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Clinical Opthalmology > Cornea > Flashcards

Cornea Flashcards

1
Q

6 layers of the cornea

A
  • epithelium - continuously regenerates
  • basement membrane
  • bowman’s layer
  • stroma
  • descements membrane
  • endothelium
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2
Q

Do corneal endothelial cells regenerate

A

No

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3
Q

What is a corneal abrasion

A
  • trauma that has taken off the corneal epithelium
  • superficial
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4
Q

What is bacterial keratitis

A
  • bacterial infection of the cornea
  • usually develops when ocular defences have been compromised
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5
Q

Risk factors of bacterial keratitis

A
  • CL (esp extended wear)
  • trauma
  • ocular surface disease such as herpetic keratitis
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6
Q

Symptoms of bacterial keratitis

A
  • reduced VA
  • pain
  • photophobia
  • possible discharge
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7
Q

Signs of bacterial keratitis

A
  • epithelial defect with infiltrate
  • circumcorneal injection
  • stromal oedema
  • folds in descements membrane
  • possible anterior uveitis with hypopyon and posterior synechiae
  • chemosis
  • eyelid swelling
  • ulceration
  • reduced corneal sensation
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8
Q

Differential diagnosis of bacterial keratitis

A
  • keratitis due to other microorganisms
  • marginal keratitis
  • sterile inflammatory infiltrates associated with CL wear
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9
Q

Treatment for bacterial keratitis

A
  • discontinuation of CL wear
  • treatment not always needed
  • antibiotic mono therapy (usually fluoroquinolone)
  • subconjunctival antibiotics (only indicated if poor compliance with topical treatment)
  • mydratics - to prevent formation of posterior synechiae
  • steroids
  • systemic antibiotics in some cases
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10
Q

What is fungal keratitis

A
  • fungal infection of the cornea
  • causes severe inflammatory response
  • corneal perforation common
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11
Q

2 types of fungi that cause keratitis

A
  • yeast
  • filamentous fungi
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12
Q

Risk factors of fungal keratitis

A
  • long term use of topical steroids
  • CL wear
  • systemic immunosuppression
  • diabetes
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13
Q

Filamentous (fungal) keratitis clinical presentation

A
  • grey/yellow stromal infiltrate
  • lid oedema
  • progressive infiltration
  • branch like extensions
  • rapid progression
  • necrosis and thinning
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14
Q

Fungal keratitis treatment

A
  • cease CL wear
  • removal of epithelium over lesion - easier penetration of anti fugal agents
  • topical anti fungals (natamycin 5%)
  • systemic anti fungal
  • cycloplegia
  • tetracycline
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15
Q

Types of viral keratitis

A

Herpes simplex virus
- epithelial keratitis
- stromal keratitis
- uveitis
- lids to retina

Herpes zoster opthalmicus

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16
Q

Herpes simplex keratitis - symptoms

A
  • FB sensation
  • photophobia
  • redness
  • blurred vision
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17
Q

Herpes simplex keratitis - signs

A

Epithelial ulcer
- dendritic pattern
- terminal bulbs
- swollen adjacent epithelium
Reduced corneal sensation
- focal or diffuse
Conjunctival injection
Underlying stromal oedema

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18
Q

Risk factors of HSK

A
  • poor general health
  • immunosuppression
  • sunlight (uv)
  • history of previous attacks
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19
Q

Herpes simplex keratitis management

A
  • referral of acute episodes with no history
  • cease CL wear

Recurrent cases
- clear diagnosis
- only epithelial involvement
- commence topical antiviral therapy

Refer if not healing after a week or if stromal involvement

Topical antiviral therapy
- aciclovir 3%, 5x daily
- review 1 week

Oral aciclovir
- 800mg 5x daily

Discontinue topical steroids

20
Q

What is herpes zoster opthalmicus

A
  • Keratitis caused by reactivation of latent virus (varicella zoster virus?)
  • Associated with altered immunity

Zoster dermatitis
- vascular rash
- general malaise
- multitude of opthalmicus signs

21
Q

Herpes zoster opthalmicus management

A
  • rest and supportive advice
  • avoid contact with immunosuppressive individuals
  • ocular lubricants
  • painkillers
  • refer if deeper layers involved
22
Q

Pseudomonas clinical presentation

A
  • produces stromal necrosis with a shaggy surface
  • endothelial inflammatory plaque
  • marked anterior chamber reaction
  • hypopyon

Slow growing, fastidious organisms
- mycobacterium
- anaerobes
- non supportive infiltrate
- intact epithelium

23
Q

What is Acanthamoeba

A
  • protozoa
  • commonly associated with CL wear and swimming
24
Q

What is the clinical presentation of Acanthamoeba

A
  • severe pain disproportionate to signs
  • initial punctate keratopathy or dendrite
  • ring ulcer
  • diagnosed by corneal scrape
  • suspected if non-responsive to conventional bacterial keratitis therapy
  • epiphora
  • photophobia
25
Q

Acanthemoeba Managment

A
  • urgent referral
  • stop CL wear and bring with solution for culture
  • corneal scrape
  • topical amoebicides
  • topical steroids
26
Q

What is neurotrophic keratitis

A

Occurs when there is a loss of trigeminal nerve innervation to the cornea, resulting in partial or complete anaesthesia
- cause loss of protective sensory stimulus
- reduced goblet cells
- epithelial breakdown and persistent ulceration

27
Q

Neurotrophic karatopathy: stage 1

A
  • punctate corneal epithelium
  • superficial vascularisation
  • stromal scarring
  • decreased TBUT
  • increased tear mucus viscosity
  • epithelial hyperplasia and irregularity
  • hyperplasia precorneal membrane
  • staining of pal-Ebola conjunctiva
28
Q

Neurotrophic keratopathy: stage 2

A
  • epithelial defect, usually in superior half of the cornea
  • smooth and rolled epithelial defect edges
  • surrounding rim of loose epithelium
  • stromal oedema
  • AC inflammation
29
Q

Neurotrophic keratopathy: stage 3

A
  • corneal ulcer
  • stromal melting
  • perforation
30
Q

What is Reis-bucklers corneal dystrophy

A
  • categorised as an anterior variant of granular stromal dystrophy and is also known as corneal basement
31
Q

Reis-Buckler corneal dystrophy signs/symptoms and treatment

A
  • severe recurrent corneal erosions in childhood
  • possible visual impairment
  • grey/white geographic sub epithelial opacities, increasing in in density with age

Treatment
- directed at redcurrant erosions
- excimer keratectomy

32
Q

What is meesmann epithelial dystrophy, and sign/symptoms

A
  • rare non-progressive abnormality of corneal epithelial metabolism
  • results in mutated gene encoding epithelial keratin

Symptoms
- may be asymptomatic
- may be recurrent erosions
- mild blurring of vision

Signs
- tiny epithelial cysts of uniform size
- cornea may be slightly thinned
- reduced corneal sensation

33
Q

What is Lattice corneal dystrophy, and sign/symptoms and treatment

A
  • associated with heterozygous mutations in TGFB1

Symptoms
- recurrent erosions At end of first decade in the classic form
- blurring may occur later

Signs
- refractile anterior stromal spots, coalescing to a relatively fine filamentous lattice that spreads gradually but spares the periphery
- generalised stromal haze
- haze may impair vision
- reduced corneal sensation

Treatment
- deep lamellar keratoplasty
- reoccurrence is common

34
Q

What is granular corneal dystrophy type 1 and its signs/symptoms

A

Symptoms
Glare and photophobia, with blurring as progression occurs.
Recurrent erosions are uncommon.

Signs
• Discrete white central anterior stromal deposits resembling sugar granules, breadcrumbs or glass splinters separated by clear stroma
o Gradual increase in number and size of the deposits with deeper and outward spread, sparing the limbus
• Gradual confluence and diffuse haze lead to visual impairment
• Corneal sensation is impaired.

35
Q

What is Macular corneal dystrophy and it’s signs/symptoms

A

Inheritance
-Autosomal recessive (AR); gene CHST6; the condition is relatively common in Iceland.

Symptoms
- Early (end of first decade) visual deterioration;
recurrent erosions are very common.

Signs
- Dense but poorly delineated greyish-white spots centrally in the anterior stroma and peripherally in the posterior stroma
There is no clear delineation between opacities, which may be elevated.
- progression of lesions occurs in conjunction with anterior stromal haze
- eventual involvement of full thickness cornea
- corneal thinning is an early feature
- reduced sensation

36
Q

What is posterior polymorphous corneal dystrophy, and its signs/symptoms

A
  • 3 forms of the disease
  • involves meta plasma of endothelial cells

Symptoms
- usually absent with incidental diagnosis

Signs
- subtle vesicular, band like or diffuse like endothelial lesions

37
Q

What is keratoconus

A
  • progressive central or paracentral stromal thinning
  • accompanied by apical protrusion and irregular astigmatism
38
Q

Symptoms of keratoconus

A
  • unilateral impairment of vision due to progressive myopia and astigmatism
  • initial presentation with acute hydrops (AH enters cornea leading to corneal oedema)
39
Q

Signs of keratoconus

A
  • oil droplet reflex
  • retinoscopy shows scissor reflex
  • deep stromal stress lines
  • epithelial iron deposits
  • progressive corneal protrusion
  • bulging of lower lid
  • steep keratomileusis readings
40
Q

Keratoconus treatment

A
  • avoid eye rubbing
  • glasses or CLs sufficient in early cases
  • RGP lenses
  • keratoplasty
  • LASIK
41
Q

What are the penetrating keratoplasty techniques

A
  • superficial anterior lamellar keratoplasty SALK
  • deep anterior lemallar keratoplasty DALK
  • DSAEK
42
Q

Recurrent Corneal Erosion - Aetiology

A
  • recurrent breakdown of corneal epithelium due to defective adhesion to basement membrane
  • repair of epithelial basement membrane and associated epithelial adhesion complex takes around 3/12 if undisturbed
43
Q

Recurrent Corneal Erosion - Risk Factors

A
  • history of superficial trauma (esp finger nail injuries)
  • corneal dystrophies (esp epithelial basement membrane dystrophy)
  • dry eye
  • diabetes
  • previous refractive surgery (esp photorefractive keratectomy)
44
Q

Recurrent Corneal Erosion - Symptoms

A
  • unilateral sharp pain, usually sudden onset on waking and opening eyes, may wake px in night
  • eyelids feel stuck to the eyeball
  • watery eyes
  • photophobia
  • blurred vision
45
Q

Recurrent Corneal Erosion - Signs

A
  • epithelial erosion - usually inferior paracentral cornea
    • stains with fluorescein
    • ‘slipped rug’ appearance with ‘loose edges’
  • intra-epithelial microcysts
  • mild stromal oedema
  • may recur over weeks/months/years
46
Q

Recurrent Corneal Erosion - Differential Diagnosis

A
  • HSK
  • exposure keratopathy
  • other corneal dystrophies
  • CL related epithelial conditions
47
Q

Recurrent Corneal Erosion - Management

A
  • artificial tears frequently
  • unmedicated paraffin based ointment (use for 3/12)
  • adv to return if symptoms persist

More severe cases:
- cycloplegic (e.g. cyclopentolate 1%) to prevent pupil spasm
- antibiotic ointment (e.g. chloramphenicol 1%)
- refer if persistent, large, or unstable/fails to respond to medical therapy

Clinical Opthalmology (7 decks)

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