ANATOMY OF ORBIT

RETINA UNIT

DR.PARESH VARSAT

The orbital bone is the cavity or socket of the skull in which the eye and its appendages are situated.

In the adult human, the volume of the orbit is 30 ml, of which the eye occupies 6.5 ml.

The orbits are conical or four-sided pyramidal cavities, which open into the midline of the face and point back into the head.

Each consists of a base, an apex and four walls. They are intended to protect the eye from mechanical injury.

PARAMETERS OF ORBIT:

0DEPTH- 42 mm along medial wall 50 mm along lateral wall0Width- 40 mm0Height- 35 mm0Orbit index-height/width x 1000Volume-30 ml in which eye ball contain 6 .5

ml

ORBIT FORMED BY-

1. Frontal2. Ethmoid3. Lacrimal4. Palantine5. Maxilla6. Zygomatic7. sphenoid

MEDIAL WALL-

0Quadrilateral 0 frontal process of maxilla0  lacrimal bone0orbital plate of ethmoid 0 a small part of the body of the sphenoid

LATERAL WALL-

0 the orbital process of zygomatic 0 the orbital plate of greater wing of sphenoid0The bones meet at the zygomaticosphenoid

suture0The lateral wall is the thickest wall of the

orbit

ROOF OF ORBIT-

0 Triangular0 Orbital plate of

frontal bone0 Lesser wing of

sphenoid0 Fossa for lacrimal

gland0 Troclear fossa near

junction of roof & medial wall

FLOOR OF ORBIT-

0Triangular0 Orbital surface

of maxilla,0Orbital surface

of zygomatic bone

0 Orbital process of palatine bone.

0 Near the middle of the floor, located infraorbital groove, which leads to the infraorbital foramen. The floor is separated from the lateral wall by inferior orbital fissure, which connects the orbit topterygopalatine and infratemporal fossa.

CLINICAL APPLICATIONS-

0 MEDIAL WALL- - ethmoditis -easily # durong injuries & orbitotomy -hemrrhoge due to injury to ethmoidal vessles0 LATERAL WALL- -comman site for orbital tumor and easier palpation -Lateral surgical approch -less hemrrhoge - zygometico sphenoid suture is imp. Landmark for kronleins operation

0FLOOR OF ORBIT- -commanly involved in blow out #0 ROOF OF ORBIT- -easily nibbled away in transfrontal orbitotomy

BASE OF ORBIT-

0Anterior open end-Superior orbital margin - formed Orbital arch of frontal bone - supra orbital notch,transmittes supra orbital nerve and artery - 10 mm medial supratrochler groove transmits supratrochlear nerve-Lateral orbit margin -zygomatic process of frontal bone -zygomatic bone

3.Inferior orbital margin -laterally zygomatic bone -medially maxilla -transmites infraorbital nerves and vesseles4.Medial orbital margin -above by frontal bone -below by anterior lacrimal crest

APEX OF ORBIT-

0 lies near the medial end of superior orbital fissure and contains the optic canal which communicates with middle cranial fossa.

0 Transmites optic nerve & opthalmic artery0 Optic nerve glioma and meningioma lead unilateral

enlargement

SUPRAORBITAL FISSURE-

FASCIA-

1)Periorbita :-periosteum lining the surface of the orbit.-Firmly adhrent to orbital margin, sup & inf orbital fissure,optic canal,lacrimal fossa and at suture.

-at apex of orbit form tendinous ring of zinn-At the post lacrimal crest it split in 2 layers to enclose lacrimal sac and reunite at the ant lacrimal crest.

2)Orbital fascia : Thin connective tissue membrane lining various intraorbital structure.As fascia bulbi,muscular sheaths,intramuscular septa,membranous expansion of extraocular muscle & ligament of lockwood

3)Tenon’s Capsule : -It envelop the globe from limbus to the optic disc.-Lower part of tenon’s capsule is thickened and take part in formation of a sling on which glob rest called Suspensory ligament of Lockwood.

SURGICAL SPACES IN ORBIT-

1)Subperiosteal space: -It is a potential space between orbital bone and periorbita.-Dermoid,epidermoid,mucocele,subperiosteal absess,myeloma,hematoma,osteomatous tumors are commonly seen in this space.

2)Peripheral orbital space:-It bound peripheri by periorbita,internall by 4EO muscles,with their intermuscular septa and ant. By septum orbitale.Posteriorly it merge with central space.-Common tumors: cip heamangioma,malignant limphoma,intrinsic neoplasm of lacrymal gland,pseudotumor Tumors in this space produce eccentric proptosis.

3)Central space (retrobulber space or muscular cone) : It bound ant. By tenon’s capsule and peripher by EO muscle and their IM septa. In post. Part it become continue with pheripheral orbital space.Causes Axial proptosisTumors:

1) Solitary neurofibroma2) Cav. Haemangioma3) neurilemomas4) orbital meningiomas5) optic nerve gliomas

4)Sub-Tenon’s space:

space around eye ball b/w sclera and tenon’s capsule.0CLINICAL IMPORATANCE- -most tumors tend to remain within the space in which they are formed.

CONTENTES OF THE ORBIT-

0 Eyeball0 Fascias: Orbital, Bulbar0 EO muscles LPS, SR, IR, LR and MR,SO,IO0 Nervel s: short ciliary nerve ,cranial nerves II, III, IV, V,

and VI0 Lacrimal gland, Lacrimal sac, Nasolacrimal duct0 Eyelids0 Orbital fat,reticular tissue0 Veesels :opthalmic artery and its branches ,infra

orbital ,orbital branch of middle meningeal aretry and sup. & inf. Opthalmic veins

THANKS FOR PATIENCES !!!!