Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OSCE PREP > Clinical 15: Visual Testing > Flashcards

Clinical 15: Visual Testing Flashcards

1
Q

What is refraction?

A

The changing direction of light waves, using travelling between mediums of different densities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the main structures that refract light in the eye?

A

The tear film, the cornea and the crystalline lens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is emmetropia and why is this important?

A

When light is focused directly onto the retina - creates a clear and in focus visions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is myopia?

A

When light rays are refracted and fall short of the retina
Causes short sightedness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is hypermetropia?

A

When light rays are refracted as fall behind the retina
Causes long sightedness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the purpose of diverging lenses?

A

Correct myopia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the purpose of converging lenses?

A

Correct hypermetropia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does a pinhole improve vision?
How can this be used in diagnose?

A

Pinhole creates small focused light beam
Unfoces rays are blocked
Focused light land on retina should form a more clear images
If improves image = refractive apparatus damage
If image does not improve = other factors contributing (may still have problem with refractive apparatus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is astigmatism?

A

Imperfection in the curvature of the eyes corea or lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What methods can be used to test visual acuity?

A

Snellen Charts
Jaeger Charts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How to tests visual acuity over long distance?

A

Snellen chart
Wear corrective glassess etc if norm worn
Check chart size and appropriate distance to stand
Cover one ear read lowest line possible - repeat on other eye
Repeat looking through pinhole to see if vision improves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do you record results from a Snellen chart?

A

Chart distance (numerator)
over the lowest line read (denominator) - this will be written on the chart.
For lowest line read should be able to read at least half letters (record the number of letters they can not read in superscript e.g -2/7
If can read all of one line and less than half of numbers on next line record this as an addition +num next line/total no on line.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do you assess visual acuity for near vision?

A

Jaeger eye chart
Wear corrective lenses if norm
Ask patient to cover one eye, ask to read smallest paragraph they can
Repeat on other eye
Should be held on comfortable reading length (40cm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you record results from a Jaeger Eye chart?

A

Record the J value of the smallest block of text you can read

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the different values commonly given on a GOS 18 prescription?

A

SPH - sphere - lens power
CYL - cylinder - lens power for astigmatism
Axis - lens medridian - direction where are cylindrical power in lens should be placed
Add - magnifying power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is meant by SPH or sphere on a prescription?

A

Represents the lens power in dioptres
+ value indicates longsighted (projects too far)
- value indicates shortsighted (doe snot project enough)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is meant by CYL or cyclinder on a prescription?

A

The amount of lens power for astigmatism
- sign corrects shortisghted astigmatism
+ sign correct longishted astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the axis on a prescription?

A

Describes the lens meridian that contains no cylinder power to correct astigmatism - defined as a number from 1 to 180.
Number 90 corresponds to the vertical meridian of the ye, number 180 corresponds to the horizontal meridian.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the Add mean on a prescription?

A

The magnifying power that should be applied to correct presbyopia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the GOS 18 form?
(general Opthalmic Services 18)

A

Used for opthalmic referall to the Hospital Eye service of notification to the GP
Will contain patient details, optometrist details, GP details.
Request action required by GP
State clinical problem/reason for referall
Prescription information

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the two different photosensitive cell types in the retina?

A

Rods and cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the features of rods?

A

Responsible for vision at low light levels (scotopic vision)
Do not mediate colour vision and haw a low spatial acuity

23
Q

What are the features of cones?

A

Active at higher light levels (photopic visions)
Capable of colour vision
Responsible for high spatial acuity
Central fovea is populated exclusively by cones.

24
Q

Where in the retina is there an absence of photoreceptors?

A

The blind spot
Portion of visual filed of each eye that corresponds to the position of the optic disk (optic nerve head) on the retina
No image detection in this area

25
Q

What method is used to assess colour vision?

A

Ishihara charts
Circle made of range of dots in diff colour and sizes - series of dots are made a certain Iso colour to make a number
Easily seen if good working colour vision
Should be at arms length away.

26
Q

What is meant by the visual field of a patient?

A

The entire area a patient can see without moving their head whilst their eyes are fixed on one point,

27
Q

How does the visual filed correspond to the vision on the cortex?

A

Flipped upside and left to right

28
Q

What is the passage of information from photoreceptors to the optic nerve?

A

Photorecepotrs - electrical signals generated
Synapse with retinal bipolar cells - rods on a many to :1 ratio and cones on a 1:1 ratio
Synapse to retinal ganglion cells
Converge at the optic disk forming the optic nerve

29
Q

What is the gross anatomy passage of the optic nerve?

A

Exits the eye travels through a defect in the lamina cribosa of the sclera
Travels through bony orbit and into middle cranial fossa through the optic canal.
Travles along floor of mid cranial fossa through medial aspect of cavernous sinus
The left and right optic nerve then converge at the optic chiasm.
Temporal fibres remain on the ipsilateral side whilst nasal fibres desciate to the contralteral side.
Now termed optic tract/
Projects to the thalamus synapse at the lateral genicular nuclues in the thalamus (bilateral)
Optic radiations then project to the occipital lobe and terminate in the calcarine sulcus of the occpital lobe where the cortical visual centre in located

30
Q

How are the different pattern of travel of the optic radiations from the thalamus to the visual cortex related to the visual field?

A

Loops through the parietal lobe - relate to the upper visual fields
Loops through the temporal bone (Meyers loop) relate to the lower visual fields.

31
Q

How can we subtly test for early visual field defects?

A

Use a white neurotip and ask the patient when they can first see the white neurotip
Repeat with red neurotip - ask to tell you when they can first see that tip is red rather than when first appears (as red cone functionality is lost first)

32
Q

What is the hypothesis behind homonymous hemianopia with macular sparing?

A

Thought to be due to visual cortex dual blood supply from MCA and PCA or posterior temporal and calcarine arteries (relevant branches of MCA and PCA). Macular survive if only one artery occluded

33
Q

What is the difference between the optic tract and the optic nerve?

A

Optic nerve - from eye to chiasm
Optic tract - from chiasm to thalamus lateral genicular

34
Q

How do you assess visual fields of a patient?

A

Sit opposite about 1m
Ask to cover one eye, cover mirror eye.
Ask patient to focus on your nose and not move head or eyes.
Central visual field loss - ask if any part of my face is missing.
Position hatpin at equal distance between both
Bring in ask when can see - repeat for each four quadrants, repeat on other eye

35
Q

How do you assess for a visual blind spot?

A

Sit directly opposite the patient at a distance of around 1 meter
Ask the patient to cover one eye with their hand - cover mirror image eye
Ask to focus on part of face and not move head or eyes
Red hatpin equal distance - start centrally slowly move laterally until red pin disappears (ask to tell you this)
Continue until red hat pine comes back into vision (ask to tell you)

36
Q

In relation to the eye what structures are under autonomic innervation?

A

The lens and the pupil
Help create in-focus image on the retina.

37
Q

What is the autonomic innervation to the pupil?

A

Sphincter pupillae muscle - PANS - pupil constriction
Dilator pupillae muscle - SANS - pupil dilation

38
Q

What is the anatomical course of the pupillary reflex pathway? (causing vasoconstriction)

A

Afferent pathway - optic nerve - chiasm - projects to synapse in pre-tectal nucleus (midbrain) - sends projections to contralateral and bilateral Edinger Westphal nucleus
Efferent - project PANs fibres of oculomotor nerve to ciliary ganglion for short ciliary nerve to sphincter pupillae causing pupil constriction

39
Q

What is the anatomical course of the sympathetic pathway to the pupil?
(pupil dilatation)

A

Sympathetic fibres descend from the ipsilateral hypothakamus through the lateral aspect of the brain stem into the spinal cord, synpase in lateral horn .

Secondary order neurons out in the anterior roots of C8 and T1, through the sympathetic chain, through brachial plexus and over lung apex.
Synpase in the superior cervical ganglion.

Post ganglionic fibres ascende the wall of the internal carotid artery and pass directly through the ciliary ganglion to project to the eye and innervate the dilator pupillae.

40
Q

What is the accomodation reflex?

A

Visual response to focusing on near objects
1. Contraction of medial recti muscles cause convergence of eyes
2. Constriction of the pupils
3. Contraction of the ciliary body -> broadens the lens, increasing the refractive power.

41
Q

How are autonomic and somatic nerve fibres arranged in the oculomotor nerve?

A

Parasympathetic - periphery of trunk - first affected by compression
Somatic - centre
Vasovasorum supplying the nerve starts in the centre and spreads out radially - often sparing pupillary function until later on in the disease process

42
Q

What are the different types od third nerve (oculomotor nerve) palsy?

A

Surgical - compression due to tumour of aneurysm
Medical - ischemia or microvascular damage e,g from diabetes.

43
Q

How do you assess for the accomodation reflex?

A

Ask the patient to focus on a spot in the distance (not using light source)
Ask to look at close fixation target
Expect constriction, move medially

44
Q

What is meant by near light dissociation?

A

Failure to constrict to light but constriction to near gaze.

45
Q

What is a relative afferent pupillary defect?

A

A condition affecting the pupil responses causing asymetrical disease in the dilatory response due to problem between the retina and optic nerve.

46
Q

How do you test for a relative afferent pupillary defect?

A

Shine a bright light for three seconds on each pupil and move the light briskly from one eye to the other
Normal pupils will show a s symmetrical response
In RAPD the weaker direct pupillary response in the affected side
Some causes include optic neurotiris, ischaemis/infective causes of retinal damage, retinal detachment and optic nerve damage.

47
Q

What are the different size light setting on an ophthalmoscope?

A

Large - dilated pupil after adminstering mydraitic drops.
Medium - non dilated pupil in dark room
Small - constricted pupil in a well-lit room

48
Q

What is the purpose of a red free on an ophthalmoscope?

A

Used to look closely at the vasculature

49
Q

What is the use of the blue light on an ophthalmoscope?

A

Used to look for corneal abrasions or ulcers with flurescein dye.

50
Q

What is the use of the slit light on an ophthalmoscope?

A

Used to look at contour abnormalities of the cornea, lens or retina.

51
Q

What is the use of the grid light on a ophthalmoscope?

A

Used to approximate the relative distance between retinal lesions.

52
Q

What setting should the dioptre dial be on when using an ophthalmoscope?

A

Is normal visual acuity adjust dial to 0.
Is you visual acuity needs correcting aka not wearing your glasses set to your prescription value.
Combine this value with the value to look at the patients eye aka high positive such as 10 to look at front of eye.

53
Q
A

OSCE PREP (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions