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Scenario 27 > Lecture 5 - Eye And Orbit > Flashcards

Lecture 5 - Eye And Orbit Flashcards

0
Q

What makes up the medial wall of the orbit? N.B. Medial wall is THIN

A

Ethmoid bone

Frontal bone

Lacrimal bone

Lesser wing of Sphenoid

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1
Q

What makes up the superior wall of the orbit?

A

Orbital part of Frontal bone

Lesser wing of Sphenoid

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2
Q

What makes up the inferior wall of the orbit? N?B inferior is thin

A

Maxilla

Zygomatic bone

Palatine bone

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3
Q

What makes up the lateral wall of the orbit? N.B. Lateral is THICK

A

Zygomatic bone

Greater wing of sphenoid

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4
Q

What are the relations to the orbit? Superior Inferior Medial

A

Frontal sinus - superior

Maxillary sinus - inferior

Ethmoid sinus - medial

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5
Q

What happens in a BLOWOUT FRACTURE? Clinical importance

A

Blunt object (slightly bigger than eyeball) collides with front of orbit.

Walls of orbit collapse - especially the thin walls (medial & lateral)

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6
Q

What can happen after a blowout fracture?

A

Air from maxillary sinus can enter. Tissue can herniate through.

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7
Q

What is the eyeball embedded in?

A

Orbital fat

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8
Q

What supports the eyeball?

A

Hammock like SUSPENSORY LIGAMENT. Thickened along the bottom.

Inferior Rectus + Inferior Oblique muscles lie in the ligament

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9
Q

What protects the eye? What do these things protect the eye from?

A

Eyelids, Tears and Conjunctiva

They prevent irritation from things like dust and excess light etc.

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11
Q

What do the Tarsal glands produce? A.k.a Meiboman Glands

A

Secrete an oily substance (MEIBUM) that contributes to tears. N.b. Add rest of explanation after listening to lecture again

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12
Q

Muscles of the eyelid

A

Levator Palpebrae Superioris Orbicularis Oculi

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13
Q

Lev. Pal. Sup. muscle - location -function - innervation - insertion

A

Muscle ONLY in upper eyelid. Raises eyelid - innervation: CN III Inserts into Tarsus

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14
Q

Lev palp sup smooth muscle fibres. Function and innervation

A

SM fibres - superior tarsal muscle (some call it part of lev palp sup) Also raises eyelid innervation by sympathetic fibres from superior cervical ganglion

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15
Q

What is the Tarsus? A.k.a Tarsal plates

A

Dense band of connective tissue, provide attachment site for muscles of the eyelid. Present in both the upper and lower eyelid.

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16
Q

What can cause loss of function of:- - lev palp sup - sup tarsal What will this cause?

A

Lev palp sup : CN III lesion Sup tarsal : sympathetic lesion Either of these will cause PTOSIS - drooping eyelid

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17
Q

What muscle closes eyelids? What are its two components? Innervation?

A

Orbicularis Oculi - orbital part - palpebral part Innervation : CN VII - facial nerve

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18
Q

Which part of orbicularis Oculi closes eyelids during blinking and sleeping? What does the rest of the muscle do?

A

Palpebral part of Orb. Oculi closes eyelids. Rest of muscle used to screw eyes tightly shut for protection.

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19
Q

What are the Conjunctiva?

A

Thin membrane which covers the posterior surface of each of eyeballs. Covers the full extent of the posterior surface of each eyeball before reflecting onto the outer sac (SCLERA) of the eyeball. Attaches to eyeball at the junction between the sclera and the cornea. Conjunctival sac formed when eyelids are closed. Upper and lower extensions of the sac are called the superior & inferior conjunctival fornices.

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20
Q

Tears a.k.a lacrimal fluid

A

Production stimulated by parasympathetic impulses from CN VII. Secreted through lacrimal ducts to surfaced of conjunctiva. Fluid is pushed medically when blinking over the cornea. Drained through medial angle of eye through lacrimal canaliculi into lacrimal sac. Nasolacrimal duct conveys fluid to nasal cavity.

21
Q

Three layers of the eyeball

A

Sclera Choroid Retina

22
Q

What is the sclera?

A

Outer layer of tough connective tissue. Dense and white, continuous with transparent cornea Muscles of eye movement insert into here.

23
Q

What is the choroid?

A

Pigmented and highly vascular, continuous with the ciliary body and iris. Middle layer, dark red-brown layer, pigmented and highly vascular - most perfusion rate per gram in the body.

24
Q

What is the retina?

A

Light sensitive, neural part of eye. Inner layer.

25
Q

Anterior and Posterior chamber

A

Contain Aqueous humor - made in the ciliary process Both lie in front of the lens

26
Q

Postremal (vitreous) chamber

A

Contains vitreous humour, behind the lens.

27
Q

What can Bell’s Palsy (damage to the facial nerve) do?

A

Lead to paralysis, preventing eyelids from closing fully and eversion of lower eyelid. This is turn can cause drying and damage to the cornea.

28
Q

What is the Choroid continuous with and what is it?

A

Ciliary body (made up of the ciliary muscle and ciliary process) - ring like thickening, muscular and vascular which provides attachment for the lens.

29
Q

What does the Ciliary process secrete?

A

Aqueous humour

30
Q

IRIS - what is it? - where does it lie?

A

Thin contractile diaphragm with a central aperature (PUPIL) for transmitting light. Lies on the anterior surface of the lens.

31
Q

Which two involuntary muscles control the size of the pupil?

A

1) Dilator pupillae 2) Sphincter pupillae

32
Q

Dilator pupillae

A

Radially arranged, sympathetic innervation

33
Q

Sphincter pupillae

A

Circularly arranged, parasympathetic innervation

34
Q

What can an opiate overdose do?

A

Increase parasympathetic drive, leading to bilateral pinpoint eyes.

35
Q

What is accommodation?

A

Adjusting lens to focus on objects at different distances

36
Q

Which muscle controls shape of lens and therefore focus?

A

Ciliary muscle

37
Q

How do you focus on near objects?

A

Ciliary muscles contract (parasym innerv, CN III) => release tension in zonal fibres => lens rounder. Increased curvature of lens means focal point shifts closer to eye

38
Q

Zonules of Zinn -ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye.

A

@ rest: tense - lens is flat Relax when ciliary muscles contract

39
Q

Ciliary process secretes…?

A

Aqueous humour into post. chamber, which flows through pupil into ant. chamber.

40
Q

Where does the aqueous humour drain through?

A

Throught the Trabecular network into the Canal of Schlemm and scleral veins.

41
Q

Cause of GLAUCOMA

A

Outflow path obstruction leading to intraocular pressure build up in the ant and post chambers -> compression of retina and retinal arteries this can cause visual field defects

42
Q

Glaucoma facts

A

10% blind registrants in UK due to glaucoma 2% of >40yrs have chronic open angle glauc. Glaucoma leads to CONSTRICTION OF VISUAL FIELDS

43
Q

Glaucoma TREATMENT

A

-eye drops to either reduce aqueous humor production or increase -drainage surgery

44
Q

OPTIC CANAL contents:

A

CN II - optic nerve Opthalmic artery

45
Q

SUPERIOR ORBITAL FISSURE contents:

A

Cranial nerves supplying eye movement: - CN III Oculomotor (sup&inf branches) - CN IV Trochlear - CN VI Abducens Opthalmic branch of CN V Trigeminal (3 branches): - frontal branch - lacrimal branch - nasociliary branch

46
Q

Blood supply to the ORBIT

A

Internal Carotid artery-> Opthalmic artery -> CENTRAL ARTERY OF RETINA

47
Q

What is special about the central artery of the retina?

A

It’s a critical end artery, only blood supply to the retina

48
Q

Venous drainage of the orbit

A

Superior + Inferior opthalmic veins drain into CAVERNOUS sinus (hence potential route for infection)

Scenario 27 (4 decks)

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