Ophthalmology Unit 1 Flashcards
What part does the prefix blepharo- refer to
Lids
What part does the prefix kerato- refer to
Cornea
What part does the prefix hyp- refer to
Anterior chamber
What part does the prefix phaco- refer to
Lens
What part does the prefix hya- refer to
Vitreous
What is redness of the conjunctiva called
Hyperemia
What is edema of the conjunctiva called
Chemosis
What type of animals have an open (incomplete) orbit, an orbit that is only partially surrounded by bone
Which animals have an enclosed orbit
Pigs and carnivores (dogs and cats) are open
Horses, oxen, sheep, cattle, and goats are closed
Which muscles that move the eye are innervated by ocular nerve III (oculomotor)
Dorsal rectus, medial rectus, ventral rectus, and ventral (interior) oblique
Which muscles that move the eye are innervated by cranial nerve VI (abducens)
Lateral rectus muscle and retractor oculi (bulbi) muscle
What muscle that moves the eye is innervated by cranial nerve IV (trochlear)
Dorsal (superior) oblique
Which muscles rotate the eye medial and lateral and which ones pull the eye dorsal and ventral
Rotates medial- medial rectus
Rotates lateral- lateral rectus
Pulls dorsal- dorsal rectus
Pulls ventral- ventral rectus
Which muscles pull the eye medial and lateral
The dorsal (superior) oblique pulls the eye medial and the ventral (inferiors) oblique pulls the eye lateral
What muscle is the only one to contribute to closure of the lid and what nerve controls it
Orbicularis oculi, cranial nerve VII (facial)
What muscle elevates the upper lid and what cranial nerve innervates it
Levator palpebral superioris, cranial nerve III (occulomotor)
What smooth muscle keeps the eyelids topically retracted
Muller’s muscle
What cranial nerves provide sensory input to the eyelids
Cranial nerve V (trigeminal) maxillary division for lateral lids and ophthalmic division for medial and ventral lids
T/F movement of the third eyelid is indirect
True
What is the conjunctiva lining the eyelids called? How about the conjunctiva covering the globe
Palpebral lines the eyelids and bulbar covers the globe
What is the junction or the blind sac of the palpebral and bulbar conjunctiva called (aka where there is a pocket created under the eyelids)
The fornix (cul de sac)
What are the three components of the precorneal tear film and the functions
Lipid- limits evaporation, serous- water part that moistens, mucous- keeps the tears on the eye
What feeds into the nasolacrimal duct
The lacrimal punctum which turns into the lacrimal canaliculus to enter the nasolacrimal duct
What glands form the lipid tear layer
The meiobomian gland and the glands of zeis
What glands form the serous layer of the tear film
The lacrimal gland and the gland of the third eyelid
What forms the mucous layer of the tear film
The goblet cells of the conjunctiva
What are the functions of the precorneal tear film
Maintaining an optically uniform surface, removing foreign material and debris, providing nourishment to the cornea, preventing infection
Which chamber is between the cornea and iris
The anterior chamber
Which chamber is between the iris and the lens
Posterior chamber
What makes up the anterior and posterior segments
The anterior segment is the front of the eye with the cornea, lens, iris, ciliary body, anterior and posterior chambers, etc.
The posterior segments contains the vitreous body in the vitreous chamber, the optic disk, retina, etc.
The globe is composed of what three layers and what is contained within these layers
Fibrous tunic- outer layer- cornea and sclera
Uvea- middle layer- iris, ciliary body, choroid
Nervous- inner layer/ central layer- retina and optic nerve
What is considered the internal media of the eye
Lens, aqueous, vitreous
Visually, the cornea is _____ when compared to the sclera which is _____
Visually, the cornea is transparent when compared to the sclera which is opaque
Name the layers of the cornea in order
Epithelium, basement membrane, bowman’s layer (in cows, primates, and birds), stroma, Descemet’s membrane (with a basal lamina/ basement membrane), and posterior epithelium (endothelium)
What makes up 90% of the cornea
The stroma
What is an important feature of the cornea in how it gets its nutrients
It is avascular so it must get its metabolic needs from tears, aqueous humor, and limbal capillaries
70% of refraction occurs where
In the cornea
What makes up the sclera
Elastic fibers and collagen fibers
What is the area called where the cornea and sclera meet
The limbus
People often compare the Irises function to that of a
Camera
What are the zones of the iris starting at the zone closest to the pupil
Pupillary border, central pupillary zone, collarette, peripheral ciliary zone
What is the largest component of the anterior uvea
The ciliary body
What produces aqueous humor and how does aqueous humor drain and what does it provide
The ciliary process on the ciliary body, it drains through the iridocorneal angle, and provides nourishment and removes waste
Where is the blood aqueous barrier
In the nonpigemented epithelium of the ciliary body
What makes up most of the mass of the ciliary body and what does this mean for function
Most of the mass is muscular and the function is accommodation through movement of the zonules which change the shape of the lens capsule and lens
What is the function of the choroid
To provide nutrition to the retina
What are the four layers of the choroid
Choriocapillaris (thin layer of capillaries), tapetum, medium sized vessel layer (choroidal vein), suprachoroidea (elastic connective tissue that is the transition between the choroid and the sclera)
What is the second most powerful refractive surface of the eye and what is its function
The lens, it focuses light onto the retina through accommodation
What has the highest protein content compared to any other organ in the body
The lens
Immunology what is the lens
It is seen as a foreign antigen
What is the lens capsule
A semipermeable membrane where the zonules attach, keeps the lens separate from the body
What is the site of most of the energy production of the lens
The anterior epithelium, uses anaerobic glycolysis (glucose) for energy
What happens to the lens as we age
It adds more protein to it every year to it gets larger and less mailable to accommodation which makes it harder to see through it
What are the layers of the lens
The capsule, cortex, and nucleus with adult, fetal, and embryonic layers
What makes up 2/3 of the volume of the globe
The vitreous, which is 98% water
Other than maintaining the shape of the eye what are other functions of the vitreous
It maintains the normal position of the retina and also functions to transmit light
What are the two components of the nervous tunic
Retina and optic nerve
How many layers is the retina made of
10, 9 neurosensory layers (neuroretina) and a single retinal pigment epithelium
What are the three functions of the retinal pigmented epithelium
It is the location of the blood retinal barrier, it transports retinol, and does phagocytosis and degeneration of the photoreceptor disc
In the synaptic body of the photoreceptor cell what is located there
Mitochondria
What does the outer segment of the photoreceptor cell contain
The discs and photopigments
What are the different photopigments and their functions
Rods- red, green, blue wavelengths (color)
Cones- Rhodopsin
Where does phototransduction take place and what is that
It is the conversion of light energy into electrical energy and it takes place in the outer segment
What is in the ganglion cell layer
The nuclei of the retinal ganglion cells
What is the in the nerve fiber layer
The axons of the ganglion cells
What makes up the orbital portion of the optic nerve and what is it considered to be
Considered to be a nerve fiber tract, the orbital portion of the optic nerve runs from the lamina cribrosa to the optic foramen
At what part (what section) of the nerve do the optic nerve fibers cross
The intracranial portion (from the optic canal to the optic chiasm)
What is the synapse of the optic tracts
The lateral geniculate body
What coordinates the orientation to visual stimuli and is sensitive to horizontal stimulus movement
The rostral colliculus
What is the efferent tract for parasympathetic oculi motor nuclei
The pretectal nucleus
What is the ocular fundus composed of
The retina, retinal vessels, optic disc, and the parts of the choroid and sclera that can be seen through the retina
What is a holangiotic retinal vascular structure and what animals have this
When there are blood vessels that cover the whole retina, most mammals have this
What is a merangiotic retinal vascular structure and what animals have this
The blood vessels are only on the meridian, lagomorphs (rabbits) have this
What is an anangiotic retinal vascular structure and what animals have this
One little area with the blood vesssles, birds have this
What is a panurangiotic retinal vascular structure and what animals have this
A circular area of blood vessels that cover part of the retina, horses have this
Describe the layers and media that make up the globe
Fibrous layer- cornea and sclera
Vascular/ pigmented layer- uveal tract- iris, ciliary body, choroid
Nervous layer- retina
Clear ocular media- tear film, aqueous humor, lens, vitreous humor
What is the adnexa
The eyelids, conjunctiva (palpebral and bulbar), and the nasolacrimal system
What makes up the orbit
The bones, extraocular membrane, vessels, and glands
What are the components of the ophthalmic exam
Neuro-ophthalmic exam- PLR, palpebral reflexes, vision, ocular motility
Exam proper- orbits, eyelids, globes
Ancillary tests- Sherman tear test, fluorescein stain, intraocular pressure measurement
What are important considerations for the history
Signalment- age, sex, species, breed, coat color,
Presenting complaint- change in vision? Pain? Discharge? Color or opacity change? How long, any treatment, any change?
Previous ophthalmic concerns or systemic signs
Medications
Travel history and exposure
Other animals effected?
What is some basic equipment for the ophthalmic exam
Finoff transilluminator
Slit beam
Ophthalmoscope
Indirect lens
Magnification
What is the use for proparacaine and a way it should never be used?
It is a topical anesthetic to cause short-acting but rapid ocular surface anesthesia to help with some procedures and cytologies
Never use for therapeutic use!
What should you evaluate before you use proparacaine (or any drops really)
Evaluate tear film quality and quantity
What is the mechanism of action of tropicamide and its use
It is a parasympatholytic that causes rapid short acting pupil dilation, used for a more thorough lens and fundic exam
What is tropicamide contraindicated for
Glaucoma
What should you evaluate before administering tropicamide
PLRs and iris tissue
What should you warn owners of if they are going to be present when you administer tropicamide
That it causes drooling because of its bitter taste
Also causes light sensitivity
How should you start your ophthalmic exam
Watching the animal from a distance and seeing how it visually tracts, looking at facial symmetry, the size and shape of the globe and orbit, the eyelid position, any discharge, the pupil size and shape
What nerve must you block in large animals to cause eyelid akinesia so you can do an ophthalmic exam
Cranial nerve VII (facial)
What are the afferent and efferent neurons stimulated by the pupillary light reflex and what is the effector muscle
Afferent- CN II (optic)
Efferent- CN III (oculomotor)
Effector muscle- Iris sphincter muscle
What are the afferent, and efferent neurons stimulated by the dazzle reflex and what is the effector muscle
Afferent- CN II (optic)
Efferent- CN VII (facial)
Effector muscle- orbicularis oculi muscle
What are the afferent and efferent neurons stimulated by the menace response and what is the effector muscle
Afferent- CN II (optic)
Efferent- CN VII (facial)
Effector muscle- orbicularis oculi muscle
What are the afferent and efferent neurons stimulated by the palpebral reflex and what is the effector muscle
Afferent- CN V (trigeminal- ophthalmic and maxillary branches)
Efferent- CN VII (facial)
Effector muscle- orbicularis oculi muscle
What are the afferent and efferent neurons stimulated by the corneal blink reflex and what is the effector muscle
Afferent- CN V (trigeminal- ophthalmic branch)
Efferent- CN VII (facial)
Effector muscle- orbicularis oculi muscle
What are the afferent and efferent neurons stimulated by the doll’s eye reflex and what is the effector muscle
Afferent- CN VIII (vestibulocochlear)
Efferent- CN III, IV, VI (oculomotor, trochlear, abducens)
Effector muscle- extraocular muscle
In order to have a direct PLR, what must all be working in the stimulated eye
Requires the retina (photoreceptors), cranial nerve II (afferent) and III (efferent), and iris muscle to all be working
What pathway must be functioning in the eye not being stimulated in order to have an indirect PLR
The efferent pathway of the non-stimulated eye (CN III and iris muscle) and a functioning afferent pathway in the stimulated eye
Is PLR a vision test and give an example why or why not
No it isn’t, a blind eye from cataracts will have a normal PLR, also a seeing eye may not have a PLR if it has severe iris atrophy and the pupil is always dilated
A dog has retinal or optic nerve disease, what will its PLR look like
This is affecting the afferent pathway so the diseased eye will not have a PLR and neither will the other eye (no consensual). When the contralateral eye is stimulated the diseased eye will have a PLR
A dog has cranial nerve III or iris disease, what will its PLR look like
This is affecting the efferent pathway so the diseased eye will not have a PLR (absent direct PLR) but the contralateral eye will have a PLR. However when the light is shone in the contralateral eye the diseased eye will not have a consensual response
Lesions affecting the afferent optic tract typically present as what
Visual impairment/ blindness
Lesions affecting the efferent optic tract typically present as what
Normal vision but iris atrophy
In terms of assessing vision, when is the PLR useful
When you are assessing to see if it is going to return. If there is an absent consensual PLR from the affected eye to the contralateral eye there is low potential for restoration of vision
Which visual reflex is a learned response so it won’t always be present in young animals
The menace response
In the neural pathways for the visual reflexes, all but one use the same interneuron. What is this interneuron and which one does not use that one and what does it use
They all use the sub-cortical interneuron except menace which uses the cortex and cerebellum
Other than examining the eye during an eye exam, what other area should you examine that isn’t the eye/orbit/eyelids and why
You should look inside the mouth at the pytergopalatine fossa (caudal to the last molar) because oral disease/ foreign bodies can enter the orbit here
How do you assess the different parts of the third eyelid
You can retropulse the globe to assess the palpebral surface and you can use a topical anesthetic and manual retraction to evaluate the bulbar aspect
When preforming retroillumination in a patient what should you look for/at
Assess facial and pupil symmetry and assess the clear ocular media (visual axis) for opacities
Why is transillumination helpful
You can shine light and observe it as it passes through transparent and translucent ocular structures
Describe the parts of a purkinje image
The first white line is the tear film/ cornea, behind it is the anterior chamber which is normally black, the beginning of the lens is the anterior lens capsule, this is followed by the “smokey” lens, then the posterior lens capsule
In terms of lesion localization, which covers which the anterior structures or the posterior ones
The anterior structures cover the posterior ones
If an object is seen in front of the iris where must it be
In the anterior chamber or the cornea
How can you tell where an object is in the eye based on how it moves
Lesions anterior to the center of the lens move in the same direction as the front of the eye, lesions posterior to the center of the lens move in opposite direction as front of the eye
What are the steps of examining the cornea
- Retroillumination
- Exam with naked eye
- Diffuse and transillumination and maybe magnification
- Focused (slit) bean
How do you examine the anterior chamber
- Retroillumination
- Diffuse and trans-illumination
- Focused (slit) beam
Compare to other eye
How do you examine the lens
- Retroillumination- look for backlit opacities
- Diffuse and trans-illumination
- Focused (slit) beam to determine depth in lens
Where are cataracts located
In the lens
When preforming direct ophthalmoscopy what eye do you use to view the left (OS) and right (OD) eyes
You use your right eye to view their right eye and you use your left eye to view their left
If an object is located on the retina at what dioptric strength when using a direct ophthalmoscope will the object be in focus, what about if the object is in front or behind the retina
If the object is on the retina it will be in focus at dioptric strength 0, if it is in front of the retina it will be + D, and behind the retina is - D
T/F the smaller the eye the less magnified it is by the direct ophthalmoscope
False, smaller eyes are more magnified
What is a good tool for screening the fundus
Monocular indirect ophthalmoscope (or binocular)
What are the benefits of direct ophthalmoscopy vs. indirect
Direct is easier to use and is a real, upright image (not inverted and reversed), it can give high magnification which is helpful for closer examination of the optic nerve or lesions
What does the schirmer tear test measure and what is the normal values for the test
The aqueous (water) component of the tear film, dogs are normally > or equal to 15mm, and <10 is abnormal, cats are variable due to sympathetic tone (not really used much with cats)
What are all the uses for the fluorescein stain
Detect defects in the ocular surface (epithelium)
Access tear film health/deficiencies
Assess the patency of the nasolacrimal tear drainage (Jones test)
Detect leakage via ocular defects (Seidel test)
What is specifically being stained by fluorescein stain
The stroma of the cornea (b/c hydrophilic)
If an animal is positive for the Jones test where will the fluorescein stain appear
The nostrils
What are the normal values for tonometry (intraocular pressure) and what does a high and low IOP signify
15-25mmHg is normal
High can be a sign of glaucoma, low can be a sign of uveitis
OR a difference between the eyes > 5-10mmHg can suggest an issue
What is the difference between how the tono-pen and tono-vet work
The tono-pen flattens the eye (applanation) and often requires topical anesthesia
The tono-vet uses induction-impact/rebound and doesn’t require topical anesthesia
What are some patient related factors that impact IOP
Age- decreases with age
Excitement/ stress- increases
Breed
What does the rose bengal stain do
It detects devitalized epithelial cells and/or tear film (mucin) deficiency, more sensitive than fluorescein which detects epithelial loss/defect
What are the ocular barriers to drugs
The tear film (dilutes)
The hydrophobic epithelium and hydrophilic stroma of the cornea
The blood eye barrier
What should be your targets if you are choosing to give a topical eye medication
The ocular surface to posterior lens capsule
When is it best to use systemic medications for eyes
When you are trying to target the lids, orbit, posterior segment, or if there is a perforated globe
What does the blood eye barrier cover
the endothelial cells of the iris blood vessels and epithelial cells of the ciliary body
give an example of when drugs can get into the uvea by crossing the blood brain barrier
uveitis- the barrier breaks down because of inflammation
What type of drug is best to use to get to the choroid
systemic, there is a blood retinal barrier
Where to the topical drugs usually go
most are onto the face, some go systemically by absorption through the conjunctiva or down the nasolacrimal duct, lastly some get into the aqueous humor by transcorneal absorption
if you are having to give different medications, how far spaced out should you give solutions and ointments
solutions should be spread out every 5 minutes and ointments every 30 minutes
what type of drugs cause dilation of the eye (mydriasis)
parasympatholytics (anticholinergic) and sympathomimetics
what type of drugs cause constriction of the eye (miosis)
parasympathomimetics (cholinergics) and sympatholytics
Give two examples of topical mydriatics that are parasympatholytics and how do they differ
1% Tropicamide- short acting and no pain relief and 1% Atropine- long acting and pain relief
Give an example of a topical mydriatic that is sympathomimetic and what are some side effects
phenylephrine- it can have some serious systemic effects- increase heart rate and cause local vasoconstriction, activates dilator muscles
what drug is often given pre-op for a cataract patient to dilate the eye
phenylephrine
What drug is often used for reflex uveitis or directly for uveitis pain
Atropine
What drug is a topical anesthetic but you can’t use it as a pain relief therapy because it dries, causes ulceration, delays healing, up-regulates pain receptors
Proparacaine HCL or tetracaine
Which topical antibiotics can be used for cat conjunctivitis
chloramphenicol and tetracyclines
which topical antibiotic is good for gram positive organisms
cefazolin
Which topical antibiotic is good for rods
aminoglycosides- neomycin, gentamicin or tobramycin; ciprofloxacin,
Which topical antibiotic is good for cocci
triple antibiotic or chloramphenicol
What is the “big gun” topical antibiotic that is used in septic keratitis with rods and can get gram negatives and aerobic positives
second generation fluoroquinolones- ciprofloxacin, ofloxacin, levofloxacin
which antibiotic is reserved for multi drug resistant infections and can get gram negative and positives well
4th generation fluoroquinolones- moxifloxacin, gatifloxacin
What are antiproteases and how are they used
It is plasma or serum given as an eye drop to treat melting corneal ulcers
how often would you give topical antibiotics for prophylactic therapy? How about septic conjunctivitis? How about septic keratitis?
prophylactic- 2-3 times a day
septic conjunctivitis- 3-4 times a day
septic keratitis- every 1-2 hours
corneal infiltrate is a hallmark of what
an infection
What animal is most likely to get a corneal fungal infection
a horse
What are the topical anti-fungals used in eyes
natamycin, itraconazole, miconazole, voriconazole
What are the three topical anti-virals used in eyes
trifluridine (most effective and expensive), Idoxuridine, Cidofovir
What are the two systemic antivirals often used in cats with herpes
L-lysine and famcyclovir
dexamethasone is often in combo with what
Neomycin and polymyxin B (NeoPoly Dex)- often cheaper than just dexamethasone too
What are the side effects of a topical steroid in the eye
They can delay corneal wound healing so NEVER use if the cornea is ulcerated
They can reactivate herpes
Lipid deposits in cornea
Iatrogenic Cushing’s
Flurbiprofen sodium Ocufen, Diclofenac Voltaren, Bromfenac Xibrom, and Keterolan Acular are all what
topical eye NSAIDS
which is better for immune-mediated inflammation and which is better for traumatic inflammation, steroids or NSAIDS
steroids are better for immune mediated and NSAIDS are better for traumatic inflammation
T/F you can give NSAIDS and steroids together topically
true
What are some challenges when treating glaucoma
there are huge differences between species and even between individuals with how they respond to the drug
What characteristics must a drug have to penetrate the cornea
The drug must be lipophilic (to diffuse through cells) and hydrophilic (diffuse between cells)
When is mannitol used
In pre-op for lens luxation
what is the prostaglandin analog (PGF2alpha agonist) used in angle closure glaucoma cases
latanoprost (Xalatan)
How does latanoprost (Xalatan) work and in what species does it work
It binds to the FP (prostaglandin F) receptor which increases uveoscleral outflow (drains aqueous humor) to decrease IOP, causes miosis, and reduces aqueous production (in dogs)
only works in dogs and humans to reduce IOP
When is it contraindicated to use latanoprost (Xalatan)
in uveitis and anterior lens luxation (and probably in cats with glaucoma cause it doesn’t reduce IOP in them)
What is oral methazolamide or dichlorphenamide (Trusopt, Cosopt, Azopt)
carbonic anhydrase inhibitors
How do carbonic anhydrase inhibitors help with glaucoma
By inhibiting carbonic anhydrase the aqueous humor is decreased
How do cholinergics work
they increase the aqueous humor outflow by causing miosis (contracting the longitudinal ciliary muscle) which in turn reopens the angle/ breaks the pupil block
what do beta-adrenergic blockers do and what causes are they used in
they decrease the aqueous production and may increase the outflow (miosis) but are a 3rd choice in secondary glaucomas or as a prophylactic
What are two causes of Keratoconjunctivitis Sicca (KCS)
quantitative- low schirmer tear test
qualitative- rapid tear break up time
What are the two t-cell modulators (tear stimulants) used for Keratoconjunctivitis Sicca (KCS) treatment and the differences
Cyclosporine A (FDA approved) and Tacrolimus (not approved cause possible carcinogen, but works just as well if not better)
What specific type of Keratoconjunctivitis Sicca (KCS) can a cholinergic be used for
neurogenic KCS, replaces the parasympathetic neurotransmitter
Which drugs are best to use as artificial tears for a mucin deficiency and how do they work
cyclosporine (stimulates), polyvinylpyrrolidone (mimics), Methylcelluloses (mimics)
Which drugs are best to use as artificial tears for a lipid deficiency (blepharitis)
Refresh Endura or soothe (oil based), sodium hyaluronate, warm compresses
What would you use if an eye had an erosion secondary to corneal edema
sodium chloride- suck out that fluid!
what is the magic drug that will dissolve a cataract?
there is none! save your money for surgery
What are the common bugs that cause feline conjunctivitis
chlamydia, herpes, mycoplasma
what are four topical antibiotics used to treat feline conjunctivitis and how often should you give the drugs
tetracyclines, erythromycin, ciprofloxacin, chloramphenicol, treat frequently! BID-TID
If you had a dog with a corneal erosion and it wasn’t infected what may you start prophylactically?
Neomycin (aminoglycoside)/polymyxin often used with bacitracin added to ointments or gramicidin added to solutions
gram neg and pos coverage
what is a good broad spectrum treatment for infected corneal ulcers
Aminoglycoside (gentamicin, tobramycin, neomycin) OR Fluoroquinolones (ciprofloxacin, ofloxacin, etc.)
AND
cefazolin
What muscle is responsible for “squeezing” and pushing the globe forward into a normal position, it relaxes when sleeping
the smooth muscle cone
What type of tone causes the smooth muscle cone to push the eye forward
sympathetic
What are some basic/ beginning parts of the orbital examination (hint there are six ones I have listed and all of them just involve your hands and eyes, no real special equipment)
Looking at facial, orbital, and globe symmetry- look from top!
Orbital rim palpation
Retropulsion of the globes- can it be done easily?
ocular motility- doll’s eye reflex, positions of base
nasal airflow
oral exam
When are radiographs helpful in ophthalmology (You can’t see eyeballs on an X-ray what the heck??)
they can be helpful for examining the orbit and surrounding structures like the sinuses, maxilla and mandible, and teeth!
What are four differentials for enophthalmos (globe recessed in orbit)
A lesion anterior to the globe that is space-occupying
A decrease in orbital volume (ex. dehydration, emaciation, etc.)
Pain
Lack of orbital smooth muscle tone (Horner’s syndrome)
What are two abnormalities you may need to differentiate from enophthalmos and how would you do this
atrophy- phthisis bulbi
microphthalmos- congenitally small globe
you look at the corneal diameter- with enophthalmos the diameter is equal and with microphthalmos or phthisis bulbi it is decreased
what commonly causes exophthalmos
a space-occupying lesion within the orbit
what other clinical signs do you often see with exophthalmos
lagophthalmos (inability to blink)
strabismus (deviation of the globe)
exposure keratitis (inflammation of cornea)
increased scleral show
sometimes third eyelid elevation
what do you need to differentiate exophthalmos from and how do you do that
differentiate from buphthalmos (enlarged globe) by assessing from above, assessing corneal diameter (equal with exophthalmos and increased with buphthalmos), and if there is resistance to retropulsion (exophthalmos will resist)
What are four clinical signs of orbital disease
third eyelid elevation
strabismus
epiphora (tearing)- due to obstruction of nasal lacrimal duct
Vascular congestion in conjunctiva, episclera, or retina
what is microphthalmos associated with (other than a small globe obviously)
a small palpebral tissue and orbit and often there will be multiple congenital ocular deficiencies, also associated with merle coat color
What is it called when there is a single eye fused at the midline
cyclopia/synophthalmos
siamese cats often have what congenital abnormality
convergent (inward) strabismus (esotropia)
brachycephalic dogs often have what congenital abnormality
divergent (outward) strabismus (exotropia)
what causes Horner’s syndrome
loss of sympathetic innervation to the orbit
what are symptoms of Horner’s in a dog? How does a horse and cow vary
Dog
-ptosis (drooping of upper eyelid)
-miosis (small pupil)
-enophthalmos (recessed globe)
-nicitating membrane/ third eyelid protrusion
Horse- in addition to dog ones, ipsilateral sweating and vascular hyperemia of face
Cow- same as dog plus a ipsilateral dry nasal planum
describe the sympathetic innervation to the orbit and know that a lesion along any of these structures can cause Horner’s syndrome
Central neuron- hypothalamus to T1-T3 (or T4)
Preganglion neuron- T1-T4 to sympathetic trunk
Autonomic ganglion- cranial cervical ganglion
Postganglionic neuron- CN V branches to orbital structures
Why does ptosis (drooping of upper eyelid) occur with Horner’s
mueller’s muscle denervation
Why does miosis occur with Horner’s (muscle effected)
denervation of iris dilator muscle
Why does enophthalmous occur with Horner’s
denervation of orbitalis muscle/ smooth muscle cone
Why is there sweating and hyperemia of the face with Horner’s
vasodilation (loss of sympathetic vasoconstriction)
What is the most common cause of Horner’s in dogs
idiopathic
How do you localize the lesion and confirm the diagnosis of Horner’s
phenylephrine- dilute will localize the lesion to post-ganglionic (if it resolves the symptoms), and 10% will confirm the diagnosis
What is phthisis bulbi (atrophy of globe) secondary to
severe/chronic inflammation, glaucoma- damage to ciliary body decreases and eventually stops production of aqueous humor
A dog presents with what appears to be orbital cellulitis or an abscess, what are some clinical signs you may see
acute onset, nictitans protrusion, usually unilateral exophalmus, resistance to retropulsion, pain upon opening of the mouth, and others
How would you drain an orbital access
general anesthesia and create a stab incision in the pterygopalatine fossa- insert hemostats and open, do not close!
what orbital disease are Goldens overrepresented for
extraocular polymyositis (swelling of extra ocular muscles)
What disease can be immune-mediated and makes dogs look “stressed” (bilateral exophthalmos)
extraocular polymyositis (swelling of extra ocular muscles)
which immune mediated disease are German shepherds and Weimaraners overrepresented that can cause blindness, bilateral exophthalmos, pain with opening the mouth
Masticatory/eosinophilic myositis
T/F orbital neoplasia is usually benign
false
What causes of exophthalmos are not painful
neoplasia and a cyst/mucocele
How could you tell apart an exophthalmos caused by an abscess vs. a myositis
accesses are usually unilateral and myositis is usually bilateral exophthalmos, but both are acute and can cause pain, fever, and anorexia
Proptosis is exophthalmos with what
entrapment of the eyelids behind the globe equator
A BDLD presents to your clinic with a proptosed eye, what is important to do while you evaluate the patient
keep the eye lubricated
Other than a lack of PLR, what is another bad sign with a proptosed eye
hyphema (pooling of blood in anterior chamber)
What rule of thumb should you use when presented with a proptosed eye in terms of enucleation
If in doubt, replace. You can always remove it later.
What has a better prognosis for their proptosed eye, a bulldog or a golden
a bulldog, brachycephalic breeds have a better prognosis!
T/F being a cat or a horse is a negative prognostic indicator for successful replacement of a proptosed eye
true
What is the rule of thumb for the number of extraoccular muscles avulsed with a proptosed eye and it being a negative prognostic factor
more than 3
what type of sutures are used in a proptosed eye surgery to preform the tarsorrhapy (temporary surgical closure of the eyelids)
horizontal mattress
what are possible sequelae to proptosis
corneal ulceration
blindness (20% K9 regain vision and 100% of felines will be blind)
Strabismus (often lateral)
KCS
lagophthalmos and exposure keratitis
What is an enucleation defined as and give an example of when it is used
removal of just the globe, lid margins, conjunctiva, and third eye lid
used for treatment of glaucoma or perforation of the globe
What is an exenteration defined as and give an example of when it is used
removal of globe and orbital contents
used for neoplasia or infection beyond sclera
What is an evisceration defined as and give an example of when it is NOT used
removal of the intraocular contents which leaves a corneal shell where an implant can go
contraindicated for intraocular neoplasia or infection
When blinking what eyelid moves the most
The upper eyelid
Where are the ducts of the mebomian glands
On the lid margin
When do eyes usually open after birth and if they don’t what is it called
10-15 days, ankyloblepharon is delayed or incomplete opening
What is it called when there is eyelid agenesis and what species is it most common in
Coloboma, more common in cats
What is euryblepharon and what species and clinical signs is it associated with
What syndrome is it also called
Macroblepharon, abnormally large palpebral fissure, associated with brachycephalic breeds and lagophthalmos (can’t fully blink) and tear film abnormalities- leads to corneal pigmentation, keratitis, and ulceration
Aka ocular brachycephalic syndrome
What occurs with an entropion
Inward rolling of all or part of the eyelid margin and the hair rubs against the conjunctiva and cornea and can cause ulcers, pigmentation, and self-trauma
What is primary vs. secondary entropion
Primary- congenitally long or lax lids, heavy brown folds
Secondary- pain/spastic or cicatricial from scarring
How can you test to see in entropion is primary or secondary
Apply a topical anesthetic to the eye and see if it goes away, if so probably secondary
What approach may you take to fix an entropion in a puppy vs. an older dog
In a puppy you may be able to use a horizontal mattress suture to tack the eyelid up temporarily
In an older dog you may need to use the Hotz-Celsus surgical repair (remove a strip of skin/muscle and close with a simple interrupted) or/and lateral canthoplasty (good for excessive lid length to remake lateral canthus
T/F with a Hotz-Celsus entropion repair you should always take a little bit more than you measure just to be sure it actually fixes it
False! You should actually err on the lower side of skin removal
what is ectropion
outward rolling of lid causing exposure of conjunctival tissue, and sometimes causing lagophthalmos (incomplete lid closure)
is ectropion a common thing to fix
no, in fact it is desirable in some breeds. Only fix if there is ongoing conjunctivitis
what is it called when you have a combined ect/entropion and what does it often look like
diamond eye, the entropion is on the sides (temporal and nasal) and then that causes an ectropion in the middle
What is distichia/ distichiasis
there are additional eyelashes coming from metaplastic meibomian glands (undifferentiated meibomian tissue) so they grow down and into the eye, may have one or many per opening
What is Trichiasis
eyelashes (cilia) that are in the right place but they are growing down and directed toward the cornea
What is an ectopic/ aberrant cilia
an eyelash (cilia) that grows through to the underside of the eyelid (it grows straight down and through the conjunctiva)
what is trichomegaly
long but normal eyelashes but they are so long they rub on the cornea
what breeds are predisposed to distichia
cocker spaniels, English bulldog, shetland sheepdog, poodles
what is the treatment for distichia
there isn’t a perfect one but cryotherapy is most common (but may kill meibomian glands)
T/F ectopic cilia is a variation of distichia
true
what are common symptoms of issues with the cilia
blepharospasm, conjunctivitis, keratitis, corneal ulceration
what is the treatment for ectopic cilia
surgical excision and you must make sure you excise them all because there can be nests of hair
Trichiasis can be primary or secondary, what would be an example of a treatment for a primary cause and a secondary cause
primary- grooming to cut the hair short enough from the eye
secondary- removal of nasal folds or hetz-celsus to remove skin folds that are pushing the hair into the eye
What is important regarding eyelid trauma
it is well vascularized so large defects often heal well, so you should always try to put it back together and not cut it off. The most important thing is accurate position of eyelid margins
what are the two types of malignant eyelid neoplasms in dogs (there are also many benign neoplasms- in fact most are benign, 85%)
mast cell and squamous cell
How should you excise an eyelid neoplasm
take 1/3 to 1/4 of the eyelid involvement using a full thickness wedge resection or 4-sided excision
what is important when removing eyelid tumors
that the lid margin comes together perfectly
other than surgical removal what is another approach for removing eyelid neoplasms and what are advantages and disadvantages
debulk and cryotherapy- it is cheaper but more likely to need repeating and can cause depigmentation
Are cat eyelid neoplasms more likely to be malignant
yes and they are locally invasive
What is the most common eyelid neoplasm in a cat
squamous cell carcinoma
A cat comes to you because the owner has noticed a weird grey mark next to its eye. What is this and what should you do
This is an apocrine hidrocystoma. You can remove it surgically or with cryotherapy but they usually come back
what is blepharitis and the clinical signs
eyelids that are hyperemic, have edema, and are chronically distorted
causes blepharospasm, exudate, alopecia, ulceration, and hyperpigmentation
(think granulomatous, crusty, hairless, nasty eyelids)
What are common causes of bacterial blepharitis (infected eyelids) in puppies and adults
puppies- juvenile pyoderma
adults- staphylococcus or streptococcus
what are parasites that cause blepharitis in dogs and cats
demodex and sarcoptes
what is a cause of immune mediated blepharitis that isn’t from an allergic reaction/insect bite
pemphigus foliaceus or erythematosus
what is a chalazion
retained meibomian secretions that leak into surrounding tissue and cause an inflammatory response and granuloma formation
What is a hordeolum
a stye, usually a staphylococcal infection of the lids that causes inflammation of glands of Zeiss and Moll or internal infection of meibomian gland
what are the glands of Zeiss and Moll
Zeiss are the sebaceous glands of the eyelid margins and Moll are the apocrine (sweat glands) near the eyelid margin
what are the conjunctival responses to disease
chemosis (edema), hyperemia, cellular exudate
what is conjunctivitis
inflammation of the conjunctiva without concurrent uveitis or intraocular disease
What is a major difference between canine and feline conjunctivitis
most of cat conjunctivitis is infectious and that is very rare in dogs
A dog has bilateral follicular enlargement of the bulbar surface of the third eyelid, what could be causing this
seasonal allergies but you need to rule out KCS
How should you treat allergic conjunctivitis
an anti-inflammatory and an antibiotic
what are the most common differentials for feline infectious conjunctivitis
feline herpes-1, chlamydia psittaci, mycoplasma
what is symblepharon and what is it usually happen in
Loss of conjunctival epithelium that causes inappropriate adherence of the conjunctiva to the eye, in young cats with herpes infections
what is the treatment for feline herpes virus
No treatment but you van help control outbreaks + topical antibiotics for a secondary infection because of ulcers
topical trifluridine (if corneal disease) or cidofivir or idoxuridine
oral antivirals like famciclovir
How is feline chlamydial conjunctivitis different than feline herpes
usually doesn’t have a URI where as that is how herpes usually starts
how do you diagnose and treat feline chlamydial conjunctivitis
conjunctival cytology or IFA and treat with tetracycline, erythromycin, ciprofloxacin, and/or oral doxycycline
What disease can cause unilateral or bilateral conjunctivitis in cats and it id diagnosed by inclusion bodies at the cell membrane
mycoplasma
What is difficult about cytology or culture for feline conjunctivitis
Usually there is a low diagnostic yield
What disease causes ropy, mucopurulent discharge with conjunctival hyperemia, chemosis, and keratitis with superficial neovascularization and pigmentation
Keratoconjunctivitis sicca (KCS)
What part of the tear film is made by the meibomian glands, is superficial, and can stabilize and prevent evaporation
The lipid layer
What part of the tear film is made by the lacrimal gland, gland of the third eyelid, and accessory glands, provides corneal nutrition and helps remove waste, and is the intermediate layer
Aqueous layer
What part of the tear film is made by the conjunctival globlet cells and provides secretory IgA and is the interface of the tear film and the hydrophobic cornea
Mucus layer
Where are the meibomian glands
In the tarsal plate
A yorkie presents with a corneal ulcer that you suspect has a secondary infection. You have tried to treat this in the past and it keeps coming back. The dog also has dry and crusty nares. What may he have?
Keratoconjunctivitis sicca (KCS)
Same yorkie with the ulcerated eye and dry, crusty nose. What test could you do to test for KCS and what value would be indicative
The Schirmer Tear test. Normal is 15-25mm/60sec, marginal is 10-15, and low is <10mm/60sec but you shoudl always evaluate the test and clinical signs together
What is the most common form of keratoconjunctivitis sicca
Idiopathic/ immune mediated
A dog presents to you and their owner said that the dog has recently undergone a surgery to remove its cherry eyes, but now it’s eyes are hyperemic with ropy discharge. What may have happened?
The third eyelid gland was probably excised when the cherry eye was removed causing keratoconjunctivitis sicca. This is why you should never remove a cherry eye and instead surgically correct it by tacking in down
What causes unilateral neurogenic dry eye
Loss of parasympathetic activation of the lacrimal gland
What is the difference between quantitative and qualitative dry eye
Quantitative is not enough production of the aqueous component of the tear film
Qualitative is a problem in the tear film breakup time (happens too fast), usually there is an issue with the mucin or lipid composition
How can you test for qualitative dry eye and what test won’t work for it
You can use meibometry to examine the lipid component. Schirmer teat test wouldn’t work because it is for measuring the quantity of the aqueous portion of the tear film
What are two causes of qualitative KCS
Loss of goblet cells (ex. from chronic inflammation) or dysfunction of the meibomian glands
How can you stimulate tear production in keratoconjunctivitis sicca
Use cyclosporine A or tacroliums for life
Or pilocarpine (but this is reserved for cases of neurogenic KCS)
When testing quantitative KCS there is a specific cut off that is used as a prognostic indicator for an individuals response to treatment. What is it?
If the Schirmer Tear Test is < 1mm/min usually only 50% will respond but if there is > or equal to 2mm/min then 80% are likely to respond
What is a specific goal of KCS treatment which has a challenge with it specific to the type of medication used
You want to decrease inflammation so you can do this with cyclosporine or topical steroids, but many cases have ulcers and you can’t use steroids on an eye with an ulcer!
Which drugs can be used with a mucin deficiency KCS as an “artificial tear” and how do they work (very basically)
Cyclosporine- stimulates the production of mucus
Polyvinlypyrrolidone- mimics mucus
Methylcelluloses- mimic mucus
Which drugs can be used with a lipid deficiency KCS as an “artificial tear”
Refresh Endurance, soothe- oil based
Sodium hyaluronate
Warm compresses
Describe a surgical treatment for KCS and what is the disadvantages
Transposition of the parotid salivary duct to the open conjunctiva but saliva are not tears so you have to clean their eyes more and there is a mineral deposition on the corneal and lid margins. Also sometimes the saliva is not comparable with the cornea
What is the most common primary conjunctival disorder in dogs
Prolapse of the third eyelid gland (cherry eye)
What causes a cherry eye (prolapse of third eyelid gland)
Weakness between the tissue attachments of the third eyelid and peri orbital tissues
How many dogs will develop KCS if their cherry eye is surgically removed
50%
Where can the third eyelid gland be anchored if a cherry eye is surgically fixed
What is another option for fixing a cherry eye
To the orbital rim
Or can use the pocket technique- two incisions make and you close the far edges of them to close it around the gland
What causes a plasmoma (chronic superficial keratitis) and what is the treatment
Plasma infiltrate of the third eyelid (a variation of pannus) and you can use topical steroids or cyclosporine
What is follicular conjunctivitis associated with
Large numbers of follicles on the bulbar surface of the conjunctiva, often associated with environmental allergens
Where is a good place for a foreign body to hide that may cause a non-healing erosion
Behind the third eyelid
What causes epiphora (excessive tearing of the eye), in regards to the nasolacrimal system
Poor drainage due to a hypoplasia or imperforate puncta or entropion
Blockage from a foreign body, inflammation or neoplasia
Is puncta aplasia (imperforate punctum) common? What breeds/species are usually affected
Yes and you see it in cocker spaniels, goldens, miniature poodles, horses, llamas, and alpacas
What is it called when you have mucopurulent discharge, epiphora (excessive watering of the eye), and may have swelling or draining fistulas in the medial can’t heal region
Dacryocystitis (inflammation of the tear ducts)
What are the functions of the cornea
Transmission of light (transparent and refractive medium)
Defense- a barrier between the eye and the environment
What are the layers of the cornea
Precorneal tear film, surface epithelium, stroma, Descemet’s membrane (the basement membrane), endothelium
What are two functions of the corneal epithelium
Refraction- tear film “smoothens” the refractive surface
Mechanical barrier to fluid imbibition from the stroma
T/F corneal edema will occur if the epithelium is damaged
True, it helps “hold in” the aqueous humor and when there is a loss of epithelium (like an ulcer) edema can occur because of fluid imbibition from the stroma
Why are corneal ulcers so painful
The stroma is richly innervated
Name four features of the normal corneal stroma
Avascular, non-pigmented and transparent, relatively dehydrated, regular collagen fibril arrangement
What could cause the collagen fibrils in the cornea to spread out
Edema
What is the meaning of corneal deturgescence and what helps the cornea achieve this
The corneal stroma is bathed in tears and aqueous humor but is still relatively dehydrated. It achieves this because tears are hypertonic and draw fluid out as they evaporate. Also, the epithelium is hydrophobic and so is the endothelium, but the endothelium has and NA-K ATPase pump to pump fluid into the anterior chamber. Lastly it is avascular
What is the corneal endothelium made of and can you make more of it
It is a mono layer of squamous epithelial cells but they are post-mitotic so you can’t make any more of them
What are the steps for stroma wound healing
- Invasion by neutrophils
- Wound margin keratocyte transformation to fibroblasts
- Fibroblasts invade wound
- Collagen and GAG synthesis
- Collagen reorganization
- Return of tensile strength
Do you want angiogenesis in stromal healing
Definitely! It is basically necessary/enhances healing
Which purkinje image is the cornea
The first one
What are the three types of corneal vascularization/ causes of red in the cornea and what does each one indicate
Superficial- usually indicate ocular surface disease
Deep- into the stroma along the brush border and indicates intraocular disease (uveitis, glaucoma etc.)
Hemorrhage- indicates vascularization
If you have a crystalline or chalky deposit in a cornea what could this be made of?
This could be a corneal deposit made of lipids (cholesterol) or mineral (calcium)
How does a corneal scar differ from a deposit
It is usually more of a wispy grey to dense white and doesn’t have well defined edges or is chunky
What does corneal cellular infiltrate look like and what can cause it
What is indicated when you have one
It is a yellow-white, creamy/soft to dense white
It can be inflammatory from infection or sterile (immune-mediated with WBCs) or neoplasia also may be associated with stromal loss or thickening
Cytology is indicated
What does corneal edema look like
Hazy grey to a dense blue and maybe a cobblestone appearance
Will thicken the cornea which you can appreciate with a purkinje image
What does cornea edema indicate
Epithelial defect (ulcer), endothelial defect/dysfunction (-itis, glaucoma, dystrophy or degeneration), or corneal vascularization
What are keratin precipitates, where are they, and what do they indicate
They are tan-ish infiltrates (often sterile inflammatory cells) on the corneal endothelial surface that indicates anterior uveitis (intraocular inflammation)
What can give you corneal pigment
Melanocytes from conjunctiva from chronic irritation or neoplasia
Or melanocytes from the uveal tract (iris) because of corneal perforation, congenital (PPM), Iridocilliary cyst, and of course neoplasia
A cat has a history of ulcers and now there is a tan-ish black mark on its cornea, what could this be
A corneal sequestrum (only in cats), this is necrotic corneal stroma
What is always indicated with a corneal ulcer
Steroids! Just kidding please don’t do this
It’s actually antibiotics because there is always a risk of secondary infection
What are the etiologies for a cornea ulcer
Trauma- either direct or secondary (foreign body, entropion, tumor, etc.)
Exposure- lagophthalmos, buphthalmos, exophthalmos
Infection- FHV-1 (and other herpes viruses)
Tear film deficiency- ex. KCS
Neurological defects- CN V (neurotropic) and VII (paralytic)
How long should it take an uncomplicated ulcer to heal
A week
Corneal ulcers cause reflex _____
Anterior uveitis
What are the specific clinical signs associated with anterior uveitis
Mitosis, aqueous humor flare in anterior chamber
T/F just because an animal has an ulcer with severe uveitis doesn’t mean the ulcer is severe
False, the severity of the uveitis usually correlates with the ulcer
Define a superficial, uncomplicated corneal ulcer
Acute and painful but has a distinct border and a tight edge. There is little corneal edema if any and no stroma loss. There also isn’t any infiltrate (uncomplicated) and no to mild reflex uveitis
What can you give to help with the pain of a corneal ulcer
Atropine or NSAIDs
What is SCCED and what is the common breeds and classic characteristics seen with them
Spontaneous chronic corneal epithelial defect, it is an indolent ulcer with non-adherent/loose epithelial edges (because the anterior stroma impairs normal epithelial adherence). Unlike other indolent ulcers there isn’t an underlying cause so it is usually a diagnosis by elimination Boxers, Corgis over represented
Will see a characteristic staining pattern where the stain seeps under the epithelial edge of the ulcer
What is required for treatment of SCCED
Debridement with a Cotten tipped applicator or a diamond burr and anterior stromal puncture/ grid keratotomy (basically dragging a needle on the exposed stroma to promote healing)
What is a descemetocele and how can you tell if you have one on an eye
Stromal loss down to Descemet’s membrane, will have a characteristic staining pattern where the Fluor. will stain a ring
What are the etiologies for corneal malacia (melting)
Endogenous proteases/collagenases
Infection (bacterial collagenases)
Topical corticosteroids (and maybe NSAIDS)
How should you assess a stromal ulcer
Look at the depth, the integrity (perforation risk, malacia), look for infiltrate, reflex uveitis and how bad it is/ if there at all, and any vascularization
What type of antibiotic should you use for a corneal ulcer (assuming you don’t have a culture yet)
A broad spectrum and maybe a combo with an anti-fungal
Ex. Fortified cefazolin (gram + cocci) and fluoroquinolones or tobramycin (gram - rods)
No ointments with current or impending perforation!
What can you use when you have a stromal ulcer with malacia to help treat the malacia
Serum, EDTA, or acetylcysteine
What do you give to help with reflex uveitis with a stromal ulcer
Topical cycloplegia/ mydriasis- cholinergic/ parasympatholytic (atropine- but not if KCS or glaucoma)
Maybe systemic anti-inflammatory but also may delay corneal healing (and definitely no topical steroids!!)
What animal is more likely to have reflex uveitis because of a stromal ulcer and what can be really bad with that animal specifically
A horse, the pain can also make them colic!
T/F you should always preform a cytology in a horse with an ulcer
True
T/f cats are the most likely to get ulcers from fungal infections
False! Way more common in horses
What are some indications you may need to preform a conjunctival flap/graft or corneal transplant for a stromal ulcer
If there is rapid progression or malacia, limited or no vascularization, perforation or active leakage
What disease is common in German shepherds, greyhounds, and some other dogs that is inherited and UV exacerbated, bilateral, chronic superficial keratitis
Pannus
What is the treatment for pannus
Long term topical steroids and avoiding UV exposure
What would cause white plaques of infiltrate in the cornea what is in cats and considered an immune-mediated keratitis. Hint- You do a cytology and see a bunch of a specific white blood cell
Eosinophilic keratitis
What are inherited corneal lipid deposits known as (often in huskies)? Is there a treatment?
Corneal dystrophy, no treatment, usually bilateral and non-painful and minimally progressive
What is an inherited/ age related change in the cornea that can cause edema and indolent ulcers
Endothelial degeneration
What is it called when there is haired skin (or any abnormal tissue growing in an abnormal location) growing on the cornea
A dermoid or choristoma
