Brainscape's Knowledge GenomeTM

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


See full index

Ophtho > Cornea (1) > Flashcards

Cornea (1) Flashcards

1
Q

How many layers are there to the cornea?

A 
Depends; if not counting tear film, 4
Epithelium
Stroma
Descemet's membrane
Endothelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Epithelium characteristics

A

5-7 layers
Hydrophobic/lipophilic barrier to drugs and fluorescein
Regular turnover

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

Stroma characteristics

A

75% water, 25% collagen
Regular (parallel) arrangement of collagen fibers
Hydrophilic/lipophobic
keratocytes

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

Descemet’s Membrane characteristics

A

BM of endothelium

Thickens with age

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

Endothelium characteristics

A

Dehydrate stroma by pumping mechanism
Monolayer of cells
Non-regenerative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Functions of the cornea

A

Anterior structure for globe
Protection of interior structures from injury/infection
Clear medium for vision
Refraction

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

Keepingthe cornea transparent

A 
Avascular
No pigment
Non-keratinized epithelium
Precise arrangement of collagen fibers
Relatively dehydrated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Corneal innervation

A 
CN V (trigeminal)
More nerve endings in epithelium/superficial cornea
Decreased sensitivity can affect healing
- Brachycephalics
- Sick foals
- Diabetics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Axonal Reflex

A

Any stimulation of corneal nerves = reflex stimulation of the CN V nerve branches to anterior uveal tract
All keratitis creates some degree of reflex uveitis
Corneal ulcer = stimulation of CN V = reflex uveitis with painful ciliary body muscle spasm
- Can relieve with cycloplegic drug such as atropine
More severe the keratitis = more severe the uveitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Epithelial loss alone heals by epithelial proliferation

A

Fact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Things to remember about corneal wound healing

A

Corneal blood vessels move at ~1mm/d
WBC move in the cornea at 8.6mm/d
Epithelial cells move at ~.6mm/d
Epithelial cells may take up to 6 wk to adhere to BM

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

Corneal disease states

A

Loss of corneal thickness

Loss of transparency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define corneal ulcer

A

Scratch, wound, or defect of the cornea in which there is a loss of variable amounts of corneal tissue
Most common presenting ophthalmic condition

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

Corneal ulcer categories

A 
Depth
- Superficial
- Stromal
- Desmetocele
- Full-thickness - iris prolapse
Etiology
- Traumatic
- Infectious
 . Bacterial
 . Fungal
- Immune-mediated
Response to therapy
- Simple
- Complicated
 . Indolent
 . Melting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Simple ulcer criteria

A

Superficial
No infection
Heals in an appropriate amount of time (a week)
No complicating factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can one tell if an ulcer is infected?

A 
Presence of cellular infiltrate
Melting
Degree of uveitis
Delayed healing
Positive cytology or culture
17
Q

What are complicating factors leading to delayed healing of the cornea?

A 
Entropion
KCS (dry eye)
Eyelid tumors
Lagophthalmos
Ectopic cilia
Trigeminal neuropathy
Systemic disease (Cushing's, DM)
Distichiasis
18
Q

Define desmetoceles

A

Epithelium and stroma lost; DM only remains
Very thin
DM will bulge into trough dt pressure from AqH

19
Q

Iris prolapse

A

DM has ruptured, leaving hole in cornea open to outside

Iris passively follows AqH and often plugs hole

20
Q

Melting cornea

A

Proteases - degredation of collagen
MMPs, serine proteases (NE)
Gelatinous appearance
Can happen within 24h

21
Q

Corneal ulcer CS

A 
Blepharospasm
Epiphora
Serous to micropurulent discharge
Miosis d/t reflex uveitis
Corneal edema
Corneal vascularization
22
Q

Management of corneal ulcers

A 
Rule infection in or out
- C&S (48h)
- Cytology
Rule out KCS
- Schirmer tear test
Stain with fluorescein
- Depth of lesion
- Epithelialization
- Stain every eye with signs of pain
23
Q

Surface properties

A

Fluorescein sodium - hydrophilic
Epithelium - hydrophobic
Stroma - hydrophilic
Descemet’s membrane - hydrophobic

24
Q

Therapy for corneal ulcers

A 
Depends on: etiology, infection, depth, melting, extent of uveitis
Goals:
- Slow collagen breakdown
- Sterilize the wound bed
- Control the secondary anterior uveitis
- Provide structural support
25
Q

T/F: During treatment, you are not actually making the ulcer heal

A

True

26
Q

Medical therapy for corneal ulcers

A 
Reduce tear protease activity
Topical antimicrobials: C&S guides selection
- SA: mostly Abx
- Horses: Abx and antifungals
Treat reflex uveitis
Provide analgesia
Prevent self-trauma
Treat etiology
27
Q

Simple ulcer medical therapy

A 
Broad-spectrum topical abx TID-QID until healed
- Prevent infection
- Broad spectrum, non-epitheliotoxic
- Neomycin, Polymyxin B, Bacitracin, Ofloxacin, Gentamicin
Treat reflex uveitis
- Topical atropine 1%
- Oral NSAID (5d)
Analgesia
Anti-protease
Prevent self-trauma

NO TOPICAL STEROIDS OR NSAIDS

28
Q

Complicated ulcer medical therapy

A 
Anti-protease (q1-6h)
- Serum, plasma, EDTA, NAC, Tetracyclines
Antimicrobials
- Based on culture/cytology - q2-4h
- Abx
- Antifungals
Treat reflex uveitis
- Topical atropine 1% solution BID-QID
- Oral NSAIDs
Provide analgesia
Consider surgical stabilization
29
Q

Topical anti-collagenase/protease q1-6h

A

Autologous serum
- Red top tube, let clot, spin down, draw off serum
- Fill 1cc syringes to dispense to client
- Replace q7d, must stay in fridge
EDTA sol’n
- Fill half a purple top tube with sterile water
- Can dispense in dropper bottle for ease of administration
N-acetylcysteine (5%)
- 5mL 20% Mucomyst in 15mL artificial tears
Tetracycline
- Terramycin ointment
- Doxycycline 5mg/kg PO q12h

30
Q

Topical Abx

A

Gr+: Cefazolin 55mg/mL / Ciprofloxacin
Gr -: Tobramycin/ Ciprofloxacin
Always give broad spectrum coverage
Remember: all Abx are toxic to epithelial cells

31
Q

Least to most toxic topical Abx

A 
Chloramphenicol
Tobramycin
Neopolygram
Gentamicin
Cefazolin
Ciprofloxacin
32
Q

Treat reflex uveitis

A

Regardless of initial cause, all ulcers associated with some iridocyclitis

  • Topical atropine 1%
  • Systemic NSAIDs
33
Q

Surgical therapy of corneal ulcers

A

Surgical grafting procedure (synthetic, corneal, conjunctival)

  • Stromal loss >50% of corneal thickness
  • Corneal perforation
34
Q

Surgical procedures

A

Conjunctival grafts
Biological graft
Corneal transplant
Corneoconjunctival transposition

35
Q

Evaluation of iris prolapse

A 
Potential to see
- Menace
- Dazzle
- PLR
- Fundic exam
Sealed perforation
- Formed anterior chamber
- Leaking aqueous humor
36
Q

Treatment of iris prolapse

A 
Add oral broad spec Abx
- Clavamox 13.25mg/kg PO q12h
Strongly consider surgical repair
No ointments (granulomatous uveitis)
No topical atropine (let iris plug hole)
Counsel owners on risk of vision loss from retinal detachment or endophthalmitis

Ophtho (5 decks)

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