Eye 1 Flashcards
1
Q
Tears are produced by what
A
Lacrimal gland
2
Q
Tears gather in
A
Tear sac
3
Q
Tears exit through and reach
A
Tear duct and reach nasal cavity
4
Q
Describe how tears drain
A
Tears drain through 2 puncta, openings on medial lid margin.
Tears flow through superior and inferior canaliculli
5
Q
Tear film function
A
Maintains smooth cornea– air surface
O2 supply to cornea (as cornea has no blood vessels)
Removal of debris
Bactericide
6
Q
3 layers of tear film
A
1) Superficial oily layer
2) Aqueous tear film
3) Mucinous layer on corneal surface to maintain surface wetting
7
Q
Functions of each of the layers
A
Superficial oily layer -reduce tear film evaporation Aq tear film -Tear gland Mucinous Layer -On corneal surface to maintain surface wetting
8
Q
Describe appearance Conjunctiva
A
Thin transparent tissue
Covers outer surface of eye
Covers visible part of eye and lies inside of eyelids
Nourished by tiny blood vessels
9
Q
What is the average anterior-posterior diameter of the orbit?
A
24mm
10
Q
Which bit of eye is responsible for 2/3rd of focusing power
A
Cornea
11
Q
3 layers of eye?
A
Sclera
Choroid
Retina
12
Q
Describe these layers
A
Sclera
- Hard and opaque
- High h2o cont
- Protective outer coat
Choroid
-Pigmented and vascular
Retina
-Neurosensory tissue
13
Q
Describe appearance of cornea
A
- Transparent, dome shaped (convex)
- Front of eye
- Continuous w sclera
- Low water content
14
Q
Function of cornea
A
Powerful retracting surface
Physical barrier
Infection barrier
15
Q
5 layers of cornea
A
Epithelium Bowman's membrane Stroma Descemet's membrane Endothelium
16
Q
Function of stroma
A
Regularity of stroma contributes towards transparency
Corneal nerve endings (cornea has no blood vessels)
17
Q
Function of Endothelium
A
Pumps fluid out of endothelial cell
No regen power
Dysfunction may result in corneal oedema and corneal cloudiness
18
Q
Appearance of cornea when hydrated
A
Turns white
19
Q
Uvea function and location
A
Vascular coat of eyeball
Lies between sclera and retina
20
Q
3 part of uvea
What happens when one part is diseased
A
Iris
Ciliary body
Choroid
21
Q
Location of choroid
A
Between retina and sclera – part of uvea
22
Q
Choroid composed of
A
Blood vessel layers that nourish back of eye
23
Q
Part of eye that does’nt have blood vessels or nerves
A
Cornea
24
Q
Part of eye with refactive power of remaining 2/3
A
Lens
25
Iris function
| where
Controls light levels
Embedded w tiny muscles that dilate and constrict w pupil size
26
Lens appearance
Outer acellular capsule
27
Function of lens
Regulate inner elongated cell fibres -- transparency
Refractive power
Accomodation-elasticity
28
Lens zonules appearance
| -consists of?
lens suspended by fibrous ring
| --> passive connective tissue
29
Retina
Structure
Function
Thin layer of tissue that lines inner part of eye
Capture light rays
Light impulses sent to brain for processing via optic nerve
30
Optic nerve
Function
Connects to eye near which structure
Visible part of optic nerve
Transmits nerve impulses from retina to brain
Connects to back of eye near macula
Optic disc
31
Structure in middle of retina, temporal to optic nerve
Macula
32
Function of macula
Small and highly sensitive part of retina responsible for detailed central vision
33
Fovea located where
Pit located at centre of macula
Macula located on retina, fovea located on macula
34
Anterior and posterior segments of eye separated by?
Lens
35
Anterior chamber
located where?
Contains?
Between cornea and lens
| Filled w aq fluid -- supplies nutrients
36
Ciliary body produces
Aq humour
37
Where is aq humour produced and where does it run into
Produced from ciliary bodies runs into anterior chamber
80% into canal of schlemm
20% into uveal scelal outflow
38
Glaucoma
Progressive death of what cell
Loss of what tissue
What happens to visual field
associated with progressive retinal ganglion cell death,
| loss of nerve fibres and visual field loss
39
Glaucoma
Optic neuropathy w characteristic structural damage to the optic nerve, associated with progressive retinal ganglion cell death,
loss of nerve fibres and visual field loss
40
Glaucoma
| Features of concern
Raised intraocular pressure
Retinal gang cell death
Enlarged optic disc cupping
41
2 types of glaucoma
Primary open angle glaucoma
| Closed angle glaucoma
42
Describe the 2 types and affect they have on trabecular meshwork
Primary open angle glaucoma
- (Left) commonest
- Trabecular meshwork dysfunction
Closed angle glaucoma
- Can be acute or chronic
- Increased pressure pushing the iris/lens complex forward.
- Blocks the trabecular meshwork
43
Risk factor of glaucoma
Small eyes-hypermetropia
| -Narrow angle at trabecular meshwork
44
How might someone with glaucoma present
Sudden painful red eye, w acute drop in vision
45
How can glaucoma be treated
W peripheral laser irditomy to create a drainage hole on the iris
46
Define optic nerve blindspot
Where optic nerve meets retina
| -there are no light sensitive cells- blind spot
47
Most sensitive part of retina and how
Fovea (centre of macula thats located on retina)
Highest conc of cones and low rods
-- Peripheral vision
48
Corresponding anatomic landmark for physiological blind spot
Optic disc
49
Which type of vision is responsible day vision Vv
Central vision
| night -Peripheral vision
50
How can Central vision be assessed
Visual acuity assessment
51
How can peripheral vision be assesssed
visual field assessment
52
Central vision responsible for?
Colour vision fovea, reading, facial recognition
53
Peripheral vision responsible for?
Shape, movement
54
Retinal structure
| 3 layers and function
```
Outer
-1st order neuron- detection of light
Middle
-2nd order neuron- local signal processing to improve contrast sensitivity, regulate sensitivity
Inner
-Retinal ganglion cells
-3rd order neruon
-Transmission of signal from eye to brain
```
55
Approximately how many rods and cones
120 million rods
| 6 million cones
56
Macula diameter
6mm
57
How long does it take for cone to adapt
7 mins
58
How long does it take for rod to adapt
```
30 mins (more rods as well)
regeneration of rhodopsin
```
59
Macula Lutea appearance
Yellow patch
60
Macula in retina appearance
a pigmented region
61
Why does fovea form a pit
Due to absence of overlying gang cell layer
62
Which part of eye has highest conc of photoreceptors,what can it clinically be assess with
Fovea
OCT scan
63
Where are photoreceptors located
In retina
| Rod and cone
64
Which photoreceptor is 100x more sensitive to light
Rod photoceptors
65
What are their responses to light like
Slow
66
What photoreceptors are responsible for night vision (scotopic)
Rod photoreceptors
67
Where is the highest conc or rod photoreceptors
20-40 degrees away from fovea
68
Test for colour perception
| what colour deficiencies do they test for
Ishihara test
| Green and red
69
Dark adaption how many phases
biphasic
70
Commonest form of colour vision deficiency in hujahs
Red green confusion
| therefore ishihara test
71
2 types of lens
Converging diverging lens
72
Shape of converging and shape of diverging lens
function
Convex
Concave
Converging lens- take light rays and bring them to a point
Diverging lens-take light ray and spread outward
73
what sits in the limbus
corneal stemcell
74
Emmetropia
perfect focusing ability
75
Ametropi
Category of condition where light rays don't fall on retina
76
Near sightedness
Myopia
77
Farsightedness
Hyperopia
78
Parallel rays converging at focal point posterior to retina leads to
Hyperopia
79
Excessive short glove (axial hyperopia) can lead to
Hyperopia
80
Insufferable refractive pwoer -- refractive hyperopia lead to
Hyperopia
81
Asthenopic symptoms
Eyepain, headachein fronal region-- where eyes are, burning sensation in eyes,
blepharoconjunctivities --asthenopic symptoms- tired eyes
82
Condition in which parallel rays come to focus in 2 focal lines rather than a single focal point
Astigmatism
83
Response triad is an adaption for?
Near vision
84
Near response triad consists of and function
```
Pupillary Miosis (Sphincter
Pupillae) to increase depth
of field
– Convergence (medial recti
from both eyes) to align
both eyes towards a near
object
– Accommodation (Circular
Ciliary Muscle) to increase
the refractive power of
lens for near vision
```
85
cause of astigmatism
Cause : refractive media is not spherical-->refract differently
along one meridian than along meridian perpendicular to it--
>2 focal points ( punctiform object is represent as 2 sharply
defined lines)
86
Symptoms and treatment of astigmatism
Astigmatism
• Symptoms
– asthenopic symptoms ( headache , eyepain)
– blurred vision
– distortion of vision
– head tilting and turning
• Treatment
– Regular astigmatism :cylinder lenses with or
without spherical lenses(convex or concave), Sx
– Irregular astigmatism : rigid CL , surgery
87
Presbyopia
• Naturally occurring loss
of accommodation
(focus for near objects)
age 40 upwards
long distance fine
reading glasses
88
Accommodation Mechanism
```
Contraction of the Circular
Ciliary Muscle inside the
Ciliary Body
– This relaxes the zonulesthat
are normally stretched
between the ciliary body
attachment and the lens
capsule attachment
– Note that zonules are passive
elastic bands with no active
contractile muscle
– In the absence of zonular
tension, the lens returns to
its natural convex shape due
to its innate elasticity
– This increases the refractive
power of the lens
• Mediated by the efferent
Third Cranial Nerve
```
89
Accomodation is mediated by which cranial nerve?
3rd
90
```
• In accommodation,
which one of the
following events does
not take place?
– A) Relaxation of Circular
Ciliary Muscle
– B) Relaxation of Zonules
– C) Thickening of Lens
– D) Increase of Lens
Refractive Power
```
– A) Relaxation of Circular
| Ciliary Muscle
91
Intracollamer lens (ICL) can be used for which conditions
Astigmatism and myopia
