Ophthamology Flashcards
What is the technical term for the eyeball?
The globe
What is the technical term for the eye socket?
The orbit
What is the technical term for everything except the globe?
The adnexa
What are the components of the anterior segment of the eye?
The cornea, anterior chamber, iris, iridocorneal angle, ciliary body, and lens
What are components of the posterior segment?
Choroid, retina, optic nerve, posterior sclera, vitreous humor
What are the 4 recuts muscles of the eye
Ventral rectus, dorsal rectus, medial rectus, and lateral rectus
What are the oblique muscles of the eye?
Dorsal/superior oblique and ventral/inferior oblique
Which muscle pulls the eye back?
Retractor bulbi muscle
What is the mucous membrane that lines the inside of the eyelid?
Palpebral Conjunctiva
What muscle elevates the upper eyelid?
What muscles closes upper and lower eyelid?
Levator palpebrae superioris
Orbicularis oculi
What is the sebaceous gland at the tip of the eyelid?
Meibomian glands
What are the components of the eyelid?
Palpebral conjunctiva, meibomian gland, tarsus, levator palpebrae superioris, and obicularis oculi
What does the meibomian gland do? And where does it open at?
Secretes lipid layer of tear film and it opens at the mucocutaneous junction
What is the collagen sheet in the eyelid?
The tarsus which gives the eye rigidity and provides a place for muscle attachment
What is the innervation of the eyelid?
V - Sensory
III and VII - Motor
Autonomic - Sympathetic nerve
What nerve innervates levator palpebrae superioris
CN III
What nerve innervates orbicularis oculi?
CN VII
What is the muscle that lowers the inferior eyelid?
Malaris Muscle
What is the Malaris muscle innervated by?
CN VII
What is the autonomic muscle of the eyelid?
Mueller’s Muscle
What does Mueller’s muscle do?
A smooth muscle that provides tone to the tarsus
What are the 2 ligaments of the eye?
The Medial and lateral canthal ligaments
What is the purpose of the canthal ligaments?
Anchor the medial and lateral canthus to periosteum of the orbital rim
What is the conjunctive?
The conjunctiva is a mobile, elastic mucous membrane
What the histological characteristics of the conjunctiva?
Non-keratinized stratified squamous epithelium + goblet cells
What is the nicitans?
Aka “third eyelid”
Triangular piece of tissue in the medial fornix
Where is the ventral fornix
At the crypt between the nictitans and the cornea
What does the nictitating membrane do?
Moves dorsolaterally
Spreads tear film across the eye, protects the globe, and removes particles from the surface
What are the components of the nictitating membrane?
Gland of the nictitans
T shaped cartilage that acts as squeegee
orbital lacrimal gland
What is the backside of the nictitans called?
The bulbar surface
What does the lacrimal apparatus do?
Produce, distribute, and drain the pre-corneal tear film
What are the layers of the pre-corneal tear film (PTF)?
Fluid Layer-> Lipid layer -> aqueous layer (thickest) -> Mucin layer
What gland produces each of the layers?
Lipid Layer: Meibomian gland
Aqueous layer: Lacrimal gland
Mucin layer: Goblet cells
What is the outflow apparatus and its parts?
The lacrimal outflow apparatus
Ocular puncta (drainage holes)
Canaliculi
Lacrimal sac
Nasolacrimal duct
Nasal puncta
What are the 3 concentric tunics of the globe?
Fibrous
Vascular
Nervous
What are the structures within the fibrous tunic?
Cornea
Sclera
What are the structures within the vascular tunic?
Choroid, ciliary bodies, iris
What are the structures within the nervous tunic?
Retina
optic nerve
Where and what is the sensory innervation of the cornea?
In the superficial 1/3 by the trigeminal nerve (V)
What are the 4 layers of the cornea?
Epithelium
Stroma (biggest)
Descemet’s membrane
Endothelium
What special structure is on the corneal epithelium and what is their purpose
Microvilli which helps to stabilize the tear film
What is the turnover rate of the corneal epithelial cells?
7 days
What percent water is the corneal stroma?
78%
Is the cornea hydrophobic or hydrophilic?
Hydrophilic, a break in epithelium will cause edema
What does ulceration of the corneal epithelium cause?
Focal corneal edema
What does damage to corneal endothelium cause?
Diffuse corneal edema
What is the endothelium’s function?
Pumps fluid out of the cornea to maintain deturgescence
What is the limbus?
Corneal-Scleral Junction, where the sclera joins cornea
This is the zone of transition to regularly arranged collagen of the cornea
Roughly what structures of the conjunctiva are around the limbus?
The bulbar conjunctiva
What collagen structure supports the axons of the optic nerve
The lamina cribosa
What is another term for the vascular tunic?
Uvea
What is the junction of iris base to inside of the cornea
the iridocorneal angle?
How does the iridocorneal junction attach?
What does it do?
Via pectinate ligaments
It is the sight of aqueous humor drainage through trabecular network
What are the components to the ciliary body?
Pars plicata = ciliary processes
Pars plana = flat portion where retina inserts
What does the smooth muscle of the ciliary body do?
Involved in accommodation (fine focusing) of the lens
What produces aqueous humor?
The non-pigmented cells of the ciliary body
Where does aqueous humor flow out of into the anterior chamber
Pupil
What is glaucoma caused by?
Blockage of the iridocorneal angle so aqueous humor cannot escape, thus increasing ocular pressure
What is the process of lens fiber formation?
Equatorial epithelial cells proliferate and elongate, this pushes cells inward and eventually, they lose their nucleus
What are the anterior and posterior sutures?
This is the formation of a Y and upside down Y respectively formed from lens cell growth
Which part of the lens capsule is the thinnest?
Posterior capsule
What is the function of the choroid?
Underlies and provides vascular support of the retina
What is the main purpose of vascularization of the choroid?
Thermal regulation
What is the tapetum part of?
It is part of the choroid and is the top layer of the choroid
What two layers of the sensory retina are we required to know?
Ganglion cell layer
Photoreceptor layer
What interaction occurs between the photoreceptor layer and the ganglion layer?
The photoreceptors send signaling up to retinal ganglion cells which is then transmitted to the optic nerve
What is CN 2 and what role does it play in the globe?
It is the optic nerve which is at the posterior end of the eye and is made up of retinal axons
What would a complete lesion of the optic nerve do?
It would causes blindness, dilated pupil, and absent PLR
What is CN3 and what does it do in the globe?
CN3 is oculomotor nerve and provides parasympathetic fibers to pupil, innervates levator palpebrae superioris, and provides motor fivers to all extraocular muscles except Lateral rectus, retractor bulbi, and superior/dorsal oblique (LRS)
What extraocular muscles are not innervated by CN3 (oculomotor nerve)
(LRS)3
Lateral rectus = 6
Retractor bulbi muscle = 6
Superior/dorsal oblique = 4
What would a lesion in CN 3 cause?
droopy top eyelid, dilated pupil
What is CN4 and what does it do in the globe?
Trochlear nerve that innervates the superior oblique
What is CN5 and what are the 3 branches?
Trigeminal nerve that has 3 branches, afferent
1. Ophthalmic branch
2. Maxillary branch
3. Mandibular branch
What does the ophthalmic branch of the trigeminal nerve do?
Sensory fibers from cornea, conjunctiva, and superior eyelid
What does the maxillary branch of the trigeminal nerve do on the globe?
Sensory to skin of lower eyelid
What does the mandibular branch of the trigeminal nerve do on the globe?
Motor to muscles of mastication (atrophy results in sunken eye)
What is CN6 and what does it do in the globe?
Abducens nerve provides motor to lateral rectus and retractor bulbi
What is CN7 and what does it do in the globe?
Facial nerve, efferent, and it provides motor to muscles of facial expression: closure to eyelids (orbicularis oculi) IT ALSO carries parasympathetic fibers to lacrimal gland
What is CN8 and what does it do with the globe?
Vestibular nerve, afferent, it controls extraocular muscle positions so that eyes can remain fixed on an object while the head turns. Causes eye drop
What is CN10 and what does it do with the globe?
Vagus nerve, efferent arm of the oculocardiac reflex (not really sure what that means but its in here)
What is the order of the 3 neuron pathway in sympathetic fibers?
First neuron: midbrain to T1-T3
Second neuron: thorax / neck
Third neuron: cranial cervical ganglion to eye
What is damage (anywhere) along the sympathetic fibers called?
Horner’s syndrome (not painful)
What would a lesion of the parasympathetic pupillary fibers cause?
Dilated pupils
What would a lesion in the parasympathetic lacrimal gland fibers cause and how would it be measured?
Decreased tear production and tested with Schirmer tear test
What is the palpebral / blink test?
Tests CN5 and CN7 by tapping around eye
What is the corneal reflex test?
Tests CN5, 6, and 7 by touching cotton to cornea, should pull eye and 3rd eyelid back
What is the pupil light reflex (PLR)
Testing the pupillary reflex, both eyes should contract
What is the swinging flashlight test?
Shine into one eye then rapidly move over to the other eye, both eyes should remain constricted
What is the dazzle reflex?
Indicated light perception, not vision. Normal response is squinting, less than 5% of retinal function is required
What is the difference between monocular and binocular vision?
Binocular: Medial visual field
Monocular: Lateral visual field
What is the menace response?
Afferent: retina and ON
Efferent: CN7 and muscles of head and neck
Pushing closed fist toward eyeball and look for either an avoidance or blink
What is the cotton ball test?
Cover 1 eye and drop cotton balls in front of eye and watch for tracking
What is the Maze test
Set up a maze in dim and bright light and assess navigation through course
What is visual placing?
You hold an animal up near a surface and check if the animal responds (reaching out to a table)
What is the outline of the vision pathway?
Optical>Photochemical>Neurologic
What is decussation?
Crossing of the optical nerves at the chiasm. This is where the monocular vision will cross
What are the medial fibers of the optic nerve?
Medial fibers are the fibers on the medial side of the eye, they absorb the lateral photons!
What is the vision pathway?
Retins>optic nerve>chiasm>LATERAL GENICULATE NUCLEUS (LGN)>Optical radiations>visual cortex
What is the lateral geniculate nucleus?
LGN is the part of the brain where both the lateral and medial fibers come back together to be spread amongst the brain via optic radiations
Where do fibers from the afferent system go to begin efferent response in the cerebrum
To the pretectal nucleus
Where do the efferent fibers originate within the cerebrum and go from there?
The Edinger Westfal nucleus > ciliary ganglion > iris sphincter
What is different between the vision and pupillary light reflex (PLR) pathway?
They are the same until right before the lateral geniculate nucleus at this point the PLR pathway breaks off and goes to the pretectal nucleus where it DECUSSATES again and synapses on the edinger westphal nucleus
What is the efferent arm of the PLR pathway responsible for?
Pupillary light reflex
How would blindness occur with normal PLR?
The PLR pathway leaves the visual pathway slightly before the Lateral geniculate nucleus so a lesion may be present in LGN, optical radiations, or the visual cortex
Where do you start with an eye exam?
Start from a distance, observe behavior (eyelid position and blinking)
What are the next steps after distance approach to an optical exam?
Menace response, palpebral reflex, PLR, and dazzle reflex
How do you assess the anterior chamber and what are you looking for?
With a bright focal light and you are looking for opacity that would allude to proteins in the aqueous humor
What is the fundic exam? What is the orientation of the image?
Helps to see more of the eye (less magnified)
Be at arms length away in a dim room and at eye level
It will be upside down, backwards, and at a low magnification
Which species do the vessels cross over the eye, which does not?
Dog: Crosses over
Cat: Does not
What are the two main reasons that most animals see better at night?
Tapetum
Rod dominant
How many rods and cones are responsible for one ganglion?
1500 rods
1 cone
What are some animals without a tapetum?
Camelid, pig, bird, squirrel, primates
What are the two major factors of visual acuity?
Well-focused image (optical factors) - refractive error caused by improperly focusing image
Makeup of the retina (retinal factors) - high level of rods
What are the 4 groups of refractive error?
Emmetropia (normal)
Myopia (near-sighted)
Hyperopia (far-sighted)
Astigmatisms (refractive error in specific quadrants)
What is refractive error measured in?
Diopters
What is emmetropia for a dog?
about 20/70 (bad vision)
