This document provides an overview of the anatomy of the orbit. It discusses the development, dimensions, walls and contents of the orbit. The orbits are pear shaped cavities containing the eyeballs and surrounding structures. They are bounded by the frontal, ethmoid, sphenoid, zygomatic and maxillary bones. The walls include the roof, medial, lateral and floor. The orbits taper posteriorly and contain the optic nerve, extraocular muscles, blood vessels and fat. Congenital abnormalities and clinical applications are also summarized.

1. ANATOMY
OF
THE
ORBIT
Presenters
Dr Nischal Ghimire
Residents ,Tilganga Institute
of Ophthalmology
Kathmandu Nepal

2. Contents
 Introduction
 Development of the orbit
 Dimensions of the orbit
 The walls of the orbit
 The contents of the Orbit

3.  The orbits are the bony cavities that contain
the globes, extraocular muscles, nerves, fat,
and blood vessels
 Pear shaped
 Each orbit has Apex, Base ,Roof , Floor ,
Medial wall and Lateral wall
 Tapering posteriorly to the apex and the optic
canal.
Orbit

4. Atlas of Anatomy by Anne
M Gilroy

5. Direction Bordering Structure
Superior Frontal sinus , Anterior Cranial Fossa
Medial Ethmoid Sinus
Inferior Maxillary Sinus
Structures Surrounding the orbit
-Atlas of Anatomy by Anne M Gilroy

6. Embryology of the orbit and its contents
Orbit and its
contents
Bones
Tendons
Connective Tissues
Adipose tissues
Striated Extra ocular
muscles
Neural
Crest
Cells
Mesoderm
-Langman’s Medical Embryology

7. Embryology of the orbit
 Neural crest cells that expands to form :
• Fronto-nasal Process
• Maxillary Process
 Lateral nasal process and Maxillary process
Gives Inferior , Medial and Lateral orbital
walls
 Capsule of the Forebrain forms the Roof of
the orbit

8. Congenital
Craniofacial
Abnormalities
Craniosynostosis
Aprets syndrome
Crouzon
Syndrome
Pfeiffer
Syndrome
Non-synostosis
Teacher collins
Syndrome
Goldenhar
Syndrome
Premature
fusion of cranial
sutures
Failure of
development of
1st and 2nd
brachial arch
-Embryology at glance, webster

13. Dimensions of the orbit
Dimensions value
Depth of the orbit 40mm
Height of the orbital opening 35mm
Width of the orbital opening 40mm
Interorbital distance 25mm
Ratio of volume of orbit: volume of globe 4.5:1
Volume of the orbit 30ml
Depth along medial wall 42mm
Depth along lateral wall 50mm
-Wolff’s Anatomy of the eye

14. -Clinical anatomy of visual system

15. -Pocket dictionery of orbit

16. Walls of the orbit
The orbit is essentially a socket for the eyeball and is bounded by four walls
 The Roof
 The Medial wall
 The Lateral wall
 The Floor
7 different bones form the orbit which are:
• The Maxillary
• The Palatine
• The Frontal
• The Sphenoid
• The Zygomatic
• The Ethmoid
• The Lacrimal -The atlas of Anatomy, Annie M Gilroy

17. Roof of the orbit
Formed by :
 Orbital plate of Frontal bone
 Lesser wing of Sphenoid Bone

18. Roof of the orbit
Relations :
 Above lies the meninges and frontal lobe of the brain
 Below lies the Frontal nerve ,Peri-orbita , trochlear nerve
LPS,SR,SO muscles and Lacrimal gland
Clinical Applications :
Sharp objects may penetrate into the orbit through the upper
Eye lid penetrates the roof of the orbit and may damage the
Frontal Lobe of the brain

20. Lateral wall
Formed by :
 Orbital surface of Zygomatic
 Greater wing of sphenoid

21. Attachments of Whitnall’s Tubercle :
 Lateral canthal tendon
 Lateral horn of levator aponeurosis
 The check ligament of LR
 Lockwood ligament (suspensory ligament of globe )
 Whitnall’s ligament
 Frontozygomatic suture (located 1 cm above the
tubercle

24. Clinical Applications :
 Thickest and strongest
 Lateral wall protects only post ½ of eyeball , ant. ½ is not covered with bone
palpation of retro-orbital tumors easier from lateral side than nasal side
 Allows wide peripheral vision
Lateral wall

25. The Floor
Formed by :
 Maxillary bone
 Palatine bone
 Orbital plate of zygomatic bone
Doesn’t extend fully upto the apex ,ends at
pterygopalatine fossa ;
Shortest wall of the orbit
Orbital floor is separated from the lateral
orbital wall by the INFERIOR ORBITAL
FISSURE

27. Infra orbital groove and infra orbital canal are
Important landmarks it transmits the infraorbital
Artery and maxillary division of the trigeminal nerve
The Floor

28. Relations:
• Above :
• Inferior oblique muscle
• Nerve to inferior oblique muscle
• Inferior rectus muscle

31. • The thinnest part of the orbital floor lies medial to the
inferior orbital canal ---BLOWOUT FRACTURES
• Infraorbital canal continues forward ---inferior orbital
margin –where it appears as INFRAORBITAL
FORAMEN ( infraorbital nerve& vessels )

32. Blow out fracture
Signs :
 Ecchymosis and edema of the
eyelids
 Limitation of up gaze or down gaze
or both
 hypoesthesia in distribution of infra-
orbital nerve
-AAO Orbit

34. Medial Wall
Formed :
 Orbital Plate of Ethmoid bone
 The lacrimal Bone
 Frontal Process of the Maxillary bone
 Small part of body of Sphenoid

35. Medial Wall
Ant. Part of medial wall bears the lacrimal sac fossa ,which
continues inferior with NLD
LACRIMO-MAXILLARY SUTURE – lies vertically in the
centre of lacrimal sac fossa
LAMINA PAPYRACEA lies behind the posterior lacrimal
crest (lateral wall of ethmoid sinuses)

36. Medial Wall
Ethmoid foramen transmit branches of the ophthalmic
artery and nasocilary nerve

45. -Jones phillip ferguson leatherbar
Ethmoiditis is the commonest cause of
orbital cellulitis in children
-Commonly eroded by chronic
inflammatory lesion , cysts and
neoplasms -- nearby air sinuses
Medial Wall
CLINICAL APPLICATIONS :

46. Anterior open end of orbit
- Bounded by orbital margins
• Superior orbital margin
• Lateral orbital margin
• Inferior orbital margin
• Medial orbital margin
Base of orbit

47. Superior orbital margin
Atlas of anatomy, Gilroy
Formed by orbital arch of frontal bone
Supraorbital notch : Lateral 2/3rd sharp+ medial
1/3rd is round

48. Lateral orbital margin
Strongest
• Formed by zygomatic process of frontal bone
superiorly & frontal process of zygomatic bone
inferiorly
• These meet at fronto-zygomatic sutures line of supra-
temporal aspect of orbit

49. Lateral orbital margin
Dermoid cyst : most common orbital cystic lesion , Origin
: pouches of ectoderm trapped in bony sutures ( fronto-
zygomatic suture )
An orbital dermoid cyst is a choristoma
(a mass of histologically normal tissue in an abnormal
location) derived from displacement of ectoderm to a
subcutaneous location along embryonic lines of closure

50. Medial orbital margin
Formed by above : frontal bone ,
Below : anterior lacrimal crest
SUTURA NOTHA containing a branch of infero-orbital
artery lies just in front of anterior lacrimal crest
higly important landmark as trauma to this during surgery
can be dangerous – Bleeding

51. Inferior orbital margin
-Formed by laterally – zygomatic bone, medially ---
maxillary bone
-Inferior orbital foramen : 4-8 mm below the central
portion of inferior orbital margin( avoid damage to
inferior orbital neurovascular bundle –during
surgeries)

52. Apex of the orbit
• Posterior end of orbit
• Two orifices : optic canal and
Superior orbital fissure
Optic canal
 Connects orbit to middle
cranial fossa
Contents:
Optic nerve
Ophthalmic artery
Dural sheath
Sympathetic nerves
Atlas of anatomy, Gilroy

53. • Comma shaped aperture
• Bounded by greater and lesser wings of sphenoid
• Divided into 3 parts by common tendinous ring
Superior Orbital Fissure

54. Inferior orbital fissure
Lies between floor and lateral wall
Transmits : Infraorbital nerve/Zygomaatic nerve/Orbital
branch of pterygopalatine ganglion / branch from inferior
ophthalmic vein

55. Orbital Apex Syndrome
Due to various etiologies involving the OA, including
trauma, neoplastic, developmental, infectious,
inflammatory as well as vascular causes
Charaterized By :
• Ophthalmoplegia
• Proptosis
• Ptosis from palsy of cranial nerves (CN) III, IV, and VI
• Hypoesthesia of the ipsilateral forehead

56. Atlas of Anatomy , Milroy

57. References