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  1. 1.  EMBRYOLOGY ANATOMY APPLIED ASPECTS- Ajay Kumar Singh- Bhumika Sharma• Department of Ophthalmology• King George‘s Medical University, Lucknow (INDIA)
  2. 2. INTRODUCTION Orbit is the anatomical space bounded:  Superiorly – Anterior cranial fossa  Medially - Nasal cavity & Ethmoidal air sinuses  Inferiorly - Maxillary sinus  Laterally - Middle cranial fossa & Temporal fossa
  3. 3. EMBRYOLOGY Orbital walls- derived from cranial neural crest cells which expand to form:  Frontonasal process  Maxillary process Lateral nasal process + Maxillary process = medial, inferior and lateral orbital walls Capsule of forebrain forms orbital roof
  4. 4. EMBRYOLOG Y Early in the human development eyes point almost in the opposite direction. As the facial growth occurs, the angle between the optic stalks decreases and is ~68˚ in an adult.
  5. 5. EMBRYOLOG OSSIFICATIONEnchondral Membranous
  6. 6. EMBRYOLOG Frontal, Zygomatic, Maxillary and Palatine bones- Intramembranous origin First bone- Maxillary (at 6 wks of intrauterine life) - develops from elements in the region of the canine tooth - secondary ossification centres in the orbitonasal and premaxillary regions Other bones develop at around 7 wks of intrauterine life
  7. 7. EMBRYOLOG Sphenoid bone- both enchondral and intramembranous origins Lesser wing of the sphenoid- 7 wks (Enchondral) Greater wing of the sphenoid- 10 wks (Intramembranous) Both wings join- 16 wks Ossification is complete at birth (except orbital apex)
  8. 8. CLINICAL SIGNIFICANCEDERMOID CYSTS: Most common orbital cystic lesions Origin: ◦ Pouches of ectoderm trapped into bony sutures ◦ Most common site frontozygomatic suture
  9. 9. EMBRYOLOGCEPHALOCOELES: Reflect orbital entrapment of neuroectoderm Most commonly- ◦ At the junction of frontal & ethmoid Pathology: ◦ Herniation of brain parenchyma into the orbit
  10. 10. EMBRYOLOGFIBROUS DYSPLASIA: Benign, developmental fibro-osseous lesion Origin: ◦ Arrest in maturation at woven bone stage Pathology: ◦ Bone replaced by fibrous tissue
  11. 11. DIMENSIONS  Quadrilateral pyramid  Base - forwards, laterally, downwards  Apex - optic foramen  Volume of orbital cavity ≈ 30 cc in adults
  12. 12. DIMENSIONS Rim:- Horizontally ≈ 40 mm- Vertically ≈ 35 mm Interorbital width  ≈ 25 mm Extraorbital width  ≈ 100 mm Depth ◦ Medially ≈ 42 mm ◦ Laterally ≈ 50 mm
  13. 13. COMPOSED OF:  7 Bones:  Ethmoid  Frontal  Lacrimal  Maxillary  Palatine  Sphenoid  Zygomatic Right orbit
  14. 14. BOUNDARIES
  16. 16. ROOF Underlies Frontal sinus and Anterior cranial fossa Formed by- ◦ 1. Frontal bone (Orbital plate) ◦ 2. Lesser wing of Sphenoid Triangular Faces downwards, and Left orbit slightly forwards
  17. 17. ROOF Concave anteriorly, almost flat posteriorly The anterior concavity is greatest about 1.5 cm from the orbital margin & corresponds to the equator of the globe. Thin, transluscent and fragile (except the lesser wing of the sphenoid)
  18. 18. ROOFLANDMARKS• 1. FOSSA FOR THE LACRIMAL GLAND-  LOCATION: behind the zygomatic process of the frontal bone  CONTENTS: lacrimal gland some orbital fat (accessory fossa of Rochon- Duvigneaud)
  19. 19. ROOF2. TROCHLEAR FOSSA (FOVEA) LOCATION: 4 mm from the orbital margin CONTENTS: insertion of tendinous pulley of Superior Obliqueo sometimes (≈10%) surmounted by a spicule of bone (Spina trochlearis)o Extremely rarely trochlea completely ossified cracks easily SURFACE ANATOMY: Palpable just within the supero-medial angle
  20. 20. ROOF 3. SUPRAORBITAL NOTCH: LOCATION: ≈15 mm lateral to the superomedial angle TRANSMITS: - Supraorbital nerve - Supraorbital vessels SURFACE ANATOMY: Right orbit - At the junction of lateral 2/3rd and medial 1/3rd - About two finger breadth
  21. 21. ROOF4. OPTIC FORAMEN: LOCATION: - Lies medial to superior orbital fissure - at the apex - Present in the lesser wing of sphenoid TRANSMITS: - Optic nerve with its meninges Left orbit - Ophthalmic artery
  22. 22. ROOF Cribra orbitalia: - apertures apparent on the medial side of anterior portion of the lacrimal fossa - for veins from diploë to the orbit - Best marked in the fetus and infant Frontosphenoidal suture: - between frontal and the lesser wing of the sphenoid - usually obliterated in the adults
  23. 23. ROOFCLINICAL SIGNIFICANCE Thin and fragile Easily fractured by direct violence (penetrating orbital injuries) Frontal lobe injury
  24. 24. ROOF Reinforced - Laterally- greater wing of sphenoid - Anteriorly- superior orbital margin So, fractures tend to pass towards medial sideAt junction of the roof and medial wall, the suture line lies in proximity to cribriform plate of ethmoid rupture of dura mater CSF escapes into orbit/nose/both
  25. 25. ROOF Since the roof is perforated neither by major nerves nor by blood vessels, so it can be easily nibbled away in transfrontal orbitotomy.
  26. 26. MEDIAL WALL Thinnest orbital wall Formed(Antero-posteriorly)  1. Frontal process of Maxilla  2. Lacrimal bone  3. Orbital plate of Ethmoid  4. Body of the sphenoid Almost parallel to each other Left orbit
  27. 27. LANDMARKS  LACRIMAL FOSSA: - Formed by: - frontal process of maxilla - lacrimal bone - Boundaries: - Anterior- anterior lacrimal crest Right orbit - Posterior- posterior lacrimal crest
  28. 28. MEDIAL WALL- Dimensions- - Length≈ 14 mm - Depth≈ 5 mm - Continuous below with bony nasolacrimal canal- Content- - Lacrimal sac
  29. 29. MEDIAL WALL ANTERIOR LACRIMAL CREST*- - upward continuation of the inferior orbital margin - Ill defined above but well marked below - Surface anatomy- - Palpable along the medial orbital margin (anteriorly) POSTERIOR LACRIMAL CREST*- - downward extension of the superior orbital margin - Surface anatomy- - Palpable along the medial orbital margin, posterior to the lacrimal fossa*significant landmarks in lacrimal sac surgery
  30. 30. MEDIAL WALL FRONTO ETHMOIDAL SUTURE LINE- Marks the approximate level of ethmoidal sinus roof- Breach of this suture may open the frontal sinus, or the cranial cavity- Anterior and posterior ethmoidal foramina are present in the suture line
  31. 31. MEDIAL WAL Anterior ethmoidal foramen - 20-25 mm posterior from the anterior lacrimal crest - Opens in the anterior cranial fossa at the side of the cribriform plate of ethmoid - Transmits- - anterior ethmoidal nerve & vessels
  32. 32. MEDIAL WALL Posterior ethmoidal foramen - 32-35 mm posterior from anterior lacrimal crest - 7 mm anterior to the anterior rim of optic canal - Transmits Left orbit - posterior ethmoidal nerve & vessels
  33. 33. MEDIAL WALWeber’s suture Lies anterior to lacrimal fossa Also known as sutura longitudinalis imperfecta Runs parallel to anterior lacrimal crest Branches of infraorbital artery pass through this groove to supply the nasal mucosa Bleeding may occur from these vessels during DCR surgeries
  34. 34. MEDIAL WALLCLINICAL SIGNIFICANCE  Anteriorly located suture indicates predominance of lacrimal bone  Posteriorly located suture indicates the predominance of maxillary bone* *If maxillary component is predominant, it becomes difficult to perform osteotomy to reach the sac during DCR, because the maxillary bone is very thick.
  35. 35. MEDIAL WALL Medial wall extremely fragile (presence of ethmoidal air cells and nasal cavity) Accidental lateral displacement of medial wall- traumatic hypertelorism Medial wall provides alternate access route to the orbit through the sinus
  36. 36. MEDIAL WAL Ethmoid - Thinnest bone of the orbit - Vascular connections with ethmoid sinus through foramina - Inflammation in the ethmoid sinus spreads readily to the orbit Tumours of the nasal cavity can breach the lamina papyracea to involve the orbit Lacrimal bone can be easily penetrated during endoscopic DCR During surgery, hemorrhage is most troublesome due to injury to ethmoidal vessels.
  37. 37. FLOOR• Shortest orbital wall• Roughly triangular• Formed by- • Orbital plate of maxilla (major) • Orbital surface of Zygomatic bone (anterolateral) • Orbital plate of Palatine Right orbit bone
  38. 38. FLOOR Bordered laterally by inferior orbital fissure and medially by maxilloethmoidal suture Overlies maxillary sinus
  39. 39. FLOORLANDMARKS Infraorbital Infraorbital Infraorbital groove canal foramen ≈4 mm inferior to the inferior orbital margin Transmits - Infraorbital nerve - Infraorbital vessels
  40. 40. FLOORCLINICAL SIGNIFICANCE BLOW OUT FRACTURES: ◦ Fractures of the orbital floor ◦ Infraorbital nerves and vessels are almost invariably involved ◦ Patient presents with  Diplopia  Restricted movements(upgaze)  Paresthesia
  41. 41. LATERAL WALL Formed by- ◦ 1. Zygomatic bone ◦ 2. Greater wing of sphenoid Thickest orbital wall Separates orbit from- ◦ Middle cranial fossa ◦ Temporal fossa At an angle of about 90° Right orbit with each other
  42. 42. LATERAL WALLLANDMARKS LATERAL ORBITAL TUBERCLE OF WHITNALL: - 4-5 mm behind the lateral orbital rim - 11 mm inferior to the frontozygomatic suture line Right orbit
  43. 43. LATERAL WALL- Gives attachment to: - Check ligament of lateral rectus - Lockwood’s ligament - Lateral canthal tendon - The aponeurosis of the levator palpebrae superioris - Orbital septum - Lacrimal fascia
  44. 44. LATERAL WALL CLINICAL SIGNIFICANCE In resection of maxilla, the Whitnall’s tubercle is spared, otherwise Damage to Lockwood’s ligament Inferior dystopia of eye ball Diplopia
  45. 45. LATERAL WAL SPINA RECTI LATERALIS: - at the junction of wide & narrow portions of the superior orbital fissure - Produced by a groove lodging superior ophthalmic vein - Gives origin to a part of Lateral Rectus
  46. 46. LATERAL WAL ZYGOMATIC GROOVE:- EXTENT: - From the anterior end of the inferior orbital fissure to a foramen in the zygomatic bone- CONTENTS: - Zygomatic nerve - Zygomatic vessels
  47. 47. LATERAL WALCLINICAL SIGNIFICANCE Lateral wall protects only the posterior half of the eyeball, hence palpation of retrobulbar tumours is easier. Frontal process of zygoma & zygomatic process of frontal bone protect the globe from lateral trauma- known as facial buttress area. Just behind the facial buttress area, is the zygomaticosphenoid suture, which is the preferred site for lateral orbitotomy.
  48. 48. LATERAL WALAnteriorly, superior margin of inferiorOrbital fissure joins suture betweenzygomatic and greater wing of sphenoid(line of relative weakness) extends to frontozygomatic suture Frequently involved in zygomatic bone fracture
  50. 50. SUPERIOR ORBITAL MARGIN- formed by- Frontal bone- concave downwards, convex forwards- sharp in lateral 2/3rd ,rounded in medial 1/3rd - at the junction- supraorbital notch (sometimes foramen)*- *Site for nerve block.
  51. 51. SUPERIOR ORBITAL MARGIN Sometimes-o Arnold’s notch/foramen Present medial to supraorbital notch Transmits medial branches of supraorbital nerve & vesselso Supraciliary canal Near the supraorbital notch Transmits nutrient artery a branch of supraorbital nerve to frontal air sinus
  52. 52. SUPERIOR ORBITAL MARGIN SURFACE ANATOMY: - Well marked prominence - More prominent laterally than medially - Eyebrow corresponds to the margin only in a part - Head- under the margin - Body- along the margin - Tail- above the margin
  53. 53. LATERAL ORBITAL MARGIN: - formed by - zygomatic process of frontal - the zygomatic bone - strongest portion of margin
  54. 54. LATERAL ORBITAL MARGINCLINICAL SIGNIFICANCE Lateral orbital rim is recessed on its deep aspect ≈ 0.75 cm above the rim margin to accommodate the lacrimal gland Prone to fracture
  55. 55. LATERAL ORBITAL MAR Narrowest and weakest part- frontozygomatic suture Prone for separation following blunt trauma
  56. 56. INFERIOR ORBITAL MARGIN: Formed by- - Zygomatic - Maxilla - suture between the two is sometimes marked by a tubercle- felt 4-5 mm above the infraorbital foramen SURFACE ANATOMY:- Palpable as a sharp ridge, beyond which the finger can pass into the orbit
  57. 57. INFERIOR ORBITAL MARCLINICAL SIGNIFICANCE At the junction of lateral 2/3rd & medial 1/3rd just within the rim- small depression- origin of Inferior oblique Prone to fracture Disruption of Inferior oblique Diplopia Penetrating injuries may severe lacrimal passages
  58. 58. MEDIAL ORBITAL MARGIN:- Formed by - Frontal process of maxilla (anterior lacrimal crest) - Lacrimal bone (posterior lacrimal crest)
  59. 59.  Orbital index= (Height/Width)X 100 1. Megaseme- ≥89% (Orbital opening-round) 2. Mesoseme- 82-88% 3. Microseme- ≤83% (Orbital opening-rectangular)
  61. 61. OPTIC CANAL Leads from the middle cranial fossa to the apex of the orbit Orbital opening- vertically oval In the middle- circular (≈5mm) Intracranial- horizontally oval Length ≈ 8-12 mm - Attained at 4-5 years of age Boundaries- - Medially- Body of the sphenoid Right orbit - Laterally- Lesser wing of the sphenoid
  62. 62. OPTIC CANAL Directed- forwards, laterally and downwards Distance between ◦ Intracranial openings≈ 25mm ◦ Orbital openings≈ 30mm Transmits- ◦ Optic nerve & its meninges ◦ Ophthalmic artery
  63. 63. OPTIC CANA Processus falciformis: The roof of the canal reaches farther forwards than the floor anteriorly, while posteriorly, the floor projects beyond the roof. Fold of dura mater filling the gap in the roof is called Processus falciformis.
  64. 64. OPTIC CANACLINICAL SIGNIFICANCE Optic nerve glioma or Meningioma may lead to unilateral enlargement of Optic canal CT-Scan showing lesion in Left Strut view of Optic optic nerve Canal (Normal)
  65. 65. SUPERIOR ORBITAL FISSURE Also known as Sphenoidal fissure Lateral to the optic foramen at the orbital apex comma-shaped gap between the roof and the lateral wall Left orbit Bounded by- Lesser and greater wings of the sphenoid
  66. 66. SUPERIOR ORBITAL FISSURERight superior orbital fissure
  67. 67. SUPERIOR ORBITAL FISSURE 22 mm long Largest communication between the orbit and the middle cranial fossa Its tip lies 30-40 mm from the frontozygomatic suture
  68. 68. SUPERIOR ORBITAL FISSURE Lateral superior part of the fissure is narrower than the medial inferior part.- At the junction of the two lies spina recti lateralis
  69. 69. SUPERIOR ORBITAL FISSURELANDMARK  Annulus of Zinn - Spans both superior orbital fissure & the optic canal - Gives origin to the four recti muscles
  70. 70. SUPERIOR ORBITAL FISSURECLINICAL SIGNIFANCE  Inflammation of the superior orbital fissure and apex may result in a multitude of signs including ophthalmoplegia and venous outflow obstruction TOLOSA HUNT SYNDROME
  71. 71. SUPERIOR ORBITAL FISSUREFracture at superior orbital fissure Involvement of cranial nerves Diplopia, Ophthalmoplegia, Exophthalmos, Ptosis, SUPERIOR ORBITAL SYNDROME (Rochon-Duvigneaud syndrome)
  72. 72. SUPERIOR ORBITAL FISSURE Manner of involvement of nerves may be helpful in predicting the site and extent of the lesion. Divisions of III’rd nerve ± VI’th nerve Annulus of Zinn (Purely intraconal lesion) III’rd, IV’th and VI’th nerve Entire length of the fissure involved
  73. 73. INFERIOR ORBITAL FISSURE Also known as sphenomaxillary fissure Between floor and the lateral wall Bounded by- o Medially- Maxilla and orbital process of palatine o Laterally- Greater wing of the sphenoid o Anterior aspect- closed by Zygomatic bone Left orbit
  74. 74. INFERIOR ORBITAL FISSURE Transmits- - Venous drainage from the inferior part of the orbit to the pterygoid plexus - neural branches from the pterygopalatine ganglion - the zygomatic nerve - the infraorbital nerve Closed in the living by the periorbita & the Muller’s muscle Serves as the posterior limit of surgical subperiosteal dissection along the orbital floor
  75. 75. CONNECTIVE TISSUE SYSTEM  Periorbita  Orbital septal system  Tenon’s capsule
  76. 76. PERIORBITA (Orbital periosteum) Loosely adherent to the bones Sensory innervation by branches of V’th nerve Fixed firmly at - Orbital margins (Arcus marginale) - Suture lines - Various fissures & foramina - Lacrimal fossa
  77. 77. PERIORBITACLINICAL SIGNIFICANCE Surgery in the orbital roof in the areas of fissures and suture lines may be complicated by cerebrospinal fluid leakage .
  78. 78. ORBITAL SEPTAL SYSTEM Includes the connective tissue septa which are suspended from the periorbita to form a complex radial and circumferential interconnecting slings. These septa surround Extraocular muscles, Optic nerve, neuro-vascular elements and the fat lobules.
  79. 79. TENON’S CAPSULE Also known as Fascia bulbi or bulbar sheath. Dense, elastic and vascular connective tissue that surrounds the globe (except over the cornea). Begins anteriorly at the perilimbal sclera, extends around the globe to the optic nerve, and fuses with the dural sheath and the sclera. Separated from the sclera by periscleral lymph space, which is in continuation with subdural and subarachnoid spaces.
  80. 80. CONTENTS OF THE ORBIT Eye ball Muscles ◦ 4 Recti ◦ 2 obliques ◦ Levator palpebrae superioris ◦ Muller’s muscle (Musculus orbitalis) Left orbit Nerves ◦ Sensory- branches of V’th Nerve ◦ Motor- III’rd, IV’th & VI’th Nerve ◦ Autonomic- Nerves to the Lacrimal gland ◦ Ciliary ganglion
  81. 81. CONTENTS OF THE ORBIT Vessels ◦ Arteries-  Internal carotid system- branches of ophthalmic artery  External carotid system- a branch of internal maxillary artery ◦ Veins-  Superior ophthalmic vein  Inferior ophthalmic vein ◦ Lymphatics-  none Lacrimal gland Lacrimal sac Orbital fat, reticular tissue & orbital fascia
  82. 82. NERVES CILIARY GANGLION- Peripheral parasympathetic ganglion- Lies between Optic nerve and Lateral Rectus muscle- ≈1cm anterior to the optic foramen- 3 posterior roots - Sensory root - Nasociliary Nerve - Motor root - Nerve to inferior oblique - Sympathetic root - Branches from internal
  83. 83. SURGICAL SPACES SUBPERIOSTEAL SPACE: ◦ Between orbital bones and the periorbita ◦ Limited anteriorly by strong adhesions of periorbita to the orbital rim
  84. 84. SURGICAL SPACES PERIPHERAL ORBITAL SPACE (ORBITAL SPACE)- Bounded: - peripherally by periorbita - internally by the four recti with their intermuscular septa - anteriorly by the septum orbitale - Posteriorly, it merges with the central space
  85. 85. SURGICAL CONTENTS: SPACES Peripheral orbital fat Muscles ◦ Superior oblique ◦ Inferior oblique ◦ Levator palpebrae superioris Nerves ◦ Lacrimal ◦ Frontal ◦ Trochlear ◦ Anterior ethmoidal ◦ Posterior ethmoidal Veins ◦ Superior ophthalmic ◦ Inferior ophthalmic Lacrimal gland Lacrimal sac
  86. 86. SURGICAL SPACES CENTRAL SPACE- Also known as muscular cone or retrobulbar space- Bounded: - Anteriorly by Tenon’s capsule - Peripherally by four recti with their intermuscular septa - In the posterior part, continuous with the peripheral orbital space
  87. 87. SURGICAL CONTENTS: SPACES Central orbital fat Nerves ◦ Optic nerve (with its meninges) ◦ Oculomotor  Superior and inferior divisions ◦ Abducent ◦ Nasociliary ◦ Ciliary ganglion Vessels ◦ Ophthalmic artery ◦ Superior ophthalmic vein
  88. 88. SURGICAL SUBTENON’S SPACE* SPACES- Between the sclera and the Tenon’s capsule- *Pus collected in this space is drained by incision of Tenon’s capsule through the conjunctiva- *Site for drug instillation
  89. 89. AGE RELATED VARIATIONS Infantile orbits are more divergent (≈115°) than those of adults (≈40-45°) Orbital axes- Lie in horizontal plane in infants- slope downwards (≈15-20°) in adults
  90. 90. AGE RELATED VARIATIONS Orbital fissures are relatively larger in childhood than in adults (owing to the narrowness of the greater wing of sphenoid) Orbital index- higher in children than in adults (transverse diameter increases relatively more in the later life) Interorbital distance is smaller in children- may give false impression of squint
  91. 91. AGE RELATED VARIATIONS Roof much larger than floor in infancy Optic canal has no length at birth- a foramen - at 1 year of age≈ 4 mm Periorbita much thicker and stronger at birth than in adults
  92. 92. AGE RELATED VARIATIONS SENILE CHANGES- Holes, particularly in the roof due to absorption of the bony wall Orbital fissures become wider
  93. 93. GENDER RELATED VARIATIONS MALES FEMALES• Glabella & • Larger supraciliary ridges • More elongated more marked • Rounder • Upper margins sharper • Frontal eminences more marked
  94. 94. TAKE HOMEMESSAGE…………………... Knowledge of orbital anatomy and its variations helps to determine the pathology as well as the site, direction and extent of the incision during elective exploration of the orbit. It is also must for understanding the clinical course and planning the management in cases of accidental incisions/explorations.