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Neuro-Ophtho > Lecture 2: Corneal Ulceration and Perforation > Flashcards

Lecture 2: Corneal Ulceration and Perforation Flashcards

1
Q

Causes of Corneal ulcers

A
  • trauma
  • corneal abrasion due to adnexal disease
  • tear film deficiency
  • exposure keratitis
  • infection
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2
Q

When we talk about bacterial infections of corneal ulcers, what context is this in?

A

generally as a complication more than a cause of corneal ulceration

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3
Q

Acute superficial ulcers can progress to which 3 directions

A
  • they can spontaneously heal
  • they can progress to a mid-stromal ulcer
  • they can progress to a chronic superficial ulcer
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4
Q

At which point can an ulcer no longer heal? How do you treat this?

A

when it becomes a descemetocoele;

it requires surgery to treat

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5
Q

what is the progression from acute superficial ulcer to corneal perforation

A

acute superficial ulcer –> mid-stromal ulcer –> deep stromal ulcer –> descemetocoele –> corneal perforation

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6
Q

Under normal circumstances, how quickly to corneal ulcers generally heal? What does healing generally depend on?

A

7-10 days, or quicker.

ulcer size, and any inhibiting factors that haven’t been addressed

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7
Q

What is the best diagnostic tool for corneal ulceration diagnosis?

A

the eyes and brain, searching for an underlying cause

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8
Q

Which diagnostic techniques MUST ALWAYS be performed when looking at eyes?

A
  • searching for the underlying cause

- schirmer tear test

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9
Q

When are you likely to perform a corneal cytology or culture?

A

when you are concerned about a bacterial infection

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10
Q

What are 5 risk factors to consider with corneal ulceration?

A
  • is tear production normal?
  • can and DOES the animal blink normally?
  • is the animal a brachycephalic breed or is there conformational exophtalmos?
  • are there any adnexal abnormalities?
  • does the ulcer appear infected?
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11
Q

Why are we concerned about tear production?

A

we want to make sure that eye is properly producing tears to lubricate the eye. Also concerned that there may be blockage, leading to other ocular issues

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12
Q

How do we assess normal blinking in an animal?

A

evaluate their menace and palpebral reflexes

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13
Q

What is Corneal Ulceration?

A

a full-thickness loss of corneal epithelium

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14
Q

T/F

corneal epithelial loss can vary greatly

A

true

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15
Q

What can loss of the protective barrier function of the corneal epithelium result in?

A
  • can allow resident microbial flora to colonize the exposed corneal stroma
  • predominantly bacteria, but can be fungal (keratomycosis)
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16
Q

what is the most common complicating factor for corneal ulcers?

A

secondary infection

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17
Q

What are diagnostics generally directed at?

A
  • identifying the cause of the ulcer
  • identifying the extent of the ulcer
  • further characterizing the disease process with regard to presence/absence of infection
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18
Q

What variables may affect your decision to perform diagnostics?

A
  • severity of disease (how deep/extensive the ulcer is)
  • duration of disease
  • presence of mucopurulent or purulent discharge (may signal an infection)
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19
Q

What does fluoroscein stain do?

A
  • enhances the ability to detect corneal ulcers
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20
Q

why doesn’t fluoroscein stain bind to the intact corneal epithelium?

A

its hydrophilic, so it binds to exposed corenal stroma instead

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21
Q

T/F

fluoroscein isn’t helpful in monitoring the healing of ulcers

A

false

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22
Q

what does fluoroscein fluoresce under?

A

cobalt blue light

23
Q

T/F

Fluoroscein stain is always required to dx an ulcer

A

false

24
Q

T/F

Tear Production measurement should be considered as almost routine diagnostic for corneal ulcers.

A

true

dry eye is a very common disorder

25
Q

When might you omit an STT?

A

in situations with copious tearing, indicating that lacrimation is not a problem

26
Q

What situations are highly recommended to perform an STT?

A
  • dogs with mucopurulent discharge (hallmark finding for canine KCS)
  • dull or lackluster appearance to the corneal surface
  • chronic non-healing ulcers
  • recurrent ulcers with an unknown underlying cause
27
Q

Why are low STT values in a cat difficult to interpret?

A

cats seem to shut down tear production when stressed

28
Q

T/F

Topical anesthetics and most sedatives/anesthetics will not reduce STT values

A

false, they will

29
Q

what are the specific indications for corneal cytology?

A
  • deepening/expanding corneal ulcers
  • apparently minor ulcers with disproportionately severe anterior uveitis
  • ulcers accompanied by severe mucopurulent discharge
30
Q

How are specimens collected for corneal cytology?

A
  • topical anesthetic given before scraping

- use of a kimura spatula or the blunt side of a scalpel blade or a specialized brush

31
Q

Why shouldn’t you use topical anesthetic for corneal cultures?

A

it may reduce bacterial yield

32
Q

In what order should you perform diagnostic tests for corneal ulcers

A
  • STT
  • Corneal culture
  • Corneal cytology
    Fluorescein stain
33
Q

what are the goals of tx for corneal ulcers?

A
  • prevention and/or treatment of infection
  • prevention and/or treatment of stromal collagenolysis
  • promotion of corneal healing
  • maintenance of patient comfort
34
Q

what must a practitioner strike a balance between when developing a patient care plan

A
  • necessity of each med
  • clinical effectiveness of each med
  • owner’s ability to comply with tx plan
35
Q

what factors can prevent or delay normal corneal healing?

A
  • presence of secondary corneal infection
  • continued corneal abrasion (from distichia, ectopic cilia, foreign body, etc.)
  • inadequate tear production
  • corneal exposure due to inadequate eyelid closure/inadequate blinking (pugs and brachycephalic conformation)
36
Q

What topical antimicrobials can be given to treat corneal ulcers?

A
  • aminoglycosides
  • neomycin
  • gentamicin
  • tobramycin
  • chloramphenicol
  • tetracyclines
  • fluoroquinolones
  • cefazolin
37
Q

In which circumstance would you use an aminoglycoside

A

broad spectrum use (both Gram + & -); bactericidal

38
Q

what antimicrobial is an excellent first line drug for prophylaxis?

A

triple antibiotics like neomycin

39
Q

what is combined with neomycin in triple antibiotic solutions

A
  • polymixin B

- gramicidin

40
Q

what is combined with neomycin in triple antibiotic ointments

A
  • polymixin B

- bacitracin

41
Q

when would you want to use Gentamicin or tobramycin? Why would you not want to use it as a first line abx? Which is considered more effective

A
  • in situations where there is infection, rather than as prophylaxis
  • resistance to gentamicin can rise fairly quickly
  • tobramycin
42
Q

T/F

chloramphenicol availability as an ophthalmic medication has been reduced in recent years

A

true

43
Q

why are tetracyclines not considered a good first choice of tx for corneal ulcers?

A
  • wide resistance by Pseudomonas, Staphylococcus, and Streptococcus spp.
44
Q

T/F

fluoroquinolones should only be reserved for established corneal ulcer infections

A

true

45
Q

Which drugs are considered for use as anti-proteolytics?

A
  • autogenous serum
  • acetylcysteine
  • tetracycline
46
Q

what is autogenous serum used for? Why is it used

A
  • to speed corneal epithelialization via growth factors present
  • contains numerous factors that theoretically reduce proteolytic degradation of the cornea
47
Q

what drug classification is atropine sulfate? how does it affect the eye?

A
  • mydriatic / cycloplegic
  • provides pain relief by causing relaxation of the ciliary body musculature
  • causes mydriasis
  • may cause severe (but reversible) decline in tear production (can impair healing)
48
Q

Acute Superficial Ulcers

  • Diagnostics
  • Treatment
  • Follow-up
A
  • look for underlying cause
  • prophylactic topical abx BID-TID (ointment) TID (drops). Atropine SID-TID, depending on extent of reflex uveitis
  • recheck 2-3 days. if no progress or worse, re-eval. recheck every 2-4 days until healed.
49
Q

what does SCCED stand for

A

spontaneous chronic corneal epithelial defect

50
Q

does a SCCED require surgical tx

A

typically yes

51
Q

Specific causes of delayed corneal healing

A
  • corneal infection
  • unresolved source of corneal abrasion
  • KCS
  • exposure keratitis
  • neutrophic keratitis
  • SCCED
52
Q

give an example of a primary infectious vector for corneal infection

A

herpesvirus infection in cats

53
Q

what is entropion, and how does it cause corneal ulcers

A
  • an inward rolling of eyelids, causing hairs to abrade the cornea
  • can be conformational or spastic
  • they keep rubbing the cornea, preventing it from healing

Neuro-Ophtho (2 decks)

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