Lacrimal Secretory System, Nasolacrimal System, Nictitating Membrane

What is the overall purpose of the pre-corneal tear film?

Ensures ocular surface health

What are the functions of pre-corneal tear film?

Lubrication between lids and ocular surface

Aids corneal refraction

Antimicrobial

Primary corneal oxygen source

Removal of debris through tear drainage

What is the primary corneal oxygen source?

Pre-corneal tear film

What are the layers of the trilaminar tear film from outside in?

Lipid

Aqueous

Mucin

What does the lipid layer of the trilaminar tear film do?

Stabilizes and prevents evaporation of the aqueous layer

What does the aqueous layer of the trilaminar tear film do?

Produce corneal nutrition and removes wast

What produces the aqueous layer of the trilaminar tear film?

Orbital lacrimal gland and third eyelid gland

What produces the lipid layer of the trilaminar tear film?

Meibomian glands

What produces the mucin layer of trilaminar tear film?

Conjunctival goblet cells

Describe the mucin layer of the laminar tear film

Thickest layer with immunoglobulins (IgA)

Interface of tear film with hydrophobic epithelium

What stimulates basal tears?

Parasympathetics of CN VII

What are stimulated tears?

Come out with ocular pain and emotion

What glands make aqueous tears?

Orbital lacrimal gland (60-70%)

3rd eyelid gland (30-40%)

What is the path of tear film drainage?

1. Puncta

2. Canaliculi

3. Lacrimal sac

4. Nasolacrimal duct

5. Nasal punctum

Where does the nasal punctum open?

Ventral lateral nasal meatus

What is a quantitative cause of tear film deficiency?

KCS due to decreased aqueous tear production

Describe a qualitative tear film deficiency

Disorder of mucin or lipid tear components

Causes tear film instability

What do tear film deficiency result in?

Desiccation and inflammation of ocular surface

What is dry eye disease?

KCS

What are the C/S of KCS?

Conjunctival hyperemia

Mucoid to mucopurulent discharge

Blepharospasm

Dull lacklaster corneal surface

Keratitis, corneal pigmentation

Corneal ulcers

Secondary bacterial conjunctivitis

What is the most common cause of KCS?

Immune mediated causing lacrimal gland adenitis

What does bilateral KCS point you to?

Immune-mediated

Drugs

Infectious/inflammatory

Metabolic

Dehydration

What does unilateral KCS point you to?

Trauma

Iatrogenic

Congenital

What is the origin of unilateral KCS?

Neurologic in CN V and CN VII

What are the signs of a neurogenic dry eye?

Acute onset in an older dog with no tear production and that it is unilateral

How do you diagnose KCS?

STT (Schirmer tear test) < 15mm/min

How do you medically treat KCS?

Immune mediation via cyclosporine or tacrolimus, and artificial tears gel or ointment and topical antibiotic

How long do you have to treat KCS?

Forever

How do cyclosporine and tacrolimus work to treat KCS?

T-cell inhibitors to prevent immune-mediated cause

When is topical/oral pilocarpine (cholinergic agent) indicated for KCS?

Neurogenic cases

What are the side effects of systemic oral pilocarpine?

Salivation

Lacrimation

Urination

Defecation

How do you surgical treat KCS?

Parotid duct transposition to use saliva as lubrication of the cornea

When do you decide to treat KCS surgically?

If medical therapy fails

What needs to be done post op of a parotid duct transposition?

Frequent small meals to stimulate salivation

What are the complications of parotid duct transposition?

Mineral deposition

Moist dermatitis

Sialolith/sialocele

What causes qualitative tear deficiency?

Abnormality in mucin or lipid layer of tear film production

What are the C/S of a qualitative tear deficiency?

Subtle signs of dry eye with a NORMAL STT

What is the third eyelid?

Nictitating membraneW

here is teh nictitating membrane located?

Ventromedial orbit

What covers the third eyelid?

Conjunctiva

How does the third eyelid maintain its shape?

T shaped hyaline cartilage

What is on the bulbar surface of the third eyelid?

Lymphoid follicles

Where is the gland of the third eyelid located?

Base of cartilage

How much tear production does the gland of the third eyelid do?

30-40%

How does the nictitating membrane move?

Passively elevates as globe moves posterior

Sympathetic smooth fibers aid in TE retration

What are the functions of the Nictitating Membrane?

Produce aqueous tears

Distribute pre-corneal tear film

Protect ocular surface

What are the main clinical problems of the nictitating membrane?

Prolapsed third eyelid gland

Scrolled third eyelid cartilage

What is cherry eye?

Prolapsed gland of the third eyelid

What age are dogs with a cherry eye?

Less than 1 year

What breeds are susceptible to cherry eye?

English bulldogs, mastiffs, beagles, cocker spaniels, bassett hounds, brachycephalics

Burmese cats

How do you treat a cherry eye?

Morgan Pocket surgery

What is the signalment for scrolled third eyelid cartilage?

Giant breed dogs

What is the pathology of a scrolled third eyelid cartilage?

Stem/neck of T cartilage is bent

What can scrolled third eye cause?

Chronic discharge and conjunctivitis

How do you treat scrolled third eyelid cartilage?

Excise or cauterize bent cartilage

What is the signalment for nictitans neoplasia?

Older patients

How do you treat Nictitans neoplasia?

Excise mass and crytotherapy

Third eyelid removal

What are some examples of Nictitans Neoplasia?

Third eyelid adenoma/carcinoma

Lymphosarcoma

Hemangioma/sarcoma

Squamous cell carcinoma

Melanocytic neoplasm

What is a bilateral cause of nictitans neoplasia?

Lymphosarcoma

What is epiphora?

Overflow of tears onto eyelids/face

What are causes of epiphora?

Overproduction

Inadequate drainage

What can cause overproduction of tears leading to epiphora?

Surface pain/irritation

Intraocular disease

What can cause inadequate drainage of tears leading to epiphora?

Imperforate hypoplastic puncta

Functional obstruction (little white dogs)

Nasolacrimal blockage

If you see epiphora what do you need to do first?

Make sure it is not due to overproduction

How do you diagnose epiphora?

Jones test

Nasolacrimal duct flush

Imaging

When do you use epiphora diagnostic tests?

For investigation into inadequate drainage

When do you do a nasolacrimal duct flush to diagnose epiphora?

If negative jones test w/ a topical anesthetic