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Medicine year 2 semester 2 > Case 21- Eye and questions > Flashcards

Case 21- Eye and questions Flashcards

1
Q

Projections of the retinal ganglion cells (RGC)

A

The retinal ganglion cell (RGC) axons project via the optic nerve, chiasm and tract to terminate in the lateral geniculate nucleus of the thalamus. They are functionally classed as either parvocellular or magnocellular. The parvocellular RGC’s give information regarding the specific detail of vision e.g. colour. The magnocellular RGC’s have information about shape and movement.

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2
Q

Parvocellular or Magnocellular pathway

A

This is important when the information reaches the primary visual cortex which is located in the occipital lobe. It sits on either side of the calcarine sulcus and is known as V1. Within the cortex, there are cortical columns that receive information from either the parvocellular or magnocellular pathways.

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3
Q

The where pathway

A

Neurones from V1 project to V2, V3 and V5.
Dorsal pathway, to the parietal region
This is an extension of the magnocellular pathway processing shape, movement and motion.

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4
Q

The what pathway

A

Neurones from V1 project to V2 and V4.
The ventral stream, to the temporal region
This is an extension of the parvocellular pathway for the analysis of details.

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5
Q

Akinetopsia

A

Caused by a lesion of the V5 area
Akinetopsia causes a patient to experience an impaired perception of motion. An object may jump from one position to another.
This could cause many difficulties, one example being that it may be hard to know when to cross the road as a car may appear to be a long way in the distance and then jump to its actual position close by.

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6
Q

Prosopagnosia

A

The inability to recognise faces.
The medial temporal lobes have a record of faces (it is right-side dominant).
Damage to the temporal lobe or ventral stream from the visual cortex can cause this condition.

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7
Q

Blindsight

A

This is an extremely rare phenomenon.
It can occur after damage to the occipital lobe e.g via a stroke.
A patient becomes cortically blind- i.e. there is no conscious awareness of sight as the primary visual cortex is damaged.
The rest of the visual pathway is still intact and the information processing can be taken over by other areas of the brain.
This means patients with blindsight cannot see but can walk down a corridor avoiding objects.

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8
Q

Lesions in the L optic nerve

A

Monocular visual loss

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9
Q

Lesions in the optic chiasm

A

Bitemporal hemianopia- no sight on the temporal side of each eye

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10
Q

Lesions in the left optic tract

A

Homonymous hemianopia- no sight on the right side of both eyes

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11
Q

Lesions in the left optic radiation- lateral fibres

A

Superior quadrantopia- no sight in the upper right

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12
Q

Lesions in the left optic radiation- medial fibres

A

Inferior quadrantopia- no sight in the lower right

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13
Q

Occipital visual cortex lesions

A

Homonymous hemianopia with or without macula sparing.

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14
Q

Pupil- afferent and efferent connections

A

Afferent= Light entering the eye-> pre-tectal area

Efferent=Pre-tectal area->sphincter pupillae

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15
Q

Sphincter pupillae

A

Circular muscle
Parasympathetic
Constriction/miosis

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16
Q

Dilator pupillae

A

Radial muscle
Sympathetic
Dilation/mydriasis

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17
Q

A patient has a lesion of CN II on the right side- what is the response of both pupils when light is shone into the right eye?

A

Right eye- no response

Left eye- no response

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18
Q

A patient has a lesion of CN II on the right side- what is the response of both pupils when light is shone into the left eye?

A

Right eye- constriction

Left eye- constriction

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19
Q

A patient has a lesion of CN III on the left side- what is the response of both pupils when light is shone into the left eye?

A

Right eye- constriction

Left eye- no response

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20
Q

A patient has a lesion of CN III on the left side- what is the response of both pupils when light is shone into the right eye?

A

Right eye- constriction

Left eye- no response

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21
Q

What other symptoms would you see with a CN III lesions

A

Dilated pupil- loss of parasympathetic supply to sphincter pupillae.
Full ptosis- loss of levator palpebrae superioris function.
Eye looks down and out- only lateral rectus and superior oblique can function.
Failure to accommodate- loss of function of sphincter pupillae, ciliary muscle and medial rectus

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22
Q

Range our visual system is sensitive to

A

The visible light range of the electromagnetic wave spectrum ranges from 380nm (purple) to 740nm (red). Most electromagnetic energy emitted by the sun is within the visible range. We have blue, red and green cones which then combine to form other colors. Our perception of the world is filtered

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23
Q

Importance of the fovea

A

Contains most of the cones (no rods)- where you have eye acuity and colour vision. The further out you go its most rods where you have night vision and movement. The photoreceptors have been pushed apart to create the foveal pit

24
Q

Optic disc

A

Where the optic nerve and blood vessels enter the eye. Is a blindspot with no rods or cones. Closest to the nose

25
Q

Macula

A

Surrounds the fovea. Has some rods but the majority is cones, important in color vision. Surrounded but the superior and inferior branch of the retinal vein or the radius from the fovea to the optic nerve. Location of central vision. The macula layer is composed of two or more ganglion cells on top of each other

26
Q

Organisation of the retina

A

Has pigmented epithelium at the back, reduces the light scatter and feeds the photoreceptors
Phtoreceptors- cell bodies are in the outer nuclear layer. The outer nuclear layer is towards the back of the eye and the inner nuclear layer is near the front. In the outer plexiform layer the photoreceptors synapse onto the bipolar cells. The photoreceptor and bipolar cell are in parallel to each other. Horizontal cells are between them in outer plexiform layer
The cell bodies of the bipolar cells are in the inner nuclear layer
The bipolar cells project to the inner plexiform layer and synapse with the inner plexiform layer. The axons from the ganglion cells become the optic nerve

27
Q

Layers of the retina

A

1) Nerve fibre layer
2) Ganglion cell layer
3) Inner plexiform layer
4) Inner nuclear layer
5) Outer plexiform layer
6) Outer nuclear layer
7) Photoreceptors outer segments
8) Pigmented epithelium

28
Q

Hormone photoreceptors produce

A

Costantly produces Glutamate which goes down to the bipolar cells in the dark which the brain interprets as there being no signal. When light hits the photoreceptors the Na+ channels close down stopping the Glutamate from being released. In low light levels some Glutamate, in high levels less. GABA, Glycine, Acetylcholine and Dopamine can be released from amacrine cells and inhibit Glutamate production. Ganglion cells fire action potentials based on how much glutamate is produced

29
Q

Columns in the retina

A

Photoreceptors, Ganglion, Muller and Bipolar cells form columns
The Horizontal and Amacrine cells form layers
Ganglion cells go along in layers
Muller cells form the innermost layer, the feet of glial cells are support cells
The synaptic

30
Q

Effects of raised intra ocular pressure on the optic disc

A

There will be a cupped optic disc with a high cup to disc ratio, cup will appear bigger
Can be due to Glaucoma

31
Q

Visual acuity and driving

A

The minimum eyesight standard for driving is 6/12

You must- have an adequate field of vision and be able to read a car number plate made after 1/09/2001 from 20m

32
Q

Visual acuity and occupation

A

Lorry and bus drivers- must have a visual acuity at least 6/7.5 in their best eye and at least 6/60 in the other eye

Other restriction- Armed forces, Air traffic control and Electrical engineers

33
Q

What nerve supplies the lateral rectus muscle

A

Abducens

34
Q

Result of right CN IV (trochlear) palsy

A

Superior oblique-normally helps pull eye down and out.

On looking forwards: elevation and extorsion of the eye.

On looking left: the eye elevates as it moves medially

35
Q

Oculomotor CNIII palsy

A
  1. ‘Down and out’ palsy
  2. Ptosis (innervates levator palpebrae superioris)
  3. Mydriasis (large pupil)– carries parasympathetic fibres
36
Q

What are the afferent and efferent branches of the corneal reflex

A

Afferent- Trigeminal (V1)

Efferent- facial nerves

37
Q

What does the greater petrosal nerve supply

A

The greater petrosal nerve (a branch of the facial nerve – CNVII) gives parasympathetic supply to the lacrimal gland. If the cornea is dry then the greater petrosal nerve may be injured

38
Q

Where does the nerves for the lacrimal gland have their cell bodies

A

Superior salivatory nucleus

39
Q

Symptoms of cataracts

A

1) Change in refractive error
2) Blurred vision
3) Glare

40
Q

Most common complication after a cataract operation

A

Endophthalamitis

41
Q

Why does Presbyopia lead to reduced accomodation

A

There is reduced lens flexibility with age

42
Q

What structure in the eye is responsible for the most refractive power

A

The cornea

43
Q

What are the visual acuity standards for lorry and bus drivers

A

visual acuity at least 0.8 (6/7.5) in your best eye
and at least 0.1 (6/60) in the other eye
glasses can’t be more than +8 (legally blind)
uninterrupted horizontal visual field of at least 160 degrees
- with an extension of at least 70 degrees left and right
- and 30 degrees up and down

44
Q

What neurotransmitter is the cause of excitotoxicity

A

Glutamate

44
Q

What neurotransmitter is the cause of excitotoxicity

A

Glutamate

45
Q

Description of phototransduction

A

Light hitting photoreceptors hyperpolarise the photoreceptors by closing Na+/Ca+2 channels thus membrane potential hyperpolarises due to K+ effluc

46
Q

What neurotransmitter is recycled by monoamine oxidase (MAO) only

A

Serotonin

47
Q

Nerve supply to the cornea

A

It has a dense nerve supply derived from the long ciliary branches of the ophthalmic division of the trigeminal

48
Q

What structure of the temporal lobe is indicated in schizophrenia and epilepsy

A

The Hippocampus

49
Q

Where is a flame haemorrhage located

A

The Nerve fibre layer

50
Q

When do you get tardive dyskinesia

A

Following chronic use of antipsychotic drugs. There is proliferation of dopamine receptors and hypersensitivity of the nigrostriatal pathway. The effects are often irreversible

51
Q

What part of the eye is affected by cataracts

A

The Lens

52
Q

Occupations where a higher standard of visual acuity is required in the Uk

A

Bus and lorry driver

53
Q

The Pharmacokinetic property of typical antipsychotics

A

High plasma protein bound

54
Q

Cause of positive symptoms in schizophrenia

A

Dysregulation of dopaminergic pathways to the subcortical and limbic systems through hyperactivity acting on dopamine D2 receptors.
The pathways to the prefrontal cortex are hypoactivated, are D1 receptor mediated and lead to negative symptoms of schizophrenia.

54
Q

Cause of positive symptoms in schizophrenia

A

Dysregulation of dopaminergic pathways to the subcortical and limbic systems through hyperactivity acting on dopamine D2 receptors.
The pathways to the prefrontal cortex are hypoactivated, are D1 receptor mediated and lead to negative symptoms of schizophrenia.

Medicine year 2 semester 2 (47 decks)

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