The orbits - presentation for master stundents

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1. THE ORBITS TOPIC;SMALL PARTS NAME OLOBULU OLE LOLTUALAN REG NO;K/240300410/MDU

2. THE ORBITS OBJECTIVES The anatomy of the orbits,eye ball and ocular muscles Ultrasound techniques of the eye Vascularity and inervation of the eye Common pathologies

3. The orbits is a pyramid shape or cone-shaped chambers immediately inferior to the anterior aspect of the cranial cavity It has the apex as optical canal and the roof, floor ,medial and lateral walls. The apex of the pyramid –shaped bony orbit is the optic foramen. The orbits are two bony sockets at the front of the face that primarily house and protect the eyes and associated structures.

4. SUPERIOR MARGINS Frontal bone Supraorbital foramen INFERIOR MARGINS Zygomatic bone Maxilla MEDIAL MARGINS Frontal bone Maxilla LATERAL MARGINS Frontal bone Zygomatic bone

5. Therefore the roof is related to the anterior cranial fossa and the brain The floor is related to the maxillary air sinus The medial wall is related to the ethmoidal air sinuses

6. ORBITAL WALLS The medial wall The medial walls of the paired bony orbits are parallel to each other. Each medial wall consists of four bones: Maxilla bone Lacrimal bone Ethmoid bone The largest contributor to the medial wall is the orbital plate of the ethmoid bone This part of the ethmoid bone contains collection of ethmoidal cell s

7. Orbital walls The roof Consist of Frontal bone Lesser wing of sphenoid The floor Consist of Zygomatic bone Maxilla Palatine Lateral wall Zygomatic bone Greater wing of sphenoid

8. The floor Bones Zygomatic bones Maxilla Palatine bone Features Infraorbital groove Infraorbital canal Related to Maxillary sinus

9. The medial wall Bones Maxilla Lacrimal bone Ethmoid bone Features Lacrimal sac fossa Anterior and posterior ethmoidal foramina Related to Ethmoidal sinuses

10. FISSURES AND FORAMINA Numerous structures enter and leave the orbit through a variety of openings Optic canal Superior orbital fissure Inferior orbital fissure Infra-orbital foramen Anterior and posterior ethmoidal foramen Infraorbital groove Lacrimal groove for lacrimal sac

11. Foramina and fissures

12. OPTIC CANAL The round opening at the apex of the pyramidal shaped orbit is the optic canal It opens into the middle cranial fossa and is bounded medially by the body of the sphenoid and laterally by the lesser wing of the sphenoid Passing through the optic canal are the optic nerve and the ophthalmic artery

13. SUPERIOR ORBITAL FISSURE Just lateral to the optic canal is a triangular-shaped gap between the roof and lateral wall of the bony orbit This allows structure to pass between the orbit and the middle cranial fossa Passing through the superior orbital fissure are: Superior and inferior branches of the oculomotor nerve (III) Trochlear nerve (IV) Abducent nerve (VI) Lacrimal, Frontal and Nasociliary branches of the ophthalmic nerve (V1) Superior ophthalmic vein

14. INFERIOR ORBITAL FISSURE Separating the lateral wall of the orbit from the floor of the orbit is a longitudinal opening, the inferior orbital fissure Its borders are the greater wing of the sphenoid and the maxilla, palatine, and zygomatic bones.

15. INFRA-ORBITAL FORAMEN It begin posteriorly as a groove (the infra-orbital groove), which continues anteriorly across the floor of the orbit This groove connects with the infra-orbital canal The canal opens onto the face at the infraorbital foramen The infra-orbital nerve, part of the maxillary nerve (V 2) and vessels pass through this structure as they exit onto the face

16. ANATOMY The eye is the organ of sight situated in the orbital cavity. It is almost spherical in shape and is about 2.5 cm in diameter. The volume of an eyeball is approximately 7 cc. The space between the eye and the orbital cavity is occupied by fatty tissue. The bony wall of the orbit and the fat helps to protect the eye from injury. Structurally the two eyes are separate but they function as a pair. It is possible to see with only one eye.

17. Structure of the Eye The eyeball has three layers namely: 1. The outer fibrous layer—Sclera and cornea 2. The middle vascular layer—Iris, ciliary body and choroid 3. The inner nervous tissue layer—Retina.

18. The Outer Fibrous Layer 1. Sclera—The sclera or white of the eye forms the firm/strong, fibrous outermost layer of the eye. It maintains the shape of the eye and gives attachment to the extraocular muscles. It is about 1 mm in thick. The sclera becomes thin ( seive -like membrane) at the site where the optic nerve pierces it and is called Lamina cribrosa Retina and choroid are maintained in the correct optical shape by the sclera. Provides rigid insertion for the extraocular muscles. Helps the eye to overcome stress and strain by disposition of fibrous ban

19. THE CORNEA 2.Cornea forms the anterior 1/6 of the eye . It is a clear transparent and elliptical structure with a smooth shining surface. It is the main refracting surface of the eye. The two primary functions of the cornea are as mojar refracting medium and protects the intraocular contents. This is possible by the cornea transparency and replacement of its tissues. Limbus—The junction of cornea and sclera is known as the limbus. There is a minute arcade of blood vessels about 1 mm broad present at the limbus

20. The Middle Vascular Layer(the uveal tract) 1. Iris—Iris is a coloured , free, circular diaphragm with an aperture in the centre —the pupil. It divides the anterior segment of the eye into anterior and posterior chambers which contain aqueous humour secreted by the ciliary body. It consists of endothelium, stroma, pigment cells and two groups of plain muscle fibres , one circular (sphincter pupillae) and the other radiating (dilator pupillae). It regulates the amount of light rays reaching the retina.

21. 2. Ciliary body—Ciliary body is triangular in shape with base forwards. The iris is attached to the middle of the base. It consists of non-striated muscle fibres (ciliary muscles), stroma and secretory epithelial cells. It consists of two main parts, namely pars plicata and pars plana. Pars plicata part of the ciliary body secretes aqueous humour . The ciliary muscle helps in accommodation of the lens for seeing near objects.

22. choroid 3. Choroid—Choroid is a dark brown, highly vascular layer situated between the sclera and retina. It extends from the ora serrata up to the aperture of the optic nerve in the sclera. The outer layers of the retina are dependent for their nutrition.

23. The Inner Nervous Tissue Layer 1. Retina—Retina is composed of ten layers of nerve cells and nerve fibres lying on a pigmented epithelial layer. It lines about 3/4 of the eyeball. Macula lutea is a yellow area of the retina situated in posterior part with a central depression called fovea centralis. It is the most sensitive part of retina. Optic disc—Optic disc is a circular, pink coloured disc of 1.5 mm diameter. It has only nerve fibre layer so it does not excite any visual response. It is known as the blind spot.

24. The optic nerve—The optic nerve extends from the lamina cribrosa up to the optic chiasma. The total length of the optic nerve is 5 cm. It has four parts namely, Intraocular — 1 mm Intraorbital — 25 mm Intraosseous — 4-10 mm Intracranial — 10 mm (Duke–Elder)

25. INTERIOR OF THE EYEBALL Aqueous Humour Both anterior and posterior chambers contain a clear aqueous humour fluid secreted into the posterior chamber by the ciliary epithelium. It passes in front of the lens, through the pupil into the anterior chamber and returns to the venous circulation through the canal of Schlemm situated in the angle of anterior chamber

26. The lens Lens is a transparent, biconvex structure of crystalline appearance placed between the iris and vitreous. It is suspended from the ciliary body by the suspensory ligament or zonule of Zinn. It is enclosed within a transparent capsule and its main functions includes Provides refractive power to the optical system of the eye Accommodation for near vision and absorption of harmful ultraviolet light. Maintain its own clarity and transparency.

27. THE VITREOUS Vitreous is an inert avascular, transparent, jelly-like structure which serves only optical functions. It contains few hyalocytes and wandering leucocytes. It consists of 99% water, some salts and mucoproteins. It is attached anteriorly to the lens (hyaloid capsular ligaments of wieger ) and posteriorly to the edge of the optic disc and macula lutea. The vitreous forms one of the refractive media of the eye

28. ACCESSORY STRUCTURES OF THE EYE Eyebrows Eyebrows are two arched ridges of the supraorbital margins of the frontal bone. Numerous hair (eyebrows) project obliquely from the surface of the skin. They protect the eyeball from sweat, dust and other foreign bodies

29. Eyelids and Eyelashes The eyelids are two movable folds of tissue situated above and below the front of each eye. There are short curved hair, the eyelashes situated on their free edges. The eyelid consists of: A thin covering of skin • Three muscles—the orbicularis oculi, levator palpebrae superioris and Müller’s muscles • A sheet of dense connective tissue, the tarsal plate and lining of the conjunctiva

30. Lacrimal Apparatus Lacrimal apparatus consists of: Lacrimal gland and its ducts Accessory lacrimal glands Lacrimal canaliculi Lacrimal sac Nasolacrimal duct The tears are secreted by the lacrimal gland and accessory lacrimal glands. They drain into the conjunctival sac by small ducts. The tears then pass into the lacrimal sac (via the two canaliculi),nasolacrimal duct and finally into the nasal cavity (inferior meatus)

31. THE EYE MUSCLES THE INTRA-OCULAR MUSCLES Two acting on the pupil of the eye Sphincter pupillae (constriction) supplied by the oculomotor nerves. Dilator papillae(dilatation) supplied by sympathetic fibers. Ciliary muscles (for accommodation)changing thickness, supplied by the oculomotor nerve

32. Extraocular Muscles of the Eye The eyeballs are moved by six extrinsic muscles, attached at one end to the eyeball( scelera ) and at the other to the walls of the orbital cavity. There are four straight and two oblique muscles. They consist of striated muscle fibres . Movement of the eyes to look in a particular direction is under voluntary control but co-ordination of movement needed for convergence and accommodation to near or distant vision, is under autonomic control The inferior oblique rotates the eyeball so that the cornea turns upwards and outwards.

33. The medial rectus rotates the eyeball adduct/inwards. The lateral rectus rotates the eyeball abduct/outwards. The superior rectus rotates the eyeball upwards/adduct. The inferior rectus rotates the eyeball downwards/adduct. The superior oblique rotates the eyeball so that the cornea turns in a downward and outward directions.

34. BLOOD SUPPLY TO THE EYE Arterial Supply The eye is supplied by the short (about 20 in number) and long ciliary (2 in number) arteries and the central retinal artery. These are branches of the ophthalmic artery, which is one of the branch of the internal carotid artery

35. Venous Drainage Venous drainage is done by the short ciliary veins, anterior ciliary veins, 4 vortex veins and the central retinal vein. These eventually empty into the cavernous sinus

36. NERVE SUPPLY TO THE EYE The eye is supplied by three types of nerves, namely motor, sensory and autonomic.

37. i . The 4th cranial nerve [trochlear]—It supplies the superior oblique muscle. iii. The 6th cranial nerve [abducens]—It supplies the lateral rectus muscle. iv. The 7th cranial nerve [facial]—It supplies the orbicularis oculi muscle

38. TECHNIQUE Linear probe of 9—18MHZ We scan the eye through a closed eyelid. Scanning in both transverse and sagittal planes, making sweeping movements in all quadrants of the eye also having the patient move their eyes(eye ball) side to side.

39. Use your pinky and heel of palm on the patients nasal bridge or forehead as an anchor

40. Pupillary light reflex The reflex is consensual: Normally light that is directed in one eye produces pupil constriction in both eyes. The consensual response is the change in pupil size in the eye contralateral eye to the one that is being illuminated. The clinical significance of this as it pertains to ultrasound is that it could be used when you want to evaluated but the eye is shut closed due to edema or other swelling.

41. Retinal Detachment Peeling of the retina from its underlying support tissue (tethered to the optic nerve). On ultrasound you’ll see a thin echogenic serpiginous structure that sways with eye movement, this membrane is tethered to the optic nerve. There are three different types of retinal detachments

42. Rhegmatogenous Most common type Hole or tear that allows fluid to accumulate under the retina The detached retina loses blood supply leading to blindness Surgical emergency, as untreated detachment can lead to permanent blindness

43. Tractional Scar tissue forms on the retina which causes the retina to pull away Seen in patients with poorly controlled diabetes mellitus

44. Exudative Fluid accumulates but there’s no tear Macular degeneration, injury to the eye, tumors or inflammatory disorders

45. Retinal vs. Vitreous Detachment Whereas in retinal detachment the retinal tissue will be attached or tethered to the optic nerve. Posterior vitreous detachment happens when the vitreous is detached from the retina. There will be a similar appearance but no tethering to the optic nerve will be present and the echogenic retinal lining will be seen still attached to the posterior wall.

46. Vitreous Hemorrhage Any blood located in the vitreous chamber is a vitreous hemorrhage. On ultrasound you’ll see a fluid fluid level within the vitreous chamber with the echogenic fluid representing blood. The blood will also swish around with eye movements (washing machine sign. Scattered mobile mildly hyperechoic dots and line in the vitreous chamber

47. Vitreous hemorrhage vs. Asteroid Hyalosis Asteroid hyalosis is a degenerative condition of the vitreous with a prevalence of 1.2% in adults. It is found to be more frequent with aging, with 0.2% prevalence in 43- to 54-year-old and 2.9% in 75- to 86-year-old patients. It has been reported to mimic vitreous hemorrhage with the similar washing machine sing seen on ultrasound. On ultrasound there may be echogenic fluid with potential multiple echogenic foci.

48. Central Retinal Artery Occlusion Blockage of the central retinal artery usually due to an atherosclerotic thrombus (typically from an internal carotid artery plaque). Presents with sudden, painless, partial or complete monocular loss of vision. Also associated with giant cell arteritis. Patient describes “shade” or “curtain” coming down over entire visual field in the affected eye. Bilateral presentation is rare. Sonographically you’ll encounter an echogenic foci posterior to the optic disc “bright dot sign” with lack of color or spectral flow distal to the thrombus

49. Increased Intracranial Pressure Research has shown a correlation of increased ultrasound sheath diameter with increased intracranial pressure and papilledema. A prospective study of ICU and ED patients with invasive intracranial pressure monitoring found that an optic nerve sheath diameter of more than 5 mm correlated with intracranial pressure. Proper measurement: 3mm from optic disc measure ONSD outer to outer, normal< 5mm

50. Age Category (Years) Normal ONSD Measurement Adults (16+) < 5 mm Children (1-15) < 4.5 mm Children (<1) < 4 mm Normal Optic Nerve Sheath Diameter by Age

51. Causes for increased intracranial pressure include: Intracranial hemorrhage Cerebral tumors Hydrocephalus Aneurysms Trauma Encephalitis Pseudotumor cerebri

52. Lens Dislocation (ectopia lentis ) Lens dislocation (ectopia lentis ) may occur after trauma or in association with ocular or systemic disease. Subluxation is the term used when the lens is partially dislocated but remains attached to the ciliary body Luxation is the term used when the lens is completely detached from the ciliary body. Luxated lenses may dislocate into either anterior or posterior chamber. Sonographically the lens will be seen either free floating or in the dependent portion of the posterior chamber, or dislocated but still anchored by the ciliary body.

53. Foreign Body In the presence of ocular trauma with projectiles you may see an echogenic structure within the eye and depending on the material of the object you may see posterior artifacts.

54. Globe Rupture Globe rupture often happens in the presence of blunt or penetrating trauma that causes a full thickness laceration or defect of the sclera. As with rupture of other organs sonographically you may see a heterogenous amorphous complex structure with varying levels of echogenicity. The normal structures like anterior chamber, lens etc may not be easily identifiable or collapsed Loss of normal spherical contour Hyperechoic layering debris

55. Masses intraocular Tumors Ocular tumors range from benign to malignant, ultrasound can be used to identify the presence of, size and sonographic appearance (i.e. cystic, solid heterogenous) of the lesion.

56. Malignant Ocular Melanoma most common ocular cancer starts in the pigment cells of the eye usually starts in the uvea/choroid

57. Osseous Choristoma Occur more in young women Can be bilateral Also called Osteoma

58. Retinoblastoma Hyperechoic and heterogenous mass Mass have shadowing due to calcification Internal vascularity on doppler develops from the immature nerve cells of the retina sometimes discovered incidentally on personal photos

59. Primary Intraocular Lymphoma blood malignancy that develop from lymphocytes (eye is an uncommon location) eye lymphoma usually non Hodgkin’s type more common in elderly and immunocompromised patients

60. Metastatic cancer that has spread from primary site breast carcinoma. lung carcinoma. gastrointestinal tract carcinomas. genitourinary tract carcinomas. cutaneous melanoma. neuroblastoma.

61. Benign Benign intraocular tumors are non cancerous lesions like choroidal hemangioma, eye moles and cavernous hemangiomas and can be seen within or behind the eye.

62. Phthisis bulbi clinical condition representing end-stage ocular response to severe eye injury or disease damage, related to a variety of causes leading to scarring, inflammation, scaring, atrophy and eventually disorganization of the globe and intraocular contents. Also called end-stage eye, phthisis bulbi can be described as a shrunken, collapsed in form, non-functional eye and presents with a small squared off shape, opaque and thickened cornea, thickened sclera, neovascularization of iris, cataract, cyclitic membrane, ciliochoroidal detachment, and retinal detachment. A mnemonic rule used to describe phthisis bulbi is ”7S” referring to : Soft – Shrunken – Shapeless – Sightless – Structureless – Squared – Sore. Deformed small eye filled with calcification .

63. Choroidal Melanoma Choroidal mass with medium level echoes. Internal flow will be present on doppler flow. Lenticular(biconvex)shaped mass

64. Ciliary melanoma Mass is found in the superior or anterior aspect of vitrous chamber Mass has medium level echoes

65. Choroidal Metastases Choroidal thickening Metastases are usually bilateral

66. Hyper echoic implant Reverberation artifacts are seen

67. Fluid in tenons capsule Fluid accumulation in tenons capsule and optic nerve sheath forms a t-sign