Eye Flashcards
(187 cards)
1
Q
What is the scientific name for the third eyelid
A
Nicitaris gland
2
Q
What is the function of the mebomian glands
A
To create lipids that form part of the tear film
3
Q
What does the levator palbebrae superioris do
A
Keeps upper eyelid elevated
4
Q
What does the orbicularis oculi do?
A
Muscle to close eyelid
5
Q
What is the function of the lacrimal punta
A
Releases tears
6
Q
What is the limbus of the eye
A
Zone between the iris and the sclera
7
Q
What is the sclera of the eye
A
White of the eye that helps maintain shape of the eye
8
Q
What is the lateral canthus of the eye
A
Corner of eye on lateral part of face
9
Q
What is the medial canthus of the eye
A
Corner of eye in middle of the face
10
Q
What is the fundus of the eye
A
Back part of the inside of the eye
11
Q
What is the function of the tapetal fundus
A
Reflects light hack the retina so in low light conditions better vision
12
Q
What is in the fundus
A
Retina
Fovea
Choroid
Optic disk
Blood vessels
13
Q
What is the function of the choroid and where is it
A
Forms vascular layer of eye (dense supply of blood vessels)
between sclera and retina
Provides o2 and nutrients to retina
14
Q
What is exophthalmos and what does the globe look like
A
Abnormal production of eye from orbit
Globe is a normal size but protruding
15
Q
What is enophthalmos and what does the globe look like
A
Abnormal recession of the eye within the orbit
Normal size/ appearance of eye but sunken
16
Q
What is hydrophthalmos and what does the globe look like
A
Enlargement of the globe and its producing, so globe looks abnormal
17
Q
What is microphthalmos and what does the globe look like
A
Congenitally (at birth) abnormal small eye
Normal position of eye within the socket
18
Q
What is the function of the orbit
A
It’s the cavity within the skull that encloses the eye
Protects the eye and separates eye from cranial cavity (brain)
Contains Foramina within walls to provide a pathway for blood vessels and nerves to reach eye
19
Q
What is the orbit like within domestic species
A
Bone come with soft tissue floor
20
Q
What is the orbit type for a herbivore
A
Closed/ complete
21
Q
What is the orbit type for a carnivore
A
Open/ incomplete
22
Q
What is the composition of the lateral wall in the orbit of the herbivore
A
Bone
Zygomatic and frontal bones are fused
23
Q
What is the composition of the lateral wall in the orbit of the carnivore
A
Soft tissue
Lateral orbital ligament
24
Q
What is the visual field like for herbivores and why
A
Wider monocular
Narrower degree of binocular (3D vision)
Eyes are on the side of the head
It’s easier to see predators coming
25
What is the visual field like for carnivores and why
Narrower monocular
Wider degree of binocular vision (3D)
Gives a greater depth perception to allow animal to be able to have greater accuracy before the jump to catch peey
26
Why do carnivores have an open/ incomplete
To be able to open jaw wider
27
What is brachycephakic breeds like
Shorter nose and flat faced
Shallow orbit and minimal protection
28
What are mesocephalic dogs like
Head of medium proportions
Medium depth orbit and medium protection
29
What are Dolicocephalic dogs like
Relatively long head
Deeper eye sockets and greater degree of protection offered
30
How many bones make up the orbit
5-7 depending on species
31
What makes up the medial limit of the bonds orbit and what is the function
Frontal bone
Separates orbit from nasal cavity
32
What bone is on the dorsal limit of the bony orbit
Frontal bone (frontal sinus)
33
What bones are on the rostral and lateral limits of the bony orbit
Zygomatic
Lacrimal
Maxillary bones
34
What bones make up the caudal limit of the bony orbit
Sphenoid bone
35
What is the function of the sphenoid bone
Optic canal and orbital fissure pass through here
36
What soft tissue is on the ventral floor of the orbit
Pterygold muscles
37
What is on the dorsolateral limit of the soft tissue or it
Temporal muscle
Orbital ligament
38
What is on the rostral and lateral limits of the orbit
Masseter muscle
39
What goes through the optic foramen
Optic nerve
40
What goes through the orbital fissure
Opthalmic nerve
Trochlear nerve
Abductees nerve
Oxulamotor nerve
Internal opthalmic artery
41
What muscles does the oculomotor nerve innervate
Dorsal rectus
Medial rectus
Ventral rectus
Ventral oblique
42
What muscles does the abductens nerve innervate
Lateral rectus
Retractor bulbi
43
What does the trochlear nerve innervate
Dorsal oblique
44
What is the intraconal space
Within space defined by four rectus muscles and periorbital fascia sheath
Shaped like an ice cream cone
45
What structures are within the intraconal space
Optic nerve and nerves supplying muscles around eye
Vesssels
Smooth muscles
Fat
Orbital lacrimal gland
46
What provides blood to the eye
The ophthalmic artery, which is derived from the internal carotid artery
47
What is the venous drainage of the eye
Through vortex veins and orbital venous veins
Can go through ophthalmic vein
Eventually all drains into the external jugular vein
48
What is anisocoria
Unequal pupil size
49
What is miosis
Excessive constriction of pupil
50
What is mydriasis
Dilation of the pupil
51
What is strabismus
Abnormal alignment of the eye
52
What is nystagmus
Rapid involuntary eye movement
53
Why do animals often stop eating with eye pain
Because the ramus (jaw bone) moves towards the glove when the mouth is opened
54
What is the vitreous humour and its function
Clear gel that fills the space between the lens and the retina of the eyes
Shock absorber
Removes waste products
Maintains intraconal anatomy
55
What did the lens develop from
The surface ectoderm,
Then invaginates, which forms lens vesicle and optic cup
56
What supports the lens
The lens zonules
57
What does the lens sit in
Hyaloid fossa
58
What supports the iris anteriorly
Lens
59
Which side of the lens capsule is thicker and why
Front lens becomes thicker as anterior lens epithelium secretes lens capsule
60
What are lens fibres like
Have thick centres and tapered ends
Meet in a Y shaped pattern, they can’t meet in a single point as not enough space
61
How does the lens age/ grow
Concentric growth
New lens fibres form from anterior epithelium and lens equator and wrap around embryonic nucleus
62
How do older fibres compare to younger fibres
Denser and less transparent
63
How does the fetus lens get nutrition
Via the tunica vasculosa lentils
(Blood vessels like hyaloid artery)
64
Why does the adult lens have no blood supply or nerves
It would obstruct vision
65
How does adult lens get nutrition
Aqueous humour
66
What would cause a cataract to develop in eye
If any amount or type of protein to change in lens
67
What is the lens composed of
35% protein
65% water
68
What is the function of the lens
1/3 refractive power of eye
Accommodation (more in birds than herbivores_
Blocks UV light from retina
69
What is the vitreous humour made from
99% water
1% protein/ cells
70
What is persistent pupillary membranes
Failure of regression of anterior portion of the tunica vasculosa lentils
71
What is the oldest part of the lens
Nucleus
72
What is nuclear sclerosis
Eyes appear greyish blue as animal ages, older fibres are denser and less transparent than younger fibres of lens
73
How would you exam for a nuclear sclerosis
Distant direct ophthalmoscopy
Look at tapetal reflection
74
What is a cataract
Any opacity of lens or its capsule
75
What are the 5 main causes of cataracts
Trauma
Metabolic (diabetes)
Other introduce disease
Hereditary (inherited)
Senile (old age)
76
What are the 4 types of classification for cataracts
Age
Aetiology (cause)
Position
Extent
77
How does diabetes cause cataract
If not enough enzyme hexokinase (which converts glucose to glucose 6 phosphate) then glucose is converted to sorbitol
Sorbitol causes water to be absorbed into lens and lens fibres smell and then white
78
What further implications can cataracts cause
1. Vision problems
2. Problems on ocular health like lens induced uveitis (when proteins break out of lens and eye reacts as not used to those
79
What structure is attached to the lens equatot to hold it into position
Lens zonules
80
What is lens subluxstiom
When the lens falls out of place, usually due to trauma, can be forwards or back
81
What is the problem of an anterior lens lucation
Lens blocks the flow of the aqueous humour
Pressure inside eye increases rapidly to cause an acute secondary glaucoma
82
What are the 3 layers of the eyelid
Haired eyelid skin on the outer surface
Muscles containing meibomian glands
Palpebral conjunctiva
83
What is the palpebral fissure
The opening between the eyelids
84
What muscle controls eyelid closing and what innervates it
Orbicularis oculi
Facial nerve
85
What muscles control eye,id opening and what innervates them
Levator palpebrae superioris (oculomotor nerve)
Muller muscle (sympathetic innervation)
Facial nerve innervates other muscles
86
What nerves give sensation to the eyelid
Branches of opthamalic and maxillary nerve from trigeminal
87
How many meibomian glands are there per eyelid
20-40
88
What do the meibomian glands produce
Meibum (lipid part of tear film)
89
What is the function of eyelids
Protects eye from gray mace
Distributes and drains tears (hydration and nutrition to ocular surface)
Removes debris from ocular surface
90
What is the anatomy of the third eyelid like
Central shaped t cartilage
Conjunctiva covering bulbs and palpebral surface
Nicititajs gland at base
91
What is the function of the nictitans gland
Produces tear film
Protects ocular surface
Distributes tear film
Contains immunologic secreting plasma cells
92
What blood vessels in eye can you normally see
Conjunctival vessels
93
What blood vessels in eye should you be concerned if you see
Episcleral vessels (as they as deeper and only usually seen during inflammation0
94
What is the function of the conjunctiva
Protects ocular surface
Goblet cells produce mucin for tear film
Many lymphocytes present
95
How does the tear drainage system work via the nasolacrimal system
Tears drain via upper and lower lacrimal puncta
Then into lacrimal canniculu and lacrimal sac
Then into nasolacrimal duct and out nose
96
How should an examination of the eyelids work
Check for blepharospasm (ocular pain) and eyelid conformatiom
Check blinking
Look for masses, extra eyelids. Swellings
Tear staining to check for extra tears productiom
97
What is entropian
Inward turning of parts or all of the eyelid
98
What is extropian
Diversion or outward turning of the eyelid
99
What is distichiasis
Extra eyelashes emerging from meibomian glands
100
What is ectopic cilia
Cilia arising from near or inside meibomian gland, through conjunctival surface of the eye
101
What is trichiasis
Hair located in the right place but facing wrong way towards ocular surfaces
102
What are the three layers of the eye
1. Fibrous outer layer (sclera and cornea)
2. Vascularised Middle layer (uveal tract)
3. Neuroectodermal inside layer (retina and optic nerve)
103
How thick is the tear film
7-8um
104
What are the four components of tear film
L- lipid- limits evaporation
A-aqueous- most of volume
M- mucin- aids spread and adherence of tear film
E- epithelium
105
What produces the aqueous layer of the tear film that
Orbital gland- 70%
Nicitans gland- 30%
106
What is the function of the tear film
Provides nutrients and oxygen to ocular surface
Provides smooth and transparent surface
Protects ocular surface from bacteria
Lubriavtes ocular surface
107
What are the 3 layers of the sclera
Lamina fusca
Sclera stroma
Episclera
108
What covers the anterior portion of the sclera
Bulbar conjunctiva
109
What is the limbus and its function
Where cornea, sclera and bulbar conjunctiva merge
Source of stem cells
110
What is Tenon’s capsule
Connective tissue sheath
Connects bulbar conjunctiva to underlying sclera
111
What is the episclera
Dense highly vascularised layer
Blends with tenons capsule
112
How thick is the cornea
0.5-0.8mm
113
What are the 3 layers of the cornea
Epithelium
Stroma
Endothelium
114
What is the structure/ function of the epithelium level
Stratified squamous epithelium
5-7 cell layers in dogs
12-15 cell layers in horses
Tight junctions between cells act as a permeability barrier, water can’t get into the stroma
115
What is th4 stroma of the cornea like
90% of corneal thickness
Regular layers of collagen
116
What is the corneal endothelium like
One cell thick layer
NA/K+ pump ions frok stroma into aqueous humour
117
What keeps the cornea transparent
Smooth optical surface
Regular arrangement of collagen fibres
Ow cell density
No blood vessels/ nerves
Dehydrated
118
What is th4 function of the cornea
Refract and transmits the light
Protection (chemical barrier )
Tensile strength
119
How can you examine tear film
Corneal reflection
Schimear test
120
How can you examine the cornea
Darkened room
Look for irregularities, opacificarion, vascularisation, pigmentation
Can use fluroscean stainign
121
How does fluroscein staining work
Orange dye that turns green in alkaline tears
Ahears to hydrophilic tissues such as exposed stroma
Can diagnose corneal ulcers
122
What is the fancy name for dry eye
Keratoconjunctivitis
123
How can you diagnose keratoconjunctivitis
STT less than 15mm/min
Corneal ulceration/ vascularisation
124
What is an ulcer
A discontinuation or break in the membrane
125
What is a corneal ulcer
break in continuity of corneal epithelium with exposure of underlying stroma
126
What can cause corneal ulcers
Trauma
Eyelid abnormalities
Eyelash lesions
Degenerations
Infections
127
What are the three types of ulcers
Superficial ulcer
Stroma ulcer
Descenmetaote
128
What are desmetaceole ulcers
Ulcers that go down to descements membrane
Flurocien stain isn’t taken up at DM
129
How is the cornea regenerated
Basal epithelial cells at limbus
130
How is an epithelial wound healed
Cell proliferation, migration and adhesion
Faster if basement membrane remains intac
131
How is stroma wound healed
Starts once re-epithelialisation is complete
Fibroblasts migrate in & lay down new collagen
Requires vascularisation
Results in scar tissue: remodelling over time
132
What could a blue cornea be a sign of
Oedema
133
What could a red cornea be a sign of
Vascularisation
134
What could a black cornea be a sign of
Pigment
135
What could a white cornea be a sign of
Scarring, lipid, calcium,
136
What are the 3 components of the uveal tract from front to back
Iris
Cilary body
Ciliary body
137
What is the cilary zone of the iris
The peripheral part of the iris
138
What is the pupillary zone
The centre part of the iris
139
What is the transition part of iris (between the ciliary and pupillary zone)
Collarette zone
140
What is the blood supply to the iris like
Incomplete artieriole circle
Anterior and posterior cilary arteries
Blood vessels come in at 3 and 9 o clock
141
What is the anatomy of the iris like
Stroma:
Made of fibrous collagen bundles
Pigmented and non pigmented sections
Blood vessels
Iris sphincter muscle (iris constrictir)
Front: MOT epithelium, (stroma border layer)
Back: epithelium level
142
What are the masses seen on the eye of horses/ ruminants called
Corpora migrant (horses)
Granula indica (ruminants)
143
What is the function of the iris
Controls the amount of light that enters the eye
When Irma part of blood ocular layer
144
What is the cilary body comprised of
Smooth muscle
Connective tissue
Blood vessels
Nerves
Double epithelium layer
145
What are pars plicata?
Folded part of cilary processes
146
What is the para plana
Flat part of ciliary body
147
What are zonular fibres
Supports the lens and keeps it in the middle of the pupil
Originates within the tips and valleys of ciliary processes
148
What is the function of the ciliary body
Production and drainage of aqueous humour
Anchors lens zonules and provides accommodation by changing shape of the lens
Blood aqueous layer
149
What processes allow aqueous humour to be produced
Diffusion
Ultrafiltration
Active secretion
150
What is the function of aqueous humour
Supplies nutrients and remove waste from avascular parts of eye (cornea, trabecular network, lens, anterior vitreous)
151
What is the aqueous humour made from
98% water
Protein, lactate, glucose, amino acids
152
What is the function of the choroid
Blood supply for retina
Blood- ocular barrier
Includes the tactum
153
What ensures the blood ocular barrier
Tight junctions between epithelium cells
All blood vessels are non fenestrated
154
What are the mechanisms to allow ocular immune privilege
Blood-ocular barriers: limiting access to eye
Absence of lymphatic pathways: limiting access to lymphatic tissues
Aqueous humour composition: ascorbic acid and other anti-oxidants
Immunomodulatory ligands on intraocular cells (esp pigmented epithelial cells)
Indigenous, tolerance-promoting antigen-presenting cells
155
How many layers does the choroid have
5
156
How would you examine the anterior uvea
Dark room
PLR
Intraocular pressure
157
What are the clinical signs of uveitis
White blood cell migration
Increased blood supply
Increased permeability of vessels
Pain
Red eye
Miosis
Low intraocular pressure
158
What are secondary consequences of uveitis
Synechia (iris is sticky and things get attached to it)
Secondary glaucoma
Cataract
Retinal detachment, retinal degeneration, optic nerve atrophy
Vision loss
159
What could cause uveitis
Trauma
Infection
Immune mediated
Metabolic
Neoplasia
Idiopathic
160
What are some causes causes of secondsey glaucoma
Lens luxurious
Uveitis
Eoplasia
161
What are some signs of a glaucoma
Red eye
Pain
In ordeal oedema
Fixed dilated pupil
Vision loss
162
What is a normal IOP in animals
Dogs- 10-25mmHg
Rabbits- 15-20mmHg
Difference in more than 8 is abnormal
163
What are the three different devices to measure IOP
Schnitz tonimotry
Rebound tonometry
App,a nation tonometry
164
Where is the retina located
Neural layer
Outside the vitreous humour
Inside the choroid then sclera
165
How many layers do the retina have
10
166
What is the simplified version of the retina with the two layers
Neurosensoru layer
Retinal pigment epithelium,
167
What are the 4 main aspects of the neurosensory layer
Optic nerve fibres
Ganglion cells
Bipolar cells
Photoreceptors
168
What is the structure of the retinal pigmented epithelium like
Outmost single layer of cells in retina
Lies in front of the tapetum
Has pigmented and non pigmented areas
169
Where are the photosensory receptors
In the RPE
170
What is the function of the RPE
Recycling “used” photopigments
Phagocytosing and renewing photoreceptor outer segments
Storing vitamin A
Melanin pigments (non-tapetal i.e. pigmented areas only) absorb stray light and scavenge free radicals
Forming part of blood-retinal barrier
Phagocytic role in retinal inflammation
171
Where are the rods and cones
In the outer nuclear layer of the neurosensory layer
172
What are rods and cones
Specialised cells that transduce light energy into electrical signals
Cones- colour and visual acuity
Rods- night vision
173
How does phototransduction work
Light energy causes opsin to change shape and then binds to transducin, causes hyper polarisation and releases neurotransmitter
Travels to ganglion cells along nerve axons to optic nerve
174
What is the function of the retina
Absorbs light rays and converts light energy into electrical energy which travels as nerve impulse up optic nerve to visual cortex
175
What are the three regions of the optic nerve
Intraocular portion
Can be directly observed in vivo
Retrobulbar portion (in orbit)
Intracranial portion
176
Is optic nerve myelinated or not
Dog- yes
Cat- no
177
What is the fundus
the portion of the posterior segment of the eye that is viewed with the ophthalmoscope
178
What is the blood supply to the retina like
High metabolic rate: dual blood supply
Inner retina: retinal blood vessels
Outer retina: choroidal blood vessels
179
What is Holangiotic
retinal blood vessels supply whole retina e.g. dog, cat, cow, sheep, goat
180
What is Paurangiotic
retinal blood vessels supply a small focal area of retina e.g. horse
181
Why can tapetum be seen
Retina is translucent
182
What is tapetum and is]to function
Part of choroid behind retina
Shiny reflective layer
Reflects light rays to retina gets rays twice
183
What can vary in the fundus colour and why
Colours in choroid +/- tapetum and RPE vary according to coat and iris color
184
If the retina has thinned, would you expect the tapetum to appear more or less reflective on ophthalmoscopy?
Less
185
Where is the retima stromglu attached
Around the optic disc
Ora ciliaris retinae (peripheral retina
186
Where does detachment of the retina occur
between neurosensory retina and RPE
187
What are the main 6 causes of retina detachment
Systemic hypertension, e.g. geriatric cats
Congenital, e.g. collie eye anomaly (inherited retinal disease)
Trauma
Inflammation
Neoplasia
Complication of lens luxation or chronic cataract
