Download Fungal Keratitis

Fungal Keratitis
Etiology
• i. Filamentous fungi :
– Aspergillus (most common), Fusarium, Alternaria,
Cephalosporium, Curvularia and Penicillium.
• ii. Yeasts: Candida and Cryptococcus.
Modes of infection
Modes of infection
• i. Injury by vegetative material such as crop leaf,
branch of a tree, straw, hay or decaying vegetable
matter.
• ii. Injury by animal tail is another mode of
infection.
• iii. Patients who are immunosuppressed
systemically or locally such as patients suffering
from dry eye, herpetic keratitis, bullous
keratopathy or postoperative cases of
keratoplasty.
Clinical features
• Symptoms :
– are similar to the central bacterial corneal ulcer
– less marked than the equal-sized bacterial ulcer
– overall course is slow and torpid.
Symptoms
Fungal
Bacterial
Signs
• Dry in appearance.
• Feathery borders
• Surrounded by a yellow line of
demarcation which gradually
deepens into a gutter
• An immune ring (Wesseley) :
deposition of immune complexes
and inflammatory cells around the
ulcer.
• Satellite lesions.
• Hypopyon : thick and immobile,
and is due to direct invasion into
the anterior chamber of fungal
hyphae enmeshed in thick
exudates.
• There is marked ciliary and
conjunctival congestion,
Laboratory investigations
• wet KOH,
• Calcofluor white,
• Gram's and Giemsa- stained films for fungal
hyphae and
• culture on Sabouraud's agar medium.
Treatment
• 1. Topical antifungal eye drops should be used
• for a long period (6 to 8 weeks:
– Natamycin (5%) eye drops
– Fluconazol (0.2%) eye drops
– Nystatin (3.5%) eye ointment.
• Systemic antifungal drugs may be required for
severe cases of fungal keratitis. Tablet
fluconazole or ketoconazole may be given for
2-3 weeks.
Viral keratitis
• Herpes simplex
• Herpes zoster
Herpes simplex
Clinical reactivation
Herpes simplex – ocular manifestations
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•
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Blepharitis,
Conjunctivitis,
Keratitis
Iridocyclitis
Primary infection
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•
Without previous viral exposure,
Usually in childhood
Subclinical or mild prodromal symptoms.
Blepharitis and follicular conjunctivitis :mild
and self-limited.
• Treatment, if necessary, involves topical
aciclovir ointment for the eye and/or cream
for skin lesions.
• The initial corneal lesion is a superficial
Punctate keratitis—
– numerous minute whitish plaques , arranged in
rows or groups.
– Desquamate  erosions heal rapidly leaving no
opacity, but are accompanied by great irritation,
lacrimation and blepharospasm.
– In all cases the cornea is relatively insensitive.
• The corneal involvement can be
– Epithelial (dendritic or geographic keratitis),
– stromal (necrotizing and non-necrotizing
stromalkeratitis) and
– endothelial
Dendritic ulcers
Swollen opaque epithelial
cells arranged in
a coarse
stellate
punctate
pattern
Central desquamation
a linear-branching (dendritic)
ulcer with terminal buds
• Floor of the ulcer stains
with fluorescein and the
virus-laden cells at the
margin take up rose
bengal.
• There is an associated
marked diminution of
corneal sensations.
fluorescein
rose bengal
Geographical ulcer
• Sometimes, the branches of
dendritic ulcer enlarge and
coalesce to form a large
epithelial ulcer with a
'geographical' or 'amoeboid'
configuration.
• The use of steroids in dendritic
ulcer hastens the formation of
geographical ulcer.
Specific treatment
• 1. Antiviral drugs are the first choice presently.
– Aciclovir
– Ganciclovir
– Triflurothymidine
– Vidarabine
• 2. Mechanical debridement : helps by
removing the virus-laden cells.
Disciform keratitis
Pathogenesis
HSV
Hypersensitivity
reaction
Disciform keratitis
Signs
> Focal disc-shaped patch of stromal oedema without necrosis,
> Folds in Descemet's membrane,
Central epithelial and stromal oedema
keratic precipitates;
Disciform Keratitis
Wessely ring precipitates
• Ring of stromal infilterate (Wessley immune
ring): It signifies the junction between viral
antigen and host antibody.
• Corneal sensations are diminished.
• Intraocular pressure (IOP) may be raised
despite only mild anterior uveitis.
• In severe cases, anterior uveitis may be
marked
Treatment
• Steroid eye drops with an antiviral cover
(aciclovir 3%).
• Steroids should be tapered over a period of
several weeks.
• When disciform keratitis is present with an
infected epithelial ulcer, antiviral drugs should
be started 5-7 days before the steroids.
• Iritis:
• Treated with a combination of topical steroids,
topical antiviral drugs and cycloplegics.
In Summary
Epithelial
keratitis due
to active viral
replication
Treated with
antivirals
Stromal
keratitis due
to immune
mechanism
Treated with
steroids
Herpes zoster
• Herpes zoster is caused by the same virus that
causes chickenpox (varicella zoster virus).
After an infection with chickenpox in childhood or youth
the virus lies dormant
Reactivation- particularly in elderly people with depressed
cellular immunity, causing the clinical picture of zoster.
• In zoster ophthalmicus the chief focus of
infection is the Gasserian ganglion from where
the virus travels down one or more of the
branches of the ophthalmic division of the
tiigeminal nerve, so that its area of
distribution is marked out by rows of vesicles
or the scars left by them.
• Fever and malaise at the onset
• Eruption is preceded by severe neuralgic pain
along the course of the nerves.
• Characteristic distribution of the lesions
especially the strict limitation to one side of
the midline of the head.
• The vesicles often suppurate, bleed and cause
small, permanent, pitted scars.
• The Hutchinson's rule,
which implies that
ocular involvement is
frequent if the side or
tip of nose presents
vesicles (cutaneous
involvement of
nasociliary nerve).
Ocular lesions
• Conjunctivitis
• Zoster keratitis
– Fine or coarse punctate epithelial keratitis.
– Microdendritic epithelial ulcers
– Nummular
– Disciform keratitis occurs
– Neuroparalytic ulceration
– Exposure keratitis
– Mucous plaque keratitis
􀁺
Microdendritic epithelial ulcers
• Usually peripheral and
stellate rather than
exactly dendritic in
shape.
• Have tapered ends
which lack bulbs.
Nummular keratitis:
multiple tiny granular
deposits surrounded by a
halo of stromal haze.
• Episcleritis and scleritis
• Iridocyclitis: hypopyon and hyphaema (acute
haemorrhagic uveitis).
• Acute retinal necrosis
• Anterior segment necrosis and phthisis bulbi.
• Secondary glaucoma
neurological complications.
• 1. Motor nerve palsies especially third, fourth,
sixth and seventh.
• 2. Optic neuritis
• 3. Encephalitis
Treatment
• Systemic therapy for herpes zoster:
• Oral antiviral drugs.
– Acyclovir in a dose of 800 mg 5 times a day for 10 days, or
– Valaciclovir in a dose of 500mg TDS
• Analgesics.
• Systemic steroids: neurological complications such as
third nerve palsy and optic neuritis.
• Cimetidine: to reduce pain and pruritis
• Amitriptyline: to relieve the accompanying depression
in acute phase
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Local therapy for ocular lesions
For zoster keratitis, iridocyctitis and scleritis
i. Topical steroid eye drops.
ii. Cycloplegics such as cyclopentolate
eyedrops or atropine eye ointment
• iii. Topical acyclovir