Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Small Animal Medicine II > Corneal Diseases > Flashcards

Corneal Diseases Flashcards

1
Q

What are the 2 functions of the cornea?

A
  1. physical and molecular barrier to injury
  2. refracts light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is the cornea able to refract light?

A

remains clear to be able to refract light to retinal cells by…

  • lacking blood vessels
  • regular arrangement of stromal collagen fibrils
  • maintains a dehydrated state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is keratitis? Corneal malacia? Corneal edema?

A

inflammation of the cornea

necrosis of corneal stroma

fluid build-up in the corneal stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a keratotomy? Keratectomy?

A

procedure on the cornea

removal of a portion of the cornea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 4 layers of the cornea?

A
  1. epithelium - cells arranged to provide orderly replacement after injury (turnover time of 7 days)
  2. stroma - 90% of thickness, mostly regularly arranged collagen
  3. Descemet’s membrane - acellular inner protective boundary that will not take up fluorescein stain
  4. endothelium - single layer of cells that maintains dehydrated state by its Na/K ATPase pumps
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do epithelial and stromal injuries to the cornea heal?

A

heals within 7 days with no scarring

more complicated healing takes longer and leaves a scar due to keratocyte to fibroblast transformation, which can decrease vision (progression to this stage often due to infection)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the most common clinical signs seen with corneal disease?

A
  • corneal cloudiness
  • vision issues
  • ocular pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are 4 corneal responses to disease?

A
  1. PIGMENT - response to exposure, dry eye, and chronic inflammation
  2. EDEMA - response to inflammation. glaucoma, and ulcers
  3. VASCULARIZATION - response to inflammation, ulcers, uveitis, and glaucoma
  4. ACCUMULATION OF LIPID/CALCIUM - response to previous disease, inflammation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a corneal ulcer? What are 4 types?

A

lesion of the epithelial surface with exposure of underlying stroma

  1. epithelial (uncomplicated) - only epithelium missing (how most start)
  2. stromal - any portion of the stroma is missing (bacterial, fungal)
  3. Descemetocele - all of stroma is missing and denuded to Descements membrane
  4. corneal perforation - penetration into anterior chamber with leakage of aqueous humor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are common signs of corneal ulcers?

A
  • blepharospasm
  • conjunctival hyperemia
  • excessive lacrimation
  • ocular discharge
  • corneal edema around ulcer
  • corneal vascularization
  • corneal malacia and cellular infiltration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the most common causes of corneal ulcers in dogs and cats? What are 2 complicating factors?

A
  • DOGS: distichiasis (eyelashes inside), lagophthalmos, KCS, FB, entropion (trichiasis), ectopic cilia
  • CATS: herpesvirus, sequestrum

opportunistic infection and not finding underlying cause

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Cornea and location of ulcer:

A
  • ectopic cilia = commonly dorsal
  • exposure = medial oval
  • FB = behind third eyelid (ventromedial)
  • entropion = ventrolateral
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do corneal ulcers present to the naked eye? What is the most reliable confirmatory test?

A

transilluminator shows focal edema, rough edges, or vascularization

fluorescein stain (does not adhere to epithelium)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does the fluorescein stain work?

A

hydrophilic stain adheres to expose stroma and illuminates green under blue cobalt light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do Descemetoceles stain?

A

Descemet’s membrane is very thin and repels stain, resulting in the stain taking up around the ulcer site, but not at the center —> donut appearance

  • usually requires referral surgical treatment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What test is commonly performed on suspected corneal perforations? What is a positive result?

A

concentrated orange fluorescein is touched directly to area of interest

river of green, indicating aqueous humor flowing from the cornea

(definitely surgical)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do complicated and uncomplicated corneal ulcers compare? What 2 things in common do they share?

A

COMPLICATED = deeper into the corneal stroa, malacic, corneal infection

UNCOMPLICATED = superficial and typically heal within 3-7 days; can be nonhealing due to underlying causes or are spontaneous chronic corneal epithelial defect (SCCEDs)

both are acutely painful and have secondary uveitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are 4 aspects to medical therapy for uncomplicated ulcers?

A
  1. Atropine (SID-BID) until dilation occurs, usually reserved for eyes that have miosis
  2. systemic NSAIDs - Carprofen, Deracoxib, Meloxicam
  3. topical antibiotics (BID-TID) - NeoPolyBac, NeoPolyGramicidin, Gentamycin, Tobramycin
  4. E-collar - recheck in 3-5 days, should heal with little to not scarring
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are deep stromal ulcers? What is indicated to aid with treatment and diagnosis?

A

enlarging, deepening, and nonhealing ulcers

corneal cytology and culture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What clinical signs are indicative of deep stromal ulcers?

A
  • erosion of corneal stroma
  • corneal necorsis
  • corneal malacia/melting
  • cellular infiltrate in cornea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the most common causes of deep stromal ulcers? 2 causes of progression?

A
  • BACTERIAL: Pseudomonas, Staphylococcus, Streptococcus, E. coli
  • FUNGI: Aspergillus, Fusarium (opportunistic invaders)
  1. not finding the underlying cause of ulcer
  2. proteinases and other enzymes released by bacteria and leukocytes breaks down collagen in stroma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What 4 medical therapies are necessary for complicated ulcers?

A
  1. topical antibiotics - frequent application (12 times/day) of Fluoroquinolones and Cephalosporins
  2. topical Atropine
  3. systemic NSAIDs
  4. anti-collagenases - autologous serum, EDTA, tetracyclines
23
Q

What surgical therapy is recommended for complicated ulcers? What are 3 indications?

A

keratectomy of unhealthy cornea + conjunctival/corneal graft

  1. depth is 50% of corneal thickness or deeper
  2. ulcer is progressing despite aggressive medical therapy
  3. corneal perforation or Descemetocele
24
Q

When is surgical therapy indicated for perforated ulcers?

A

consensual PLR and positive dazzle reflex

  • if vision is not possible, enucleate
25
Q

What are the goals of corneal ulcer therapy?

A
  • control pain and infection
  • reduce inflammation
  • maintain clarity and visual acuity
  • if vision cannot be saved, can save globe if not painful
  • if painful, enucleate
26
Q

What are the most common causes of non-healing ulcers in cats? Middle-aged dogs?

A

herpesvirus, corneal sequestrum

spontaneous chronic corneal epithelial defects (SCCEDs) - indolent/Boxer ulcer

27
Q

What signalment and breed predisposition is associated with SCCEDs? What are the most common clinical signs?

A

> 6 y/o (middle-aged) Boxers

  • blepharospasm
  • conjunctival hyperemia
  • corneal edema
  • vascularization
28
Q

What is diagnostic of SCEED?

A

fluorescein stain seeps under ulcer margin due to loose epithelial edges - superficial with NO cellular infiltrate or malacia

  • seen in any location on the cornea, most common centrally/axial
29
Q

What is the pathophysiology of SCEEDs?

A
  • an epithelial defect that has not healed for at least 7 days forms hyalinized zone of anterior stroma due to inflammation
  • anchoring fibrils and hemidesmosomes within the epithelial basement membrane is now unable to attach to stroma
30
Q

How do SCCEDs progress? What 4 therapies are recommended?

A

persists for months and will not heal with medical therapy alone —> procedures that address hyalinized zone of anterior stroma are recommended

  1. debridement wit cotton-tipped applicator - 50%, peels away epithelium and roughens up surface
  2. grid/multiple punctate keratotomy - 70%, ONLY FOR DOGS, 25 g needle opens channels for epithelial cells to be able to attach
  3. diamond burr debridement - 70-95%, more intense debridement burrs off hyaline tissue
  4. superficial keratectomy - 100%, removes thin layer of diseased cornea resulting in rapid and predictable healing (needs GA and microscope)
31
Q

What medical therapy is recommended in addition to procedures for SCCEDs?

A
  • systemic NSAIDs - Carprofen, Deracoxib, Meloxicam
  • topical antibiotics - Tobramycin, Ofloxacin, NeoPolyGramicidin (BID-TID)
  • topical atropine for cycloplegic effects
  • topical doxycycline or oxytetracycline for epithelial effects

recheck in 10-14 days

32
Q

What is the most common corneal foreign body? How is it addressed?

A

plant material

  • flushed with hydropulsion
  • use proparacaine and a 25 g needle to undermine the FB and remove
  • full-thickness into anterior chamber = referral
33
Q

What is corneal lipid dystrophy and degeneration?

A

white, well-defined, avascular crystalline opacities in the corneal stroma made out of cholesterol and calcium and located under the epithelium

  • does not take up stain!
34
Q

What is the difference between corneal lipid dystrophy and degeneration?

A

DYSTROPHY - primary, genetic issue, resulting in symmetrical, bilateral circular/oval lesions —> Boston Terriers, Chihuahuas later in lifetime (4-6 y/o)

DEGENERATION - acquired and associated with inflammation (uveitis, keratitis) and is unilateral and any shape —>

35
Q

How can corneal lipid dystrophy and degeneration be dangerous?

A

deposition of cholesterol and calcium can predispose the eye to ulcers

36
Q

What clinical sign is indicative of corneal lipid dystrophy and degeneration?

A

nonpainful, slowly progressive corneal edema, which can progress to blindness and corneal ulceration

37
Q

What treatment is preferred for corneal lipid dystrophy and degeneration? What are 2 other options?

A

Gunderson conjunctival flap - blood vessels pulled over edema (and in periphery to maintain vision) to absorb fluid from the edematous lesion

  • corneal transplant - several complications
  • corneal endothelial transplant - very new
38
Q

Corneal lipid dystrophy and degeneration:

A

hazy edema

39
Q

In what animal is chronic superficial keratitis (Pannus) most common? What is thought to be the cause?

A

German Shepherds and Greyhounds with high incidence in those with increased UV light exposure (young = progressive, severe; old = less severe, slower)

hypersensitivity to cornea-specific antigens = chronic inflammation

40
Q

How is chronic superficial keratitis (Pannus) diagnosed?

A

appearance - does not take up stain, vascularized conjunctival/corneal pigmented lesion typically beginning from the ventrolateral limbus and progressing centrally

  • pigmentation can cause blindness
  • nonpainful
41
Q

What therapy is recommended for Pannus? What 3 things do severity and prognosis depend on?

A

lifelong therapy with topical steroids/cyclosporine, sunglasses to protect for UV light +/- radiation

  1. age of onset (younger = more severe)
  2. attitude
  3. geographical location
42
Q

What is a common variation of pannus? How does it present?

A

plasmoma - plasma cell infiltration of the third eyelid

thickening, depigmentation, and follicle formation of the third eyelid

(most common in German Shepherds, same treatment)

43
Q

What are the 2 pathognomonic corneal changes for feline herpesvirus infection?

A
  1. dendritic ulceration
  2. symblepharon - permanent healing of conjunctiva to cornea
44
Q

What corneal ulceration is characteristic of feline herpesvirus infection?

A

early dendritic/branching ulcer that can rapidly develop into larger areas and become indolent or develop sequestrum

45
Q

What topical and systemic antivirals are recommended for feline herpesvirus infection? What are some other parts of the treatment plan?

A
  • TOPICAL = Cidofovir (BID), Ganciclovir (TID)
  • SYSTEMIC = Famciclovir (BID), only one used for cats

topical antibiotics - Tobramycin or Oxytetracycline to prevent secondary bacterial infection

46
Q

What are non-healing ulcers commonly associated with in cats? What treatment is used? Avoided?

A

FHV-1 infection

medical therapy and cotton swab debridement +/- superficial keratectomy

grid keratotomies - may predispose to sequestrum formation (necrotic center on cornea)

47
Q

In what animals is corneal sequestrum most common? What are 5 common causes?

A

cats

  1. FHV-1
  2. breed-related exophthalmos/lagopthalmos causes exposure
  3. chronic ulceration
  4. chronic irritation (entropion)
  5. iatrogenic trauma from grid keratectomy
48
Q

What is corneal sequestrum? What clinical signs are associated? What is seen on examination?

A

stromal collagen degradation and necrosis

blepharospasm and epiphora

accumulation of brown pigment on cornea, ulcerated edges, vascularization, and corneal edema (pathognomic appearance is diagnostic)

49
Q

How are corneal sequestra treated?

A

surgical removal - lamellar keratectomy with possible grafting or tectonic and vascular support

50
Q

How does eosinophilic (proliferative) keratitis present? How is diagnosis confirmed?

A

uni/bilateral pink/white proliferative lesion causing ocular discomfort —> cause unknown

eosinophils of cytology

51
Q

What 3 treatments are recommended for eosinophilic (proliferative) keratitis?

A
  1. prednisolone acetate
  2. topical megestrol acetate (oral has severe side effects)
  3. cyclosporine
52
Q

What is a dermoid?

A

slow growing, cystic masses, lined by skin and filled with oil and old skin cells

53
Q

What is a persistent pupillary membrane?

A

fetal vasculature (usually used to provide nutrition ot the fetal eye) doesn’t regress when eyes open around 10 days —> may interfere with sight, but usually left alone

Small Animal Medicine II (57 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions