Conjunctiva and Lacrimal System Flashcards
Conjunctiva basics
Analogous to a mucous membrane Non-keratinized stratified columnar cells Richly vascularized May be pigmented 3 regions - Bulbar (on globe) - Palpebral (on eyelid) - Fornix (cul-de-sac)
Conjunctival physiology
Produce mucous component of tear film (goblet cells- mucin)
Provide a smooth, lubricated surface for eyelids to contact cornea
Disperse tear film
Remove debris from ocular surface
Protective/immunologic fxn (lymphoid follicles, IgA production)
Epithelium is continuous with cornea
Has normal population of bacteria
- Gr+
Few Gr -
- Interpret cultures with caution
Conjunctival uses
Easy to examine mucous membrane
Can give clues about pt systemic health
Look for petechiae, icterus, hemorrhage, palor
Conjunctivitis basics
Inflammation of conjunctiva Very non-specific response Variable CS Tx varies with cause Common in all species Cause varies by species
Common viral causes of conjunctivitis
FHV-1
Canine distemper
Canine herpesvirus
Bacterial causes of conjunctivitis
Uncommon in dogs and cats!
Secondary to KCS
Chlamydia in sheep, cats
Mycoplasma in goats
Parasitic causes of conjunctivitis
Thelazia Onchocerca Habronema Hepatozoon Leishmania
Common non-infectious causes of conjunctivitis
Immune mediated (KCS in dogs)
Allergic/environmental
- Follicular conjunctivitis
Always look for primary cause
FHV-1
Common cause of conjunctivitis in cats Wide spectrum of CS More common in young, stressed cats Tx: Reduce stress Cidofovir .5% sol'n BID or Famciclovir 40mg/kg TID or 90mg/kg BID
Allergic conjunctivitis
Follicular conjunctivitis
Chronic allergic stimulation
More common in dogs (very rare in cats)
May have concurrent skin allergies/atopy
May be seasonal
Conjunctival follicles (including conjunctiva of third eyelid)
Epiphora or mucoid ocular discharge
Dx of exclusion (cytology/biopsy: hyperplastic lymphoid tissue)
Tx: topical anti-histamines or anti-inflammatories
Diagnostic techniques
Complete ophthalmic examination Schirmer tear test Cytology Biopsy C&S Vital stains - Fluorescein - conjunctival ulcers/erosions - Rose Bengal - mucin deficiency
Conjunctivitis Tx
Depends on etiology - Targeted therapy . tear stimulants if KCS . Antiviral tx if herpes . Systemic tx if OMSD - Anti-inflammatories - Abx - Lubricants - Eye wash - NOT contact lens sol'n
Conjunctival neoplasia basics
Usually primary Often malignant FNA or biopsy to Dx Many amenable to local excision and adjunctive therapy (cryoablation, chemotherapy, hyperthermia) Enucleation may be required
Non neoplastic conjunctival masses
Dermoid
Inflammatory (nodular granulomatous episcleritis)
Parasitic granuloma (onchocerca)
Retrobulbar fat prolapse
Dermoid
Normal tissue, abnormal location
Tx: Sx
Traumatic abnormalities
Chemosis, hyperemia, lacerations, hemorrhage Lacerations rarely need suturing Hemorrhage - Blunt trauma - Proptosis - Strangulation - Coagulopathy
Nasolacrimal apparatus
Secretory components - Orbital lacrimal gland - Gland of TE Drainage system for tears - Upper and lower eyelid puncta (medial canthus) enter short canaliculi - Connect at lacrimal sac - NL duct opens in nasal vestibule
Drainage system
Puncta to canaliculus to lacrimal sac to nasolacrimal duct to nasal puncta
Tear film
3 layers
- Outer lipid layer - meibomian glands
- Middle layer - lacrimal glands
- Inner mucin layer - goblet cells, epithelial cells
Lubricate, cleanse, and protect globe
Surface health depends on both sufficient quantity and stability
7 fxn of tear film
Smooth ocular surface for refraction of light
Lubrication of the ocular surface and eyelids
Provide oxygen and nutrients to the corneal surface
Give WBC access to cornea and conjunctiva
Remove debris and foreign material from ocular surface
Defend ocular surface from pathogens
Keratoconjunctivitis sicca
Most common form: quantitative - Deficiency of aqueous layer - dogs most frequently affected Less common form: qualitative - Deficiency of mucus or lipid layers - Harder to Dx - Treat with HAbased drop or gel
Causes of KCS
Immune-mediated: #1 cause (T cell mediated destruction of lacrimal tissue) Metabolic disease (DM) Drug induced (sulfas, Etodolac NSAID, Atropine temporary) Infectious: CDV Congenital hypoplasia/aplasia of lacrimal gland Anesthesia/sedation Neurogenic (CNVII) Vitamin A deficiency Loss of CN V afferent fxn Radiation Trauma Iatrogenic
KCS predisposed breeds
English bulldogs, WHWT, Lhasa Apso
CS of KCS
Mucoid, ropy, tenacious discharge Conjunctival hyperemia/conjunctivitis Corneal vascularization Corneal pigmentation Corneal fibrosis Corneal ulceration Lackluster corneal surface Blepharitis Loss of vision
Schirmer tear test
Quantitative assessment of tear fluid
Normal 15-25mm/min
Quantitative tear deficiency = KCS
Perform in all cases of conjunctivitis
Tear film breakup time
Indication of tear stability Fluorescein applied Lids blink, then hold open Tear film is observed under cobalt-blue light and the time between the last blink and appearance of the first break in tear film is recorded <10sec abnormal
Medical Tx of KCS
Lacrimostimulants
- Cyclosporine A or Tacrolimus
- Inhibit T cells from infiltrating and destroying lacrimal gland
- 2-3 mo to reach efficacy
Tear replacement
- Gel or ointment preferable - longer lasting
- More frequent admin until tear stimulant has reached efficacy
Cyclosporine
Increases tear production in 80% of cases
Has T helper cell inhibitory activity
Reduces pigmentary keratitis
Treat for 4-8 wk before considering treatment failure
Alternative related drugs: tacrolimus, Pimecrolimus
Potential complications of a parotid duct transposition
Excessive tear flow and facial dermatitis
Ca precipitates can deposit on the cornea creating a keratopathy
Sialoliths can also cause blockage and necessitate Sx repair
