Anatomy: The Orbit

Front 1

Fasciae: Cranial dura mater continues into the orbit to form?

Back 1

Periorbita, Muscle Fascia, check ligaments, and optic nerve sheath

Front 2

Periorbita

Back 2

The perisoteal lining of the roof, floor, and walls of the orbit

Front 3

Muscle Fascia

Back 3

The fascia of the extraocular muscles

Front 4

Check Ligaments

Back 4

Ligaments that maintain eye movements within normal limits

Front 5

Optic Nerve sheath

Back 5

-outer membranous portion of optic nerve
- consists of extensions of the dura mater, arachnoid membrane, and pia mater
- contains space occupied by CSF; central retinal artery and vein pass through space and layers of optic nerve sheath

Front 6

Tenon's Capsule

Back 6

- encloses posterior 2/3 of sclera and provides for smooth movement of the eyeball. (The bulbar conjunctiva covers anterior 1/3 of sclera)

Front 7

Eye Movements

Back 7

-Rotation around transverse axis = elevation/depression
- Rotation around Vertical axis = abduction/adducion.
- Rotation around Anterior/posterior axis = intorsion/extorsion

Front 8

Muscles of the Orbit

Back 8

Extraocular muscles: striated mm. that insert into sclera of the eye and produce eyeball movement (SR, IR, SO, IO, MR, LR)

Other Muscles: Levator palpebrae superioris m. (striated), Mueller's m.(smooth m.), and within the iris ; sphincter pupillae, and dilator pupillae (smooth mm.).

Front 9

Extraocular mm. Continued

Back 9

- Rectus (straight) mm. originate from the common ring tendon that anchors the mm. to the back of the orbit.
- Common ring tendon encircles part of the optic foramen and superior orbital fissure.

- IO m originates frm anterior-medial aspect of orbit floor.
- SO has a trochlea (pulley mechanism) that changes the direction of pull of muslce on eyeball.

Front 10

Superior Rectus m.

Back 10

Innervation: Oculomotor nerve (CN III)

Action: Elevates eye

Front 11

Inferior Rectus m.

Back 11

Innervation: Oculomotor n. (CN III).

Action: Depresses eye.

Front 12

Inferior Oblique m.

Back 12

Innervation: Oculomotor n. ( CN III).

Action: Elevation and extorsion of eye.

Front 13

Medial Rectus m.

Back 13

Innervation: Oculomotor n. (CN III).

Action: Adducts eye.

Front 14

Lateral rectus m.

Back 14

Innervation: Abducens n. (CN VI).

Action: Abducts eye.

Front 15

Superior Oblique m.

Back 15

Innervation: Trochlear n. (CN IV).

Action: Depression and intorsion of eye.

Front 16

Levator Palpebrae superioris m. and Sphinctor Pupillae m.

Back 16

Innervation: Oculomotor n. via parasympathetic fibers: Pre-CN 3, Post-Ciliary Ganglion.

Front 17

Dilator Pupillae m. and Mueller's m.

Back 17

Innervated by sympathetic nerve fibers: Pre-T1-T3 spinal nerves and Post-Superior Cervical Ganglion

Front 18

Innervation Sources to Eye

Back 18

-Oculomotor n. gives off oculomotor root (parasympathetic) via Ciliary ganglion to eye.
- Superior cervical ganglion (sympathetic) over internal carotid a. to eye.
- Nasociliary n. = ganglionic branch (sensory) passing through ciliary ganglion + long ciliary n. (sensory) passing directly to eye.

Front 19

Short Ciliary n.

Back 19

Nerve containing parasympathetic (ciliary ganglion), sympathetic (superior cervical ganglion), and sensory fibers (nasociliary n.) formed after fibers passed through ciliary ganglion.

Front 20

Intraocular mm. (3)

Back 20

- smooth mm.
- sphincter pupillae m, ciliary body m, and dilator pupillae m.

Front 21

Sphincter Pupillae m.

Back 21

- found in Iris
- cirlcular, parasymp., CN 3
Action: Constricts pupil
Injury: Mydriasis ( fixed, dilated pupil)

Front 22

Ciliary Body m.

Back 22

- cicular component, parasymp., CN 3

Action: Constricts eyeball to thicken lens.
Injury: Diminishes near vision.

Front 23

Dilator Pupillae m.

Back 23

- Radial, sympathetic, Superior Cervical ganglion.
Action: Dilates pupil
Injury: Miosis (pupil constriction).

Front 24

Diplopia (double vision) during lateral gaze eye movements (left and right)

Back 24

Could be caused by weaknes of active mm. ; Lateral and Medial rectus mm.

Front 25

Lateral Rectus m. weakness

Back 25

CN 6 dysfunction (Abducens n.) = Medial strabysmus, adducted eye.

Front 26

Medial Rectus m. weakness

Back 26

CN 3 dysfunction (Oculomotor n.) = Lateral strabysmus, abducted eye + dilated pupil- eyelid ptosis- disruption of near vision.

Front 27

H testing method

Back 27

Determines muscle weakness of the elavators of the eye (superior rectus/ inferior oblique) and the depressors of the eye (Inferior rectus/ superior oblique)

Front 28

Best elevators and depressors in an abduction position of eyes

Back 28

Rectus mm.

Front 29

Best elevators and depressors in an adduction position of eyes

Back 29

Oblique mm.

Front 30

Superior Oblique m. weakness

Back 30

- Dysfunction of trichlear n.
- frequently leads to head tilt to the side opposite the weakness.

Front 31

Damage to Right Oculomotor n. (CN III)

Back 31

A.: Paralysis of levator palpebrae superioris = ptosis of upper eyelid.
B.: Paralysis of sphincter pupillae m. = mydriasis and lateral strabysmus
C.: Paralysis of medial rectus m. = No adduction.
D.: Eye abducts to side of lesion due to functioning lateral rectus m.
E.: paralysis of superior rectus m. = No upward movement of R. eye
F.: Superior oblique m. can not depress abducted eye = No downward movement of eye.

Front 32

Damage to Left Trochlear n. (CN IV)

Back 32

- Left superior oblique m. paralysis
- extorted left eye, causing double vision.
- head tilts to unaffected side, right eye intorts.

- Difficulty depressing eyeball when turned inward
- Difficulty walking down stairs when eyes need to be turned downward and inward.

Front 33

Damage to Right Abducens n. (CN IV)

Back 33

- Lower motor neuron paralysis of lateral rectus m.
- looking straight ahead, affected eye is slightly adducted (medial strabysmus)
- On lateral gaze to normal side, affected eye adducts normally.
- On lateral gaze to damaged side, affected eye fails to abduct; causing diplopia.

Front 34

Sensory Nerves entering Orbit

Back 34

- Division (V1) of Trigeminal n.
NFL
- Nasociliary n. (crosses over Optic n. from lateral to medial)
- Frontal n.
- Lacrimal n.

Front 35

Branches of Opthalmic a. to Know

Back 35

- Supraorbital a.
- Lacrimal a.
-Central retinal a ( first branch of opthalmic a., becomes located in optic n. and retina)
-Ciliary aa. ( to eyeball)
-Anterior Ethmoidal a.
- Also Superior Opthalmic vein

-

Front 36

Course of Opthalmic a.

Back 36

Crosses over optic n. from lateral to medial, course and branches similar to nasociliary n.

Front 37

Ciliary aa.

Back 37

Form arterial plexus in choroid layer, which supplies, by diffusion, the photoreceptor cells

Front 38

Fovea Centralis (part of Retina)

Back 38

-Visual acuity area
- Cone receptors (for daylight vision)
- Color vision

Front 39

Central retinal a. branches

Back 39

-Supply retina near vitreous body
- Radiate out from optic disc

Front 40

Cause of Papilledema (swelling of optic papilla)

Back 40

-Collapse of the central retinal vein as it passes through the fluid space in the optic n. sheath
- With increased intracranial pressure

Front 41

Frequent results of increased intracranial pressure

Back 41

-papilledema
-medial strabysmus

Front 42

Glaucoma

Back 42

- condition resulting from increased intraocular pressure.
- usually caused by impaired outflow of its drainage from anterior chamber.
- Can result in retinal and optic n. damage.

Front 43

Aqueous Humor Flow

Back 43

1.) Secreted by ciliary body epithelium
2.) posterior chamber
3.) Pupil
4.) Anterior chamber
5.) Trabecular meshwork
6.) Absorbed by Canal of Schlemm

Front 44

Middle Vascular Coat (Uvea)

Back 44

Formed by Choroid, Ciliary body, and Iris.

Front 45

Near vision adjustment

Back 45

- Due to Oculomotor n. activity
- Accommodation of lens = contraction of ciliary body m. constricting the eyeball---- releases tension of zonule fibers--- allows lens to become rounded and thicker---- to focus divergent near light rays onto fovea centralis.

Other features = convergence of eyes and pupillary constriction

Front 46

Distant vision

Back 46

- Unnaccommodated
- Ciliary muscles relaxed

Front 47

Lacrimal n. (V1)

Back 47

- most lateral of three nerves and is directed towards lacrimal gland
-receives communicating branches from pterygopalatine ganglion (parasympathetic), seceretomotor in function
- secretion of gland due to Facial n.

Front 48

Frontal n. (V1)

Back 48

- largest and middle one of three nerves
- extends towards superior orbital margin
- larger branch is the Supraorbital n.

Front 49

Trochlear n. (CN IV)

Back 49

- most medial of the three nerves
- passes over levator palpebrae superioris m. to enter border of superior oblique m.

Front 50

Three nerves positioned superiorly in Orbit

Back 50

Lacrimal n., Frontal n., and Trochlear n.

Front 51

Three nerves located on deeper plane, enter orbit through part of superior orbital fissure and enclosed by common ring tendon

Back 51

Oculomotor n., Abducens n., and Nasociliary n.

Front 52

Oculomotor n. (CN III)

Back 52

- located lateral to optic n. and divides into superior and inferior divisions.
- Inferior division has a branch (oculomotor root) containing preganglionic parasympathetic nerve fibers which synapse on the ciliary ganglion.

Front 53

Ciliary ganglion

Back 53

-Small parasympathetic ganglion located between the lateral rectus m. and optic n. ~2cm. from back of orbit
- postganglionic parasymp. fibers innervate two intraocular mm. (sphinctor pupillae m. and ciliary body m.)

Front 54

Abducens n. (CN VI)

Back 54

- located on medial surface of lateral rectus m.
- innervates lateral rectus m.

Front 55

Nasociliary n.

Back 55

- sensory branch of opthalmic division of the trigeminal n.
- branches = ganglionic branch, long ciliary n., posterior/anterior ethmoidal nn.

Front 56

Long ciliary n.

Back 56

- branch of Nasociliary n.
- pass from nasociliary n. directly to eyeball.

Front 57

Posterior and Anterior Ethmoidal nn.

Back 57

- enter ethmoidal air cells through foramina in media wall of orbit
- supply sensory innervation to sphenoid sinus and ethmoid air cells
- anterior ethmoidal n. has additional distribution to anterior nasal cavity and skin of lower part of nose.

Front 58

Opthalmic a.

Back 58

- branch of internal carotid a.
- enters orbit by passing through optic canal in company with optic n.
- first branch is central retinal a., which enters the optic n. with central retinal v. at mid-orbital course of the nerve
- enters the eyeball at optic papilla and gives rise to 4 branches which supply the quadrants of the retina.