Session 8: Functional Anatomy of the Eye

Question 1

Describe the bones forming the walls of the orbit, particularly in relation to those most vulnerable to fracture in orbital injuries i.e. orbital blow out fracture, & the clinical manifestations of such an injury. LO

1. What shape is the orbit? Contains?
2. The orbit can be thought of as a pyramidal structure, with the apex pointing posteriorly & the base situated anteriorly. The boundaries of the orbit are formed by how many bones?
3. It is also important to consider the anatomical relations of the orbital cavity – this is clinically relevant in the ?

Answer 1

1. pyramidal
   eyeball, its muscles, nerves, vessels and most of the lacrimal apparatus
2. seven bones
3. spread of infection, and in cases of trauma

Question 2

Q. The borders and anatomical relations of the bony orbit are as follows: ( roof, floor, medial and lateral wall, apex, base)

Answer 2

A. Roof (superior wall) –frontal bone & the lesser wing of the sphenoid. The frontal bone separates the orbit from the anterior cranial fossa.
Floor (inferior wall) –maxilla, palatine and zygomatic bones. The maxilla separates the orbit from the underlying maxillary sinus.
Medial wall – ethmoid, maxilla, lacrimal and sphenoid bones. The ethmoid bone separates the orbit from the ethmoid sinus.
Lateral wall –zygomatic bone & greater wing of the sphenoid.
Apex – Located at the opening to the optic canal, the optic foramen.
Base – Opens out into the face, and is bounded by the eyelids. It is also known as the orbital rim

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Question 3

Q. What are the three bony openings arising from/towards the apex of the orbit?

Answer 3

A. Superior orbital fissure
Inferior orbital fissure
Orbital canal

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Question 4

Q. 1. Which bones (and therefore walls) of the orbit are the weakest and thus most vulnerable to fracture in orbital trauma?

2. Why are the bones/walls you have listed in 1.3 the most easily fractured?
3. What structure is found within the lacrimal fossa (see image above), in the anteromedial part of the orbit?

Answer 4

A.1. Maxilla (floor)
Maxillary, ethmoid, lacrimal (medial)
2.air filled sinuses thus are thin
3.

Question 5

Q. Cornea: this is the main refractor of the eye; why do you think it is avascular?
Does the cornea have a conjunctival membrane?

Answer 5

A.transoarent
Yes

Question 6

Q. What are the two muscles of the iris ?

Answer 6

A. Iris sphincter/constrictor, iris dilator, ciliary

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Question 7

1. What are the two muscles of the iris ?
2. What structure delineates the anterior chamber from the posterior chamber?
3. What is found in these chambers?

Answer 7

1. Iris sphincter/constrictor, iris dilator, ciliary
2. Iris
3. Aqueous humour (then where is vitreous?)

Question 8

Q. How does it exit the eye?

Answer 8

A. • Drains through iridocorneal angle (between iris & cornea)
• Via trabecular meshwork into canal of Schlemm (circumferential venous channel draining into venous circulation)

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Question 9

Muscle:

Levator palpebrae superioris
Palpebral part of orbicularis oculi
Superior tarsal muscle

State their: Nerve supply Action Consequence of damage

Answer 9

Question 10

Answer 10

Question 11

Q. The bony orbit contains the eyeballs and their associated structures: (5) (i.e. what else does the orbit contain?

Answer 11

A. Extra-ocular muscles – These muscles are separate from the eye. They are responsible for the movement of the eyeball and superior eyelid.
Eyelids – These cover the orbits anteriorly.
Nerves: Several cranial nerves supply the eye and its structures; optic, oculomotor, trochlear, trigeminal and abducens nerves.
Blood vessels: ophthalmic artery (primarily). Venous drainage is via the superior & inferior ophthalmic veins.
Any space within the orbit that is not occupied is filled with orbital fat. This tissue cushions the eye, and stabilises the extraocular muscles.

Question 12

Answer 12

Question 13

1. What do the eyelids (palpebrae) contain
2. There are three main pathways by which structures can enter and leave the orbit: (3) strate what these structures transmit

Answer 13

1. – Protect the eye when palpebral fissure is closed (Contain fibrous structures)
   – Tarsal plates and muscles
   – Glands at the edges of the eyelids (Can block)
2. Optic canal: optic nerve & ophthalmic artery
   Superior orbital fissure: lacrimal, frontal, trochlear (CN IV), oculomotor (CN III), nasociliary and abducens (CN VI) nerves. It also carries the superior ophthalmic vein.
   Inferior orbital fissure: maxillary nerve (a branch of CN V), the inferior ophthalmic vein, and sympathetic nerves.

Question 14

Q. 1. Main arterial supply is ?

2. Venous drainage?
3. State the nerve for General sensory from the eye (including conjunctiva, cornea)
4. State the nerve for Special sensory vision from retina
5. State the nerve for Motor nerves to muscles

Answer 14

A. 1. ophthalmic artery and its branches

2. Ophthalmic veins drain venous blood into cavernous sinus, pterygoid plexus and facial vein
3. Optic
4. Oculomotor, sensory and abducens

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Question 15

Answer 15

Question 16

1. There are other minor openings into the orbital cavity:
2. What bones are most vulnerable to fracture in orbital injuries

Answer 16

1. Nasolacrimal canal, which drains tears from the eye to the nasal cavity, is located on the medial wall of the orbit.
   supraorbital foramen and infraorbital canal – they carry small neurovascular structures.
2. maxillary and ethmoid

Question 17

Q. Clinical Relevance: Fractures of the Bony Orbit. There are two major types of orbital fractures:

Answer 17

A. Orbital rim fracture & ‘Blowout’ fracture

Question 18

Q. What is an orbital rim fracture?

Answer 18

A. This is a fracture of the bones forming the outer rim of the bony orbit. It usually occurs at the sutures joining the three bones of the orbital rim – the maxilla, zygomatic and frontal.

Question 19

Q. What is a blow out fracture?

Answer 19

A. partial herniation of the orbital contents through one of its walls. This usually occurs via blunt force trauma to the eye. The medial and inferior walls are the weakest, with the contents herniating into the ethmoid and maxillary sinuses respectively.

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Question 20

Q. Which bones are susceptible in an orbital blowout fracture

A.

Question 21

Answer 21

Trying to look up
Can’t due to anchoring of the inferior contents
Not due o the muscl e
Eye can’t physically look up
Bottom of orbital contents is trapped

Orbital contents and blood can prolapse into maxillary sinus; the fracture site can ‘trap’ structures e.g. soft tissue, extra orbital muscle located near floor or orbit

Question 22

Q. Signs of blowout fracture

Answer 22

A. • Periorbital swelling, painful
• Double vision (especially on vertical gaze)
• Impaired vision
• Anaesthesia over affected cheek (upper teeth & gums) on affected side
(Numbness over the cheek
Cutaneous branches of the maxillary division
Infraorbital nerve runs through the floor of the orbit
Comes out through the infraorbital foramen to innervate the check)

Question 23

1. Cause of blowout fracture
2. Investigations for blowout fractures

Answer 23

1. Sudden increase in intra-orbital pressure (e.g. from retropulsion of eye ball [globe] by fist or ball) fractures floor of orbit

Orbital contents and blood can prolapse into maxillary sinus; the fracture site can ‘trap’ structures e.g. soft tissue, extra orbital muscle located near floor or orbit

2. Plain Radiography & Coronal View (CT)

Question 24

1. What clinical sign will you witness in both of these fractures and why.

Answer 24

Any fracture of the orbit will result in intraorbital pressure, raising the pressure in the orbit, causing exophthalmos (protrusion of the eye). There may also be involvement of surrounding structures, – e.g haemorrhage into one of the neighbouring sinuses.

Question 25

1. Important anatomical relations of the orbit include: (3)
2. Implications for
3. Medial wall and floor of the orbit are the weakest parts of the orbital cavity. Why?

Answer 25

1. – Paranasal air sinuses (maxillary & ethmoid)
   – Nasal cavity
   – Anterior cranial fossa
2. • Orbital trauma
   • Spread of infection
3. A. Paranasal air sinuses (maxillary and ethmoid)

Question 26

Describe the functional anatomy of the eye, including the lacrimal apparatus, & note in particular those structures allowing for the passage, refraction & focus of light onto the retina LO

1. Photosensitive Layer of Retina Generates Action Potentials in Response to Light

• Light (photons) must reach the photosensitive retina to be detected by photoreceptors (rods/cones)

– Action potentials generated in response to light

– Pass via ganglion cells whose axons collect in area of optic disc -> optic nerve

• Light must reach and be focused on retina

– Transparent medium

– Refraction (bending of light)

• Pathology affecting the retina, the transparency of structures anterior to retina or
ability to refract light will cause visual disturbance

2. Refraction is the
3. Light will be refracted as it passes through a number of structures and ‘fluids’
   from outside eye towards retina. State the structures which refract light. (3)

Answer 26

1.

2. Change in Direction of Light on Passing Through Boundary of Two Different Mediums
3. – From air into liquid tear film -> refract
   – Through cornea -> refract (most refraction of light occurs at the air-cornea interface)
   – Through lens & vitreous humour before reaches retina

Question 27

1. Objects which a closer/further require a greater refraction of light. What is this called?
2. Why is it that light rays from close objects require greater refraction?
3. Eye can accommodate to do this. Explain how the eyes accommodate.

Answer 27

1. Closer, Accommodation Reflex
2. Light rays from near-objects are more divergent and require greater refraction to bring them into focus on retina
3. – Pupil constricts
   – Eyes converge (image is brought to focus on same point of retina in both eyes)
   – Lens becomese more biconcave (fatter)

Question 28

Answer 28

Question 29

Answer 29

Question 30

Q. For light to focus on the retina it must be refracted (bent). The conjunctiva, cornea, and aqueous/vitreous humour within the eye all act to refract light that enters the eye, bringing it to a point of focus on the retina. The main refractor of the eye is actually the cornea; however, with very near objects, the light rays are more divergent and greater refraction is required. Our ability to focus on near objects and maintain a clear image from a distant gaze to a near point is because of a reflex called accommodation; the lens plays an important part in this reflex. The accommodation reflex consists of three main components: automatic contraction of the pupil, convergence of the eyes and thickening of the lens. Pupillary constriction during the accommodation reflex occurs to ensure that light from the near-object passes through the centre of the lens, and convergence occurs to ensure that both retinae are focusing on the one object. What also happens, which is not directly visible to the examiner performing the test, is the change in the shape of the lens due to the contraction of the ciliary muscle. This contraction moves the ciliary body closer to the lens, and so the pull of the circular suspensory ligaments on the lens ‘loosens’. The inherent elasticity of the lens allows it to become more biconvex (rounder), and provide better focus of the near- object on the retina. However, as we age the lens becomes dense, less elastic and more difficult to change shape. Thus, the ability to accommodate and focus on near-objects becomes impaired as we get older (presbyopia). Evidence of this is seen when people have to hold items that normally require near-focus (e.g. food menus) at arms -length in order to focus. Fortunately, presbyopia can be corrected with glasses, allowing near-objects to be focused more comfortably. The following very short video demonstrates the process of accommodation very clearly (it is worth watching)!

A.

Q. How many layers is the eyeball?

A. three layers (outer, middle and inner)

Question 31

Q. What are the three layers called? And what are each of the layers composed of?

Answer 31

A. – Outer: fibrous, tough sclera (white of eye) continuous anteriorly as transparent cornea*
– Middle: vascular consisting of choroid, ciliary body & iris
– Inner: retina (inner photosensitive layer lying on an outer pigmented layer)

Question 32

Q. Eyeball is maintained in position by (3)

Answer 32

A.– Suspensory ligament (sits underneath like a sling)
– Rectus muscles
– Orbital fat

Question 34

Answer 34

Question 35

1. What does the fibrous sclera form anteriorly?
2. Function of the sclera?
3. What covers the sclera?

Answer 35

1. Transparent cornea
2. attachment for the extra-ocular muscles, gives shape to the eyeball and is continuous with the dural sheath covering the optic nerve at the back of the eye
3. thin transparent layer of cells called the conjunctivae

Question 36

Q. 1. The conjunctivae extends up to?

2. What runs through the conjunctivae?
3. Clinical significance? (Common cause)
4. Symptoms of conjunctivitis

Answer 36

A. 1. The edge of the cornea (the limbus) & is reflected onto the inner surface of the upper & lower eyelids.

2. Blood vessels
3. Conjunctivae can inflame (conjunctivitis) -> blood vessels dilate and the eye appears red. Most often of viral aetiology (highly contagious and can easily spread to the patient’s other eye or other people!)
4. feeling uncomfortable & ‘gritty’ (rather than painful) with accompanying tearing of the eye

Question 37

Q. 1. What is the iris?

2. The iris gives the?
3. What two muscles are found in the iris
4. What controls the movement of the muscles

Answer 37

A. 1. thin contractile diaphragm with a central aperture (the pupil) for transmission of light

2. Colour to the eye (e.g. blue, green, brown)
3. sphincter & dilator pupillae (form the iris and control the size of the pupil)
4. ANS

Question 38

Q. 1. What Is the lens?

2. It is without nerve innervation or blood supply, receiving its nutrients entirely from the aqueous humour that surrounds and bathes it. The edges of the lens capsule are attached to the ciliary body by a?
3. As we age, degradation of the proteins in the lens can cause it to become clouded and less transparent. What is this condition called?
4. Treatment ?
5. What is ciliary muscle contraction under the influence of?
6. At rest the ciliary muscle is relaxed what happens to the suspensory ligament and the lens

Answer 38

A. 1. transparent biconvex structure enclosed in a capsule.

2. circular suspensory ligament.
3. Cataracts occur gradually and cause significant visual impairment
4. surgery
5. parasympathetic nervous system, alters the tension in the suspensory ligaments. This allows for changes in the shape of the lens and thus its refractive power.
6. Suspensory ligaments are pulled taut, keeping the lens relatively flat. However, the shape of the lens can change, becoming ‘fatter’, to allow for focusing on near-objects.

Question 39

Q. What is Conjunctivae?

Answer 39

A. A secretory mucosa lubricating the conjunctival & corneal surfaces

Question 40

Q. What is the relationship between the lacrimal sac & conjunctivae

Answer 40

A. Lacrimal apparatus also involved in secretion of tears into conjunctival sac
– Lacrimal gland (arranged around edge of levator palpebrae superioris)
– Lacrimal sac
– Nasolacrimal duct
• Blinking washes tear film across front of eye, rinsing and lubricating the conjunctivae and cornea

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Question 41

Q. Function of blinking

Answer 41

A. Washes tear film across front of eye, rinsing and lubricating the conjunctivae & cornea

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Question 42

Answer 42

Question 43

Q. Eyelids & The Lacrimal Apparatus

1. What protects the eye?
2. What are they protecting the eye from ?
3. The eyelids are strengthened & given their shape by ?
4. What do tarsal plates contain?
5. Function of the TG?
6. What would happen if one of these TG got blocked?​

Answer 43

A. 1. eyelids & lacrimal glands

2. Prevent drying out (cornea) or being injured by small particles
3. tarsal plates (dense bands of connective tissue)
4. tarsal glands (Meibomian glands)
5. • lubricate the edge of the eyelids
     - mix with the tear film over the surface of the eye preventing the tears from evaporating too quickly
6. Meibomian cyst can develop

Question 44

Answer 44

Question 45

Answer 45

Question 46

Q. Eyelids and Orbital Septum

1. Function of Tarsal plates
2. What is the orbital septum made up of? What does it blend in with?
3. Function of the orbital septum

Answer 46

A. 1. Provide a CT skeleton to the eyelid
– Firmness and shape
2. Thin sheet of fibrous tissue originating from orbital rim
– Blends with tendon of LPS and tarsal plates
3.• Separates intra-orbital contents from eyelid fat & orbicularis oculi muscle
• Acts as a barrier against infection spreading from the pre-septal space (In front of tarsal plates localised to the eyelids) to post-septal (orbital cavity proper)(most concerning)

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Question 47

Q. Diagnose the patients.
What are both of these images showing.
Causes.
Which one is worse and why

Answer 47

Q. Right: Post-septal orbital cellulitis
Left: Pre-septal orbital cellulitis

• Cellulitis of orbital structures increasing degrees of severity
• Secondary to infection from bites, periorbital trauma, sinuses (fronto- ethmoidal sinuses)
• image on the right -> Complications include abscesses formation and spread of infection
intracranially cavernous sinus thrombosis

Question 48

Q. Veins of orbit drain to

Answer 48

A. cavernous sinus, pterygoid venous plexus and facial veins

Question 49

Q. The lacrimal apparatus consists of ?

Answer 49

A. lacrimal glands, lacrimal ducts & lacrimal canaliculi

Question 50

Answer 50

Question 51

1. The gland, which secretes the lacrimal fluid (tears), lies in a fossa on the superolateral part of the orbit. This gland is under what control? By which nerve?
2. What happens to the Lacrimal fluid?
3. Conjunctiva is a transparent mucous membrane produces?

Answer 51

1. parasympathetic control via the facial nerve
2. lacrimal gland -> conjunctival sac through lacrimal ducts -> lacrimal lake at the medial angle of the eye -> lacrimal sac (S) (drain) -> nasal cavity via the nasolacrimal duct (N)
3. mucous & tears

Question 52

1. What does the conjunctiva cover?
2. Is it vascular?

Answer 52

1. white of eye (sclera) & lines inside of eyelids (forming a conjunctival sac); does not cover over cornea

• Inflammed & injected in infections e.g. conjunctivitis
• Haemorrhage from blood vessel readily visible as a subconjunctival haemorrhage

2. A Highly vascular with small blood vessels within the membrane

Question 53

Q. 1. What is this image showing? 2. Cause 3. Treatment

Answer 53

A. subconjunctival haemorrhage/ ‘red eye’

2. Conjunctival blood vessels ruptures (often spontaneously)
3. None, haemorrhages are common, are not painful and require only to reassure the patient that it will slowly resolve much like any bruise would elsewhere on the body

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Question 54

Answer 54

Question 55

Outline the production and flow of aqueous humour between the anterior & posterior chambers of the eye and relate your understanding to the pathophysiology of glaucoma. LO

Q. The eyeball has three chambers;

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Answer 55

A. an anterior, posterior, & a vitreous chamber most posteriorly

Question 56

Q. What is each chamber filled with?

Answer 56

A. vitreous chamber -> transparent, jelly-like vitreous humour
Anterior & posterior chambers -> aqueous humour (transparent liquid)

Question 57

Q. What is the anterior chamber between? How does it communicate with the posterior chamber?

Answer 57

A. cornea & the iris
through the pupil

Question 58

Q. 1. The posterior chamber is between? 2. What is found in this chamber? 3. Function of what is found in the chamber? 4. Function of the aqueous humour? 5. What does this humour drain though?

Answer 58

A. 1. iris & the lens

2. ciliary body and processes
3. secrete the aqueous humor filling both these chambers of the eye
4. • supporting the shape of the eyeball (along with the vitreous humour) by the pressure it exerts
     - nourishment to the lens and cornea, which do not have their own blood supply
5. irido-corneal angle (the space between the anterior surface of the iris and the posterior extremity of the cornea) into the canal of Schlemm via a trabecular meshwork and subsequently back in the venous circulation.

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Question 59

Q. How is aqueous humour produced & drained?

Answer 59

A. • Aqueous humour secreted by ciliary processes within ciliary body
• Flows from posterior chamber, through pupil into anterior chamber
• Nourishes lens & cornea
• Drains through iridocorneal angle (between iris & cornea)
• Via trabecular meshwork into canal of Schlemm (circumferential venous channel draining into venous circulation)

Question 60

Q. Function of aqueous humour?

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Answer 60

A. Cornea has no blood supply still need nourishment to cornea & lens
Why does the corneas has aqueous humour

Question 61

Q. Glaucoma: Common Cause of Blindness
• Drainage of aqueous humour from anterior chamber can be blocked. There are two types of glaucoma what are they? How does this lead to blindness?

Answer 61

A. – Trabecular meshwork deteriorates (age: chronic): open angle glaucoma
– Narrowing of iridocorneal angle (acute): closed angle glaucoma

• Rise in intra-ocular pressure & damage to optic nerve
– Optic disc cupping

• Sight-threatening

Question 62

Q. What is this image showing?

Answer 62

A. Acute Angle-Closure Glaucoma Ophthalmological Emergency

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Question 63

1. What is glaucoma?
2. If left untreated glaucoma leads to irreversible damage and death of the optic nerve, causing

Answer 63

1. A clinical condition leading to a rise in intra-ocular pressure
2. Impairment of vision or even blindness

Question 64

Q. 1. How else can Glaucoma arise?

Answer 64

A. 1. If the irido-corneal angle (angle between cornea & iris) is narrowed by the peripheral edge of the iris. This is called closed-angle glaucoma (or acute angle-closure glaucoma) and is less common.

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Question 65

Q. In this type of glaucoma the problem is not within the trabecular meshwork but rather access to the trabecular meshwork is blocked off, leading to a rapid rise in intra-ocular pressure. Patients with this type of glaucoma present with?

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Answer 65

A. - sudden onset of a painful red eye
- blurred vision or halos around objects (due to corneal oedema), a fixed or sluggish, semi-dilated often irregular, oval-shaped pupil (see image below) and nausea and vomiting. The eye will feel hard and tender to palpate through the upper eyelid

Question 66

Q. Why is it an ophthalmological emergency? Treatment?​

Answer 66

A. Irreversible sight loss can occur within a few hours
muscarinic eye drops e.g. pilocarpine, strong analgesia and drugs to reduce intra-ocular pressure

Question 67

Q. Who is at most risk of closed-angle glaucoma

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Answer 67

A. Long-sighted middle aged or elderly people (with shallow anterior chambers) tend to be most at risk of.

Question 68

Q. How are the eyes of these patients likely to present

Answer 68

A. Acute Angle-Closure Glaucoma: note the irregularly shaped pupil and conjunctival injection (red eye)

Question 69

Q. Draw a diagram showing how galactose is broken down into its substrates

Answer 69

Question 70

Q. How will the diagram above change if you have a galactokinase deficiency ?
What will this result in?
Signs/symptoms.

Answer 70

Question 71

In Galactosaemia individuals are unable to utilise galactose obtained from the diet because of a lack of the kinase or transferase enzyme. The absence of the kinase is relatively rare and is characterised by accumulation of galactose in tissues. The absence of the transferase is more common and more serious as both galactose and galactose 1- phosphate accumulate in tissues.
Accumulation of galactose in tissues leads to its reduction to galactitol (aldehyde group reduced to alcohol group) by the activity of the enzyme aldose reductase:
This reaction depletes some tissues of NADPH. In the eye the lens structure is damaged, (cross linking of lens proteins by –S-S- bond formation) causing cataracts. In addition, there may be non-enzymatic glycosylation of the lens proteins because of the high concentration of galactose and this may contribute to the cataract formation. The accumulation of galactose and galactitol in the eye may lead to raised intra-ocular pressure (glaucoma) which if untreated may cause blindness. Accumulation of galactose 1-phosphate in tissues causes damage to the liver, kidney and brain and may be related to the sequestration of Pi making it unavailable for ATP synthesis.

Question 72

Describe the important anatomical relations of the orbit and orbital structures & the implications for spread of infection (e.g. cavernous sinus, anterior cranial fossa, nasal cavity) & extension of injury from orbital trauma. LO

Q. 1. The eyeball receives arterial blood primarily via the ?

2. This is a branch of the?
3. The ophthalmic artery gives rise to many branches, which supply different components of the eye. Which is the most important branch & why.

Answer 72

A. 1. ophthalmic artery

2. internal carotid artery, arising immediately distal to the cavernous sinus.
3. The central artery of the retina is the most important branch – supplying the internal surface of the retina. Occlusion of this artery will quickly result in blindness.

Question 73

Q. Venous drainage of the eyeball is carried out by the?

Answer 73

A. Superior & inferior ophthalmic veins. These drain into the cavernous sinus, a dural venous sinus in close proximity to the eye.

Question 74

Identify & explain with reference to the relevant anatomy common & important conditions involving the eye and its associated structures including styes, Meibomian cysts, blepharitis, conjunctivitis, subconjunctival hemorrhage & papilloedema.

Q. What is papilloedema?

Answer 74

A. Papilloedema refers to a swelling of the optic disc, visible during ophthalmoscopy (a visual inspection of the eye using an ophthmoscope). The optic disc is the area of the retina where the optic nerve enters.

The swelling occurs secondary to raised intra-cranial pressure. The high pressure within the cranium resists venous return from the eye. This causes fluid to collect in the retina, producing a swollen optic disc.

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Question 75

Q. Glands of the Eyelid and Eyelid Disease
Name and locate the two main glands of the eyelid

Answer 75

Question 76

Q. Diagnose these patients

Answer 76

A Left: Meibomian Cyst
Right: Stye

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Question 77

Q. Explain how each of these are caused

Answer 77

A. Glands within the tarsal plate secrete an oily (lipid-rich) substance onto edges of lid; help prevent evaporation of tear film and tear spillage: can block causing a Meibomian cyst

Eyelash follicles can also block (infection-staph) causing styes
Hot compress

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Question 78

Q. Blepharitis is a common eye condition characterized by inflammation of the eyelid, resulting in inflamed, irritated, itchy, and reddened eyelids. A number of diseases and conditions can lead to blepharitis. It can be caused by the oil glands at the base of the eyelashes becoming clogged, a bacterial infection, allergies, or other conditions. The severity and course can vary. Onset and resolution can be acute, resolving without treatment within 2–4 weeks (this can be greatly reduced with lid hygiene), but often blepharitis is a long-standing chronic inflammation of varying severity.

Blepharitis is characterized by chronic inflammation of the eyelid, usually at the base of the eyelashes.[2][3][4] This results in inflamed, irritated, itchy, and reddened eyelids.[2][3]

It is typically caused by bacterial infection or blockage of the eyelid’s oil glands, although sometimes it is caused by allergies.[3] Various diseases and conditions can lead to blepharitis, such as rosacea, herpes simplex dermatitis, varicella-zoster dermatitis, molluscum contagiosum, allergic dermatitis, contact dermatitis, seborrheic dermatitis, staphylococcal dermatitis, and parasitic infections (e.g., Demodex and Phthiriasis palpebrarum)

Question 79

Answer 79

Question 80

1. The middle layer of the eyeball (deep to the sclera) is a much richer vascular area & includes the choroid, which continues anteriorly as the? The ciliary body, which is vascular and muscular (consisting of a ?) connects the choroid with the iris.
2. What is urea?

Answer 80

1. ciliary body & iris, ciliary process and muscle
2. collective term for the choroid, ciliary process and iris

Question 81

Q. 1. What is uveitis?

2. How do patients present?
3. It is typically associated with autoimmune conditions such as?
4. Treatment

Answer 81

A. 1. Inflammation of the choroid layer can occur (rare)

2. Red, painful eye, which is often made worse when trying to focus or looking at bright lights (why do you think this is?) Ciliary body contract, suspensory ligaments relax, lens fattens ????
3. • ankylosing spondylitis
     - inflammatory bowel disease
4. Ophthalmology for treatment (corticosteroids)

Question 82

Answer 82

Question 83

Q. The inner layer of the eye consists of the retina, the light detecting part of the eye. The retina itself is composed of two cellular layers:

Answer 83

A. Neural layer – Consists of photoreceptors; the light detecting cells of the retina. It is located posteriorly & laterally in the eye.
Pigmented layer – Lies underneath the neural layer and is attached to the choroid layer. It acts to support the neural layer, & continues around the whole inner surface of the eye.

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Question 84

Q. Anteriorly, the pigmented layer continues but the neural layer does not – this is part is known as the ? Posteriorly & laterally, both layers of the retina are present. This is the ? of the retina.

Answer 84

A. non visual retina, optic part

Question 85

Q. The optic part of the retina can be viewed during ?

Answer 85

A. ophthalmoscopy

Question 86

Q. The centre of the retina is marked by an area known as the ?

Answer 86

A. macula

Question 87

Q. 1. Describe how the macula looks.
2. The macula contains?

Answer 87

A. 1. yellowish in colour, & highly pigmented.
2. A depression called the fovea -> high conc of light detecting cells -> high acuity vision

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Question 88

Q. The area that the optic nerve enters the retina is known as the ?

Answer 88

A. optic disc – it contains no light detecting cells (blind spot)

Question 89

Q. Within the eyeball, there are structures that are not located in the three layers. These are the

Answer 89

A. lens & the chambers of the eye.

Question 90

Q. The lens of the eye is located anteriorly, between the?

Answer 90

A. Vitreous humor & the pupil.

Question 91

Q. How is the lens shape changed?

Answer 91

A. Ciliary body, changing its refractive power

Question 92

1. The inner layer is the retina which consists of?
2. Cells are either part of?

Answer 92

A. 1. photosensitive and non-photosensitive parts
2. Neurosensory cell layer or a pigmented epithelial cell layer.

Question 93

Q. The pigmented layer lies between the? What does it cells contain?

Answer 93

A. Choroid & neurosensory layer of the retina and its cells contain melanin.
Melanin helps absorb scattered light that has passed into the eye, reducing reflection & allowing us to focus images appropriately on to the retina.

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Question 94

Q. Clinical Significance of the pigmented layer

Answer 94

A. Retinal Pigment & Albinism People who have albinism (a congenital disorder causing partial or complete absence of melanin in skin, hair and eyes) wear tinted sunglasses or contact lens to help reduce the scattering of light that enters the eye, given the pigmented retinal layer, like much of the rest of their body, is absent of melanin.

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Question 95

Q. Albinism is associated with a number of vision defects, such as

Answer 95

A. photophobia, nystagmus, and amblyopia

Question 96

Q. What is the mode of inheritance in albinism?

Answer 96

A. recessive gene alleles

Question 97

Q. In humans, there are two principal types of albinism:

Answer 97

A. oculocutaneous, affecting the eyes, skin and hair, and ocular affecting the eyes only.

Question 98

Answer 98

Question 99

• Describe the location and arrangement of the extrinsic (extra-ocular) & intrinsic (of iris and ciliary body) muscles of the eye, and eyelid, their actions & the consequences of interruption to their nerve supply (i.e. CN III, IV and VI palsies, and CN III and VII lesions and their effect on the eyelid muscles).

• Relate your understanding of the anatomy of the orbit, extraocular muscles and
eye to the steps involved in a clinical examination of the eye.
o Note, part of the clinical examination of the eye involves visualisation of the
retina using an ophthalmoscope: this is difficult! Do not worry if you are not
successful- there are images of the retina within the workbook.