Cornea Flashcards
6 layers of the cornea
- epithelium - continuously regenerates
- basement membrane
- bowman’s layer
- stroma
- descements membrane
- endothelium
Do corneal endothelial cells regenerate
No
What is a corneal abrasion
- trauma that has taken off the corneal epithelium
- superficial
What is bacterial keratitis
- bacterial infection of the cornea
- usually develops when ocular defences have been compromised
Risk factors of bacterial keratitis
- CL (esp extended wear)
- trauma
- ocular surface disease such as herpetic keratitis
Symptoms of bacterial keratitis
- reduced VA
- pain
- photophobia
- possible discharge
Signs of bacterial keratitis
- 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
Differential diagnosis of bacterial keratitis
- keratitis due to other microorganisms
- marginal keratitis
- sterile inflammatory infiltrates associated with CL wear
Treatment for bacterial keratitis
- 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
What is fungal keratitis
- fungal infection of the cornea
- causes severe inflammatory response
- corneal perforation common
2 types of fungi that cause keratitis
- yeast
- filamentous fungi
Risk factors of fungal keratitis
- long term use of topical steroids
- CL wear
- systemic immunosuppression
- diabetes
Filamentous (fungal) keratitis clinical presentation
- grey/yellow stromal infiltrate
- lid oedema
- progressive infiltration
- branch like extensions
- rapid progression
- necrosis and thinning
Fungal keratitis treatment
- cease CL wear
- removal of epithelium over lesion - easier penetration of anti fugal agents
- topical anti fungals (natamycin 5%)
- systemic anti fungal
- cycloplegia
- tetracycline
Types of viral keratitis
Herpes simplex virus
- epithelial keratitis
- stromal keratitis
- uveitis
- lids to retina
Herpes zoster opthalmicus
Herpes simplex keratitis - symptoms
- FB sensation
- photophobia
- redness
- blurred vision
Herpes simplex keratitis - signs
Epithelial ulcer
- dendritic pattern
- terminal bulbs
- swollen adjacent epithelium
Reduced corneal sensation
- focal or diffuse
Conjunctival injection
Underlying stromal oedema
Risk factors of HSK
- poor general health
- immunosuppression
- sunlight (uv)
- history of previous attacks
Herpes simplex keratitis management
- 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
What is herpes zoster opthalmicus
- Keratitis caused by reactivation of latent virus (varicella zoster virus?)
- Associated with altered immunity
Zoster dermatitis
- vascular rash
- general malaise
- multitude of opthalmicus signs
Herpes zoster opthalmicus management
- rest and supportive advice
- avoid contact with immunosuppressive individuals
- ocular lubricants
- painkillers
- refer if deeper layers involved
Pseudomonas clinical presentation
- 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
What is Acanthamoeba
- protozoa
- commonly associated with CL wear and swimming
What is the clinical presentation of Acanthamoeba
- 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
Acanthemoeba Managment
- urgent referral
- stop CL wear and bring with solution for culture
- corneal scrape
- topical amoebicides
- topical steroids
What is neurotrophic keratitis
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
Neurotrophic karatopathy: stage 1
- 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
Neurotrophic keratopathy: stage 2
- epithelial defect, usually in superior half of the cornea
- smooth and rolled epithelial defect edges
- surrounding rim of loose epithelium
- stromal oedema
- AC inflammation
Neurotrophic keratopathy: stage 3
- corneal ulcer
- stromal melting
- perforation
What is Reis-bucklers corneal dystrophy
- categorised as an anterior variant of granular stromal dystrophy and is also known as corneal basement
Reis-Buckler corneal dystrophy signs/symptoms and treatment
- 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
What is meesmann epithelial dystrophy, and sign/symptoms
- 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
What is Lattice corneal dystrophy, and sign/symptoms and treatment
- 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
What is granular corneal dystrophy type 1 and its signs/symptoms
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.
What is Macular corneal dystrophy and it’s signs/symptoms
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
What is posterior polymorphous corneal dystrophy, and its signs/symptoms
- 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
What is keratoconus
- progressive central or paracentral stromal thinning
- accompanied by apical protrusion and irregular astigmatism
Symptoms of keratoconus
- unilateral impairment of vision due to progressive myopia and astigmatism
- initial presentation with acute hydrops (AH enters cornea leading to corneal oedema)
Signs of keratoconus
- oil droplet reflex
- retinoscopy shows scissor reflex
- deep stromal stress lines
- epithelial iron deposits
- progressive corneal protrusion
- bulging of lower lid
- steep keratomileusis readings
Keratoconus treatment
- avoid eye rubbing
- glasses or CLs sufficient in early cases
- RGP lenses
- keratoplasty
- LASIK
What are the penetrating keratoplasty techniques
- superficial anterior lamellar keratoplasty SALK
- deep anterior lemallar keratoplasty DALK
- DSAEK
Recurrent Corneal Erosion - Aetiology
- 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
Recurrent Corneal Erosion - Risk Factors
- history of superficial trauma (esp finger nail injuries)
- corneal dystrophies (esp epithelial basement membrane dystrophy)
- dry eye
- diabetes
- previous refractive surgery (esp photorefractive keratectomy)
Recurrent Corneal Erosion - Symptoms
- 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
Recurrent Corneal Erosion - Signs
- 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
Recurrent Corneal Erosion - Differential Diagnosis
- HSK
- exposure keratopathy
- other corneal dystrophies
- CL related epithelial conditions
Recurrent Corneal Erosion - Management
- 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
