4. Diseases of the lacrimal glands and duct. Keratitis sicca

What are the components of the nasolacrimal system?

Puncta lacrimalis, canaliculi lacrimalis, saccus lacrimalis, ductus nasolacrimalis, puncta nasalis

Where is the nasolacrimal system located?

In the medial canthus, internally

What is epiphora?

Tear overflow due to impaired tear drainage (wet eye)

What are examples of causes of epiphora/wet eye?

1. Imperforate puncta/congenital puncta

2. Obstruction of nasolacrimal system (tear duct)

3. Dacryocystitis

What can cause blockage of the lacrimal punctum?

Congenital (imperforate puncta) or acquired obstructions (inflammatory cells, debris, foreign material)

What is imperforate puncta/congenital puncta?

A congenital condition where the tear duct opening has not developed properly, or the canaliculi are misplaced

What are the clinical signs of imperforate puncta?

Excessive tearing (epiphora), wetness/staining of fur around the eyes, recurrent eye infections, and conjunctivitis

How is imperforate puncta diagnosed?

Clinical signs, inability to cannulate the duct (ballooning on flushing), culture, fluorescein testing, and imaging studies with contrast

What are the differential diagnoses for imperforate puncta?

Blocked tear ducts (nasolacrimal duct obstruction), corneal ulcers, and eyelid abnormalities

How is imperforate puncta treated?

Topical lubricants/ointments. For chronic epiphora, surgery (punctoplasty [opening or widening of puncta] or dacryocystorhinostomy [creation of a new tear drainage pathway]) may be performed

What causes obstruction of the nasolacrimal system (tear duct)?

1. Congenital absence of the inferior canaliculus, imperforate puncta

2. Acquired factors (dacryocystitis, foreign bodies, scarring from trauma/inflammation)

What is the pathogenesis of nasolacrimal system obstruction?

Blockage or narrowing of the tear ducts disrupts normal tear flow from the eyes to the nasal cavity, resulting from inflammation, scarring, or structural abnormalities

What are the clinical signs of nasolacrimal system obstruction?

Epiphora, stained fur around the eyes, recurrent eye infections, mucopurulent discharge, conjunctivitis, pain, and abscesses

How is nasolacrimal system obstruction diagnosed?

Clinical signs, negative fluorescein passage into nasal cavity, and dacryocystorhinography (fluoroscopic contrast examination of nasolacrimal apparatus)

What are the differential diagnoses for nasolacrimal system obstruction?

Imperforate puncta, corneal ulcers, eyelid abnormalities, and primary ocular diseases

How is nasolacrimal system obstruction treated?

Flushing, fluorescein passage check, topical antibiotics and corticosteroids, and conjunctivorhinostomy (create passage)

What is dacryocystitis?

Inflammation of the lacrimal sac

What causes dacryocystitis?

Obstruction by inflammatory cells, debris, foreign bodies, or masses pressing on the duct

What is the pathogenesis of dacryocystitis?

Nasolacrimal duct obstruction leads to tear stasis in the lacrimal sac, creating an environment for bacterial growth and infection

What are the clinical signs of dacryocystitis?

Epiphora, conjunctivitis, a fistula draining into the medial lower eyelid, and swelling in the medial lower eyelid

How is dacryocystitis diagnosed?

Negative fluorescein passage and X-ray with contrast

What are the differential diagnoses for dacryocystitis?

Other causes of eye irritation, discharge, and swelling, such as conjunctivitis, corneal ulcers, eyelid abnormalities, or orbital cellulitis

How is dacryocystitis treated?

Topical antibiotics, tubing, nasolacrimal cannulation, and potentially conjunctivorhinostomy

What are types of disorders causing dry eyes?

1. Dry eye syndrome/keratoconjunctivitis sicca

2. Meibomian gland dysfunction

3. Mucin abnormality

4. Cysts and neoplasia of the lacrimal secretory system

What is dry eye/keratoconjunctivitis sicca (KCS)?

A common canine ocular disorder characterised by aqueous tear deficiency leading to desiccation and inflammation of the conjunctiva and cornea, ocular pain, progressive corneal disease, and reduced vision

What are some causes of aqueous tear deficiency in KCS?

1. Infectious causes: Canine distemper virus, chronic blepharoconjunctivitis, and other ocular surface infections

2. Congenital: Acinar hypoplasia, lacrimal gland hypoplasia

3. Drug-induced: Systemic sulfonamide or topical atropine

4. Metabolic disease hypothyroidism, cushings, diabetes mellitus

5. Immune-mediated: lacrimal gland adenitis

What are the clinical signs of KCS?

Vary depending on the stage.

Early stage: red and inflamed eyes with intermittent mucoid/mucopurulent discharge. Blepharitis and periocular dermatitis are common.

Progressive disease: increased discomfort and persistent blepharospasm

What are the pathological changes seen in KCS?

Epithelial defects, inflammation, vascularisation, and scarring.

Decreased tear production or altered tear composition on microscopic examination of tear film

How is KCS diagnosed?

Clinical signs, ocular staining, Schirmer tear test (less than 15 mm/min is suggestive; < 8 mm/min is severe), and Rose Bengal stain (detect devitalised cells). IOP is normal.

What are the differential diagnoses for KCS?

Infectious or immune-mediated conjunctivitis, corneal dystrophies/degenerations, neurogenic keratitis, and meibomian gland dysfunction

How is KCS treated medically?

1. Tear stimulation with pilocarpine (oral or topical)

2. Artificial tear replacement/lubrication

3. Topical/oral ATB

4. Mucolytics (sodium hyaluronate & cyclorine A)

5. Cyclosporine ointment (immunosuppressive for 4 weeks)

6. Anti-inflammatories

How is KCS treated surgically?

• Parotid duct transposition: saliva & tear are nearly normal in osmolality & pH, & may substitute lack of tears

• Partial tarsorrhaphy: May be beneficial in some dogs to protect cornea.

• Replacement of prolapsed nictitans gland

• Conjunctival or nictitans flap for ulcers & protection of cornea

What is meibomian gland dysfunction?

An important cause of evaporative dry eye, potentially due to developmental eyelid defects or acquired abnormalities like marginal blepharitis and meibomianitis.

Which breeds are predisposed to meibomian gland dysfunction?

King Charles Cavalier and Shih Tzu

What are the clinical signs of meibomian gland dysfunction?

Increased evaporative loss, premature tear film break-up, and dry eye

What are the pathological changes in meibomian gland dysfunction?

Inflammation, hyperkeratosis, glandular duct obstruction/dilation (chalazion), and glandular atrophy

How is meibomian gland dysfunction diagnosed?

Swabs, impression smears/scrapes of eyelid margins, culture/sensitivity, biopsy, and tear break-up time (TBUT) test

How is the tear break-up time test carried out?

Add fluorescein, let blink and hold eye to see how fast the fluorescein forms dark spots on cornea aka breaks (normal: 20 seconds in dog)

What are the differential diagnoses for meibomian gland dysfunction?

Aqueous deficiency dry eye (KCS), allergic conjunctivitis, and infectious conjunctivitis

How is meibomian gland dysfunction treated?

Tear stimulation, tear replacement, topical/oral antibiotics, mucinolysis, and anti-inflammatories

What is a mucin abnormality?

A problem with the production or distribution of mucin (a component of the tear film that helps the aqueous layer adhere to the cornea) → evaporative dry eye.

Where is the mucin layer produced?

Goblet cells of the conjunctiva

What can cause mucin abnormalities?

1. Genetic disorders

2. Autoimmune diseases (e.g., Stevens-Johnson syndrome)

3. Inflammatory conditions (e.g., allergic conjunctivitis, chronic blepharitis)

4. Environmental factors (toxins or pollutants)

What are the clinical signs of mucin abnormalities?

Usually chronic keratoconjunctivitis, often with no ocular discharge and normal aqueous production. Poor response to treatment or recurrence after treatment stops

How are mucin abnormalities diagnosed?

Clinical signs, fluorescein break-up test (TBUT <5 seconds is suggestive), and conjunctival biopsy to quantify goblet cells

What are the differential diagnoses for mucin abnormalities?

Aqueous deficiency dry eye (KCS), meibomian gland dysfunction, allergic conjunctivitis, infectious conjunctivitis, and neurotrophic keratitis

How are mucin abnormalities treated?

Topical mucomimetics/mucin replacers and topical corticosteroids

What are cysts and neoplasia of the lacrimal secretory system?

Uncommon conditions that may originate from orbital or nictitans glands.

What causes cysts in the lacrimal system?

Obstruction or dilation of lacrimal ducts

What can cause neoplasms in the lacrimal system?

Genetic predisposition, inflammation, trauma, or environmental factors

What are the clinical signs of lacrimal system cysts and neoplasia?

Palpable masses/swelling in the lacrimal gland region, ocular discharge, changes in tear production/quality (dry eye), ocular discomfort, and secondary ocular/periocular inflammation

What are the pathological findings in lacrimal system cysts and neoplasia?

Cysts: cystic structures lined by epithelial cells.

Neoplasms: abnormal cell proliferation

How are lacrimal system cysts and neoplasia diagnosed?

Clinical signs, ultrasound, and FNA/biopsy

What are the differential diagnoses for lacrimal system cysts and neoplasia?

Dacryoadenitis, infection/abscess, and benign (pleomorphic adenoma) or malignant tumours (adenocarcinoma)

How are lacrimal system cysts and neoplasia treated?

Treatment depends on the type, nature, and extent of the lesion.

Options include surgical excision, drainage/aspiration of cysts, anti-inflammatory/antimicrobial therapy, and radiation/chemotherapy for neoplasia

What is instability of the tear film (paradox in poodles)?

Certain breeds or dogs will have epiphora or normal eyes but suffer from dry eyes. So they may have enough tear volume, but if the mucin layer is insufficient or the lipid layer is compromised, the tear film cannot effectively adhere to the ocular surface.

What drugs are used for KCS?

Topical cyclosporine, lubricant and daily cleaning with NaCl