Unit 1 - Lacrimal Gland and 3rd Eyelid Flashcards
Precorneal tear film is crucial for ________ _______ health. It is only __-__ um thick.
ocular surface
7-10 um thick
What are the functions of precorneal tear film?
Lubrication between lids and ocular surface Aids corneal refraction Antimicrobial properties Primary corneal oxygen/nutrition source Removal of debris through tear drainage
What are the layers of the trilaminar tear film?
Lipid (outermost), aqueous (intermediate), and mucin (innermost)
What produces the lipid layer of trilaminar tear film?
Meibomian glands
What is the function of the lipid layer of trilaminar tear film?
Stabilizes and prevents evaporation of the aqueous layer
What produces the aqueous layer of trilaminar tear film?
The orbital lacrimal gland (~2/3) and the gland of the third eyelid (~1/3)
What is the function of the aqueous layer of trilaminar tear film?
Provides corneal nutrition, primary tear proteins, and removes waste products
What produces the mucin layer of trilaminar tear film?
Conjunctival goblet cells
The mucin layer of trilaminar tear film is the _____ layer and contains immunoglobulin ___.
thickest; IgA
What is the function of the mucin layer of trilaminar tear film?
Anchors tear film to the corneal epithelium
What controls the production of basal aqueous tears?
Parasympathetics and CN VII
What controls the production of stimulated aqueous tears?
Ocular pain (corneal irritation)
Emotions in humans
What glands contribute to aqueous tear production?
Orbital lacrimal gland (60-70%), 3rd eyelid gland (30-40%), and accessory glands (Harder’s, Wolfring, and Krause)
What structures are responsible for tear film drainage?
Puncta, canaliculi, lacrimal sac, nasolacrimal duct, and nasal punctum
There is a superior and inferior puncta. _____ only have an inferior. _____ only have a superior.
Rabbits, pigs
Where does the nasal punctum open?
Into the ventral lateral meatus
50% of dogs also have an opening into the oral cavity
What is quantitative tear film deficiency?
When there is a decreased amount of aqueous tear production
What is qualitative tear film deficiency?
A disorder of mucin or lipid tear components which causes tear film instability
What do tear film deficiencies result in?
Desiccation and inflammation of the ocular surfaces
___________________ is also known as dry eye disease and is due to insufficient aqueous tears?
Keratoconjunctivitis Sicca
What result is considered normal for the Schirmer tear test (STT)?
15-25 mm/min
What result of the STT is indicative of KCS? What result is marginal?
KCS - <10 mm/min
Marginal - 10-15 mm/min
What species is KCS common in?
dogs
What clinical signs are associated with KCS?
Conjunctival hyperemia, mucoid to mucopurulent discharge, secondary bacterial conjunctivitis, blepharospasm +/- blepharitis, dull lusterless corneal surface, keratitis, and corneal ulceration
What is the most common cause of KCS?
Immune-mediated/idiopathic
What are other causes of KCS?
Infectious/inflammatory, trauma, iatrogenic, systemic metabolic diseases, congenital acinar hypoplasia, neoplasia of the lacrimal gland or third eyelid gland, neurologic dysfunction, drug toxicity, and transient tear reduction
What drug toxicity can cause KCS?
Etolodac, Trimethorpim/sulfonamide, sulfasalazine, sulfadiazine, phenazopyridine, 5-aminosalicylic acid
What can cause transient tear reduction resulting in KCS?
Atropine, general anesthetics, topical anesthetics, and debilitation/dehydration
What breed group are at a higher risk of KCS?
Brachycephalic
How is KCS diagnosed?
Based on STT results and clinical signs
When should you suspect KCS if you get a marginal result from the STT?
IF there are concurrent clinical signs
What can cause a false elevation in the STT?
pain
KCS is rare in cats, when should you suspect it?
If STT is <9 mm/min and concurrent signs
How do you treat KCS?
Tear stimulation, tear replacement, +/- supplement therapy, client education
There are episcleral cyclosporine implant or parotid duct transposition surgery options
What immunomodulating lacrostimulants can be used in treatment of KCS?
Cyclosporine A and Tacrolimus
Pimecrolimus and Sirolimus are under investigation
How do immunomodulating lacrostimulants work?
Inhibit T cell activation, anti-inflammatory effects, reduce corneal pigment and scarring, and stimulate lacrimation
T/F: It may take weeks to months for tear value increase with the use of immunomodulating lacrostimulants.
True - it is important to recheck in 4-6 weeks
What is the protocol for using immunomodulating lacrimostimulants?
Give 1 drop of cyclosporine or tacrlimus BID (every 12 hours) or TID in refractory cases
If positive response, use diligently for life
When may a cholinergic lacrimostimulant be indicated?
Pilocarpine may be indicated in cases of neurogenic KCS resulting from parasympathetic denervation
What are lacrimomimetics?
Tear substitutes
How often should lacrimomimetics be used?
4-6 times daily
Ocular cleansing minimizes _______ accumulation and is important before ___________ appliation.
debris; lacrimstimulant
What mucinolytic agent is used BID-QID initially and facilitates the removal of copious exudates?
Acetylcysteine 5%
When are antibacterial medications used in the treatment of KCS?
When there are secondary bacterial infections or concurrent corneal ulcers
What antibacterial medication is preferred for the treatment of KCS?
Triple-antibiotic ophthalmic ointment (neomycin, polymyxin B, and bacitracin) - TID-QID for 2-3 weeks
T/F: Anti-inflammatory therapy is recommended topically when treating KCS
False
Why may you not need anti-inflammatory therapy for treatment of KCS?
Improving tear production and providing lubrication reduces ocular inflammation, corneal scarring, vascularization, and pigmentation
Topical steroids should be used for select cases only. Steroids delay the healing of ______ and potentiate _______. They should never be used when ______ _______ is very low.
ulcers; infection; tear production
What is used to lubricate the cornea in place of tears when you do a parotid duct transposition surgery?
saliva
When is PDT surgery recommended?
If KCS medical therapy fails
What complications are associated with PDT surgery?
Mineral deposition, moist dermatitis, and sialolith/sialocele
T/F: You still will need medications post-op from PDT surgery/
True
Why are episcleral cyclosporine implants typically not done?
Because they have limited duration and a variable success rate
What clinical signs are associated with qualitative tear deficiency?
Conjunctival hyperemia and dull appearance to the eye
Keratitis consisting of variable pigmentation, edema, and multifocal areas of fluorescein stippling or erosions
Marginal blepharitis, meibomianitis, or multiple chalazia
+/- corneal ulcers
How is qualitative tear deficiency diagnosed?
Normal STT with an abnormal tear film breakup time (TBUT)
How do you determine TBUT?
Apply concentrated fluorescein.
Do not rinse
Blink eyelits to distribute dye across cornea
Illuminate with cobalt-blue light
Hold lids open and monitor for ‘dark spots’ in green corneal tear film
What is the normal tear break-up time?
> 20 seconds
What is the TBUT for mucin deficiency?
<5 seconds
How is qualitative tear deficiency treated if there is a lipid deficiency?
Warm compress to alleviate impacted glands
For meibomianitis - systemic and topical abx, +/- systemic steroids
For hordeolum or chalazia - manual expression or surgical incision and curettage
Lipid substitutes - ophthalmic ointment lubricant
How is qualitative tear deficiency treated if there is a mucin deficiency?
Artificial tears with mucinomimetic properties and topical cyclosporine or tacrolimus BID
What are the general management practices for qualitative tear deficiency?
Treat secondary bacterial infections and corneal ulcers if present
DO NOT use topical steroids
Address confounding ophthalmic or conformational issues
What are some supplemental therapy options for tear film deficiencies?
Systemic doxycycline to provide anti-inflammatory effects, improve tear film stability and reduce ocular irritation
Omega-3 fatty acid supplementation to provide an anti-inflammatory effect and improved tear film
What is epiphora?
Overflow of tears onto eyelids
What are the different causes of epiphora?
Overproduction and/or inadequate drainage
What can cause overproduction of tears resulting in epiphora?
Surface pain/irritation or intraocular disease
What can cause inadequate drainage of tears resulting in epiphora?
Imperforate/hypoplastic puncta, functional obstruction, and nasolacrimal blockage
What are the diagnostic tests for epiphora?
Jones test, nasolacrimal duct flush, and imaging
How is the Jones test done?
Place fluorescein in the eye and hold the nose downward for up to 5 minutes. Observe for fluorescein exiting nares.
A positive test indicates that the NL duct is patent. It is negative if there is no passage
How is the nasolacrimal duct flush done?
Apply a topical anesthetic (proparacaine).
Insert a 24 g IV catheter (attached to syringe with eyewash) into the puncta.
Flush and look for flow from the opposite puncta, then occlude and look for nasal flow (may observe swallowing if draining into the mouth)
What imaging can be done to diagnose the cause of epiphora?
Skull radiography, computed tomography, and contrast study (dacryocystorhinography)
Imperforate puncta is puncta _______. It is common in cocker spaniels, goldens, miniature poodles, horses, llamas, alpacas, and others. It can affect ____, _____, or both puncta. It can be unilateral or biateral. It usually affects the _____ puncta in small animals. You may see conjunctiva over the _________ bulge during nasolacrimal flush from other punctum.
apalasia; superior, inferior; inferior; canaliculus
How is imperforate puncta treated?
Surgical resection of conjunctiva, +/- temporary placement of nasolacrimal stent, postop topical antibiotic/steroid drop
What does a functional obstruction of the tear duct result in?
excessive epiphora with tear staining
How is a functional obstruction diagnosed?
Negative jones test but positive NL flush
What causes a functional obstruction?
Ventromedial entropion ‘pinches off’ the lower punctum/canaliculus
Medial canthus trichiasis often contributes by wicking tears
In what breeds are functional obstructions common in?
Toy and brachycephalic breeds
What are the options for treatment of functional obstructions?
Surgical options, tetracycline abx or probiotics, and/or eyelid cleansing
What is the most common treatment for functional obstruction?
eyelid cleansing
What are the surgical options for functional obstruction treatment?
Temporary tacking to decide if sx would be beneficial
Hotz-Celsus if entropion
Medial canthoplasty for trichiasis +/- entropion
The use of tetracycline antibiotics or probiotics to treat functional obstructions may decrease ______, but does not alter _______.
staining, epiphora
What clinical signs are associated with dacryocystitis?
Mucopurulent discharge, epiphora, swelling or draining fistulas in medial canthal region
What is dacryocystitis usually secondary to?
foreign bodies, but we rarely find them
How is dacryocystitis treated?
Repeated nasolacrimal duct flushing
Culture discharge to determine appropriate abx
+/- surgery
Placement of temporary nasolacrimal stent and topical abx drops
What is another term for the third eyelid?
The nictitating membrane
The nictitating membrane is located on the ________orbit. It is covered with _________ and is a __-_______ hyaline cartilage. There are lymphoid follicles located on the ______ surface. The gland of the third eyelid surrounds the ______ base and is a ______ gland that is responsible for 30-40% of the basal tear production.
Ventromedial conjunctiva T-shaped bulbar cartilage seromucous
What aids in the retraction of the third eyelid?
Sympathetic smooth muscle fibers
What are the functions of the third eyelid?
Production of aqueous tears
Distribution of precorneal tear film
Protection of the ocular surface
What can cause third eyelid elevation?
Pain, enophthalmos or small globe, exophthalmos, neoplasia of the third eyelid neurologic, tranquilizers, tetanus, ‘Haws syndrome’ in cats, or it is an illusion
What neurologic disorders can cause third eyelid elevation?
Horner’s syndrome and dysautonomia
What is cherry eye?
When the gland of the third eyelid prolapse
What is the signalment for cherry eye?
Young dogs less than a year of age
Breed predisposition - english bulldogs, mastiffs, beagles, cockers, bassett hounds, and brahcycephalics
Burmese cats
How is a prolapsed third eyelid gland treated?
manual replacement - temporary
surgical replacement
T/F - You should never excise a prolapsed third eyelid gland.
True
What techniques can be done to surgically correct a third eyelid gland prolapse?
Morgan pocket technique, orbital tacking procedure, rectus muscle tacking, and others
What breed of dogs is everted third eyelid cartilage common in?
large/giant breed dogs
What causes everted third eyelid cartilage?
The stem/neck of the T cartilage is bent and everted outwards
What can everted third eyelid cartilage causE?
chronic discharge and conjunctivitis
How is everted third eyelid cartilage treated?
Surgically excise the folded portion of the cartilage
With low energy electrocautery, treat the posterior surface +/- cartilage tips to remodel and reform
