Healthcare and Medicine Reference
In-Depth Information
Nematodes Keratitis
Onchocerca volvulus is fi larial nematode. The infection is transmitted to
humans by the bite of a female blackfl y of the genus simulium. Parasitic
infections of the cornea may be due to direct ocular inoculation or occur
during systemic infection.
Clinical Features: Symptoms and Signs
Its signs involve punctate keratitis, sclerosing keratitis and others.
Punctate keratitis is the result of an infl ammation reaction to degenerating
microfi lariae in the cornea. In most cases, the patient is asymptomatic with
minimal visual impairment. Sclerosing keratitis is a stromal infl ammation
characterized by prolonged invasion of the cornea by microfi lariae. Corneal
opacifi cation occurs as a result of stromal invasion by blood vessels (Smolin
et al. 2005).
Fungal Keratitis
Most of the fungi implicated in keratitis may be called opportunistic
organisms and are ubiquitous as plant pathogens or in the soil. The most
common causes appear to be those most frequently encountered after an
apparently negligible trauma (Kanski 1994).
Fungal keratitis should always be considered if the differential diagnosis
of suppurated bacterial keratitis and herpetic stromal necrotic keratitis is
suspected (Smolin et al. 2005). It primarily affects the corneal epithelium
and stroma, although the endothelium and anterior chamber of the eye
may be involved in more severe disease.
The clinical appearance of fungal keratitis varies with the infectious
agent and stage of the disease. Filamentous fungal keratitis is usually caused
by Aspergillus or Fusarium spp. , occurs in previously healthy individuals,
most frequently secondary ocular trauma with organic matter (wood).
Candida keratitis usually develops in association with pre-existing chronic
corneal disease or in an immune-compromised or debilitated patient.
Clinical Features: Symptoms and Signs
There are two features that should lead to suspecting a fungal infection;
stromal infi ltrates with feathery, hyphate edges, and infi ltrates that tend to
be dry, grey, and somewhat elevated above the level of the corneal surface.
Endothelial plaques or an anterior chamber reaction usually indicate a
more severe infection with penetration of fungal elements into the anterior
chamber. However, fungal keratitis may be an indolent infection.
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