Cornea Flashcards
(140 cards)
1
Q
Sensory to cornea
A
- V
2
Q
Characteristics of corneal epithelium (pigmentation/myelination)
A
- Not pigmented
- Not myelinated
3
Q
Which layer of cornea provides the most strength?
A
- The stroma
4
Q
What’s the inner layer of the cornea?
A
- Endothelium
5
Q
How thick is the endothelium of the cornea?
A
- 1 cell layer thick
6
Q
Basement membrane of the corneal endothelium - name?
A
- Descemet’s membrane
7
Q
What are three primary characteristics of the cornea?
A
- Refractile
- Densely innervated
- Transparent
8
Q
Which layer of cornea is most densely innervated?
A
- Superficial layer most densely innervated
9
Q
What keeps the cornea transparent?
A
- No blood vessels or pigment
- Nerves are non-myelinated
- in a state of relative dehydration (deturgescence)
10
Q
What maintains the relative state of dehydration in the cornea?
A
- endothelial ATP pump
11
Q
How thick is the corneal epithelium?
A
Approximately 4-9 layers of epithelial cells
12
Q
Is corneal epithelium lipophilic or hydrophilic?
A
- Lipophilic - will not take up stain
13
Q
Is corneal stroma lipophilic or hydrophilic?
A
- Hydrophilic and takes up fluorescein stain
14
Q
What does exposed stroma indicate?
A
- Ulcer
15
Q
How does the cobalt filter help with fluorescein stain?
A
- Excites it to make it more visible
16
Q
What is a superficial corneal ulcer?
A
- Loss of epithelium only
- NO stromal loss
17
Q
Appearance of superficial corneal ulcer
A
- Distinct edge
- Takes up stain (bright green)
- NO change in corneal contour
18
Q
Pain of superficial corneal ulcer
A
- VERY PAINFUL
- Exposed nerves in superficial stroma
19
Q
Function of corneal stroma
A
- Bulk of corneal thickness and tectonic strength
- Bundles of collagen fibers perfectly arranged and spaced for transparency
20
Q
Appearance of corneal stromal ulcer?
A
- Hydrophilic –> + fluorescein stain
- Change in corneal surface or contour (depression
21
Q
What is Descemet’s membrane?
A
Basement membrane of endothelium
22
Q
Where is Descemet’s membrane?
A
- Deep to stroma
23
Q
Is Descemet’s membrane hydrophilic or lipophilic?
A
- Lipophilic
- DOES NOT TAKE UP STAIN
24
Q
What should you do if you see Descemet’s membrane?
A
- THIS IS TROUBLE
- IMPENDING GLOBE RUPTURE
- REFER IMMEDIATELY
- EMERGENCY
25
Which part of the corneal endothelium keeps the cornea dehydrated?
Na-K+ ATPase pump
26
What will happen if you lose corneal endothelium?
- Corneal edema
27
Regeneration potential of corneal endothelial cells
- DO NOT REGENERATE
| - Cell #'s and function decrease with age
28
What does the cornea lack to maintain transparency?
- Lymphatics
- Pigment
- Myelin
- Lymphatics
29
How is collagen oragnized in the corneal stroma to maintain transparency?
- They are arranged and spaced perfectly for transparency I guess
30
What do red, White/blue, and brown on the cornea correspond to?
- Red = blood vessels
- Brown = pigment
- White = corneal edema
31
What can cause corneal pigment?
- Pigmentation
- Melanoma
- Iris prolapse
- Sequestrum
32
What can cause blue or white appearance of the cornea?
- Blue is usually diffuse edema
- There can be cell infiltrate (inflammatory cells)
- Lipid deposition
- Calcium degeneration
33
What can cause redness in the cornea?
- Blood from vessels
- Blood out of vessels
- Hyphema
34
What will happen if blood vessels infiltrate the cornea?
- "Ghost" vessels will remain
| - Permanent loss of corneal clarity
35
How does corneal epithelium maintain dehydration?
- Barrier against water entering stroma from the surface
36
How does corneal endothelium maintain dehydration?
- Water pump
| - Pumps aqueous out of cornea and back into the anterior chamber
37
What two mechanisms can lead to corneal edema?
- Loss of either corneal epithelium or corneal endothelium
38
Normal corneal thickness in dogs, cats, and horses?
- 500-600 µM in dog and cat
| - 1 mM in horse
39
Appearance of corneal edema?
- Thickening of the cornea
| - Blue or white appearance
40
What are causes of corneal edema secondary to endothelial dysfunction?
- Corneal endothelial dystrophy
- Glaucoma
- Uveitis
- Trauma
- Immune mediated
41
Blue eye - what is it?
- Generalized corneal edema resulting from endothelial damage from immune complexes due to Adeno1 virus (hepatitis) vaccine or wild strain
- Rarely does but can occur due to Adenovirus 2 vaccine
42
Which breed group will most commonly get blue eye?
- Sight hounds
43
Signs of corneal ulcerative diseases
- PAIN
- Epiphora
- Blepharospasm
- Photophobia
- Head shy or avoidance
- Miosis
- Enophthalmos
- Conjunctival hyperemia/chemosis
44
Causes of corneal ulcers
- Trauma
- KCS
- Exposure (lagophthalmos)
- Facial nerve paralysis
- Immune mediated
- Infectious agents (herpes in cats)
- Metabolic
- Dystrophic
- Neutrophic
- Chemical (chlorhexidine, alcohol, shampoo, acid, base)
45
Causes of corneal trauma in domestic animals
- Scratch/laceration/perforation
- Foreign body
- Ectopic cilia
- Eyelid abnormalities
- Caustic agents
46
Treatment of a corneal flap
- Suture in place or if superficial (<1/3 thickness) it can be excised
- REFERRAL PROCEDURE
47
Treatment for corneal perforation and lens laceration
- Surgical repair of the perforation
- Likely removal of the lens by phacoemulsification (if cataract is present)
- THIS IS REFERRAL AND EMERGENCY
48
What can happen if suture material is left exposed over the conjunctiva?
- Irritate or ulcerate the cornea
49
Splinter foreign body treatment
- Make sure it's not full thickness and no fibers left in the tract
- Plant hulls you can try to flush out, but if not, must refer
- Referral procedure
50
Distichia temporary removal - why do?
- can be temporarily plucked until the ulcer heals
| - Ultimately will grow back
51
Which infectious disease is a PRIMARY cause of corneal ulceration in cats, dogs, and horses?
- Herpesvirus
52
Are most causes of corneal ulceration primary or secondary?
- SECONDARY MOST OFTEN
53
Why are animals with KCS at increased risk of corneal ulceration?
- Epithelium dries out and loses integrity more quickly
54
Immune mediated keratitis appearance
- Blood vessels, edema, pigmentation
55
Differentials for immune mediated keratitis
- Neoplasia, infection
56
Chemical causes of keratitis
- Shampoo
- Alcohol
- Chlorhexidine
- Scrubs
- OTHERS
57
Treatment for chemical keratitis
- Keratectomy
| - REFERRAL
58
Approach to corneal ulcer diagnosis and treatment
1. STT prior to applying anesthetic or stain (not necessary if tears are streaming down the face)
2. Fluorescein stain (examine in a DARK room with Cobalt filter and mag)
3. Assess depth of ulcer (stroma?)
4. Look for the cause of an ulcer (e.g. Entropion, dystichia, KCS, trauma)
5. Is it infected (cytology) or melting?
59
What are the 5 steps of healing for a superficial corneal ulcer, and when do you expect them to occur?
1. Epithelial cells at wound margin retract within the first hour
2. Neutrophils from tear film arrive in the first 1-3 hours
3. Epithelial cells slide and cover defect after 3-6 hours
4. Mitosis to replace thickness in 1-2 days
5. With appropriate treatment, an uncomplicated ulcer should heal in 3-5 days
60
Treatment for uncomplicated superficial corneal ulcer treatment?
- Topical antibiotic to prevent infection
- Atropine 1% topically for pain
- Oral pain medication
- E-collar!
61
What is a good choice of topical antibiotic in dogs and horses?
- BNP
62
What is a good choice of topical antibiotic in cats?
- Terramycin or erythromycin
| - NOT BNP (Anaphylaxis and doesn't work in cats)
63
When would you reach for ofloxacin for a superficial corneal ulcer?
- If there was an infection
64
Atropine 1% topical for superficial corneal ulcers - how does it work?
- Mydriatic and cycloplegic
- Prevents painful ciliary spasm
- Helps prevent reflex uveitis
- VERY IMPORTANT FOR HORSES BUT MUST MONITOR FOR COLIC
65
How much atropine to give topically?
- Use to effect (dilation)
| - Often ONE application for an uncomplicated ulcer is adequate
66
Contraindications for topical atropine?
- use sparingly with KCS as it will decrease tear production
- Do not use with glaucoma as it may increase IOP
67
How long can atropine last in dogs and horses?
- 1-7 days in dogs
| - 14 days in normal horses
68
Oral pain management for superficial corneal ulcers - dogs
- Tramadol or gabapentin for dogs
- Buprenorphine for small dogs
- NSAIDs may delay healing - both topical and oral but needed with uveitis
- Morphine can be compounded into a topical solution
69
Oral pain management for superficial corneal ulcers - cats
- Buprenorphine for cats
- NSAIDs may delay healing - both topical and oral but needed with uveitis
- Morphine can be compounded into a topical solution
70
Oral pain management for superficial corneal ulcers - horses
- Flunixin (IV or oral)
- NSAIDs may delay healing - both topical and oral but needed with uveitis
- Morphine can be compounded into a topical solution
71
Caveats of NSAIDs and when to use
- May delay healing (topical and oral applications)
| - Needed with uveitis
72
Steroids with superficial corneal ulcers
- DO NOT USE
| - Oral or systemic are both No-nos!
73
When to re-evaluate a superficial corneal ulcer?
- 5-7 days
74
What should you change if there has not been superficial corneal ulcer healing in 5-7 days?
- YOUR DIAGNOSIS
| - NOT your antibiotic
75
At what point do blood vessels enter the cornea to try to heal a corneal ulcer?
7 days
76
Re-evaluation of non-healing ulcers - 3 steps
1. Repeat STT
2. Look for a missed cause: FB, ectopic cilia, distichia, lid abnormality, infection
3. Look for loose epithelial edges (test with cotton swab
77
What does SCCED stand for?
- Spontaneous chronic corneal epithelial defect
78
Other names for SCCED
- Indolent ulcer
- Boxer ulcer
- Non-healing ulcer
79
Who gets SCCED? And what age?
- ANY breed over 5-6 years
| - NOT a younger dog problem (except in Boxers, who can get it at any edge)
80
What is the primary defect with SCCED?
- Epithelium does not adhere to stroma
81
When to diagnose SCCED?
- I'm assuming you'd run a bunch of tests to rule out other things
- If no contributing factors can be identified on examination, that's most likely an adhesion defect
82
Signs of SCCED?
- Wadded up on the edge of the ulcer
- Stain will go UNDERNEATH the epithelium
- Corneal blood vessels and edema
83
How much do corneal blood vessels travel per day approximately?
- 1 mm/day
84
Treatment for ulcers with unattached or loose epithelium
- Debridement to healthy attached epithelium with cotton tipped swab
- Contact lens if possible
- Pain management (morphine)
- E-collar
- Doxycycline maybe
- Topical antibiotic
- Atropine ONCE
85
When are contact lenses contraindicated?
- Not on deep ulcers or infected corneas
86
When do you refer a superficial uncomplicated ulcer?
- After appropriate treatment and ONE cotton tip debridement
87
If you have been treating an ulcer for 2 weeks and it has not healed, what is your next step?
- CONSULT WITH AN OPHTHALMOLOGIST
- REFER
- VERY PAINFUL
88
Grid keratotomy what is it?
- Superficial scraping of the stroma to debride epithelium??
- Painful and scarring
89
When should you do a grid keratotomy?
- UMM REALLY NOT RECOMMENDED!!!!
| - Especially not with a young dog
90
When should you REALLY not do a grid keratotomy?
- Ideally never
| - BUT ESPECIALLY NOT ON DEEP ULCERS, infected ulcers, cats, or horses
91
What is recommended to help with pain after a grid keratotomy?
- SHould be fitted with a contact lens after
| - If you can't do that, not recommended
92
What should you do if a superficial ulcer becomes a stromal ulcer in the face of treatment?
- REFER ASAP
| - Doing something wrong or missing something
93
Treatment for an acute injury resulting in a stromal ulcer and when to refer?
- If it's under 50% depth, treat AGGRESSIVELY
- If no improvement or worse in 48 hours, refer it
- If an ulcer is very deep, start treatment and recommend referral
94
What is a stromal ulcer?
- Any ulcer depth into stroma but not to Descemet's membrane
- The cornea lacks strength so you MUST BE CAREFUL
95
Treatment for a stromal ulcer
- AGGRESSIVE MEDICAL TREATMENT
- Topical antibiotic q6 hr, serum, or EDTA
- E-collar, oral doxycycline
96
When is a surgical graft indicated for a stromal ulcer?
- If more than 50% depth or fails to heal with medical management, a surgical graft is indicated
- Requires MONTHS to regain normal strength
97
Descemetocele appearance
- Stain uptake around inner rim where the stroma is exposed, but not over Descemet's membrane
98
Descemetocele treatment
- SURGICAL repair needed
99
Corneal perforation treatment
- IMMEDIATE surgical intervention and referral
- Corneal graft
- Conjunctival graft
- A-cell or Biosist graft
100
Here's a reminder: should you ever use steroids on a superficial corneal ulcer?
NO NO NO
101
Why are steroids so bad for corneal ulcers?
- Promote collagenase activity
- Drive ulcer deeper leading to potential melting and perforation
- Inhibit PMN migration and adherence
- Suppress lymphocyte activity
- Delay healing
102
Appearance of a melting ulcer
- soupy mess
| - Will rapidly progress to perforation
103
Treatment of a melting ulcer
- Anti-collagenase HOURLY
- Serum
- Tetracycline
- Oral doxycycline
- EDTA
- E-collar
- Acetylcysteine
104
Role of EDTA in treatment of melting ulcers
- Chelates divalent cations and reverses degradation process of the melting ulcer
105
How do cats respond with melting ulcer treatment in general?
- Very well
106
How do horses respond with melting ulcer treatment in general
- Poorly
107
Which topical abx to give for a melting ulcer?
- Neomycin/polymixin/gramicidin
108
Role of terramycin with melting ulcer tx?
- Anti-collagenase
109
Role of chloramphenicol in melting ulcer treatment?
- Penetrates cornea
| - Reserved in general for horses
110
When to give doxycycline or clavamox orally for melting ulcer tx?
- Doxycycline, clavamox
111
Fluoroquinolones on a melting ulcer
- MAY promote melting
112
Surgical repair of melting ulcer
- Debride (surgically) unhealthy cornea
| - Conjunctival graft to provide blood supply and strength
113
WHo should perform corneal surgery?
- ONLY board certified ophthalmologists or ophthalmology residents in training
114
Explain rotating conjunctival graft for corneal defects
- Very thin layer of conjunctival epithelium is bluntly dissected from the bulbar conjunctiva and sutured to the cornea
- Magnification and 8-0 suture are used
- The graft can be cut down in 6-8 weeks after healing
115
Describe the main characteristics of german shepherd pannus
- Sub-epithelial inflammatory cell infiltrate
- Proliferation of blood vessels
- Corneal edema
- Pigmentation
116
Is GSD pannus normally ulcerative?
- Usually not
117
Causes of german shepherd pannus
- Immune-mediated
| - Exacerbated by UV light
118
Where does GSD pannus usually start on the eye?
- Usually starts laterally but is progressive if not controlled
119
Which breeds get pannus in general?
- GSD
- Belgian Tervuren
- Greyhound
- Border collies
120
Breeding animals with pannus?
- Don't do it
121
What will happen once you get pannus under control?
- Pigment persists, with regression of blood vessels, edema, and cell infiltrate
122
How long must you manage pannus?
- FOREVER
123
Treatment principles for pannus
- Aggressive steroids (Prednisolone acetate or NPDex every 6-8 hours and tapered to control)
- Cyclosporine or tacrolimus twice a day
- Dog goggles and avoid UV light
- Oral doxycycline may be helpful initially in severe cases
- Exclusion diet such as Z/D might help to redcue antigenic stimulation
124
Who gets pigmentary keratitis?
- Brachycephalic breeds with exophthalmos and lagophthalmos
125
What is lagophthalmos?
- Inability to close the eyelid over the eye completely
126
What causes pigmentary keratitis?
- Chronic injury or irritation to the cornea
- Exposure
- Aberrant cilia
- KCS/poor tear film
127
What do you think about putting steroids on a brachycephalic dog, especially with pigmentary keratitis
- Don't do it
128
Appearance of pigmentary keratitis?
- Pigmentation on the eye
129
How does cyclosporine help dry eyes?
- Tear production
- Tear film quality
- Reduces corneal pigmentation
130
Treatment for pigmentary keratitis
- Protect cornea with lubrication and reducing palpebral fissure size
- Eliminate cause of possible (trichiasis, KCS, eyelid mass)
- Intervene before pigmentation causes visual loss (refer early)
- Cyclosporine or tacrolimus
131
Dermoid
- Skin growing in an abnormal ocation
132
Treatment for dermoid
- Surgical excision (superficial keratectomy)
| - REFERRAL PROCEDURE
133
Corneal subepithelial lipid dystrophy appearance
- Lipid deposit
- It's on the cornea not the cataract
- May be horseshoe shaped
- Can get brittle
- Don't breed
134
Characteristics of corneal subepithelial lipid dystrophy
- Hereditary
- Bilateral
- Non-painful
- Progressive
135
Treatment for corneal subepithelial lipid dystrophy
- Low fat diet to reduce the cholesterol crystal deposits
136
Pathophys of corneal subepithelial lipid dystrophy
- Calcium deposits over the cholesterol crystal can lead to corneal degeneration?
137
Plasmoma
- Depigmentation and thickening of the third eyelid due to inflammatory cells (plasma cells) infiltrating the area
138
Limbal melanoma
- Don't take the eye out
- Don't often metastasize
- Refer?
- GSD and labs get it
139
Corneal SCC in a horse tx
- Keratectomy or freeze
| - Could be malignant
140
What can be long term side effects from cyclosporine/tacrolimus?
- Squamous cell carcinoma
