Corneal Pathology

Question 1

describe corneal ulcers (5)

Answer 1

1. AKA ulcerative keratitis
2. epithelial loss/defect
   -erosion/abrasion, ulceration/stromal exposure
3. green corneal opacity from fluorescein uptake
4. indicates trauma, exposure, unhealthy/predisposed cornea, or herpes viral infection!!
5. risk of secondary infection when present
   -topical antibiotics ALWAYS indicated until healed bc are very susceptible to infection now

Question 2

describe the 3 varieties of corneal ulcers

Answer 2

1. erosion/abrasion/ulceration:
   -epithelium and basement membrane
   -superficial and uncomplicated
   -SCCED: secondary indolent
2. stromal loss:
   -superficial, midstromal, deep stromal, descemetocele, perforation
   -infiltrated, infected, melting
   -edematous
   -vascularized?
3. facet: epithelialized: fluorescein negative, stromal loss post ulceration
   -there was an ulcer, it’s healed but the thickness of the cornea has not remodeled yet

Question 3

describe corneal ulceration etiologies (5)

Answer 3

1. trauma
   -direct
   -secondary: foreign body, entropion, trichiasis, distichiasis, ectopic cilia, eyelid tumor
2. exposure:
   -conformational/lagophthalmos
   -buphthalmos
   -exophthalmos
3. infection:
   -FHV1; primary corneal pathogen, or other species specific herpesviruses; dendritic ulcers PATHOGNOMONIC although non-specific geographic ulcers may occur

-primary infectious keratitis rare except in cats; secondary bacterial and or fungal infection in face of ulceration much more common!

4. tear film deficiency
   -KCS/dry eye:
   –lacrimal gland dysfunction of any cause
   –neurogenic (lacrimal nerve)
   -less commonly QTFD: qualitative tear film deficiency
5. neurologic deficits
   -CN V (sensory): neurotopic
   -CN VII (palpebral blink with exposure): paralytic

Question 4

describe evaluation considerations with corneal ulcers (3)

Answer 4

1. look for/rule out underlying cause
2. ulcer often guides you to problem
3. uncomplicated ulcer should heal within a week
   -if it has not:
   –inciting cause remains: secondary trauma, infiltrated/infected
   –indolent/nonhealing: primary/SCCED, or secondary (esp if inciting cause remains)

Question 5

describe reflex uveitis (3)

Answer 5

1. corneal ulcers cause reflex uveitis
2. a neuronal reflex from corneal nerves to anterior uveal tract with specific clinical signs
   -miosis
   -aqueous humor flare in the anterior chamber
   –+/- hypopyon
   –indicates BAB breakdown
3. severity of uveitis usually correlates with that of ulcer

Question 6

describe a superficial, uncomplicated, corneal ulceration (6)

Answer 6

1. acute and PAINFUL
2. distinct border/tight edge
3. no to mild corneal edema
4. no stromal loss (erosion, superficial ulceration)
5. no infiltrate (uncomplicated)
6. none to mild reflex uveitis

Question 7

describe treatment of a superficial, uncomplicated corneal ulceration (4)

Answer 7

1. still look for underlying cause
2. prevent/reduce risk of secondary infection
   -broad spectrum topical antibiotics TID
3. address discomfort and reflex uveitis
   -+/- topical atropine: alleviates clilary spasm
   +/- PO NSAID (or other)
   -NEVER proparicaine or topical anti-inflammatories!! (delay healing)
4. recheck in 1-2 weeks

Question 8

describe SCCED (4)

Answer 8

1. spontaneous chronic corneal epithelial defect, also called indolent ulcer, boxer ulcer, non-healing ulcer, PED (persistent epithelial defect)
   -boxers, goldens, corgis, and others overrepresented
2. characteristic nonadherent/loose epithelial edge
   -characteristic fluorescein staining pattern
3. SAME as superficial uncomplicated, just doesn’t heal!!
4. issue with anterior stroma impairing normal epithelial adherence (don’t stick down)

Question 9

describe SSCED treatment (7)

Answer 9

1. cotton tipped applicator debridement
   -topical anesthetic to remove loose epithelial edges until tight
   -may even use diamond burr debridement
   (like priming a wall before you paint it, easier for epi to stick down if no loose edges)
2. anterior stromal puncture/grid keratotomy
   -stromal intervention promotes healing
   -25g needle bevel up
   -drag, don’t push
   -generally avoided in cats
3. bandage contact lens/TEL flap
4. still check for underlying cause
   -if find one, was not SCCED but secondary indolent
   -address issue and debridement only (stromal alteration not indicated)
5. prevent secondary infection!
   -broad spectrum topical Ab TID
6. address discomfort and reflex uveitis
7. E collar

Question 10

describe corneal stromal ulcers (3)

Answer 10

1. variable depth (stromal LOSS)
   -superficial, mild, or deep stromal or descemetocele; perforation (often with fibrin or iris prolapse in pugs)
2. variable infiltration, infection, malacia, edema, vascularization
3. variable anterior uveitis:
   -miosis, flare, hypopyon, fibrin in AC, hypotone
   -if raging uveitis, even if ulcer doesn’t LOOK bad, it IS bad

Question 11

describe descemetocele (2)

Answer 11

1. stromal loss down to descemet’s membrane
2. characteristic fluor. staining pattern

Question 12

describe corneal perforation

Answer 12

if we go full thickness through the cornea, stuff comes up to plug the hole

pigment or hemorrhage in stroma suggestive of perf

Question 13

describe corneal malacia etiologies (3)

Answer 13

1. endogenous proteinases/collagenases
   -leukocytes
   -corneal cells themselves that ramp up during injury
2. infection- most common!
   -bacterial collagenases
3. topical corticosteroids (and NSAIDS??)
   -potentiation of collagenase activity
   -local immunosuppression

Question 14

describe assessment of stromal ulcers (5)

Answer 14

1. depth
2. integrity: perforation risk (depth again), malacia, anterior chamber depth
3. infiltrate
4. reflex uveitis status
5. vascularization

Question 15

describe treatment of stromal ulcers (5)

Answer 15

1. topical antimicrobials (oral too if perforation)
   -broad spectrum, bug guns +/- antifungals
   -indeally absed on severity, cytology, C&S
   -fortified cefazolin to cover gram + cocci
   -fortified tobramycin or fluroquinolones to cover gram - rods
   -no ointments in eyes with current or impending perforation!
   -may be needed up to hourly at first!
2. topical proteinase/collagenase inhibitors
   -address malacia
   -serum: donor commonly
   –alpha-2 macroglobulin helps with melting
   –keep in fridge, handle aseptically, discard after 7 days
   -EDTA
   -acetylcysteine
3. for reflex uveitis:
   -topica; cycloplegia/mydriasis
   –cholinergic/parasympatholytic: atropine, contraindiacted wth KCS and glaucoma, may cause drooling
   -decreases pain from ciliary muscle spasm
   -reduces visually significant synechiae
   -may stabilize BAB reducing further uvetis
4. systemic anti-inflammtories
   -address pain and uveitis
   -MAY delay corneal healing but topical WILL delay and potentiate malacia so NO TOPICAL
5. other pain meds/sedation/e-collars

Question 16

describe additional considerations of medial treatment of stromal ulcers in horses (4)

Answer 16

1. reflex uveitis more prominent/significant even with relatively minor ulceration
   -pain from that can cause colic
   -can monitor to help gauge disease status
2. ALWAYS perform cytology +/_ C/C (aerobic, bacterial, fungal) of ulcers
3. SPL (sub-palpebral lavage) often necessary to allow safe, effective, frequent treatment
4. topical anti-fungal therapy more routine

Question 17

describe surgical treatment of stromal ulcers

Answer 17

1. indicated when:
   -at least or more than 50% stromal loss
   -rapid progression of malacia
   -none to limited or distant vascularization
   -perforation or active leakage
2. mechanical stabilization with various graft material; also promote healing through vascularization
   -conjunctival flap/graft, as the glue for for corneal transplant
   -often NOT optical

Question 18

describe corneal pannus

Answer 18

1. inherited (UV exacerbated) immune-mediated chronic superficial keratitis

2 GSD, greyhounds, random others

clinical signs:
1. ALWAYS bilateral (but not always symmetric) inferior temporal LP corneal infultrate, vascularization, and variable pigmentation
2. +/- LP nodular inflammation of the TEL (atypical pannus)

Question 19

describe diagnosis and treatment of pannus

Answer 19

diagnosis:
1. signalment
2. clinical signs
3. corneal cytology: LP

treatment:
1. long term topical steroid and or corticosteroids (probably forever, we don’t cure this we control it)
2. reduced/avoid UV exposure

Question 20

describe eosinophilic keratitis

Answer 20

1. immune mediated keratitis/keratoconjunctivits
   -FHV-1 associated in some cases
   -CATS
   -horses also get a variation

clinical signs:
1. uni or bilateral proliferation, yellow-white plaque infiltrate with vascularization of cornea and/or conjunctiva

diagnosis:
1. clinical signs
2. corneal cytology: if see ANY eosinophil on surface of eye, this is happening

treatment:
1. long term topical steroid
2. caution due to possible underlying FHV1
-consider anti-viral topical or oral because could cause flareup

Question 21

describe calcific degeneration (deposits)

Answer 21

1. age-related/degenerative
2. risk of painful slough with ulceration

Question 22

describe endothelial degeneration

Answer 22

1. inherited (dystrophy, degeneration in specific breeds) or age related; common in dogs
2. clinical signs:
   -corneal edema
   -bullous keratopathy (blisters at the surface under uphappy waterlogged epithelium) leading to recurrent/secondary indolent ulcers
3. diagnosis: signalment and rule out other causes of edema
4. treatment:
   -topical hypertonic saline, address ulcers
   -surgery

Question 23

describe corneal dystrophy (deposits)

Answer 23

1. inherited corneal lipid deposits
2. in dogs, rare in cats; usually young animals and breed specific
3. clinical signs:
   -bilateral and usually pretty symmetric
   -usually minimally progressive
   -non-painful/quiet
4. no treatment

Question 24

what are other ways to get corneal deposits (other than dystrophy?)

Answer 24

1. steroid induced (steroid keratopathy)
2. post-inflam
3. associated with systemic metabolic diseases
   -hypothryoidism or other issue with fat metabolism
   -other mineral imbalances (uncommon)

Question 25

describe dermoids

Answer 25

1. also called choristoma (normal tissue in abnormal location)
2. usually haired skin at the temporal limbus
3. treatment: benign so neglect of monitoring, or karatectomy (remove)

Question 26

describe corneal neoplasia

Answer 26

1. SCC, hemangioma, melanocytoma, papilloma
2. common in horses and cattle; less common in cats and dogs

3, diagnosis: cytology and/or biopsy

4. treatment:
   -keratectomy +/- adjunct (cryo, radiation)
   -enucleation or extenteration if invasive (globe or orbit)

Question 27

describe sequestrum

Answer 27

1. in cats! persian/himalayan (and others) predilection
2. nonspecific response of cat cornea to chronic irritation
   -conformation or FHV-1
3. clinical signs:
   -characteristic tea-stain ed to black corneal opacity with variable vascularization
4. diagnosis: pathognomonic appearance
5. treatment:
   -allow it to slough!
   –lubricate +/- prophylactic topical antibiotic
   –some risk of deep ulceration or perforation
   -keratectomy +/- grafting if bothering cat or to avoid risk of ulceration