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Revision > Eye > Flashcards

Eye Flashcards

0
Q

A lesion at the optic chiasm has what effect?

A

Bitemporal hemianopia

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1
Q

A lesion at the right optic tract has what effect?

A

Homonymous hemianopia of the left side

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2
Q

A lesion to the right optic nerve (before the chiasm) has what effect?

A

Monocular loss of vision

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3
Q

A lesion at the right occipital pile has what effect?

A

Homonymous hemianopia with central sparing

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4
Q

A lesion at the left parietal radiation has what effect?

A

Lower homogynous quadrantanopia (rt. side)

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5
Q

A lesion at the right temporal radiation has what effect?

A

Upper homogynous quadrantanopia

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6
Q

Sympathetic nerves have what effect on pupil size?

A

They contract the radial muscles of the iris –> Dilating the pupil

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7
Q

What effect do parasympathetic nerves have on pupil size?

A

They contract circumferential muscles in the iris –> Contraction of the pupil

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8
Q

What is the difference between Rods and Cones?

A

Cones see colour and have the highest visual acuity. Rods have no colour vision but are most adept at low light vision

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9
Q

What part of the eye has the most focussing power?

A

Cornea

The lens fine tunes the focus (accommodation)

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10
Q

What controls the lens size and shape?

A

Cilliary muscles attach to the lens via suspensory ligaments

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11
Q

Where is the highest level of visual acuity and why?

A

The fovea, it has only cones and they’re smaller and more closely spaced in the fovea allowing for easier differentiation between the cells stimulated. There is nothing in front of them (ganglion cells and bipolar cells are off to the side).

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12
Q

What is the main photosensitive pigment in rod cells?

A

Rhodopsin

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13
Q

Where is the blind spot and what is it?

A

The temporal side of the field of vision, it falls on the optic disk (nasal side of the retina) where there are no photoreceptors.

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14
Q

What is glaucoma and what types are there?

A

Raised intraocular pressure:
Open/wide angle
Narrow/closed angle

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15
Q

What happens in closed angle glaucoma and what are the symptoms?

A

Aqueous humour cannot flow from the posterior to the anterior chamber causing and acute increase in pressure.
MEDICAL EMERGENCY.
Extremely painful, red, ‘halo’ vision around the eyes, headaches, N&V.

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16
Q

What happens in open angle glaucoma?

A

Flow of aqueous humour out through the trabecular meshwork is reduced due to degeneration = chronic increase in pressure.
It’s usually painless and can lead to optic nerve atrophy.

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17
Q

What nerves are involved in afferent pupillary defects?

A

CNII- optic nerve

CNIII- occulomotor nerve

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18
Q

What is consensual pupillary reflex?

A

When the brain receives signal that a strong light is shining in 1 eye (via CNII- afferent), both occulomotor nerves signal for the pupil to constrict therefore both pupils constrict when light is only shone in 1 eye.

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19
Q

What is a relative afferent pupil defect?

A

If a light is shined in the working eye, both pupils will constrict, if it is shined in the non-working eye then neither pupil will constrict- this is due to damage to the afferent pathway. Efferent pathway still works normally.

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20
Q

What is Horner’s syndrome and what can cause it?

A

Ptosis, constricted pupil, anhydrosis of that side of the face. Can be caused by many things, e.g. bronchogenic carcinoma, trauma

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21
Q

What happens in third nerve (efferent) palsy?

A

The affected eye points down and out with a dilated pupil that doesnt respond to light in either eye.

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22
Q

What are cataracts?

A

The lens of the eye becomes opaque.

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23
Q

What are the muscles controlling eye movement and what CN innervate them?

A

Superior rectus- abduction and elevation: CNIII (occulomotor)
Lateral rectus- abduction: CNVI (abducens)
Inferior rectus- Abduction and depression: CNIII (occulomotor)
Inferior oblique- Adduction and elevation: CNIII (occulomotor)
Medial rectus- Adduction: CNIII (occulomotor)
Superior oblique- Adduction and depression: CN IV (Trochlear)

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24
Q

What are some causes of sudden loss of vision?

A

Retinal detachment
Vitreous haemorrhage
Vascular occlusion
Acute optic neuropathy- Leber’s hereditary optic neuropathy

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25
Q

What nerves keep the eyelid open?

A

CNIII innervates the levator muscle which keeps the upper lid lifted.
CNVII innervates the muscles that close the upper lid

==> Ptosis isn’t caused by facial nerve palsy

26
Q

What is the term for a divergent squint and what can cause it?

A

Strabismus and it can be caused by CNIII- occulomotor palsy.

27
Q

What effect do sympathomimetic drugs have on the eye?

A

They cause myadriasis and act on a-1 receptors

28
Q

What is an example of a sympathomimetic drug for the eye andwhat are it’s side effects?

A

Phenylephrine

-photophobia, blurred vision, acute glaucoma, HTN and arrhythmias.

29
Q

What effect do antimuscarinic ocular drugs have and how do they do this?

A

They cause myadriasis (pupil dilatation) by blocking Ach @ muscarinic receptors

30
Q

What are some antimuscarinic drugs?

A

Atropine, cyclopentolate, troicamide

31
Q

What is the treatment for Uveitis? and What are possible side effects?

A

Cyclopentolate:

- raised IOP, photophobia, blurred vision, dry mouth, flushing and confusion.

32
Q

What effect do parasympathomimetics have on the eye?

A

Mimic the action of Ach on muscarinic receptors and open up the drainage channels in the trabecular meshwork and reverse myadriasis.

33
Q

What parasympatheticomimetic ocular drug is used for the treatment of glaucoma?

A

Pilocarpine

34
Q

What keeps the Na+/Ca2+ channel in photoreceptors open?

A

cGMP

35
Q

What voltage is a photoreceptor at rest and what NT does it produce?

A

-40mV and releases glutamate

36
Q

What happens when a photon hits the photoreceptor?

A

Rhodopsin is split by light as 11-cis retinal changes into trans retinal, this doesn’t fit into opsin.

The activated opsin activates phosphodiesterase

This converts cGMP to 5’GMP which closes Na+/Ca2+ gate

–> hyperpolarisation and \/ glutamate release

37
Q

Why do both pupils react to light stimulation in either eye?

A

fibres from each eyes pass through both Erdinger-Westphal nuclei.

–> fibres from each nuclei pass to the ipsilateral iris via the ciliary ganglion

38
Q

Where do the axons travel from the optic chiasm?

A

Lateral geniculate bodies

39
Q

What are the branches of the trigeminal nerve?

A 
V1= Opthalmic- sensory
V2= Maxillary- sensory
V3= Mandibular- sensory and motor
40
Q

What does CNV1 branch into?

A 
Largest= Frontal
Mid= Nasocilliary
Smallest= Lacrimal
41
Q

Where does the frontal nerve travel?

A

Beneath the orbital roof and above the levator palpebrae superior

42
Q

Where does the Nasocilliary nerve pass?

A

It passes above the optic nerve and crosses from lateral to medial lying above the medial rectus

43
Q

Where does the lacrimal nerve pass and where does it end?

A

It travels along with the lacrimal artery and ends at the lacrimal gland.

44
Q

What is Hutchinson’s sign?

A

Skin lesion to the nose preceding opthalmic herpes zoster infection due to the nasocilliary nerve innervating both the cornea and the tip of the nose

45
Q

What nerves innervate the lacrimal gland?

A

Lacrimal nerve

Zygomatic nerve

46
Q

What is the erdinger-westphal nucleus?

A

Accessory parasympathetic cranial nerve nucleus of the oculomotor nerve which supplies the constricting muscles of the iris

47
Q

What muscles constrict the pupil and what nerve controls it?

A

Sphincter pupillae

Occulomotor nerve- parasympathetic

48
Q

What affect does the sympathetic NS have on the size of the pupil?

A

Dilation

  • Contract the radial muscles of the iris
49
Q

What is aniscoria?

A

Mismatched pupil size

50
Q

What is Adie pupil?

A

A defect in parasympathetic postganglionic fibres that supply the sphincter pupillae –> large atonic pupil

51
Q

What happens to the pupil in Horner’s syndrome?

A

Defect in the sympathetic supply to the dilator pupillae –> constricted pupil (miosis)

52
Q

What is the blood supply for photoreceptor cells?

A

Choriocapillaries

53
Q

What function does cGMP have in phototransduction?

A

It keeps the Na+/Ca2+ channel open maintaining the polarisation

54
Q

What NT do the photoreceptor cells produce when they are polarised and what effect does this have?

A

Glutamate

- Inhibitory –> stops AP firing in ganglion cells

55
Q

What are the symptoms of retinal detachment?

A 
Flashes of light
Increased floaters
'Heavy' feeling
Dense shadow
Straight lines appear curved
Veil/curtain over vision
56
Q

What occurs in retinal detachment?

A

Retina peels away from the supporting tissue –> \/ O2 and nutrient supply leading to rapid vision loss/ blindness

57
Q

What is Nystagmus?

A

Involuntary movement of the eye

58
Q

What are the colours different cone cells are sensitive too and what are their wavelengths?

A

Blue- 450nm
Green- 550nm
Red- 600nm

59
Q

What do retinal ganglion cells do?

A

Contain melanopsin, these regulate melatonin production

60
Q

What’s the function of melatonin?

A

Regulation of circadian rhythms and antioxidant properties

61
Q

What is the macula?

A

Highly pigmented ‘yellow’ circle near the centre of the retina in the centre of which is the fovea.

62
Q

What results from damage to the macula?

A

loss of central vision

63
Q

What is lateral inhibition?

A

Strongly stimulated cones inhibit more weakly stimulated neighbours = /\ clarity/acuity

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