Anatomy Of Orbit and Eye Flashcards
(75 cards)
1
Q
What is the Orbital cavity?
How many walls does it have?
A
A pyramid shaped bony cavity with the apex pointing posteriorly
4 walls (Superior/ Roof, Inferior/ Floor, Medial and Lateral)
2
Q
Which walls of the Orbit are the weakest?
Of these 2 bones which one most often fractures?
What does direct impact to front of eye result in?
A
- Inferior/ Floor and Medial Walls
- Inferior Wall/ Floor
- Sudden increase in intraorbital pressure
3
Q
What do you call a fracture of Inferior/ Medial wall of the Orbit?
A
An orbital blow-out fracture
4
Q
What bone forms the Medial wall of the orbit?
What do we call the part of this bone in particular that forms the medial wall?
A
- Ethmoid
- Lamina Papyracea
5
Q
Despite the Medial Wall of the Orbit being thinner than the Inferior Wall, why does the inferior wall more often fracture upon impact?
A
Walled air cells (Ethmoid air sinuses) in the Medial Wall add extra strength to the wall
6
Q
The Walled Air Cells of the Medial Wall of the Orbit can become infected (Acute Sinusitis).
What can this lead to, given their proximity to the orbit?
A
- Infection can break through the thin Lamina Papyracea and track into the orbit OR into cranial cavity
- Causing Orbital Cellulitis
7
Q
List the 3 holes of the Orbit and state what structures pass through each
A
Optic Canal;
- Optic nerve
- Ophthalmic artery
Superior Orbital Fissure;
- CN III, IV and VI
- CN Va
- Superior Opthalmic Vein
Inferior Orbital Fissure;
- Inferior Opthalmic Vein
- Infraorbital nerve
8
Q
How might a fracture of the Floor of the Orbit affect eye movement?
A
- Fracture site can ‘trap’ structures (such as Extra-ocular muscles) located near orbital floor
- Prevents upwards gaze on affected side
9
Q
List the layers of the eyeball from superficial to deep
A
- Sclera
- Choroid
- Retina
10
Q
Describe the Sclera in 4 ways
A
- Fibrous and continuous anteriorly as the Cornea (transparent)
- Provides attachment for the extra-ocular muscles
- Gives shape to eyeball
- Continuous with Dural sheath covering the Optic Nerve at the back of eye
11
Q
What is the Limbus?
A
Junction between Sclera and Cornea
12
Q
What happens to the blood vessels running in the Conjunctivae when it becomes inflamed? (Conjunctivitis)
What do patients with Viral Conjunctivitis often report?
A
- Vessels dilate and eye appears red
- Eye feels uncomfortable and Gritty (as opposed to painful), with tearing of the eye (watery eyes)
13
Q
Conjunctivitis is highly contagious and can spread very easily.
How do we generally treat?
A
- Reassurance
- Hygiene advice
- Topical chloramphenicol eye drops
14
Q
Suggest a cause of Conjunctivitis in the neonatal period and a treatment
A
Chlamydial conjunctivitis picked up from mother’s vaginal mucosa
Systemic antibiotics (Erythromycin)
15
Q
Describe the layer that covers the Sclera
A
- Thin, transparent cellular layer called the Conjunctivae
- Extends to edge of the Limbus anteriorly
- Running posteriorly, reflects onto inner surfaces of eyelids
16
Q
Other than Conjunctivitis suggest and describe a conjunctival cause of ‘Red Eye’
A
Subconjunctival haemorrhage;
- Small conjunctival vessels rupture and blood is under conjunctivae
- Looks worse than it is
- Common, Painless
- Only need to reassure that it will slowly resolve
17
Q
Describe the Middle Layer of the eyeball
A
Choroid;
- Vascular area
- Continues anterior as the Ciliary Body and Iris
- Ciliary body is both Vascular and Muscular (Consists of a Ciliary Process and muscle)
18
Q
What structure is made up of the Ciliary Body, Iris and Choroid
A
Uvea
20
Q
How does Uveitis present?
What is it typically associated with?
A
- Red Eye
- Painful, worse when focusing/ looking at bright lights
Autoimmune conditions such as;
- Ankylosing Spondylitis
- Inflammatory Bowel Disease
21
Q
What is Iritis?
List 3 ways it presents
A
Anterior uveitis (Inflammation of iris)
- Painful
- Red Eye
- Photosensitivity
22
Q
Presence of Red Eye with Acute Pain requires urgent referral.
Give an example of such a condition and state 2 possible complications
How may it be treated?
A
- Uveitis, Inflammation of the Choroid Layer
- Can lead to Cataracts and Glaucoma
- Corticosteroids
23
Q
Briefly describe the inner layer of the eyeball
A
Retina;
- Photosensitive and Non-photosensitive parts
- Neurosensory and Pigmented Epithelial Cell layers
24
Q
Describe the Pigmented Epithelial Cell Layer of the Retina as well as its cells and their function
A
- PECL lies between Choroid and NSL
- Its cells contain Melanin which absorbs scattered light that has passed into the eye
This;
- Reduces reflection, allowing us to focus images appropriately onto the retina
- Absorbs excess light preventing damage
25
Q
Very briefly, describe the Neurosensory Layer of the Retina
A
- Area of retina that senses light
- Where the Photoreceptors (Cones and Rods) are found
26
Briefly, describe the Cones’ function and state where many of them are concentrated
- Responsible for High Visual Acuity and Colour Vision
| - Many are concentrated in the Macula (Centre of your vision)
27
How does the Macula appear on fundoscopy?
What is the Fovea? What Photoreceptors are found here?
- Slightly darker area of retina, lying just lateral to the Optic Disc
Fovea;
- Centre of Macula
- Only Photoreceptors present are Cones
28
What are the types of Cones?
Name and describe the condition resulting from the absence/ dysfunction of one of these cones
Red, Green and Blue-sensitive cones
Colour blindness;
- Inherited
- Affects males more frequently than females
29
How many more Rods are there than Cones?
What do they do?
Where are they more abundant?
- 20 times
- Responsible for vision in Low Intensity Light (Do not discern colours)
- Peripheral parts of retina
30
How do the Rods work?
Light energy converted into electrical impulses, which reach Optic Disc
Impulses move along visual pathway to Occipital Lobe
31
Describe the Optic Disc
- Represents accumulation of Retinal Axons leaving as Optic Nerve
- Devoid of Photoreceptors, thus called the ‘Blind Spot’
32
Name 2 structures involved in protecting the surface of the eye
- Eyelids
- Lacrimal Glands
(Protect from drying out or being injured)
33
By what structures are the eyelids strengthened and given their shape?
What glands do these structures contain?
Tarsal Plates, contain Tarsal/ Meibomian Glands
34
State the functions of the oily secretions of the Tarsal/ Meibomian Glands
Lubricate edge of eyelid and mix with tear film, preventing tears from evaporating too quickly
35
What can develop if a Tarsal/ Meibomian gland becomes blocked?
How does this present?
- Meibomian Cyst/ Chalazian
| - Presents as a lump within the eyelid
36
A Stye can also cause an eyelid lump
How does this present? How is it caused?
- Painful
| - Caused by an infected/ blocked Eyelash Follicle OR Sebaceous Gland
37
Blepharitis can also cause an eyelid lump.
What is Blepharitis?
Inflammation of eyelids (Including skin, lashes and Meibomian glands)
38
What is the Orbital Septum?
Thin sheet of fibrous tissue that fills the base of the orbital cavity
- Blends with Orbital Rim Periosteum and Tarsal Plates
39
Describe the function of the Orbital Septum and Tarsal Plates
Separate Subcutaneous tissue of Eyelid and Orbicularis Oculi from Intra-orbital contents
40
What is Peri-orbital/ Pre-septal Cellulitis?
State 3 features
- Infection occurring within eyelid tissue
- Superfical to Orbital Septum
- More common children
- Ocular function unaffected
- Can be difficult to differentiate between Peri-orbital and more severe orbital cellulitis
41
How would you treat Pre-Septal/ Peri-Orbital Cellulitis?
IV Antibiotics and Surgical Drainage
42
What is Orbital/ Post-Septal Cellulitis?
Suggest 2 causes
Infection within the orbit, deep to the Orbital Septum
- Infection spread from Paranasal air sinuses
- Pre-Septal infection spread
43
How does Orbital/ Post-Septal Cellulitis present?
- Proptosis/ Exopthalamos
- Reduced eye movements, may be painful
- Reduced Visual Acuity
44
The Lacrimal Apparatus refers to the structures involved in tear film production and drainage.
List these structures
- Lacrimal gland (Secretes tears/ Lacrimal fluid)
- Lacrimal ducts
- Lacrimal Canaliculi
45
What are the 3 components of Tear Film?
| Which glands secrete each component?
- Outer Oily layer, from Meibomian gland
- Middle Water layer, from Lacrimal gland
- Inner Mucus layer, from Goblet cells in Conjunctiva
46
Describe the movement of Lacrimal Fluid after release fro Lacrimal Gland
- Enters conjunctival sac through Lacrimal Ducts
- Passes into Lacrimal lake at medial angle of eye
- Drains into Lacrimal Sac, then through the Nasolacrimal Duct into the Nasal cavity
47
What can obstruction to Lacrimal Drainage result in?
Epiphora (Overflow of tears over lower eyelid)
48
What can result from dirt/particles damaging the cornea?
Why does the Cornea easily regenerate if damaged?
- Corneal abrasions and ulceration (very painful)
- Outer epithelial layer is constantly undergoing mitosis (Injuries beyond epithelial layer can lead to permanent scarring and visual impairment)
49
What are the 3 chambers of the eye?
What are they filled with
Anterior and Posterior;
- Both filled with transparent Aqueous Humour
Vitreous;
- Filled with transparent Vitreous Humour
50
Describe the Anterior Chamber and state how it communicates with the Posterior chamber
- Space between Cornea and Iris
| - Communicates with posterior chamber through the pupil (The aperture in the Iris)
51
Describe the Posterior Chamber and its contents
- Space between Iris and Lens
- Contains Ciliary Body and Processes (in body)
- Ciliary Processes secrete Aqueous Humour which fills Anterior and Posterior chambers
52
What are 2 functions of the Aqueous Humour?
- Support shape of eyeball
| - Provides nourishment to Lens and Cornea (don’t have their own blood supply, are avascular)
53
Describe drainage of the Aqueous Humour
- Drains through Irido-Corneal angle in Anterior Chamber
- Into Canal of Schlemm, via Trabecular Meshwork
- Eventually enters Venous Circulation
54
Describe the Blood Supply to the Eye
Branches of Ophthalmic Artery supply eye structures
Retina supplied by;
- Central Retinal Artery
- Underlying Choroid layer
- Ciliary arteries (posterior and anterior) feed extensive capillary bed in Choroid Layer
55
Name 4 branches of the Ophthalmic Artery
- Supratrochlear artery
- Supraorbital artery
- Central Retinal artery
- Ciliary arteries
56
What are 2 ways the Retina appears in Central Retinal Artery Occlusion
Why is Choroid still perfused?
- Pale due to Ischaemia
- ‘Cherry red spot’ represents Macula
Choroid supplied by Ciliary arteries
57
Suggest 3 structures that lose supply when the Ciliary arteries are occluded
- Choroid
- Optic nerve
- Deep layer of Retina (Including photoreceptors)
58
Describe the Iris in 3 ways
- Thin, contractile diaphragm
- Gives colour to eye
- Consists of 2 muscles, Sphincter and Dilator Pupillae
59
Describe the Lens
- Transparent, Biconvex, Enclosed in a capsule
- Aneural and Avascular, only receives nutrients from Aqueous Humour
- Edges of Lens Capsule attached to Ciliary Body by Suspensory Ligaments
60
As we age, proteins in the lens degrade causing it to become Clouded and less transparent.
What is this called? How can it be treated?
Cataracts, can be treated with surgery
| Occur gradually and cause significant visual impairment
61
How is your sight affected if your eyeball is too;
- Long
- Short
Too long;
- Short sightedness (Myopic)
Too short;
- Long sightedness (Hypermetropic)
62
At rest describe the;
- Ciliary muscle
- Suspensory ligaments
- Lens
CM: Relaxed
SL: Taut
Lens: Relatively flat
63
How does the Lens change to focus on nearer objects?
Becomes fatter/ more biconvex (rounder)
64
List the structures of the eye that acts to refract light to focus it onto the retina.
Of these, which is the main refractor?
- Cornea (Main one)
- Conjunctiva
- Tear Film
- Aqueous and Vitreous Humour
65
In what 3 ways does the eye increase its refractive power when looking at very near objects?
Via the Accommodation Reflex;
- Pupil Constriction (less light comes through)
- Eye Convergence (ensures that both retina are focused on same object at one time)
- Lens thickening (via Ciliary muscle contraction)
66
Why does the Accommodation Reflex weaken with age?
What is this called?
Lens becomes stiffer and less able to change shape
Presbyopia (Age related inability to focus on near object)
67
Describe how the Lens changes in the Accommodation Reflex
- Ciliary muscle contracts, reducing tension of Suspensory Ligaments
- Elasticity of Lens causes it to become more Biconvex/ fatter
68
What 3 key anatomical structures maintain the eyeball’s position?
- Suspensory ligaments (Sits underneath like a sling)
- Extra ocular muscles
- Orbital fat
69
What is Astigmatism?
What is the most common cause of adult blindness in the UK?
Irregularity of Corneal surface
Age related Macular degeneration
70
With age, aqueous humour drainage can get obstructed leading to raised Intra-ocular pressure (IOP).
What can this lead to if untreated?
Glaucoma (Irreversible damage and death of Optic nerve) causing visual impairment or even blindness
71
What is the most common type of Glaucoma?
| What causes it?
Open-angle Glaucoma, caused by blockage within the Trabecular Meshwork (drains aqueous humour into Canal of Schlemm)
72
List 2 signs of Open-Angle Glaucoma
| It develops painlessly, initially asymptomatic
- Optic disc cupping
| - Gradual loss of Peripheral Vision
73
How can Open-Angle Glaucoma be treated?
Topical medications that reduce AH production and/ or increase its drainage, reducing IOP
Surgery may be needed
74
What is Closed-Angle Glaucoma caused by?
(This is an emergency, as permanent sight loss can occur in a few hours)
How does it present?
Narrowing of the Irido-Corneal Angle-> Rapid rise in IOP
- Sudden onset painful, red eye
- Blurred vision/ Halos around lights (due to corneal oedema)
- Semi-dilated, Irregular, Oval-shaped pupil
- Nausea and Vomiting
- Eye fees Hard and Tender to palpate through upper eyelid
75
How is Closed-Angle Glaucoma treated?
- Diuretics
- Muscarinic eye drops (cause pupil constriction, opening IC Angle)
- Analgesia
Surgery: Making a hole in the Iris (Iridotomy)
76
What is Papillary Oedema?
Swelling of the optic nerve as it enters the back of the eye due to raised intracranial pressure
