Lacrimal System and Nictitating Membrane Flashcards
Pre-corneal Tear Film
- Crucial for ocular surface health
- Numerous functions
– Lubrication between lids and ocular surface
– Aids corneal refraction
– Antimicrobial properties
– Primary corneal oxygen source
– Removal of debris through tear drainage
Trilaminar Tear Film
- layers
Aqueous Tear Production
Tear Film Drainage
lacrimal system and nictitating membrane (meekins)
Tear Film Deficiency
- *Quantitative = KCS
– Keratoconjunctivitis sicca
– Decreased aqueous tear production - Qualitative
– Disorder of mucin or lipid tear components
– Causes tear film instability - Result in desiccation and inflammation of the ocular surface
lacrimal system and nictitating membrane (meekins)
Keratoconjunctivitis Sicca (KCS)
- what
- who
lacrimal system and nictitating membrane (meekins)
Keratoconjunctivitis Sicca (KCS)
- Clinical Signs
lacrimal system and nictitating membrane (meekins)
KCS Causes
lacrimal system and nictitating membrane (meekins)
KCS Causes
• Neurologic dysfunction
lacrimal system and nictitating membrane (meekins)
Diagnosis of KCS
lacrimal system and nictitating membrane (meekins)
Summary: Treatment of KCS
- Tear stimulation – lacrimostimulants
- Tear replacement – lacrimomimetics
- +/- supplemental therapy
– Secondary bacterial infections - Client education
– Must use medications as often as directed
– May take a month or more to see STT improvement
– Tear stimulant therapy is lifelong! - Parotid duct transposition surgery option
lacrimal system and nictitating membrane (meekins)
Lacrimostimulants
- Cyclosporine A
- Optimmune® 0.2% ointment
- Compounded 1% or 2% drops or ointment
- Tacrolimus
- Compounded 0.02% or 0.03% formulations
- 10-100 times more potent than CsA in vitro
- T cell inhibitors with anti-inflammatory, anti-pigment, and possibly anti-fibrotic effects
- Use BID for life!
- Reputable compounding pharmacy is important
- Cholinergic agent (Pilocarpine)
- Indicated in cases of neurogenic KCS resulting from parasympathetic denervation
- Dilute topical (0.125%, compounded) or very careful oral dosing
- Warn owners of side effects!
- Salivation
- Lacrimation (desired!)
- Urination
- Defecation
- Warn owners of side effects!
lacrimal system and nictitating membrane (meekins)
Lacrimomimetics
• Tear replacements or substitutes
• Many OTC products
– Choose one with increased viscosity (not ‘rewetting drops’)
• Use 4-6 times daily+
– While tear production is decreased
– Ointments can be used before bedtime
Ocular Cleansing
- Frequently remove discharge
- OTC eyewash/saline
- Minimizes debris accumulation
- Important before lacrimostimulant application
- Ensure drug contacts ocular surface tissues
Antibacterial Medications
- Used for secondary bacterial infections or concurrent corneal ulcers (to prevent infection)
- Broad-spectrum topical antibiotic
– Triple antibiotic ophthalmic ointment preferred (NeoPolyBac)
– TID to QID for 2-3 weeks - Bacterial culture and sensitivity testing is warranted if purulent discharge persists
lacrimal system and nictitating membrane (meekins)
Surgical Treatment
• Parotid duct transposition (PDT)
- Saliva is used to lubricate the cornea in place of tears
- Recommended if medical therapy fails
• Must give adequate time for medical therapy response - Frequent small meals fed post-op to stimulate salivation
- Complications possible
• Mineral deposition
• Moist dermatitis
• Sialolith/sialocele - Most still need medications post-op
lacrimal system and nictitating membrane (meekins)
Qualitative Tear Deficiency
- what
- clinical signs
- Abnormality in mucin or lipid layer of tear film
- Clinical signs
- Conjunctival hyperemia and dull appearance to the corneal surface
- Keratitis consisting of variable pigmentation, edema, multifocal areas of fluorescein stippling or erosions
- With normal STT
- Marginal blepharitis, meibomianitis, chalazion
- Both cause and clinical sign
- Corneal ulcers possible (but less likely)
- Signs may be subtle
lacrimal system and nictitating membrane (meekins)
Qualitative Tear Deficiency
• Diagnosis
- Normal aqueous production (STT 15-25 mm/min)
- Lipid deficiency
- Inspect Meibomian glands/secretions
- Mucin deficiency
- **Tear film breakup time**
- Apply fluorescein dye
- Normal
- >20 sec dogs
- >17 sec cats
- **Tear film breakup time**
lacrimal system and nictitating membrane (meekins)
Qualitative Tear Deficiency Treatment
- lipid
- mucin
lacrimal system and nictitating membrane (meekins)
Nictitating Membrane
- what
- properties
Nictitating Membrane
- movement
- functions
- Movement
– Passively elevates as globe moves posterior in orbit
– Sympathetic smooth muscle fibers aid TE retraction (cats) - Functions
– Production of aqueous tears
– Distribution of pre-corneal tear film
– Protection of the ocular surface
– It’s there for a reason – don’t just cut it out!
lacrimal system and nictitating membrane (meekins)
Causes: Third Eyelid Elevation
lacrimal system and nictitating membrane (meekins)
Prolapsed Gland of the Third Eyelid
- common name?
- who?
lacrimal system and nictitating membrane (meekins)
Prolapsed Gland Treatment:
lacrimal system and nictitating membrane (meekins)
“Scrolled” Third Eyelid Cartilage
lacrimal system and nictitating membrane (meekins)
Nictitans Neoplasia
lacrimal system and nictitating membrane (meekins)
Epiphora
- what
- causes
lacrimal system and nictitating membrane (meekins)
Epiphora Diagnostic Tests
lacrimal system and nictitating membrane (meekins)
Dacryocystitis
- Clinical signs
- Mucopurulent discharge, epiphora, swelling or draining fistulas in medial canthal region
- Typically no blepharospasm, minimal conjunctival hyperemia
- Usually secondary to foreign bodies but rarely find them
- Treatment: repeated NL flushing, topical antibiotic + steroid solution
- May require surgery if FB is identified
Purulent discharge from lower lacrimal punctum
lacrimal system and nictitating membrane (meekins)
Summary
- KCS is the most commonly diagnosed tear film abnormality in…
- Major third eyelid abnormalities include…
- When epiphora is diagnosed…
- Dacryocystitis is…
- KCS is the most commonly diagnosed tear film abnormality in dogs
- Major third eyelid abnormalities include prolapsed NM gland and scrolled cartilage
- When epiphora is diagnosed, increased production vs. inadequate drainage must be determined
- Dacryocystitis is an uncommon problem, generally resulting in purulent ocular discharge without blepharospasm
