ANATOMY OF ORBIT AND RELATED CLINICAL POINT.pptx

Anatomy of Orbit

1. ANATOMY OF ORBIT Presenter - Dr. Tanmoy Kar Moderator - Dr. Samhitha HR

2. Anatomy Of Orbit Quadrangular truncated pyramidal in shape. Bounded by- Superiorly- Anterior cranial fossa Medially- Nasal cavity and ethmoidal air sinuses Inferiorly- Maxillary sinus Laterally- Middle cranial fossa and Temporal fossa.

3. Dimensions Volume : 30cm3 Rim: Horizontally- 4cm Vertically- 3.5cm Intra orbital width: 2.5cm Extra orbital width: 10cm Depth: Medially- 4.2cm Laterally- 5.0cm Ratio of vol. of orbit : vol. of globe: 4.5:1

4. Bony Orbit Seven bones make up the bony orbit : Frontal bone Zygomatic Bone Maxillary bone Ethmoid bone Sphenoid bone Lacrimal bone Palatine bone

5. Walls Of The Orbit The bony orbit has four walls: Medial wall Lateral wall Roof Floor

6. Medial Orbital Wall The medial wall is formed from front to back by the: Frontal process of maxilla Lacrimal bone Orbital plate of the ethmoid bone Body of the sphenoid bone.

7. Medial Orbital Wall Clinical applications: It is the thinnest wall of the orbit, so it is frequently fragmented as a result of indirect blow out fractures and during orbitotomy operations. Frequently eroded by chronic inflammatory lesions, neoplasms, cysts. Medial wall provide alternate access route to the orbit through sinus. Haemorrhage can occur due to trauma to ethmoidal vessels. Accidental lateral displacemet of medial wall causes traumatic hypertelorism .

8. Lateral Orbital Wall Thickest and strongest. Formed by two bones: Zygomatic Greater wing of sphenoid.

9. Lateral Orbital Wall Clinical applications: The anterior half of globe is not covered by bone on lateral side. Hence, palpation of retrobulbar tumours is easier from the lateral side. The zygomatico -sphenoid suture is an important landmark in creating the flap in lateral orbitotomy . It is the strongest portion of the orbit and needs to be sawed open in lateral orbitotomy . Since lateral wall is almost devoid of foramina, bleeding is less.

10. Roof Of Orbit Underlies frontal sinus and anterior cranial fossa. Formed by- Orbital plate of frontal bone Lesser wing of sphenoid. Triangular. Faces downwards and slightly forwards.

11. Roof Of Orbit Clinical applications: Thin and periorbita peels away easily. Objects piercing upper eyelid penetrate roof and damage frontal lobe. In old age roof may be absorbed so that periorbital and duramater comes into contact. Any trauma of dura mater and CSF escapes into orbit or nose or both.

12. Floor Of Orbit Shortest orbital wall. Formed by: Maxillary bone- medially Zygomatic bone- laterally Palatine bone- posteriorly. Triangular in shape. Bordered laterallly by inferior orbital fissure and medially by maxilloethmoidal sinus. Overlies maxillary sinus.

13. Floor Of Orbit Clinical applications: Commonly involved in Blow out fractures of the orbit. Infra orbital vessels and nerves almost always involved. Diplopia is the main symptoms of blow-out fracture. Easily invaded by tumors of the maxillary antrum . Figure- Mechanism of blow-out fracture from displacement of the globe itself into the orbital walls. The globe is displaced posteriorly, striking the orbital walls and forcing them outward.

14. Base Of Orbit The anterior open part. Bounded by four orbital margins- Superior orbital margin Inferior orbital margin Medial orbital margin Lateral orbital margin. It gives attachment to the septum orbitale .

15. Apex Of Orbit Orbital apex is the posterior end of the orbit. Four orbital walls converge. Two orifices: Optic Canal Superior orbital fissure

16. Optic Canal It connects the orbit to the middle cranial fossa. It transmits: Optic Nerve Ophthalmic artery.

17. Superior Orbital Fissure Structure passing: Upper lateral part: Lacrimal and frontal nerves Trochlear nerve Superior ophthalmic vein Recurrent branch of ophthalmic artery. Middle part: Superior and inferior divisions of occulomotor nerve Nasociliary branch of ophthalmic division of trigeminal nerve. Abducent nerve. Lower medial part: Inferior ophthalmic vein.

18. Superior Orbital Fissure Clinical applications: Radiographic enlargement of superior orbital fissure may accompany pathologic processes, Aneurysm Meningioma Choroidoma Pituitary adenoma tumours of orbital apex. Idiopathic inflammation involving the superior orbital fissue - “ Tolosa Hunt syndrome”. (Painful ophthalmoplegia)

19. Periorbita Periorbita refers to periosteum lining the orbital surface of the bones of orbit. Loosely adherent to the bones. Fixed firmly at- Orbital margins Suture lines Various fissures and foramina Lacrimal fossa. Applied Anatomy- Surgery in the orbital roof in the areas of fissures and suture lines may be complicated by cerebrospinal fluid leakage.

20. Orbital Fascia It is a complex interwoven thin connective tissue membrane joining the various intraorbital contents. Parts- Fascia bulbi , Muscular sheaths, Intermuscular septa, Membranous expansions of the extraocular muscles, Ligament of Lockwood.

21. Extraocular Muscles Voluntary Muscles : Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique Levator palpebrae superioris . Involuntary Muscles : Superior tarsal or Muller’s muscle, Inferior tarsal muscle.

22. ARTETY SUPPLY OF ORBIT

23. ARTETY SUPPLY OF ORBIT

24. NERVES OF ORBIT

25. Surgical Spaces In Orbit Orbit is divided into 4 surgical spaces- Subperiosteal space Peripheral orbital space/ Extraconal space Central orbital space/ Intraconal space Subtenon’s space

26. Surgical Spaces In Orbit Importance of these spaces- Most of the orbital tumours tends to remain with in a space in which they are formed unless they are large or malignant or represents an infiltrative process such as pseudotumour .

27. Subperiosteal Space Lies between orbital bone and periorbita . tumours arising from bone separates periorbita from bone. Here periorbita acts as a effective barrier against spread of tumour to eye.

28. Subperiosteal Space tumours in this space are- Dermoids cyst Epidermoid cyst Mucocele Subperiosteal abscess Osteomatous tumour

29. Peripheral Orbital Space Known as extraconal space. Lies between periorbita at periphery, extraocular muscles and their intermuscular septa internally and orbital septum anteriorly. Posteriorly it merges with central space. tumours in this space are usually approached by anterior orbitotomy and sometimes by lateral orbitotomy .

30. Peripheral Orbital Space tumours in this space produce eccentric proptosis . tumours in this space are- Malignant Lymphoma Capillary haemangioma of childhood Intrinsic neoplasm of lacrimal gland Pseudotumours .

31. Central Orbital Space Known as muscle cone/ retro-orbital space/posterior space/ intraconal space. Bounded by- Anteriorly tenon’s capsule Posteriorly by 4 recti and intermuscular septa. In posterior part, space become continuous with peripheral space.

32. Central Orbital Space tumours of this space- Cavernous haemangioma of adults Solitary neurofibroma Neurolemoma Nodular orbital meningiomas Optic nerve glioma . Produce axial proptosis . tumours are approached through lateral orbitotomy .

33. Subtenon’s space Space around eyeball between sclera and tenon’s capsule. Pus collection in this space is drained by incision on tenon’s capsule through conjunctiva.

34. Contents Of The Orbit Eyeball Fascia: Orbital and bulbar. Muscles: Extraocular . Vessels: Ophthalmic artery Superior and inferior ophthalmic vein Lymphatics . Nerves: Optic,Oculomotor , Trochlear, Abducent , Branches of ophthalmic nerves and sympathetic nerves. Ciliary ganglion Lacrimal gland and lacrimal sac Orbital fat.

35. CONGENITAL ANOMALY OF ORBIT

36. Microphthalmia with orbital cyst F ailure of the choroidal fissure to close in the embryo

37. CRANIOFACIAL DEFORMITIES F ailure of NCC migration and a failure of fusion of facial processes

38. APERT SYNDROME

39. ORBITAL TRAUMA

40. Midfacial (Le Fort) Fractures (A ll the fractures extend posteriorly through the pterygoid plates )

41. Zygomatic Fractures Zygomaticomaxillary complex (ZMC) fractures Also referred to as Q uadripod fractures

42. Medial Orbital Fractures Naso - orbital- ethmoidal (NOE) fractures usually result from the face striking a solid surface. Traumatic telecanthus with rounding of medial canthus

43. ORBITAL FLOOR FRACTURE