Disorders of the Conjunctiva & Nictitating Membrane

Question 1

What bacteria comprises the conjuntiva’s normal flora

Answer 1

gram (+) organisms

• staphylococcus
• streptococcus

Question 2

Conjuntiva function

Answer 2

immunological protection barrier for eye; contributes to tear film (via mucin production); facilitate lid & eye movements

Question 3

Normal range of Schirmer tear test

Answer 3

15-25 mls per minute

Question 4

Clinical signs of conjunctivitis (5)

Answer 4

1. Hyperemia (increase in blood vessels//vascularization)
2. Chemosis (edema)
3. Exudate / discharge
4. Tissue proliferation (epithelial)
5. Ulceration

Question 5

Primary Conjunctival Diseases (4)

Answer 5

1. Infectious
2. Allergies
3. Frictional Irritants
4. Immune-mediated

Question 6

Secondary Conjunctival Diseases are…(2)

Answer 6

1. Manifestations of ocular disease (eyelid, orbital, intra-ocular)
2. Manifestations of systemic disease (vasculitis, metabolic diseases, metastatic neoplasia, etc.)

Question 7

What is one of the only exceptions of a primary bacterial conjunctivitis?

Answer 7

Infectious Bovine Keratoconjunctivitis by Moraxella bovis

Question 8

What is the most common cause of conjunctivitis in cats?
- Etiology?
- Diagnosis?
- Treatment?

Answer 8

Feline Herpesvirus
- a respiratory and corneoconjunctival disease that is ubiquitous // highly contagious
- diagnosis: hx, clinical signs, rose bengal corneal stain; virus isolation
- tx = topical or oral anti-virals

Question 9

Symblepharon

Answer 9

When conjunctivia gets stuck to cornea, preventing eye movemt. Chornic sign of inflammation.

Feline Herpesvirus

Question 10

What is a dendritic lesion?

Answer 10

Branching, linear lesion with a terminal bulb and swollen epithelial borders

Feline Herpesvirus (hallmark lesion in herpesviruses)

Question 11

Feline Chlamydial Conjunctivitis
- clinical signs
- diagnosis
- treatment
- main differential dx

Answer 11

Chlamydophila felis = gram (-), obligate intracellular bacterium

Clinical signs = Chemosis!+++++, Unilateral -> Bilateral

Diagnostic technique = cytology
Treatment
- topical, broad-spectrum: Terramycin (oxytet + Polymyxin B)
- PO (doxycycline, azithromycin)

DDx = Mycoplasmis felis

Question 12

What are the two most common drugs that cause drug-reaction conjunctivitis (hypersensitivity)?

Answer 12

Neomycin (cats - aminoglycoside, hydrophilic) and
Dorzolamide (dogs - carbonic anhydrase inhibitor)

Question 13

Clinical presentation of Allergic Conjunctivitis?

Answer 13

Chemosis++ (not as severe as in feline herpes)
Mucoid discharge, hyperemia

Question 14

Canine Follicular Conjunctivitis
- Pathogenesis
- Signalment
- Treatment

Answer 14

Lymphoid follicles in the conjunctiva become overstimulated by immune system => hypertrophy (esp. of the nictitans)
- Young, large breeds. (< 2 y/o)
- Tx = Oral immunosuppressives

Question 15

Frictional Irritants
- Causes
- Diagnosis
- Treatment

Answer 15

• Endogenous & exogenous irritants (eyelid abnormalities, cilia /hair abnormalities, foreign bodies) (entropion, eyelid masses; trichiasis = misdirection of eyelashes toward the globe, distichiasis = extra row of eyelashes)
• Dx = exam
• Tx = address underlying cause, treat any 2º ocular disease

Question 16

What causes Keratoconjunctivitis Sicca (KCS)? Clinical signs?

Answer 16

Any condition that impairs the ability to produce adequate amounts of tear film can result in dry eye.

Clinical signs: Crusty, muco-purulent d/ch, conjunctival hyperemia, keratitis

Question 17

Nicitating Membrane = ?

Answer 17

The third eyelid

Question 18

Nictitating Membrane functions (3)

Answer 18

1. Corneal protection (passive, active; windshield wiper effect)
2. Tear production (nictitan produces 1/3 of the aq. portion of the tear film!)
3. Immunologic (lymphoid aggregates on bulbar / posterior surface)

Question 19

How to examine nictitating membrane

Answer 19

Gently retropulsing the globe to get the 3rd eyelid to passively prolapse

Question 20

Third Eyelid Gland Prolapse (Cherry Eye)
- Clinical signs / signalment
- Pathogenesis
- Treatment Options

Answer 20

• Presents unilateral or bilateral
• young dogs (< 3 y/o) ; bulldogs, mastiffs, cocker spaniels, beagles, lhasa apso, pekingese
• tx: medical (pre-op topical anti-inflammatories) -> surgical (repositioning. of the gland)

Question 21

Why should you never remove the third eyelid gland? What is the only case where you would?

Answer 21

Never remove it b/c it provides 1/3 of the tear film. Removing it greatly. predisposes Pt to developing KCS!

Only indication to remove the gland = neoplasia

Question 22

Scrolled Cartilage
- clinical signs
- signalment
- pathogenesis
- treatment

Answer 22

• cosmetic aberration, conjunctivitis, ocular discharge
• congenital, large breeds
• base or wings of the nictitating cartilage becomes inverted or everted
• if causing clinical signs, can perform surgery

nictitating membrane = supported by a T-shaped cartilage structure

Question 23

Third Eyelid Elevation
- DDxs
- Causes

Answer 23

• DDx = Scrolled Cartilage and Cherry Eye
• Causes: horner’s syndrome, exophthalmos, endophthalmos, phtisis bulbi (globe shrinkage), uveitis, dehydration (cats), tetanus

Question 24

Plasmoma - Atypical Pannus
- Inciting cause
- Clinical signs
- Treatment

Answer 24

• Immune-mediated / inflammatory condition - infiltration of nictitans with plasma cells
• clinical signs: thickening, depigmentation, follicle formation
• tx = lifelong. immunosuppressives (topical +/- oral)

Question 25

Nictitan neoplasms common in…
1. Young dogs
2. Cats
3. Horses

Answer 25

1. Papilloma
2. Melanoma
3. Squamous Cell Carcinoma

Others: hemangiosarcoma, adeonomacarcinoma,