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Investigative modalities in infectious keratitis
1Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi-110 029 India.
Abstract:
Standard recommended guidelines for diagnosis of infectious keratitis do exist. Based on an extensive Medline literature search, the various investigative modalities available for aiding the diagnosis of microbial keratitis have been reviewed and described briefly. Preferred practice patterns have been outlined and the importance of routine pre-treatment cultures in the primary management of infectious keratitis has been highlighted. Corneal scraping, tear samples and corneal biopsy are few of the specimens needed to carry out the investigative procedures for diagnosis and for initiating therapy in cases of microbial keratitis. In bacterial, fungal and amoebic keratitis, microscopic examination of smears is essential for rapid diagnosis. Potassium hydroxide (KOH) wet mount, Gram's stain and Giemsa stain are widely used and are important for clinicians to start empirical therapy before microbial culture results are available. The usefulness of performing corneal cultures in all cases of suspected infectious keratitis has been well established. In cases of suspected viral keratitis, therapy can be initiated on clinical judgment alone. If a viral culture is needed, scrapings should directly be inoculated into the viral transport media. In vivo confocal microscopy is a useful adjunct to slit lamp bio-microscopy for supplementing diagnosis in most cases and establishing early diagnosis in many cases of non-responding fungal and amoebic keratitis. This is a non-invasive, high resolution technique which allows rapid detection of Acanthamoeba cysts and trophozoites and fungal hyphae in the cornea long before laboratory cultures give conclusive results. Other new modalities for detection of microbial keratitis include molecular diagnostic techniques like polymerase chain reaction, and genetic finger printing by pulsed field gel electrophoresis.
Insights
Diagnosing infectious keratitis involves various methods, including corneal scraping and microscopy. Prompt laboratory cultures and advanced techniques like in vivo confocal microscopy aid in rapid and accurate diagnosis for effective treatment.
Area of Science:
- Ophthalmology
- Microbiology
- Medical Diagnostics
Background:
- Infectious keratitis requires timely and accurate diagnosis for effective management.
- Standard diagnostic guidelines exist, but a review of investigative modalities is beneficial.
Purpose of the Study:
- To review and describe investigative modalities for diagnosing microbial keratitis.
- To outline preferred practice patterns and highlight the importance of pre-treatment cultures.
Main Methods:
- Extensive Medline literature search.
- Review and brief description of diagnostic investigative modalities.
- Emphasis on microscopic examination of smears (KOH wet mount, Gram's, Giemsa stains) and corneal cultures.
- Discussion of in vivo confocal microscopy and molecular diagnostic techniques (PCR, PFGE).
Main Results:
- Microscopic examination of smears is crucial for rapid diagnosis of bacterial, fungal, and amoebic keratitis.
- Corneal cultures are essential for all suspected infectious keratitis cases.
- In vivo confocal microscopy offers early and non-invasive detection of Acanthamoeba and fungi.
- Molecular techniques provide advanced diagnostic capabilities.
Conclusions:
- A combination of traditional and advanced diagnostic methods ensures accurate and timely diagnosis of infectious keratitis.
- Routine pre-treatment cultures and prompt microscopic examination are vital for initiating empirical therapy.
- In vivo confocal microscopy and molecular diagnostics represent significant advancements in detecting challenging cases.
