OCULAR ANATOMY (CFE)

ORBIT

Also called the Bony or Obit Cavity.

Designed to support and provide protection to the orbital soft tissues.

Intended essentially as a socket for the eyeball, containing the muscles, orbital fats, nerves, and vessels proper to it.

1.5 mm

The widest part of the orbit is (?) behind the orbital margin.

Superiorly

Anterior Cranial Fossa

Medially

Nasal Cavity and Air Sinuses

Inferiorly

Antrum of Highmore (Maxillary Sinus)

Laterally

Middle Cranial and Temporal Fossa

40 mm

Depth of the Orbit

35 mm

Height of the Orbit

40 mm

Width of the Orbit

Interorbital Distance

25 mm

Volume

30 mm

5.5:1

Volume ratio of the Orbit to the Eye

Paired Bones

• Zygomatic

• Maxillary

• Lacrimal

• Palatine

Unpaired Bones

• Sphenoidal

• Frontal

• Ethmoid

Superior Orbital Margin

Formed by the Frontal Bone

It is concave downwards, convex forwards.

Supra Orbital Notch/Foramen

Transmits the Supraorbital artery and nerve.

Supraorbital Grooves

Found 10 mm medial to the supraorbital notch.

It transmits the supratrochlear nerves and arteries

Supreciliary

It is small opening near the supraorbital notch and it transmits the number artery and a branch of the supraorbital nerve to the frontal air and sinus.

Inferior Orbital Margin

Formed by the Zygomatic bone and the Maxillary bone

This Margin is raised slightly above the floor or the orbit

Lateral Orbital Margin

Formed by the Zygomatic bone and the lateral angular process (Zygomatic process) of the frontal bone.

The thickest among the margins but it is also the most exposed to injury.

Medial Orbital Margin

Formed by the anterior lacrimal crest on the frontal process of the maxilla and the posterior lacrimal crest on the lacrimal.

Comminuted Fracture

Breakage of three or more pieces of the bones forming the orbital margin.

Blowout Fracture

Caused by blunt force that increases pressure inside the eye socket, making the thinnest bones buckle or crack.

Orbital Index

It is the relationship between the height and the width of the orbit.

Megaseme

The index is 89 or more, and is a characteristic of Mongolian races, except the Esquimatic. The opening is round.

Mesoseme

Orbital index between 88-84 as found in Caucasians.

Microseme

Small orbital index that measures 83 or less.

Characteristics of the black races. The opening is rectangular.

WALLS OF THE ORBIT: ROOF/VAULT

Triangular in shape

This is the lesser wing of sphenoid

It is thin, translucent and fragile expect where formed by the lesser wing of the sphenoid, which is 3mm thick

Translucency is also observed near the extension of the frontal sinus.

It is invaded by the frontal sinus and sometimes the ethmoidal air sinuses.

Lacrimal Fossa

STRUCTURES FOUND ON THE ROOF (?)

Lies behind the zygomatic process of the frontal bone

it contains the main lacrimal gland and some orbital fat.

Fovea for the Trochlea of the Superior Oblique

STRUCTURES FOUND ON THE ROOF (?)

Small depression close to the fronto-lacrimal suture about 4mm from the orbital margin.

Frontal spenoid suture

STRUCTURES FOUND ON THE ROOF (?)

this suture lies between the orbital plate of the frontal bone and the lesser wing of the sphenoid.

WALLS OF THE ORBIT: MEDIAL WALL

Quadrilateral in shape.

It is the thinnest of the orbital bones (2-4mm).

Made up by the following bones:

- Frontal process of the maxilla

- Lacrimal bone

- Orbital plate of the ethmoid (lamina papyracea)

- Lesser wing of the sphenoid.

Medial Wall: Lacrimal Fossa

STRUCTURE FOUND:

Depression on the nasal side formed by the maxilla and lacrimal bone.

FLOOR

It is triangular in shape and it slopes downward and laterally

It has a measurement of 47.6 mm.

Formed by the following bones:

- Orbital plate of the maxilla

- Orbital surface of the zygomatic bone

- Orbital process of the palatine bone

Antrum of Highmore (maxillary sinus).

Below the floor is (?)

Enopthalmos

Recession of the eyeball to the orbital floor due to trauma of loss of orbital fats.

LATERAL/OUTER WALL

It is triangular in shape.

Formed by the following bones:

- greater wing of the sphenoid (posterior)

- zygomatic bone (anterior).

The wall exposed to stress, this is the thickest among the walls of the orbit especially at the orbital margin area.

Spina Recti Lateralis

Structures found at the lateral wall:

Small bony projection on the inferior margin of the superior orbital fissure.

Zygomatic Groove and Foramen

Structures found at the lateral wall:

For the zygomatic nerve vessels.

Lateral Orbital Tubercle

Structures found at the lateral wall:

A small elevation on the orbital surface of the zygomatic bone.

This gives attachment to:

- Check ligament of the lateral rectus

- Suspensory ligament of the eyeball

- Aponeurosis of the levator palpebrae superioris

4mm

The optic canal has no length at birth; it is just considered a foramen. At 1 year its length is about (?).

SUPERIOR ORBITAL FISSURE

Medial to the eye, lateral to the optic foramen.

Divides the sphenoid into lesser and greater wing.

STRUCTURES PASSING:

CN#3 – Oculomotor Nerve

CN#4 – Trochlear Nerve

CN#5 – ophthalmic divisions thru its branches (frontal, lacrimal, and nasociliary nerves)

CN#6 – Abducens Nerve

Superior Ophthalmic Vein

INFERIOR ORBITAL FISSURE

Lies between the floor of the orbit and the lateral wall.

Below the SOF

STRUCTURES PASSING

CN#5 – maxillary division thru it’s the infraorbital nerve and zygomatic nerve

Infraorbital Artery

Inferior Ophthalmic Vein

Sympathetic Nerve

Infraorbital Nerve

Exits thru the infraorbital foramen to carry sensation to: lower lids, cheek, upper lips and teeth.

OPTIC FORAMEN AND CANAL

Located at the lesser wing of sphenoid, measures 4-10mm.

STRUCTURES PASSING

CN#2 - Optic Nerve

Ophthalmic Artery

Sympathetic Nerve

ETHMOIDAL FORAMINA

It lies between the roof and the medial wall of the orbit.

ANTERIOR AND POSTERIOR ETHMOIDAL CANAL

Located at the fronto-ethmoidal suture.

STRUCTURES PASSING

Ethmoidal Nerves

NASOLACRIMAL CANAL

Extends the lacrimal fossa to the inferior meatus of the nose.

STRUCTURES PASSING

Nasolacrimal Duct