Flashcards in Ophthalmology Eye Anatomy Deck (59):
What is the Superior Orbital Wall made up of?
Orbital Plate of the Frontal Bone
Orbital Plate of the Sphenoid Bone
What is the Medial Orbital Wall made up of?
Orbital Plate of the Ethmoid Bone
Orbital Plate of the Lacrimal Bone
Orbital Plate of Part of the Maxillary Bone
What is the Inferior Orbital Wall made up of?
Orbital Plate of the Maxillary Bone
What is the Lateral Orbital Wall made up of?
Orbital Plate of the Zygomatic Bone
Orbital Plate of the Sphenoid Bone
What are the edges of the Orbit called?
These make up the Orbital Pyramid.
Superior Orbital Rim/Margin
Medial Orbital Rim/Margin
Inferior Orbital Rim/Margin
Lateral Orbital Rim/Margin
Which orbital rim contains the Supracondylar Notch?
Superior Orbital Rim
What is the Apex/Tip of the Orbital Pyramid?
What are the foraminae of the Orbit?
What does the Optic Canal contain?
Ophthalmic Artery which supplies the Retina
What does the Supraorbital Fissure contain?
Ophthalmic Nerve (CN V1)
Oculomotor Nerve (CN III)
The Trochlear Nerve (CN IV)
The Abducens Nerve (CN VI)
Superior Branch of the Ophthalmic Vein
What does the Infraorbital Foramen contain?
Maxillary Nerve (CN V2)
Inferior Branch of the Ophthalmic Vein
What makes the Medial Wall and Orbital Floor so thin?
Due to the presence of Ethmoid Sinuses in the Ethmoid Bone of the Medial Wall
and Maxillary Sinuses in the Maxilla of the Inferior Wall
What are Blowout Fractures of the Eye?
Direct blow to eye causes intraorbital pressure to increase dramatically.
This results in fracture of the Medial and Inferior Orbital Walls.
What is the most common nerve deficit found with Orbital Blowout Fractures?
Paraesthesia to Facial Skin
How may Diplopia occur with Orbital Blowout Fractures?
If Zygoma bone is involved in fracture, it will pull the eye inferiorly and medially due to ligamentous attachments, results in Diplopia.
Patients can blow their noses soon after a Blowout fracture?
FALSE, PATIENTS CANNOT BLOW THEIR NOSES FOR 2 WEEKS AFTER FRACTURE
Blowing the Nose will pump Air into the Orbit through the Fractured Orbital Walls, increasing the Intraorbital Pressure and Distends the Orbit, resulting in Extreme Pain and Crackly Skin
What are the Tarsal Plates?
What are their functions?
2 Thick, Elongated Plates of Tissues found in Each Eyelid
Secrete Lipids which keep the Eye Moist with Blinking spreading those Lipids across the Eye
Which muscles open the eyelids?
Levator Palpebrae Superioris
Fibres of Muller's Muscle are buried amongst the Fibres of the Levator Palpebrae Superioris
Which muscle closes the eyelid?
What are the 3 types of tears?
Which nerves are involved in the Lacrimal Pathway?
Parasympathetic innervation via
CN VII (Afferent)
CN V2 then CN V1 (Efferent)
What is the Sclera?
White, Outer Layer of the Eyeball (i.e. The White of the Eye). It is Fibrous.
What is the Cornea?
Outermost, Transparent Layer of the Eye which helps to Focus Vision. It covers the Iris and is CONTINUOUS with the Sclera.
What is the Limbus?
Point/Junction at which the Sclera and Cornea merge together which can be seen as a 'ring' around the Iris.
What is the Uvea?
Pigmented Layer of the Eye, lying beneath the Sclera and Cornea and Consists of the Iris, Choroid and Ciliary Body. It is Highly Vascular.
What is the Iris?
Thin, Circular Structure of the Eye, responsible for Controlling the Diameter and Size of the Pupil and therefore, the Amount of Light reaching the Retina
What is the Lens?
Transparent, Crystalline Structure that sits Behind the Iris and bends Light Rays that enter the Eye to focus them so that they produce a clear image at the back of the eye.
What is the Ciliary Body?
Structure that Controls the Iris, Changes the Shape of the Lens and Secretes Aqueous Humour.
What is the Pupil?
Hole in the Centre of the Iris that allows Light to enter the Eye and Strike the Retina.
What is the Choroid?
Vascular Layer of the Eye that lies between the Retina and Sclera
What is the Retina?
Thin Layer of Tissue that lines the Back of the Eye and receives the Light that entered the Eye and was focused by the Lens. It passes Backwards to form the Optic Disc.
What is the Optic Disc?
Point of Exit for Ganglion Cell Axons leaving the Eye, which together form the Optic Nerve. It corresponds to a Small Blind Spot in Each Eye as there are NO Rods or Cones present.
What is the Macula?
Central Area of the Retina and is the Region of the Eye that provides us with our Best, Clearest Point of Vision.
What is the Conjunctiva?
Mucous Membrane that covers the Front of the Eye and Lines the Inside of the Eyelids. It is an External Barrier against Dust and often, the Conjunctival Vessels are Prominent and can be seen.
What is the Trochlea?
Pulley-Like Structure of the Eye through which the Tendon of the Superior Oblique Muscle passes, along with the Superior Oblique Muscle.
What are the 3 cells of the Retina?
Ganglion Cells and their Axons
What are the 2 Segments of the Eye?
Anterior Segment (in front of the lens and aqueous humour)
Posterior Segment (behind the lens and vitreous humour)
What are 2 Chambers of the Eye (that make up the Anterior Segment)?
Anterior Chamber (Cornea and Iris)
Posterior Chamber (Iris and Suspensory Ligaments)
What is the Arterial Supply to the eye?
Ophthalmic Arteries, from the ICA, give off Central Branches to the Retina
Posterior Ciliary Arteries are also derived from the Ophthalmic Artery
What is the Venous Drainage to the eye?
Superior and Inferior Ophthalmic Veins
Inferior Ophthalmic Vein drains into the Superior Ophthalmic Vein
What is the function of the Superior Rectus muscle?
Pulls the eye Superiorly, allowing it to look upwards
What is the function of the Inferior Rectus?
Pulls the eye Inferiorly, allowing it to look downwards
What is the function of the Medial Rectus?
Pulls the eye Medially, allowing it to look inwards
What is the Function of the Lateral Rectus?
Pulls the eye Laterally, allowing it to look outwards
What is the function of the Superior Oblique?
Abduct, Depress and Internally Rotate (Intorsion) the Eye as well as Pull the Sclera forwards
What is the function of the Inferior Oblique?
Extorsion, Elevation and Abduction of the Eye.
What is the Nerve Supply to the eye muscles?
SO4 LR6 AO3
Superior Oblique = CN IV
Lateral Rectus = CN VI
All other muscles = CN III
Where do all the eye muscles attach?
Describe the Blinking Reflex
CN V1 senses stimulus and relays Action Potentials which are conducted from the Cornea.
Action Potentials are then carried to the Trigeminal Ganglion, where they travel along to the Brainstem.
Action Potentials then passed to CN VII which stimulates the Eyelid/Palpebral Part of the Orbicularis Oculi, causing Blinking.
Describe the Vestibulo-Ocular Reflex
When the Eyes turn in the Opposite Direction to a Head Movement to allow Gaze to be Stabilised onto an Object during Head Movement.
Involves CNS Connections between CN VIII with CN III, IV and VI.
Describe the Oculocardiac Reflex?
Reflex Bradycardia occurs in Response to Tension on the Extra-Ocular Muscles or Pressure on the Eye(s).
ONLY CNS Connections present are between CN V1 and X.
Describe the Sympathetic Reflex Actions
Involuntary Eye Widening to increase Field of View and Light going into Eyes
Pupil Dilation to get More Light into Eyes
Focus on Far Objects so you can see what is coming and make a decision based on what you see.
Describe the Parasympathetic Reflex Actions?
Function of Orbicularis Oculi
Can be done by BOTH; Somatic Motor (Voluntary) and Parasympathetic (Involuntary) Innervation e.g. when sleeping
Pupil Shrinkage to get Less Light into Eyes
Focus on Near Objects
What is the function of the Dilator Pupillae?
Muscle of the Iris of the Eye that Dilates the Pupil.
Composed of Radially Arranged Fibres originating around the External Circumference of the Iris and Insert around the Internal Circumference of the Iris
(think of Spokes in a Wheel)
ONLY supplied by Sympathetic Fibres and its Contraction results in Pupil Dilation as it Decreases the Size of the Iris to Open Up the Pupil (Hole).
Which muscle mediates Pupillary Constriction?
Fibres encircle the Pupil. When it contracts, it Closes Off the Pupil.
Describe the Bilateral Pupillary Light Reflex?
Reflex Constriction of BOTH pupils in response to light
The Sensory Afferent of the Reflex is the Ipsilateral CN II, which is Special Sensory as it provides Vision.
The CNS Connections occur in the Midbrain, which result in Action Potentials travelling along CN IV.
The Efferent/Motor Aspect of the Reflex are the Bilateral CN III.
Sympathetics are involved in Lens Control. True/False?
How does Lens Control occur?
Suspensory Lens Ligaments connect its Circumferences to the Ciliary Body, which extend All Around the Circumference of the Lens.
Ciliary Muscle relaxes in Far Vision, tightening the Suspensory Ligaments, causing the Lens to Flatten Out.
NO PARASYMPATHETICS ARE INVOLVED IN FAR VISION AND SO, THEY ARE SWITCHED OFF.
Ciliary Muscle contracts in Near Vision and becomes 'Smaller', allowing the Suspensory Ligaments to Relax and Lens becomes circular.
PARASYMPATHETICS ARE SWITCHED ON HERE AND BECOME INVOLVED.