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Ophthalmology > Cornea > Flashcards

Cornea Flashcards

1
Q

Sensory to cornea

A
  • V
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2
Q

Characteristics of corneal epithelium (pigmentation/myelination)

A
  • Not pigmented

- Not myelinated

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3
Q

Which layer of cornea provides the most strength?

A
  • The stroma
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4
Q

What’s the inner layer of the cornea?

A
  • Endothelium
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5
Q

How thick is the endothelium of the cornea?

A
  • 1 cell layer thick
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6
Q

Basement membrane of the corneal endothelium - name?

A
  • Descemet’s membrane
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7
Q

What are three primary characteristics of the cornea?

A
  1. Refractile
  2. Densely innervated
  3. Transparent
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8
Q

Which layer of cornea is most densely innervated?

A
  • Superficial layer most densely innervated
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9
Q

What keeps the cornea transparent?

A
  • No blood vessels or pigment
  • Nerves are non-myelinated
  • in a state of relative dehydration (deturgescence)
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10
Q

What maintains the relative state of dehydration in the cornea?

A
  • endothelial ATP pump
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11
Q

How thick is the corneal epithelium?

A

Approximately 4-9 layers of epithelial cells

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12
Q

Is corneal epithelium lipophilic or hydrophilic?

A
  • Lipophilic - will not take up stain
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13
Q

Is corneal stroma lipophilic or hydrophilic?

A
  • Hydrophilic and takes up fluorescein stain
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14
Q

What does exposed stroma indicate?

A
  • Ulcer
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15
Q

How does the cobalt filter help with fluorescein stain?

A
  • Excites it to make it more visible
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16
Q

What is a superficial corneal ulcer?

A
  • Loss of epithelium only

- NO stromal loss

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17
Q

Appearance of superficial corneal ulcer

A
  • Distinct edge
  • Takes up stain (bright green)
  • NO change in corneal contour
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18
Q

Pain of superficial corneal ulcer

A
  • VERY PAINFUL

- Exposed nerves in superficial stroma

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19
Q

Function of corneal stroma

A
  • Bulk of corneal thickness and tectonic strength

- Bundles of collagen fibers perfectly arranged and spaced for transparency

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20
Q

Appearance of corneal stromal ulcer?

A
  • Hydrophilic –> + fluorescein stain

- Change in corneal surface or contour (depression

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21
Q

What is Descemet’s membrane?

A

Basement membrane of endothelium

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22
Q

Where is Descemet’s membrane?

A
  • Deep to stroma
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23
Q

Is Descemet’s membrane hydrophilic or lipophilic?

A
  • Lipophilic

- DOES NOT TAKE UP STAIN

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24
Q

What should you do if you see Descemet’s membrane?

A
  • THIS IS TROUBLE
  • IMPENDING GLOBE RUPTURE
  • REFER IMMEDIATELY
  • EMERGENCY
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25
Q

Which part of the corneal endothelium keeps the cornea dehydrated?

A

Na-K+ ATPase pump

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26
Q

What will happen if you lose corneal endothelium?

A
  • Corneal edema
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27
Q

Regeneration potential of corneal endothelial cells

A
  • DO NOT REGENERATE

- Cell #’s and function decrease with age

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28
Q

What does the cornea lack to maintain transparency?

A
  • Lymphatics
  • Pigment
  • Myelin
  • Lymphatics
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29
Q

How is collagen oragnized in the corneal stroma to maintain transparency?

A
  • They are arranged and spaced perfectly for transparency I guess
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30
Q

What do red, White/blue, and brown on the cornea correspond to?

A
  • Red = blood vessels
  • Brown = pigment
  • White = corneal edema
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31
Q

What can cause corneal pigment?

A
  • Pigmentation
  • Melanoma
  • Iris prolapse
  • Sequestrum
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32
Q

What can cause blue or white appearance of the cornea?

A
  • Blue is usually diffuse edema
  • There can be cell infiltrate (inflammatory cells)
  • Lipid deposition
  • Calcium degeneration
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33
Q

What can cause redness in the cornea?

A
  • Blood from vessels
  • Blood out of vessels
  • Hyphema
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34
Q

What will happen if blood vessels infiltrate the cornea?

A
  • “Ghost” vessels will remain

- Permanent loss of corneal clarity

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35
Q

How does corneal epithelium maintain dehydration?

A
  • Barrier against water entering stroma from the surface
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36
Q

How does corneal endothelium maintain dehydration?

A
  • Water pump

- Pumps aqueous out of cornea and back into the anterior chamber

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37
Q

What two mechanisms can lead to corneal edema?

A
  • Loss of either corneal epithelium or corneal endothelium
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38
Q

Normal corneal thickness in dogs, cats, and horses?

A
  • 500-600 µM in dog and cat

- 1 mM in horse

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39
Q

Appearance of corneal edema?

A
  • Thickening of the cornea

- Blue or white appearance

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40
Q

What are causes of corneal edema secondary to endothelial dysfunction?

A
  • Corneal endothelial dystrophy
  • Glaucoma
  • Uveitis
  • Trauma
  • Immune mediated
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41
Q

Blue eye - what is it?

A
  • 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
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42
Q

Which breed group will most commonly get blue eye?

A
  • Sight hounds
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43
Q

Signs of corneal ulcerative diseases

A
  • PAIN
  • Epiphora
  • Blepharospasm
  • Photophobia
  • Head shy or avoidance
  • Miosis
  • Enophthalmos
  • Conjunctival hyperemia/chemosis
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44
Q

Causes of corneal ulcers

A
  • Trauma
  • KCS
  • Exposure (lagophthalmos)
  • Facial nerve paralysis
  • Immune mediated
  • Infectious agents (herpes in cats)
  • Metabolic
  • Dystrophic
  • Neutrophic
  • Chemical (chlorhexidine, alcohol, shampoo, acid, base)
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45
Q

Causes of corneal trauma in domestic animals

A
  • Scratch/laceration/perforation
  • Foreign body
  • Ectopic cilia
  • Eyelid abnormalities
  • Caustic agents
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46
Q

Treatment of a corneal flap

A
  • Suture in place or if superficial (<1/3 thickness) it can be excised
  • REFERRAL PROCEDURE
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47
Q

Treatment for corneal perforation and lens laceration

A
  • Surgical repair of the perforation
  • Likely removal of the lens by phacoemulsification (if cataract is present)
  • THIS IS REFERRAL AND EMERGENCY
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48
Q

What can happen if suture material is left exposed over the conjunctiva?

A
  • Irritate or ulcerate the cornea
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49
Q

Splinter foreign body treatment

A
  • 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
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50
Q

Distichia temporary removal - why do?

A
  • can be temporarily plucked until the ulcer heals

- Ultimately will grow back

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51
Q

Which infectious disease is a PRIMARY cause of corneal ulceration in cats, dogs, and horses?

A
  • Herpesvirus
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52
Q

Are most causes of corneal ulceration primary or secondary?

A
  • SECONDARY MOST OFTEN
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53
Q

Why are animals with KCS at increased risk of corneal ulceration?

A
  • Epithelium dries out and loses integrity more quickly
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54
Q

Immune mediated keratitis appearance

A
  • Blood vessels, edema, pigmentation
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55
Q

Differentials for immune mediated keratitis

A
  • Neoplasia, infection
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56
Q

Chemical causes of keratitis

A
  • Shampoo
  • Alcohol
  • Chlorhexidine
  • Scrubs
  • OTHERS
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57
Q

Treatment for chemical keratitis

A
  • Keratectomy

- REFERRAL

58
Q

Approach to corneal ulcer diagnosis and treatment

A
  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
Q

What are the 5 steps of healing for a superficial corneal ulcer, and when do you expect them to occur?

A
  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
Q

Treatment for uncomplicated superficial corneal ulcer treatment?

A
  • Topical antibiotic to prevent infection
  • Atropine 1% topically for pain
  • Oral pain medication
  • E-collar!
61
Q

What is a good choice of topical antibiotic in dogs and horses?

A
  • BNP
62
Q

What is a good choice of topical antibiotic in cats?

A
  • Terramycin or erythromycin

- NOT BNP (Anaphylaxis and doesn’t work in cats)

63
Q

When would you reach for ofloxacin for a superficial corneal ulcer?

A
  • If there was an infection
64
Q

Atropine 1% topical for superficial corneal ulcers - how does it work?

A
  • Mydriatic and cycloplegic
  • Prevents painful ciliary spasm
  • Helps prevent reflex uveitis
  • VERY IMPORTANT FOR HORSES BUT MUST MONITOR FOR COLIC
65
Q

How much atropine to give topically?

A
  • Use to effect (dilation)

- Often ONE application for an uncomplicated ulcer is adequate

66
Q

Contraindications for topical atropine?

A
  • use sparingly with KCS as it will decrease tear production
  • Do not use with glaucoma as it may increase IOP
67
Q

How long can atropine last in dogs and horses?

A
  • 1-7 days in dogs

- 14 days in normal horses

68
Q

Oral pain management for superficial corneal ulcers - dogs

A
  • 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
Q

Oral pain management for superficial corneal ulcers - cats

A
  • Buprenorphine for cats
  • NSAIDs may delay healing - both topical and oral but needed with uveitis
  • Morphine can be compounded into a topical solution
70
Q

Oral pain management for superficial corneal ulcers - horses

A
  • 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
Q

Caveats of NSAIDs and when to use

A
  • May delay healing (topical and oral applications)

- Needed with uveitis

72
Q

Steroids with superficial corneal ulcers

A
  • DO NOT USE

- Oral or systemic are both No-nos!

73
Q

When to re-evaluate a superficial corneal ulcer?

A
  • 5-7 days
74
Q

What should you change if there has not been superficial corneal ulcer healing in 5-7 days?

A
  • YOUR DIAGNOSIS

- NOT your antibiotic

75
Q

At what point do blood vessels enter the cornea to try to heal a corneal ulcer?

A

7 days

76
Q

Re-evaluation of non-healing ulcers - 3 steps

A
  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
Q

What does SCCED stand for?

A
  • Spontaneous chronic corneal epithelial defect
78
Q

Other names for SCCED

A
  • Indolent ulcer
  • Boxer ulcer
  • Non-healing ulcer
79
Q

Who gets SCCED? And what age?

A
  • ANY breed over 5-6 years

- NOT a younger dog problem (except in Boxers, who can get it at any edge)

80
Q

What is the primary defect with SCCED?

A
  • Epithelium does not adhere to stroma
81
Q

When to diagnose SCCED?

A
  • 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
Q

Signs of SCCED?

A
  • Wadded up on the edge of the ulcer
  • Stain will go UNDERNEATH the epithelium
  • Corneal blood vessels and edema
83
Q

How much do corneal blood vessels travel per day approximately?

A
  • 1 mm/day
84
Q

Treatment for ulcers with unattached or loose epithelium

A
  • 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
Q

When are contact lenses contraindicated?

A
  • Not on deep ulcers or infected corneas
86
Q

When do you refer a superficial uncomplicated ulcer?

A
  • After appropriate treatment and ONE cotton tip debridement
87
Q

If you have been treating an ulcer for 2 weeks and it has not healed, what is your next step?

A
  • CONSULT WITH AN OPHTHALMOLOGIST
  • REFER
  • VERY PAINFUL
88
Q

Grid keratotomy what is it?

A
  • Superficial scraping of the stroma to debride epithelium??
  • Painful and scarring
89
Q

When should you do a grid keratotomy?

A
  • UMM REALLY NOT RECOMMENDED!!!!

- Especially not with a young dog

90
Q

When should you REALLY not do a grid keratotomy?

A
  • Ideally never

- BUT ESPECIALLY NOT ON DEEP ULCERS, infected ulcers, cats, or horses

91
Q

What is recommended to help with pain after a grid keratotomy?

A
  • SHould be fitted with a contact lens after

- If you can’t do that, not recommended

92
Q

What should you do if a superficial ulcer becomes a stromal ulcer in the face of treatment?

A
  • REFER ASAP

- Doing something wrong or missing something

93
Q

Treatment for an acute injury resulting in a stromal ulcer and when to refer?

A
  • 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
Q

What is a stromal ulcer?

A
  • Any ulcer depth into stroma but not to Descemet’s membrane
  • The cornea lacks strength so you MUST BE CAREFUL
95
Q

Treatment for a stromal ulcer

A
  • AGGRESSIVE MEDICAL TREATMENT
  • Topical antibiotic q6 hr, serum, or EDTA
  • E-collar, oral doxycycline
96
Q

When is a surgical graft indicated for a stromal ulcer?

A
  • If more than 50% depth or fails to heal with medical management, a surgical graft is indicated
  • Requires MONTHS to regain normal strength
97
Q

Descemetocele appearance

A
  • Stain uptake around inner rim where the stroma is exposed, but not over Descemet’s membrane
98
Q

Descemetocele treatment

A
  • SURGICAL repair needed
99
Q

Corneal perforation treatment

A
  • IMMEDIATE surgical intervention and referral
  • Corneal graft
  • Conjunctival graft
  • A-cell or Biosist graft
100
Q

Here’s a reminder: should you ever use steroids on a superficial corneal ulcer?

A

NO NO NO

101
Q

Why are steroids so bad for corneal ulcers?

A
  • Promote collagenase activity
  • Drive ulcer deeper leading to potential melting and perforation
  • Inhibit PMN migration and adherence
  • Suppress lymphocyte activity
  • Delay healing
102
Q

Appearance of a melting ulcer

A
  • soupy mess

- Will rapidly progress to perforation

103
Q

Treatment of a melting ulcer

A
  • Anti-collagenase HOURLY
  • Serum
  • Tetracycline
  • Oral doxycycline
  • EDTA
  • E-collar
  • Acetylcysteine
104
Q

Role of EDTA in treatment of melting ulcers

A
  • Chelates divalent cations and reverses degradation process of the melting ulcer
105
Q

How do cats respond with melting ulcer treatment in general?

A
  • Very well
106
Q

How do horses respond with melting ulcer treatment in general

A
  • Poorly
107
Q

Which topical abx to give for a melting ulcer?

A
  • Neomycin/polymixin/gramicidin
108
Q

Role of terramycin with melting ulcer tx?

A
  • Anti-collagenase
109
Q

Role of chloramphenicol in melting ulcer treatment?

A
  • Penetrates cornea

- Reserved in general for horses

110
Q

When to give doxycycline or clavamox orally for melting ulcer tx?

A
  • Doxycycline, clavamox
111
Q

Fluoroquinolones on a melting ulcer

A
  • MAY promote melting
112
Q

Surgical repair of melting ulcer

A
  • Debride (surgically) unhealthy cornea

- Conjunctival graft to provide blood supply and strength

113
Q

WHo should perform corneal surgery?

A
  • ONLY board certified ophthalmologists or ophthalmology residents in training
114
Q

Explain rotating conjunctival graft for corneal defects

A
  • 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
Q

Describe the main characteristics of german shepherd pannus

A
  • Sub-epithelial inflammatory cell infiltrate
  • Proliferation of blood vessels
  • Corneal edema
  • Pigmentation
116
Q

Is GSD pannus normally ulcerative?

A
  • Usually not
117
Q

Causes of german shepherd pannus

A
  • Immune-mediated

- Exacerbated by UV light

118
Q

Where does GSD pannus usually start on the eye?

A
  • Usually starts laterally but is progressive if not controlled
119
Q

Which breeds get pannus in general?

A
  • GSD
  • Belgian Tervuren
  • Greyhound
  • Border collies
120
Q

Breeding animals with pannus?

A
  • Don’t do it
121
Q

What will happen once you get pannus under control?

A
  • Pigment persists, with regression of blood vessels, edema, and cell infiltrate
122
Q

How long must you manage pannus?

A
  • FOREVER
123
Q

Treatment principles for pannus

A
  • 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
Q

Who gets pigmentary keratitis?

A
  • Brachycephalic breeds with exophthalmos and lagophthalmos
125
Q

What is lagophthalmos?

A
  • Inability to close the eyelid over the eye completely
126
Q

What causes pigmentary keratitis?

A
  • Chronic injury or irritation to the cornea
  • Exposure
  • Aberrant cilia
  • KCS/poor tear film
127
Q

What do you think about putting steroids on a brachycephalic dog, especially with pigmentary keratitis

A
  • Don’t do it
128
Q

Appearance of pigmentary keratitis?

A
  • Pigmentation on the eye
129
Q

How does cyclosporine help dry eyes?

A
  • Tear production
  • Tear film quality
  • Reduces corneal pigmentation
130
Q

Treatment for pigmentary keratitis

A
  • 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
Q

Dermoid

A
  • Skin growing in an abnormal ocation
132
Q

Treatment for dermoid

A
  • Surgical excision (superficial keratectomy)

- REFERRAL PROCEDURE

133
Q

Corneal subepithelial lipid dystrophy appearance

A
  • Lipid deposit
  • It’s on the cornea not the cataract
  • May be horseshoe shaped
  • Can get brittle
  • Don’t breed
134
Q

Characteristics of corneal subepithelial lipid dystrophy

A
  • Hereditary
  • Bilateral
  • Non-painful
  • Progressive
135
Q

Treatment for corneal subepithelial lipid dystrophy

A
  • Low fat diet to reduce the cholesterol crystal deposits
136
Q

Pathophys of corneal subepithelial lipid dystrophy

A
  • Calcium deposits over the cholesterol crystal can lead to corneal degeneration?
137
Q

Plasmoma

A
  • Depigmentation and thickening of the third eyelid due to inflammatory cells (plasma cells) infiltrating the area
138
Q

Limbal melanoma

A
  • Don’t take the eye out
  • Don’t often metastasize
  • Refer?
  • GSD and labs get it
139
Q

Corneal SCC in a horse tx

A
  • Keratectomy or freeze

- Could be malignant

140
Q

What can be long term side effects from cyclosporine/tacrolimus?

A
  • Squamous cell carcinoma

Ophthalmology (8 decks)

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