall

ROOF

ROOF• Frontal bone and lesser wing of

sphenoid

• Located - ant cranial fossa and frontal sinus

• Impt landmarks in roof –

> Lacrimal gland fossa

> Fossa for TROCHLEA

> Supra orbital notch

> optic canal (lies b/w roof & body of sphenoid)

FLOOR

FLOORMaxillary ** , Palatine ,

Zygomatic bones Roof of maxillary sinus Impt. Landmarks seen are :

> infra orbital groove

> Inf. Orbital fissure ( separates the

lateral wall and floor)

THE THINNEST WALL / Lamina Papyracea

MEDIAL WALL*• Ethmoid ,Lacrimal ,Maxillary & Sphenoid

bones

• Location – adj. ethmoid and Sphenoids sinuses and Nasal cavity

• Ethmoidal sinus infection can lead to ORBITAL CELLULITIS

• Impt. Landmarks seen here are –

> Fronto ethmoid suture – Ethmoidal arteries

enters the orbit.

ORBITAL CELLULITIS• It is a dangerous infection • Usually caused by bacterial infection from

the sinuses ( mainly Ethmoid sinus)• Which is behind the septum• Clinical findings – Proptosis - restriction of ocular motility - pain on movement of globe

PRESEPTAL CELLULITIS

 It is an inflammatory condition  that affects the tissue of the eyelid.

 The disease  can be limited by the location of the orbital septum, which  provides a barrier to prevent spread into the orbit.

That  could result in the development of orbital cellulitis.

 Clinical Findings - Swelling, redness, discharge, pain, conjunctival injection, fever (mild), slightly blurred vision, teary eyes, and some reduction in vision.

THICKEST WALL

LATERAL WALL***

• Zygomatic , greater wing of sphenoid bones

• Location – adj. middle Cranial & temporal fossa

• Impt. Landmarks seen –

> Tubercle of WHITNALL’S

> Superior Orbital fissure

ORBITAL MARGINS1.Supra orbital notch – is medial to the center of

the superior orbital margin

2.Supratrochlear notch – Nerves and Vessels pass through this groove

- present Superiorly in medial corner

4.Lateral area which is strongest is most exposed to injury

5.Infraorbital foramen – found in inf. Margin

- it is formed by maxillary bone and the zygomatic

bone

APERTURES IN ORBITAL CAVITY

Ethmoidal foramen - > Place for ethmoidal arteries to pass through it

> In medial orbital wall

> It is the route for infections to spread from

sinuses

Superior orbital fissure - > It separates Greater and Lesser wing of sphenoid bone

> It is seen between roof and lateral wall

Inferior orbital Fissure - > Seen in between Orbit and Lateral wall

> Allows the passage of blood vessels and nerves

Annulus of Zinn - > Fibrous ring , it is the origin for recti muscles

> Nerves – Lacrimal ,frontal ,trochlear , sup and inf. divisions of Oculomotor ,nasociliary , Abducens nerves > Sup Ophthalmic vein , Opthalmic artery pass through this Common Tendinous Ring .

Optic canal – > It is 8-10 mm long , 6.5 mm in diameter > located in Lesser wing of sphenoid > Optic strut can be noticed

SINUSES

− Mucosa lined : Air filled cavities − Decreases the weight of skull and

helps in resonance of voice

There are 4 sinuses o Frontal SinusoEthmoid Sinus oSphenoid Sinus oMaxillary Sinus

Frontal Sinus : > Present above the orbit > these 2 sinuses are separated by inter sinus septum

Ethmoid Sinus : > thin walled cavities > infection can lead to ORBITAL CELLULITIS

Sphenoid Sinus - > present within the body of sphenoid

> Visual loss and Visual field abnormalities → Sphenoid sinus

Maxillary Sinus - > It is the largest sinus > Infraorbital nerve and artery travel along the roof of Maxillary Sinus

Soft tissues present in Orbit PERIORBITA - It is basically covering - At apex it fuses with Dura matter - Ant : cont. with the orbital septum - ARCUS MARGINALISORBITAL FAT - Spaces which is not occupied by ocular content ,there is presence of Adipose tissue - predominant at orbital APEXORBITAL SEPTUM – Palpebral fascia / Septum Orbitale - At margins peri osteum continues with this Connective tissue - Strong barriers of Infection

VASCULATURE

– Ophthalmic Artery ← Internal Carotid Artery

The major branches of Ophthalmic artery are - → Branches to the EOM → Central Retinal Artery → Post. Ciliary Arteries

– External carotid Artery

INNERVATION

Sensory innervation – Ophthalmic and maxillary divisions of CN V

Frontal and Lacrimal nerve – Medial canthus , upper lid , fore head

Nasociliary branch – ciliary branchesShort and Long ciliary nerves-

Iris ,Cornea , Ciliary muscle Para sympathetic innervation –

accommodation , pupillary constriction , lacrimal gland stimulation

Sympathetic innervation – pupillary dilation , vasoconstriction .

REFERENCE

Kersten CR,Codere F,Dailey AR Jerry KP,et al.Orbit,Eye lids and Lacrimal System .San Francisco: Dondrea LC;2005-2006.

Remington AL .Clinical Anatomy and Physiology of the Visual System.3rd ed .Elsevier:Duncan L ;2012.

Thank you to Mrs .KARUNA - Mentor

Thank You