External Ocular Pathology

Question 1

Developmental anomalies of the globe

Answer 1

Anophthalmia
Microphthalmia
Cyclopia

Question 2

Developmental anomalies of globe

Answer 2

Dermoid
Coloboma
Collie eye anomaly
Merle ocular dysgenesis

Question 3

Anophthalmia

Answer 3

No development of optic vesicle
Usually bilateral
Uncommon - often misdiagnosed as severe microphthalmia

Question 4

Microphthalmia

Answer 4

Miniature globe in normal sized orbit/socket
Involution following injury to globe
-in utero trauma
-ischemic injury
- infection

Question 5

Cyclopia*

Answer 5

Single midline globe
If diplication of Intra ocular structures = Synophthalmia - often misdiagnosed

Question 6

cause of cyclopia

Answer 6

Spontaneous - RARE
Ewe ingests Veratrum califonicum on day 14 of ingestion
Usually other developmental anomalies in other organs

Question 7

Dermoid

Answer 7

Presence of haired skin in the corneal or conjunctival epithelium
CLIN SIG: depends on degree of corneal irritation caused by hair

Question 8

Coloboma

Answer 8

Defect resulting from incomplete closure of optic fissure
Can result in outpouching of retina
One in the lesions of collie eye anomaly

Question 9

Collie eye anomaly

Answer 9

Heritable disease of rough and smooth collies
Multiple concurrent anomalies
- choroid hypoplasia & hyperpigmentation
- posterior Coloboma
- retinal detachment
- microphthalmia

Question 10

Merle ocular dysgenesis

Answer 10

Merle gene = color dilute
Homozygous dogs have light coat and can have multiple congenital ocular lesions

Question 11

Merle gene congenital ocular lesions

Answer 11

Microphthalmos
Iris abnormalities: Coloboma, hypoplasia, persistent pupillary membranes
Lens abnormalities: microphakia (small lens), cataract, lens luxation
Sclera Coloboma
Retinal dysplasia or detachment

Question 12

Extra ocular neoplasia

Answer 12

Squamous cell carcinoma
Meibomian Adenoma
Melanocytic neoplasms

Question 13

Squamous cell carcinoma

Answer 13

Common in cattle & horses w non pigmented eyelids /conjunctiva exposed to sunlight
Cats: affects eyelids of white faced cats
Dogs = uncommon

Question 14

Meibomian adenoma

Answer 14

Most common tumor of eyelid in dogs
Meibomia- modified sebaceous gland in eye
Similar to sebaceous adenoma = benign

Question 15

Melanocytic neoplasms

Answer 15

Eyelid = benign —> melanocytoma
Limbus = benign
Conjunctiva = malignant melanoma

Question 16

Corneal epithelium

Answer 16

Keeps tear film out of cornea

Question 17

Corneal endothelium*

Answer 17

Not endothelium, specialized epitheliu, cells
Main job to actively pump out fluid /aqueous humor from the anterior chamber to keep cornea dehydrated

Question 18

Corneal edema

Answer 18

Fluid in the interstitial space = blindness

Question 19

Corneal responses to injury

Answer 19

Adaptive cutaneous metaplasia
Epithelial stromal necrosis
Wound healing/repair

Question 20

Adaptive cutaneous metaplasia

Answer 20

Reponse to persistent mild irritation
Keratinization, epithelial hyperplasia, neovascularization - sprouting of new blood vessels from limbus

Question 21

Epithelial/stromal necrosis

Answer 21

Response to more severe external injury
Corneal ulceration - secondary edema

Question 22

Causes of epithelial/stroma necrosis

Answer 22

Dessication (KCS) - keratoconjunctivitis sicca, when eyelids don’t fully cover eye or inadequate production of eye fluid /tears
Mechanical injury
Chemicals
Infection

Question 23

Keratomalacia

Answer 23

Secondary softening of the cornea, a result of infected corneal ulcer

Question 24

desemetocele

Answer 24

Deep central corneal ulcer
High risk of rupturing leading to perforating ulcer

Question 25

Wound healing/repair

Answer 25

Epithelium - sliding of cells followed by mitosis Stroma - repaired stroma/collagen, not transparent with chronic/larger damage

Question 26

Feline corneal sequestrum

Answer 26

Increased superficial stromal necrosis compared to normal corneal epithelial injury Accumulation of brown pigment from tear film into corneal stoma Central dark brown corneal pigment from iron(porphyria’s) Persians and Himalayan’s= predisposed

Question 27

Canine ulcerative keratitis

Answer 27

Endogenous trauma -eye lash disorders, e troponin, KCS Can result in secondary bacterial infection

Question 28

Canine persistent ulcer syndrome

Answer 28

Boxer ulcer

Question 29

Infectious bovine keratoconjunctivitis

Answer 29

“Pink eye” Caused by moraxella bovis Specific virulent strains are able to colonize in cornea Transmitted by flies, direct contact or fomites Differentiate from IBR

Question 30

lesion for pink eye

Answer 30

Corneal ulcer that progresses to suppurative keratomalacia Similar lesions in sheep/goats - chlamydia, mycoplasma

Question 31

Feline herpes virus I

Answer 31

Causes keratitis and corneal ulceration VERY COMMON Corneal edema is secondary to ulceration

Question 32

Canine pannus keratitis

Answer 32

German shepherd pannus Chronic superficial keratitis Lesions begin at lateral limbus and spreads toward central cornea = bilateral Response to immunosuppressive therapy

Question 33

Equine mycotic keratitis

Answer 33

Due to secondary fungal infection of corneal wound (exogenous trauma) Aspergillus most common (like descemets membrane) Can progress to suppurative keratomalacia and corneal perforation

Question 34

Bovine conjunctivitis

Answer 34

Infectious bovine rhinotracheitis Parasitic conjunctivitis

Question 35

Infectious bovine rhinotracheitis

Answer 35

Caused by bovine herpes virus I Does not produce corneal ulceration Primary differential DX - infectious bovine keratoconjunctivitis = corneal involvement, pink eye starts in cornea

Question 36

Parasitic conjunctivitis

Answer 36

Thelazia Inhabit conjunctival sac and lacrimal duct Larvae transmitted by flies

Question 37

Canine conjunctivitis common causes

Answer 37

Allergic disease Mechanical irritation Dessication

Question 38

Nodular granulomatous episcleritis

Answer 38

NGE - canine conjunctivitis Nodular lesion of episclera or conjunctiva Proliforation of - histiocytes - fibroblasts - lymphocytes - Plasma cells

Question 39

Feline conjunctivitis

Answer 39

Feline herpes virus I Initial infection in young cats = keratitis (cornea)+ conjunctivitis Recurring infection in older cats may cause conjunctivitis alone Chlamydiophila felis

Question 40

equine conjunctivitis

Answer 40

Habronemiasis Nematode larvae of habronema deposited in conjunctiva Lesion = eosinophilic granulomas