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Clinical Science and Practice I > Opthalmology > Flashcards

Opthalmology Flashcards

1
Q

describe the extracranial visual pathway

A

optic nerve converges and receives impulses from photoreceptors

this optic nerve leaves bony orbit and enters cranial cavity

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2
Q

describe the intracranial visual pathway

A

optic nerve from each eye meets at optic chiasm

fibres from the medial half of each retina cross over to contralateral optic tract

fibres from lateral half of each retina remain ipsilateral

these fibres meet at LGN

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3
Q

What is the lateral geniculate nucleus (LGN)?

A

projection of thalamus that meets with the optic nerve

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4
Q

what fibres make up left optic tract?

A

retinal fibres:
left lateral and
right medial fibres

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5
Q

what fibres make up right optic tract?

A

retinal fibres:
right lateral and
left medial

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6
Q

where do the optic tracts meet and synapse in the thalamus?

A

lateral geniculate nucleus (LGN)

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7
Q

What do axons from the LGN do and where do they go?

A

axons from the LGN carry visual info via pathway called optic radiation

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8
Q

Describe upper optic radiation

A

fibres carried from superior retinal quadrant
travels through parietal lobe to Primary visual cortex (PVC)

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9
Q

Describe lower optic radiaiton

A

fibres carried from inferior retinal quadrant
travels through temporal lobe (Meyers loop) to Primary visual cortex

when info at PVC then brain processes this info

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10
Q

Which cells process high intensity light?

A

cone cells

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11
Q

Which cells process low intensity light?

A

rod cells

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12
Q

What is lens structure and function?

A

muscle which refracts light to fall onto retina

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13
Q

Function of aqueous & vitreous humour?

A

aqueous: supplies nutrients to eyeball - anterior

vitreous: transmits light, nutrient supply - posterior

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14
Q

Function of cornea?

A

mainly responsible for light refraction
initial refraction onto lens, which then refracts it onto retina

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15
Q

What is the choroid layer?

A

middle layer between the sclera (outer) and retina (inner)
contains melanocytes to absorb colour

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16
Q

What is the retina?

A

inner layer which contains photoreceptos

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17
Q

How does light focus on the retina?

A

as light moves from air to eye
passes through cornea, aqueous humour, lens, vitreous humour
then passes through an entire neural layer
to excite the photoreceptors that are next to the
pigmented layer

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18
Q

What is the fovea and why is VA high here?

A

centre of macula where visual acuity is the highest due to high no of cone cells

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19
Q

What is the macula?

A

part of retina at back of eye which contains high no of rod + cone cells

allows us to see fine details in centre of visual field

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20
Q

What are some causes of acute red eye?

A

subconjunctival haemorrhage
keratitis
conjunctivitis

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21
Q

What are the extrinsic eye muscles and functions?

A

lateral rectus - moves eye laterally
medial rectus - moves eye medially
superior rectus - upwards
inferior rectus - downwards
superior oblique - down and out
inferior oblique - up and out

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22
Q

Which cranial nerves innervate the extrinsic eye muscles?

A

lateral rectus - VI abducens
medial rectus - III oculomotor
superior rectus - III oculomotor
inferior rectus - III oculomotor
superior oblique - IV trochlear
inferior oblique - III oculomotor

LR6 SO4 R3

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23
Q

Which CN innervates the levator palpabrae superioris muscle (eyelid)?

A

CN III - Oculomotor

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24
Q

What happens when light enters the eye? Describe the entire process.

A

it passes retina (nerves) unaffected

travel straight to choroid

bounces back onto retina

light falls on rods and cones

these photoreceptors pick up the light and send signals to bipolar cells

bipolar cells relay to ganglion cells

send the nerve along the surface of the retina to optic nerve

optic nerves meet at optic chiasm

signal then enters thalamus then goes to visual cortex

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25
Q

what are common causes of blepharitis?

A

S aureus
rosacea
pollen allergy
seborrheic dermatitis

26
Q

what is 1st line treatment for blepharitis?

A

The patient’s symptoms and examination findings suggest anterior blepharitis, likely with a staphylococcal infection.

The NICE guidelines recommend chloramphenicol ointment as the first-line treatment for this condition, to be used for six weeks.

Chloramphenicol is effective against a broad spectrum of bacteria, including Staphylococcus species, commonly associated with blepharitis.

27
Q

chalazion vs hordeolum

A

chalazion - blockage of meiboman gland that appears on the inside of the eyelid, usually surfacing as a bump. - firm, non-erythematous, mobile, inner eyelid - warm compress, resassurance, goes away spontaneously

An eye stye (or hordeolum) - smaller pimple-like bump that appears on the upper or lower eyelid due to a blocked oil gland. It is typically near the eyelash and lives on the outside of the eyeli

28
Q

What is keratitis and what is the most common bacteria that causes it?

A

inflammation of the cornea = corneal ulcer

causes:
Pseudomonas and S. aureus - Pseudomonas v common in ocular presentation

29
Q

What are viral causes of Keratitis?

A

HSV 1 - cold sore
VZV - part of shingle

30
Q

z

A
31
Q

What are symptoms of keratitis?

A

red, sticky, painful eye
gritty sensation in eye
significant photophobia
some vision loss
contacts can make it worse

32
Q

Why can contacts cause keratitis?

A

These organisms may live on the surface of a contact lens or contact lens carrying case. The cornea may become contaminated when the lens is in your eye, resulting in infectious keratitis.

33
Q

Treatment for keratitis?

A

bacterial - fluoroquinolone (eg ciprofloxacin) drops hourly for 38h, then 4x day for 5 days

viral - aciclovir drops 6x daily for 2 weeks

34
Q

What are causes of conjunctivitis?

A

bacterial -

allergic -

chemical - alkali

Autoimmune -

35
Q

What are symptoms of viral conjunctivitis?

A

red sticky eyes
gritty sensation of eyes
URTI symptoms - cough/cold

36
Q

What viruses can cause conjunctivitis?

A
  • viruses cause 80% of conjunctivtis cases
  • ask if recent cold (adenoviruses most common cause)
  • very contagious if eye is red + gritty

less common viruses:
EBV
Herpes Simplex
VZV

37
Q

What bacteria can cause conjunctivitis and how to treat?

A

staph and strep bacteria
Haemophilius influenzae - bacteria that cause pneumonia
Moraxella catarrhlis - bacteria that cause ear + sinus infections
also v contagious - need chloramphenicol eye drops

38
Q

What is management of acute bacterial conjunctivitis (<3 day hx)?

A

According to NICE guidelines, including the initial management involves reassurance that this is a self-limiting condition, typically resolving within 5 to 7 days without the need for treatment. The use of saline to clean away purulent discharge can be advised. Antibiotic therapy, such as chloramphenicol or fusidic acid eye drops, is generally reserved for cases that do not improve or worsen over a period of 3 days, particularly in children under 2 years old.

39
Q

What are allergic conjunctivitis causes and treatment?

A

allergen - eg pollen, pet dander, mites
not contagious

40
Q

what is an enlarged blind spots typically associated with?

A

swollen optic disc - papilloedema
caused by raised ICP (eg brain tumour, intracranial haemorrhage)

41
Q

what is strabimus?

A

when eyes do not line up in the same direction (cross-eyed)

42
Q

what is orthotropia?

A

straight alignment of the eyes - no shift in contralateral eye

43
Q

what is heterotopia?

A

when you do the cover test, you occlude one eye and observe the contralateral eye for a shift in fixation

shift indicates heterotropia = strabismus

44
Q

what are the 4 types of strabismus?

A

esotropia - inward turning

exotropia - outward turning

hypotropia - downward turning

hypertropia - upward turning

45
Q

what is nystagmus and what does it indicate?

A

rhythmical, repetitive, involuntary eye movement

indicates vestibular nerve pathology or stroke

46
Q

what condition is associated with optic neurtis?

A

multiple sclerosis

47
Q

what is optic neuritis and symptoms?

A

inflammation of optic nerve (CN II)

pain at back of eye
pain on moving the eye

48
Q

what is the clinical relevance of the optic chiasm?

A

pituitary gland is very close to optic chiasm
so pituitary adenoma (benign) will compress on the optic chiasm

Compression to the optic chiasm particularly affects the fibres that cross over from the nasal half of each retina.

This produces a visual defect affecting the peripheral vision in both eyes, known as bitemporal hemianopia - aka tunnel vision

49
Q

if there is damage to optic radiation what will occur

A

homonymous hemianopia
associated with stroke or any damage to this part of the brain

50
Q

what would optic nerve damage lead to

A

depending on which side would be anopia

51
Q

what are the risk factors associated with glaucoma?

A

diabetes
genetic
family hx
black ethnic origin

52
Q

risk factors of cataracts

A

steroids - avoid topical eye steroid
old age
caucasian
sun exposure
diabetes
eye trauma
family history of cataracts

53
Q

risk factors of AMD?

A

Older age
Smoking
Family history
Cardiovascular disease (e.g., hypertension)
Obesity
Poor diet (low in vitamins and high in fat)

54
Q

Which nerves are involved in regulating pupil size?

A

CN II and III

55
Q

what condition is RAPD associated with?

A

MS

56
Q

palsy associated with CN III

A

with pupil involvement

vertical diplopia
ptosis
dilated pupil
with CN III palsy, other nerves (superior oblique) overpower, so eye would appear down and out

57
Q

causes of 3rd nerve palsies?

A

medical
surgical - PCOM aneurysms - posterior communicating artery presses against the 3rd nerve

dilated pupils

58
Q

what does 4th cranial nerve supply?

A

supplies superior oblique - depresses the eye

59
Q

what does 4th CN palsy present as?

A

therefore eye will appear higher than the normal

diplopia - double vision
vertical - seeing 2x things side by sie
horizontal - seeing 2x things top & bottom - therefore pt will have trouble going down stairs
also to compensate their neck will be tilted to the side

60
Q

what muscle does CN VI supply and what does palsy to this area present as?

A

lateral rectus palsy

therefore to compensate the eye will be deviated medially

61
Q
A

Clinical Science and Practice I (14 decks)

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