Lacrimal System Flashcards
What glands provide the aqueous layer of the tear film?
Lacrimal gland
Gland of third eyelid
How do you diagnose production of aqueous layer?
Superficial corneal and conjunctival inflammation = keratoconjunctivitis
Schirmer tear test I
<15mm wetting/minute = sicca (dry)
What are causes of quantitative KCS?
- Immune mediated destruction of lacrimal tissue *
Excision of third eyelid gland
Parasympathetic nerve lesions
Canine distemper
Drugs - atropine and sulfa drugs, anesthetics
What breeds are susceptible to KCS?
Small toy breeds
Cocker spaniel
Yorkshire terriers
West highland terrier
Bulldogs
T/F: KCS is usually bilateral
True
Clinical signs associated with acute KCS?
Mucopurleunt discharge
Blepharitis
Keratitis (superficial corneal neovascualrization) — seen dorsally first as tear film settles to ventral cornea
Conjunctivitis ( conjunctival hyperemia)
Chronic clinical signs due to KCS?
Corneal pigmentation
Treatment for KCS?
Topical cyclosporine — lifelong therapy
Tcell inhibitor and prevents destruction of lacrimal tissue
Anti-inflammatory effects
Should see response in 4-6weeks
What can you try to give a patient for KCS if they are unresponsive to cyclosporine A?
Tacrolimus (ophthalmic)
What are the 4 objectives of KCS treatment?
Replace tears (lubricate with artificial tear ointment)
Simulate more tears
Anti inflammatory
(Cyclosporine)
Antibiotic
- clear infection while tear film recovers
What is the cause of neurogenic KCS?
Loss of PSNS innervation to lacrimal gland and ispilateral nostril (dry nostril = xeromycteria)
— trauma, otitis interna, neoplasic, idiopathic
Treatment for neurogenic KCS?
Pilocarpine. — simulate PSNS
Can be oral or topical
What virus causes destruction of lacrimal glandular epithelium leading to KCS?
Canine distemper
Young dogs without proper vaccination (acute and severe)
What surgical therapy is used to treat KCS?
Parotid duct transposition
— when medical therapy fails
— parotid salivary duct is moved to lower conjunctival fornix and saliva replaces tears (must feed small and frequent meals)
What are disadvantages of parotid duct transposition?
Reaction to higher pH of tears
Moist pyoderma from overproduction
Mineral deposition in cornea and eyelids
What produces the lipid layer of the tear film which is important to stabilize the aqueous layer and prevent evaporation?
Meibomian glands
If you have clinical signs associated with keratoconjunctivitis but a normal shimmer tear test, what is this likely caused by?
Qualitative keratoconjunctivitis sicca
Check meibomian glands
Or disorders of mucin layer (goblet cells)
What clinical signs can be associated with qualitative keratoconjunctivitis sicca?
All KCS — blepharospasm, epiphora, hyperemia, superficial conjunctivitis, and keratitis
Corneal fibrosis — disorganized epithelium and storm create a whitish hazy appearance
What is the tear film breakup time test?
The time it takes fluorescin stain to break up on the ocular surface
Normal = 20sec
Abnormal <20sec indicated mucin deficiency
Treatment of qualitiative KCS?
Replace tears — lubricate with artificial tears
Reduce inflammation and stimulate tear production — immunomodulation
What do you call an overflow of tears on the face?
Epiphora
Causes of epiphora?
Poor drainage
— imperforate or hypoplastic puncta
— entropion
Blockage
—foreign body
— inflammation
— neoplasia
Diagnostics for epiphora?
Jones test — flurorescin stain in eye, observe in nostril (+ means patency)
Flushing of NL duct
-inert catheter into puncta and look for flow from opposite puncta, then occlude puncta and look for flow out nostril
What breeds do you see imperforate punctum? What is the treatment?
Cocker spaniel
Golden
Miniature poodle
Surgical resection and temporary placement of stent with topical antibiotics
