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Soskob and biopsy of the cornea
Last reviewed: 20.11.2021
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Scraping of the cornea is performed with a Kimura spatula, a curved end of the needle (for the hypodermis), or a blade. After instillation of a local anesthetic without preservatives, the edges and the bottom of the lesion (usually ulcers) are gently and carefully scraped under the control of the slit lamp. Also it is necessary to investigate contact lenses.
The material of the cornea is placed on a slide for Gram stain and the appropriate media:
- blood agar (for most bacteria and fungi);
- Thioglycolic broth (for most bacteria);
- chocolate agar (for Neisseria and Haemophilus);
- agar Sabouraud (for fungi); is incubated at a temperature of about 37 ° C;
- meat-peptone concentrated broth (for fungi that do not grow on Sabouraud agar);
- non-nutrient agar on plates plated with E. Coli (for acanthamoeba);
- buffered agar from yeast extract (for acanthamoeba).
NB: The medium must be kept at room temperature before sowing.
A corneal biopsy is performed by trephine or by an open layered dissection with a sharp blade.
Indications for corneal biopsy
- Keratitis with negative or non-indicative scrapings and sowing on medium.
- Deep infiltration of the cornea, to establish the nature of which simple scraping is impossible.
- Difficulties in diagnosing corneal dystrophies or rare genetically caused diseases of accumulation with the pathology of the cornea.