Eye And Orbit Flashcards
Borders of the orbit & their orientation
Base
- orbital margin surrounding the orbital opening
- anterolateral orientation
Apex
- At the optic canal in the lesser wing of the sphenoid, just medial to the superior orbital fissure
- Posteromedial
Walls of the orbit and structures that form them
For Sir, MOLS Many Parang Zoo ZS
Superior
- Frontal (orbital part)
- Sphenoid (Lesser wing)
Medial
- Maxillary (Frontal process)
- Orbital part of the ethmoid bone
- Lacrimal
- Sphenoid
Inferior
- Maxillary
- Palatine
- Zygomatic
Lateral
- Zygomatic (Frontal process)
- Sphenoid (Greater wing)
Demarcation of the inferior and lateral walls?
Inferior orbital fissure
Openings into the orbital cavity/Structures passing through
Opening
1. Optic canal - ophthalmic a., optic n.
- Superior orbital fissure
- lacrimal n., frontal n., trochlear n., oculomotor n., abducens n., nasociliary n., superior ophthalmic v. - Inferior orbital fissure
- Maxillary n. & its zygomatic branch
- Inferior ophthalmic v.
- Sympathetic n.
Orbital Fascia
Periorbita Periorbital Fascia
Bulbar Fascia
Muscular Fascia
Moveable folds of skin that cover the eyeball anteriorly when closed? Difference of the two? Elliptical opening between the two?
Eyelid!
Upper eyelid - larger and more mobile
Lower eyelid - limited movement
Elliptical opening in between the two eyelids: palpebral fissure
Layers of the eyelid
- Skin
-thin outermost layer/thinnest in the body
-contains hair follicles
-2 types of glands:
A. Sebaceous glands of Zeis/ciliary glands
B. Sweat glands of molls - Subcutaneous tissue
- next to the skin - Muscular Layer
-w/ palpebral portion of the orbicularis oculi ms.
-Superior Tarsal (Muller’s) Ms
>Smooth ms which helps elevate the Levator Palpebrae Superioris ms in the eyelid.
-supplied by sympathetic fibers - Tarsofacial Layer
- comprised of tarsus (dense fibroelastic plate) which support the eyelid
- surrounded by Tarsal gland (modified sebaceous gland) - Conjuctivae
- innermost layer
- Palpebral conjunctiva
- Bulbar conjunctiva
- Superior and inferior conjunctival fornices
- Conjunctival sac
Ptosis
Sty/Hordeolum
Conjunctivitis
-
Lacrimal apparatus portions
Secretory portion: lacrimal gland
Excretory portion:
>lacrimal canaliculi
>lacrimal sac
>lacrimal duct
What can you use to identify laterality of the eye?
Lacrimal gland
Nerve supply of the lacrimal gland
Presynaptic parasympathetic fibers: Facial n., greater petrosal n., nerve of pterygoid canal to the pterygopalatine ganglion
Synapse of pre- and postsynaptic fibers: occur at pterygopalatine ganglion
Postsynaptic: maxillary, infraorbital, zygomatic, lacrimal n.
Flow of tears?
Lacrimal puncta -> lacrimal canaliculi -> lacrimal sac -> nasolacrimal duct -> inferior nasal meatus
Movements of the Eyeball
AP axis - lat and med rotation
Vertical axis - abduction and adduction
Transverse axis - elevation and depression
Extraocular muscles
1. Innervation
- Innervation: CN III (Oculomotor n.) EXCEPT
>Lateral rectus: Abducens n (CN VI)
>Superior Oblique: Trochlear n. (CN IV)
Action
All RECTI muscles are adductors EXCEPT the lateral rectus which is an abductor.
All OBLIQUE muscles are ABductors
All superior muscles are intorters (MEDIAL rotators).
All inferior muscles are extorters (LATERAL rotators).
SO & IR are depressors.
IO & SR are elevators.
Levator Palpebrae Superioris
- Fxn
- Innervation? What happens if you disrupt its innervation?
- Elevates and depresses eyelids
2. CN III (Oculomotor n.); interruption produces constant ptosis
- Primary blood supply of the eye?
- Branch of which artery?
- Enters which canal and terminates as?
- Branches?
- Ophthalmic a.
- Branch of ICA
- Enters at the optic canal and terminates as the supratrochlear a.
- Branches:
A. Ocular: Within the eye
A.1. Central artery of the retina
A.2. Ciliary arteries
B. Orbital: Surrounds the eye
>DRMCPLESS
Venous Drainage of the Eye
Ophthalmic veins
- Superior ophthalmic v.
- drains into the cavernous sinus - Inferior ophthalmic v
- drains into the pterygoid venous plexus - Vorticose v.
- empties vascular layer of the eyeball into the 2 ophthalmic veins or the facial v.
Tunics of the Eyeball
- Outer/Fibrous Layer
A. Cornea
B. Sclera - Middle/Vascular Layer: Uvea
A. Choroid
B. Ciliary Body
C. Iris - Inner/Nervous Layer: Retina
Layers of the Cornea
EBSDE
Junction where cornea becomes continuous with the sclera? Function?
> Limbus/Corneoscleral junction
> Fxn: Site of epithelializatin
> Stroma becomes vascular: Canal of Schlemm (Scleral venous sinus) - contains aqueous humor
Responsible for the red-orange reflex
>Layers
Choroid
-has the highest gram rate vasculature perfusion in the whole body
Layers:
A. Choroidocapillary Layer
B. Bruch’s membrane
Flow of aqueous humor. Obstruction in the pathway can lead to?
Ciliary Process -> Posterior Chamber -> Pupil -> Anterior Chamber -> Canal of Schlemm
Obstruction can lead to Glaucoma.
Most anterior part of the uveal tract which divides the anterior segment of the eye into the anterior and posterior chambers
Iris
What determines the color of the eye?
Melanin granules in the posterior surface of the iris
Muscles of the posterior surface of the iris?
- Sphincter pupillae ms. - constrictor; circularly arranged
2. Dilator pupillae ms. - dilator; longitudinally arranged
