Tear Film Diseases Flashcards
How does the nasolacrimal system work?
- lacrimal gland creates the aqueous portion of tears
- lacrimal puncta wick away excessive tears into the canaliculi and into the NL duct —> nasal punctum
What are 4 functions of precorneal tear film?
- maintain smooth and lubricated optical surface
- protect from dessication and bacteria
- provide the eye with nutrients and growth factors
- waste removal
What are the 3 parts of precorneal tear film? Functions of each?
- LIPID - meibum prevents evaporation and tear overflow (expressed by blinking)
- AQUEOUS - flushing, lubrication, nutrition, antibacterial, protease inhibitors, smooths surface
- MUCIN - stabilizes, helps tears stick to corneal epithelium (hydrophobic), fills in corneal defects, bacteria resistance
What is keratoconjunctivitis sicca? What happens when left untreated?
quantitative dry eye disease due to deficiency of aqueous portion of tear film (most common cause of conjunctivitis in dogs!)
BLINDNESS —> corneal scarring, vascularization, pigmentation
How is KCS diagnosed?
Schirmer tear test I WITHOUT proparacaine to measure reflex (irritation) and basal tearing over a minute
- quantified aqueous tear production
What is the normal value for Schirmer tear tests? What are abnormal values?
> 15 mm/min
- 11-14 mm/min = early or subclinical KCS
- 6-10 mm/min = moderate or mild KCS
- <5 mm/min = severe KCS
What is thought to be the most common cause of KCS? How does it present? What treatment is recommended
immune-mediated - breakdown of blood/tear barrier allows immune destruction of lacrimal glands (usually not associated with other immune diseases)
usually bilateral lymphocytic-plasmacytic infiltrates in lacrimal glands
immunomodulatory therapy - topical Cyclosporine
What are 4 additional causes of KCS?
- infectious - distemper, herpes (cats)
- neurogenic - loss of parasympathetic innervation to lacrimal glands
- trauma - facial or trigeminal nerves
- removal of gland of the third eyelid or prolonged uncorrected prolapse
What specific drugs can cause KCS?
- sulfa drugs
- Etodolac (NSAID)
- topical atropine (dries secretions)
- sedation/anesthesia
- radiation therapy
check STT prior to starting these meds!
What is unique about neurogenic KCS?
usually presents unilaterally with a dry nostril
What is the most common congenital cause of KCS?
congenital alacrima - lacrimal gland hypoplasia or aplasia —> Boston Terrier, Yorkie, Pug puppies with painful eyes upon opening
What 3 metabolic diseases can cause KCS?
- hypothyroidism
- DM* - decreased corneal sensitivity, neuropathy
- Cushing’s
decreased tear production
How does immune-mediated KCS compare to other etiologies? What are 3 common signs? What 2 signs are due to chronic irritation/poor nutrition?
tends to be more progressive rather than acute
- red eye
- intermittent mucoid/mucopurulent discharge = mucin overcompensates + prone to bacterial infection due to decreased aqueous compartment of tears
- blepharospasm
corneal vascularization + pigmentary keratitis
What are 5 less common signs of KCS?
- lackluster cornea
- corneal scarring
- ropy, mucoid discharge (white or yellow)
- blepharitis
- periocular alopecia
What is severe purulent discharge indicative of with cases of KCS? How is it diagnosed/treated?
secondary bacterial conjunctivitis or corneal ulcers
conjunctival/corneal cytology
broad-spectrum topical antibiotics + dry eye therapy
KCS, secondary bacterial infection:
corneal ulcer = chronicity
- prone to infection and deepening
What are 3 aspects of KCS medical treatment?
- lacrimostimulation - topical immunomodulation with cyclosporine A or Tacrolimus
- lacrimomimetics - artificial tears —> hyaluronic acid, methycellulose, petrolatum
give both daily, 2-3x a day
What 5 effects do cyclosporine A and Tacrolimus have when treating KCS? How are they able to do this?
- increase aqueous teat production
- decrease inflammation
- normalizes mucin production
- decreases pigmentation
- decreases vascularization
absorned into lacrimal glands
How is response to therapy typically dependent on the severity of KCS?
STT > 2 mm/min = 80% respond to medical therapy, usually within 4-6 weeks
STT < 2 mm/min = 50% respond to medical therapy, can take up to 6 months for response
KCS, medical treatment:
- pigment dispersion
- decreased vascularization
What surgical therapy is available to treat KCS? When is it recommended?
parotid duct transposition - substitutes saliva for normal tears (technically challenging!)
cases of severe and non-responsive KCS (typically congenital)
What 3 complications are associated with parotid duct transposition?
- mineral deposits on cornea
- overproduction
- blepharitis - saliva doesn’t have the same immunoregulatory effects
What is qualitative tear film dysfunction? Most common etiology?
poor tear quality due to mucin or lipid deficiency
previous severe conjunctivitis or blepharitis
What are 4 signs of qualitative tear film dysfunction?
- blepharospasm
- corneal vascularization
- pigmentation
- (milder) mucoid discharge
What is the diagnostic of choice for qualitative tear film dysfunction? Why?
tear film break up time —> will have a normal STT because tears are still produced, just with a different composition that makes them evaporate quicker or slide off the eye
How is qualitative tear film dysfunction treated?
- artificial tears
- cyclosporine A or tacrolimus
How is a tear film breakup time (TFBT) performed?
- place fluorescein on the eye and blink it, keep it open without rinsing
- wait to see breaks in the fluorescein to appear, seemingly darker and drier spots indicative of tear evaporation (use UV (cobalt) blue light for observation!)
- NORMAL = 8-9 s
TFBT:
dark spots = tear film breakup
- normal = 8-9 s
What are the 3 most common signs of feline dry eye disease? How does this compare to canine?
- dull, lackluster cornea
- (non)ulcerative keratitis
- conjunctivitis
more corneal presentation, uncommon to have mucoid/purulent discharge
What is thought to be the 3 most common causes of feline dry eye disease? What do they cause?
- previous/current FHV-1 infection
- neurogenic
- concurrent ocular disease - eyelid agenesis, symblepharon, corneal sequestrum
decreases corneal sensitivity
What are 3 diagnostics used for feline dry eye disease?
- STT - normal = > 9mm/30s / > 15 mm/min
- TFBT - normal = 8-9s
- corneal touch threshold (+ cotton swab wisp)
What is epiphora? What is the most common cause? Some others?
excessive lacrimation
painful diseases causes reflex production of tears - corneal ulcers, distichia, ectopic cilia, entropion
- breed-related
- imperforate puncta = decreased drainage
- dacryocystitis
What are the 2 overall causes of epiphora? What are the most common clinical signs?
- increased tear production
- decreased tear drainage
- differentiated with good optho exams (disease causes pain vs. discharge), Jones test, and flushing of NL duct
tear staining, wetness on face
What are 5 indications for performing NL duct flushes or Jones test?
- epiphora
- mucopurulent punctal, ocnjunctival, or nasal discharge
- swelling of ventral medial canthal region or fistulas
- suspected punctal/duct FB
- eyelid trauma
What is Jones test? Why are false negatives common?
fluorescein dye passage test - time pass of dye from eye to nares, commonly 5 mins —> not seen or takes longer with complete vs. partial obstructions
time needed for passage based on duct/nostril size, may need an additional flush if unsure
(positive = epiphora NOT caused by blockage, rather caused by increased production of tears)
Where are the puncta located? How is a NL duct performed?
2-5 cm from medial canthus + 1-2 mm bulbar to eyelid margin
flush saline though cannula to determine if NL is patent or to dislodge FB —> no excessive force, point downward and watch for exit from nostril
What is the point of NL flushes?
indicated for suspected obstruction (epiphora, mucopurulent discharge)
- physiologic - entropion, imperforate micropunta, dacryocystitis, neoplasia, stenosis
What is breed-related conformational epiphora due to? What breeds are most common? How do they present?
tight eyelid conformation + hair grows long and drains down the fur = can’t drain very well
small breeds (Maltese, Poodle) - no underlying ocular disease. normal NL system that flushes normally
What is imperforate puncta? When is this most common? How is it diagnosed?
puncta does not develop properly, causing epiphora
younger dogs - Goldens, Bulldogs
go to flush and observe outpouching of conjunctiva overlying the imperforate puncta ventrally
What treatment is recommended for imperforate puncta?
cut conjunctival where the tissue outpouching is observed —> most common on ventral puncta
+ treat with anti-inflammatories to discourage stricture while healing
What is dacryocystitis? What is the most common etiology?
inflammation of the NL duct/sac
focus of infection or FB
- common in outdoor dogs (FB) and rabbits (tooth roots cause occlusion)
What are 5 signs of dacryocystitis?
- epiphora
- thick, mucopurulent discharge from medial canthus
- conjunctivitis (medial!)
- painful dermatitis at medial canthus
- abscessation of sac with fistula formation
How is dacryocystitis diagnosed?
- purulent material from puncta
- inability to flush
- dislodgement of a FB on flush
- culture
- dacryocystorhinography, CT with contrast, MRI, cannulation
How is dacryocystitis treated?
- topical or oral steroids/antibiotics
- flushing daily for the first few days
- catheterization
- advanced surgery if needed
What is cicatricial NL duct obstruction? How is it treated?
scarring of the NL duct slows drainage of tears
flush under anesthesia and cannulate, leaving it in place until full healing takes place (3.5 Fr catheter or suture)
What is the most common disease of the third eyelid? What is the most common signalment?
prolapsed gland of the nictitating membrane
young Bulldogs, Mastiffs, Pugs, or Chihuahuas - floppy third eyelids
What underlying cause is thought to be responsible for prolapsed gland of the nictitating membrane? How does it appear?
laxity of the connective tissue of the third eyelid
mass-like protrusion behind 3rd eyelid
How is prolapsed gland of the nictitating membrane treated? What is the most common procedure?
surgical replacement (no removal!!) - can bring tear production to 35-40%
Morgan pocket technique - 2 conjunctival incisions on the posterior (bulbar) surface of the third eyelid around the gland, tuck it back in the pocket, and use 5-0 or 6-0 vicryl with knots on anterior surface
What signalment is most common affected by scrolled (everted) nictitating membrane cartilage? How does it affect patients?
young Great Danes, Mastiffs, or Bassets
typically cosmetic only, but can predispose to corneal ulcers
How is scrolled (everted) nictitating membrane cartilage corrected?
surgical removal of the bent/rolled over piece of cartilage
What 3 third eyelid tumors are most common? Which is a little more rare in dogs?
- adenocarcinoma
- hemangioma, HSA
- conjunctival lymphoma
(overall uncommon, typically affects gland or tissues)
SCC —> more common in cats and horses
Why are third eyelid tumors harder to diagnose?
can look like a prolapse, should biopsy for older patients
How is third eyelid neoplasia most commonly treated?
- edge of third eyelid = removal of third eyelid + histopathology —> often curative, removes gland, good margins
- expansion into orbit —> enucleation/extenteration
What is dacryops? What signalment is most commonly affected? How is it treated?
ectopic NL gland tissue reported as a cyst periorbitally, commonly within maxilla, near the medial canthus, or conjunctiva
young Bassett Houds or labradors
surgical removal or injection of sclerosing agent
