Vision Flashcards
1
Q
What is refraction?
A
Bending of light when it passes from one optical medium to another
The bending of light rays to form a sharp image on the retina
2
Q
What is accommodation?
A
The focusing of a far off or near object by how much we bend the light rays
3
Q
What is a refractive erros?
A
When there is a mismatch of bending the light rays
4
Q
Which components of the eye are transparent?
A
Cornea
AH
Lens
VH
5
Q
What are the two main benders of light in the eye?
A
Cornea
Lens
6
Q
What is the most powerful bender of light?
A
Cornea
7
Q
What are the 3 things that cause accommodation?
A
Pupil constricts
Eyes converge
Lens changes shape
8
Q
What is the sequence of events that occur to thicken the lens?
A
o Want to thicken the lens – ciliary muscle
o Ciliary muscle contracts making the ciliary body bulge
o Space in the middle decreases and the suspensory ligaments become lax
o This means the lens is no longer being pulled
o Basically just flops down and becomes more spherical (thicker)
o This bends the divergent rays
9
Q
Do eyes converge or diverge when an object is up close?
A
Convege
10
Q
Which muscles causes convergence?
A
Medial Rectus
11
Q
Which CN controls the medial rectus?
A
CN III
12
Q
Which muscle is thicker medial or lateral rectus?
A
Medial
13
Q
Which of the 3 aspects of accommodation is examinable?
A
Pupillary constriction
14
Q
Which part of the NS controls the constriction of pupils?
A
Parasympathetic innervation
15
Q
What is myopia?
A
Short sightedness
16
Q
What is hyperopia
A
Long sightedness
17
Q
What is a astigmatism?
A
Non-spherical curvatures of the cornea
18
Q
What is prebyopia?
A
Long sightedness of old age
19
Q
What is short sightedness?
A
When close objects appear clear and distant ones hazy
20
Q
What is the most common cause of myopia?
A
Eyeball is too long
21
Q
Where does the image form in myopia?
A
In front of the lens
22
Q
What are the symptoms of myopia?
A
Headaches
Complain of not being able to see board or distant objects
23
Q
What are infant symptoms of myopia?
A
Loss of interest in sports/people
More interested in books/pictures
24
Q
What is the treatment for myopia?
A
Bi concave lenses
Spectacles
Contact lenses
Laser eye surgery
25
What is long sightedness?
When distant objects appear clear
| Close objects appear hazy
26
What is the main cause of hyperopia?
Eyeball is too short
| Or lens is too flat
27
Where is the image formed in hyperopia?
Behind the retina
28
Why can accommodation not just be used to correct hyperopia?
Use more and more power for seeing close up until all accommodative power has gone
29
What are the symptoms of hyperopia?
Glasses
Contact lenses
Laser eye surgery
30
What can be seen in children with hyperopia?
Convergent squint
31
Why is immediate correction of convergent squint in children necessary?
To preserve vision
| and prevent a lazy eye
32
What is astigmatism?
When close and distant objects appear hazy
33
What contact lenses are needed in astigmatism?
Toric lenses
34
Which glasses are neededin astigmatism?
Cylindricallens
35
What is the cause of presbyopia?
With age the lends becomes less elastic
| Accommodation power weakens
36
When does presbyopia usually start?
In the 5th decade of life
37
What is phototransduction?
The conversion of light energy to an electrochemical response by the photoreceptors
38
What are the 2 types of photoreceptors?
Rods and cones
39
What do the phototransduced rods and cones need to activate?
Optic nerve neurons
| To generate and AP
40
What is the visual pigment in rods?
Rhodopsin
41
What is the visual pigment in cones?
Opsin
42
What are the 3 types of cones?
S, M and L
43
What do the 3 different types of cones all respond to?
Different wavelengths of light
44
What does rhodopsin consist of/
Opsin + 11-cis Retinal
45
Where is vitamin A supplied?
Through the diet
46
What is rhodopsin?
Integral transmembrane helical protein
47
What is retinal?
Chromophore
48
What is retinal derived from?
Vitamin A
49
What is opsin?
A G-coupled protein
50
What are the 2 conformations of retinal?
Cis and trans
51
What happens when light hits retinal?
Changes from cis to trans conformation
52
Why does rhodopsin split?
Because not all trans-retinal can fit into the opsin
53
How is visual pigment regenerated?
Dietary vitamin A goes back to form 11 cis -retinal
This then joints the opsin
Forms rhodopsin
54
Why is a constant supply of vitamin A require?
because not all vitamin A is regenerate to form retinal
| some of it does not combine with opsin and gets used instead to form an ester
55
In what conditions can vitamin A deficiency occur?
Coeliac
| Sprue
56
What is your visual field?
Everything you see with one eye including the periphery
57
How are images of objects in your filed of vision formed?
Upside down
58
Where are upside images inverted?
on the retain
59
Where is the left half of the visual field seen?
On the right side of the retina
60
Where is the right visual field seen?
On the left side of the retina
61
Where do fibres from the optic nerve pass?
The optic chiasma
62
At the optic chiasma which fibres cross?
Medial ones
63
Which fibres cross over at the chiasma nasal or temporal?
Nasal
64
Where do fibres from the optic tracts synapse?
At the LGB of the thalamus
65
Where do optic fibres pass from the LGB?
Behind the internal capsule to reach the primary visual cortex
66
What is area 17?
Primary visual cortex
67
Where is area 17 located?
Occipital lobe
68
Which cortex sees the left half of the visual field?
Right cortex
69
Which cortex sees the right half of the visual field?
Left cortex
70
When the right optic nerve is damaged what do you expect to see?
Blindness in the right eye
| Entire eye has been affected
71
When the optic chiasma is interrupted in the middle what do you expect to see?
Bitemporal hemianopia
| Naso fibres are affects meaning lateral vision is lost
72
When the right optic tract is damage what do you expect?
Left side blindness
| Contralateral homonymous hemianopia
73
What is the function of intrinsic muscles of the eye?
Control pupil diameter an alter lens curvature (accommodation)
74
What is the function of extrinsic eye muscles?
To move the eyeball
75
What are the muscles of the eye?
```
MR
LR
SR
IR
IO
SO
```
76
Where do the recti muscles arise from??
Apex of the orbit from an annular fibrous ring
77
Where does the SO muscle arise?
The roof of the orbit posteriorly
78
Where does the IO arise from?
The roof of the orbit anteriorly
79
Which is the only eye muscle to originate anteriorly?
IO
80
Which muscle lies just above the SR?
LPS
| Levator palpebrae superioris
81
Which muscles closes the eyelid?
LPS
82
Where do the recti muscles insert?
Onto the sclera anteriorly
83
Where do the oblique muscles insert?
On to the sclera posteriorly
84
Which CN supplies the extrinsic muscles of the eye?
SO CN IV
LR CN VI
and everything else by CN III
85
What term is used to describe eye movements of both eyes?
Binocular
86
What is meant by uniocular?
Movement of 1 eye
87
When LR has abducts the eye what does SR and IR cause?
SR - elevation
| IR - depression
88
When MR has adducted the eye what does SR and IR cause?
SR - intorsion
| IR - extorsion
89
When the eye ball is adducted what does SO and IO cause?
SO - depression
| IO - elevation
90
When the eyeball is abducted what does SO and IO cause?
SO - intorsion
| IO - extorsion
91
What is the primary action of the extrinsic eye muscles?
```
MR - adduction
LR - abduction
SR - elevation
IR - depression
SO - intorsion
IO - extorsion
```
92
What is the secondary action of SR, IR
| SO, IO?
SR - adduction
IR - abduction
SO - depression
IO - elevation
93
What is the tertiary action of SR, IR, SO ,I O?
SR - intorsion
IR - Extorsion
SO - Abduction
IO - adduction
94
What is esotropia?
Convergent squint
95
What is exotropia?
Divergent squint
96
What is amblyopia?
Lazy eye
| Where brain supresses the image of one eye leading to poor vision in that eye
97
How is amblyopia treated?
With an eye patch to try and stimulate the lazy eye
98
What is diplopia?
Double vision
99
What are the intrinsic muscles of the eye?
Ciliaris muscle
Constrictor pupillae
Dilator pupillae
100
What is the ection of the cilaris muscle?
Muscles that contracts to make the lens thicker
101
Where is the constrictor pupillae found?
In the iris at the pupillary border
102
What is the action of the constrictor pupillae?
Constrict the pupil
103
Which part of the NS innervated the constrictor pupillae?
Parasympathetic
104
Where is the dilator pupillae found?
Radially running muscle in the iris
105
What is the action of dilator pupillae?
Works to dilate the pupils
106
What is the pupillary reaction to increased illumination?
- parasympathetic system innervated
| - both pupils constrict
107
What is the pupillary reaction to decreased illumination?
Sympathetic system innervated
| Both pupils dilate
108
How do you elicit the pupillary reflex?
Start in dimly lit room
Put pen torch in front of the eye
Both pupils should be dilated
109
Where is CN III nuclei located?
In the midbrain
110
Where do fibres destined to activate the pupillary reflex go?
Leave the optic tract and go to the midbrain where CN III nuclei is located
111
DO fibres destined to activate the pupillary reflex go to the LGB?
No
112
What are common causes of absent/abnormal pupillary reflex?
Any abnormality of the afferent, centre of efferent part of the reflex
Diseases of the retina
Diseases of the optic nerve
Diseases of CN III
113
Where is optic neuritis commonly seen?
MS
114
Which is the afferent limb of the pupillary reflex?
CN II
115
Which is the efferent limb of the pupillary reflex?
CN III
116
What is anisocria?
Pupils of different side
117
What is ptosis?
Drooping of the eyelid
118
Which segment of the NS has thoracolumbar outflow?
Sympathetic
119
What is horners syndrome?
Horner syndrome is a combination of signs and symptoms caused by the disruption of a nerve pathway from the brain to the face and eye on one side of the body.
120
What are the common symptoms of horners syndrome?
Typically, Horner syndrome results in a decreased pupil size, a drooping eyelid and decreased sweating on the affected side of your face.
