Disorders Of Conjunctiva & Nictitating Membrane

Question 1

Conjunctival anatomy

Answer 1

Mucous membrane
– Bulbar surface
– Palpebral surface
– Fornices
Non-keratinized stratified squamous epithelium
Lymphoid nodules
– Most prominent on bulbar conjunctiva of the third eyelid • Goblet cells
– Most prominent in the ventronasal fornix

Question 2

Normal flora and cytology

Answer 2

Gram + organisms predominate
– Bacterial overgrowth seen with various conditions, most
commonly KCS –
Fungi are normal inhabitants in equine and ruminants. Rarely seen in dogs.
• Cytology
– Non-keratinized squamous epithelium – Goblet cells – Rare leukocytes and bacteria

Question 3

Conjunctival Function

Answer 3

• Immunologic protection of the eye
– Conjunctiva associated lymphoid tissue (CALT)
• Contributes to the tear film –
Mucin production (goblet cells)
• Facilitate lid and eye movements
– Accordion movements

Question 4

Diagnosing conjunctival diseases

Answer 4

Visual inspection for localization
Schirmer test - how much aqueous fluid is being produced, rule out dry eye (15-25mL/min)
Conjunctival cytology & culture, biopsy or histo

Question 5

Features mistaken for pathology

Answer 5

Prominent epibulbar veins
Conjunctival pigmentation
Palpebral vs bulbar

Question 6

Conjunctivitis is… and is not …

Answer 6

Is a clinical sign
Is not a diagnosis

Question 7

Conjunctivitis signs of

Answer 7

LIU, KCS, glaucoma, orbital disease, corneal ulcer, diabetes

Question 8

conjunctivitis etiologies

Answer 8

Primary - infectious, allergies, friction, immune mediated
Secondary - ocular disease - eyelid, orbital, intra ocular
Systemic disease - vasculitis, metabolic disease, metastatic neoplasia

Question 9

Primary conjunctival disease

Answer 9

Infectious – Allergies – Frictional irritants – Immune-mediated

Question 10

Secondary conjunctival disease

Answer 10

Manifestation of ocular disease
– Eyelid, orbital, intraocular –
Manifestation of systemic disease
– Vasculitis, metabolic diseases, metastatic neoplasia, etc

Question 11

Infectious conjunctivitis

Answer 11

Bacterial - IBK exception
Viral
Rickettsial
Parasitic

Question 12

Feline infectious conjunctivitis

Answer 12

Most common/important
Calcivirus
Chlamydophila felis
Mycoplasma

Question 13

Feline herpes virus

Answer 13

Respiratory and conjunctival disease - highly contagious
Rose bengal corneal stain** PCR, cytology
Topical antibiotics for eyes

Question 14

Clinical signs of herpes

Answer 14

Unilateral or bilateral lesions
Herpetic keratitis
Dendritic ulcers - rose bengal stains
Symlephron - chronic sign of inflammation
Corneal sequestrum
Herpetic dermatitis

Question 15

Feline chlamydial conjunctivitis

Answer 15

INTENSE chemosis, unilateral but can be bilateral
Cytology**
Treat w topicals /systemic - doxycycline*
Main differential is mycoplasma felis

Question 16

Allergic conjunctivitis

Answer 16

Atopic conjunctivitis
- mild, pruritic, seasonal
Drug reaction conjunctivitis (hypersensitivity)
Severe, acute
Drugs: neomycin

Question 17

Canine follicular conjunctivitis

Answer 17

Very common, young dogs, large breeds
Conjunctival hyperemia, mucopurulent discharge
conjunctival follicle hypertrophy
Immunosuppressives, +/- oral, recurrences common until 2 years old

Question 18

Frictional irritants

Answer 18

Endo/exo irritants
- eyelid, cilia, foreign bodies
Address underlying cause, treat any developed 2nd disease

Question 19

KCS

Answer 19

Aqueous tear film deficiency
Most common cause of conjunctivitis in dogs***
Schirmer tear test
Treatment - immunosuppressives, Antimicrobials, ocular lubricants

Question 20

Conjunctival neoplasia

Answer 20

Hemangiosarcoma
Lymphosarcoma infiltration
Squamous cell carcinoma
Papilloma
Melanoma

Question 21

Miscellaneous conjunctival findings

Answer 21

Trauma
Hemorrhage
Icterus

Question 22

Nicitating membrane

Answer 22

Third eyelid

Question 23

Common disorders of NM

Answer 23

Third eyelid gland prolapse
– Scrolled cartilage
– Third eyelid elevation
– Plasmoma
– Third eyelid neoplasia

Question 24

NM anatomy

Answer 24

Located in inferonasal orbit - retracted by smooth muscle
T-shaped cartilage - swings contour to corneal surface, base holds the gland of the third eyelid
Responsible for 30% of aqueous humor for the eye
Lymphoid aggregates

Question 25

NM function

Answer 25

Corneal protection Passive in - dogs, EQ, Ruminants Active in - cats, birds Tear production - 30% Lymphoid / immune protection

Question 26

Cherry eye

Answer 26

Third eyelid gland prolapse Uni or bilateral, common in young dogs

Question 27

Scrolled cartilage

Answer 27

Cosmetic aberration, conjunctivitis, ocular discharge Common in large breeds Base or wings of the cartilage is affected - in or eversion Surgical*

Question 28

3rd eyelid elevation

Answer 28

Differentiate from scrolled cartilage and prolapsed 3rd eyelid gland

Question 29

Causes of 3rd eyelid elevation

Answer 29

Space occupying orbital lesions Horner syndrome Enophthalmos/phthisis bulbi – Uveitis – Dehydration – Tetanus

Question 30

Plasmoma - atypical pannus

Answer 30

Immune-mediated / inflammatory disease • Clinical signs – Thickening – Depigmentation – Follicle formation • Treatment –Immunosuppressives (topical +/- oral) – Life long therapy

Question 31

Appearance of plasmoma

Answer 31

Depigmentation and thickening of 3rd eyelid

Question 32

3rd eyelid neoplasia

Answer 32

Removal is ideal treatment Melanoma - malignant in cats Squamous cell carcinoma - common in horses Papilloma - common in young dogs Adenocarcinoma Hemangiosarcoma

Question 33

Hyperemia

Answer 33

Congestion of conjunctival vessels