Fungal Keratitis Clinical Presentation

Updated: Sep 08, 2017
  • Author: Michael Ross, MD; Chief Editor: Hampton Roy, Sr, MD  more...
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Presentation

History

A history of outdoor eye trauma often is reported.

In patients presenting with possible fungal keratitis, inquire about possible risk factors (see Causes).

Symptoms include the following:

  • Foreign body sensation

  • Increasing eye pain or discomfort

  • Sudden blurry vision

  • Unusual redness of the eye

  • Excessive tearing and discharge from the eye

  • Increased light sensitivity

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Physical

The clinical diagnosis of fungal keratitis is based on risk factor analysis and characteristic corneal features.

The most common signs on slit lamp examination are nonspecific and include the following:

  • Conjunctival injection (See images below.)

    Fungal corneal ulcer, with excessive vascularizati Fungal corneal ulcer, with excessive vascularization.
    Marginal ulcer, fungus positive. Marginal ulcer, fungus positive.
  • Epithelial defect

  • Suppuration (See images below.)

    Fungal abscess. Fungal abscess.
    Fungal corneal abscess/ulcer. A proven case of fun Fungal corneal abscess/ulcer. A proven case of fungal infection, 5 days' duration. Intense infiltration around the abscess.
  • Stromal infiltration

  • Anterior chamber reaction

  • Hypopyon

Presenting clinical features that are specific to fungal keratitis include an infiltrate with feathery margins, elevated edges, rough texture, gray-brown pigmentation, satellite lesions, hypopyon, and endothelial plaque. The spread of infection occurs through the channel network of the cornea. This mode of spread fully explains the satellite lesions.

  • Fine or coarse granular infiltrate within the epithelium and anterior stroma

  • Gray-white color, dry, and rough corneal surface that may appear elevated

  • Typical irregular feathery-edged infiltrate

  • White ring in the cornea and satellite lesions near the edge of the primary focus of the infection

  • In advanced cases, suppurative stromal keratitis associated with conjunctival hyperemia, anterior chamber inflammation, hypopyon, iritis, endothelial plaque, or possible corneal perforation

Although these highly characteristic signs may be present, obtaining a sample of the lesion by scraping or corneal biopsy is important before initiating treatment with antifungal therapy (see Procedures). Several unfortunate cases have been reported in which antifungal therapy had been initiated before fungi were seen or isolated, with resultant misdiagnosis and progression of the process. In warm developing countries, it is wise to start antifungal agents on mere suspicion since hot weather promotes rapid fungal growth.

Mixed bacterial and fungal infections are common in the developing countries. The patients may present after many days or weeks. While antibacterial therapy is started in most clinics in the periphery, fungal infection may not be considered. The most practical approach in good clinics in developing countries is to examine a scraping from the ulcer, both for bacteria and fungi. If hyphae and/or spores are found, the treatment efforts are mainly directed toward the fungus, but broad-spectrum antibiotics are also used to cover for bacteria.

Once a few fungal ulcers or fungal keratitis cases have been carefully examined, it becomes easy to make a presumptive diagnosis of fungus infection. In the developing countries and tropics, fungal cases are very common in the hot summer months.

Advanced severe filamentous fungal and yeast keratitis are indistinguishable and resemble keratitis caused by virulent bacteria, such as Staphylococcus aureus and Pseudomonas aeruginosa.

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Causes

Aspergillus is the most common cause of fungal keratitis worldwide. However, the epidemiology of fungal keratitis is climate specific. In the southern United States, Fusarium species are the most common cause of fungal keratitis, with an especially high incidence in Florida. In contrast, Candida and Aspergillus species are the most common pathogens in the northern United States.

Common risk factors for the development of fungal keratitis include the following:

  • Trauma (eg, contact lenses, foreign body); in a study of fungal keratitis from south Florida, trauma with vegetable matter was the major risk factor in 44% of patients

  • Topical corticosteroid use

  • Corneal surgery such as penetrating keratoplasty, clear cornea (sutureless) cataract surgery, photorefractive keratectomy, or laser in situ keratomileusis (LASIK)

  • Chronic keratitis due to herpes simplex, herpes zoster, or vernal keratoconjunctivitis

  • Young males

  • Healthy

  • No significant ocular disease

  • Previous history of trauma (vegetable matter)

  • Agricultural occupations

Risk factors for Candida keratitis are as follows:

  • Older patients

  • Preexisting ocular disease

  • Exposure keratopathy

  • Chronic keratitis

  • Long-term steroid use

  • Immunosuppressive disease

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