Corneal scraping is a procedure to collect cells from the surface of your eye. It is done for two purposes, that are diagnostic purpose and therapeutic purpose.
Diagnostic purpose: for identification of the cause of ulcer.
Therapeutic purpose: for starting the medication for the treatment of ulcer.
When to do corneal scraping?
Scraping may be indicated if the ulcer is large, central, not responding to current treatment or if an atypical infectious organism is suspected. Usually corneal scraping is done only under 3, 2, 1 guideline that is
- 3: The ulcer is 3mm or greater in size at its widest diameter,
- 2: There are two or more ulcers,
- 1: The ulcer is within 1mm of the visual axis.
Every guideline have exceptions, for instance it may be advisable to culture an ulcer that is smaller and peripheral if it has suspicious characteristics. If there is any initial concern for a fungal infection, perform culture early in the presentation as it can take up-to two weeks for fungus to grow on agar.
Is corneal scraping painful?
Corneal scraping is done under topical anesthesia therefore, it is a non painful procedure. The topical anesthesia is preferably installed two drops of 0.5% proparacaine, or tetracaine, or xylocaine in the inferior fornix, but mostly 0.5% proparacaine is the first choice as it has the least amount of bactericidal action as compared to other agents. General anesthesia and sedation may be required in children , uncooperative adults or mentally impaired patients.
Equipments used for Corneal Scraping
- Wire speculum (optional)
- Kimura spatula/bard parker blade/platinum spatula
- Three glass slides: (For gram stain, For KoH wet mount, Optional for special stain i.e AFB, Giemsa, Calcofluor)
- Cover slip
- Blood agar
- Chocolate agar
- Sabouraud’s dextrose agar
- Thioglycollate broth
Procedure of corneal scraping
- First, all the equipments are prepared.
- Then the patient is laid down in supine position on the surgical bed comfortably,
- Then 0.5% proparacaine is installed in their eye,
- The doctor will wash their hands and put on surgical gloves, gown, mask and head cover to prevent any further infection,
- Doctor will use platinum spatula and heat it for 10 seconds and scrape the edge of the lesion where the organisms are most active avoiding the visual axis possible,
- Starting with glass slide the sample is placed between the circle area to make easy to locate the sample,
- Next making sure not to break the agar surface inoculation of sample in the plate is done in cross hatch streaks until sample is fully transferred,
- For the broth medium the spatula is stirred thoroughly in the fluid until the sample is transferred,
- Antibiotic topical drop is installed in the patients eye to avoid further infectious which may occur dur to scraping and the patient is sent home under follow up,
- The inoculated samples are sent to the microbiology laboratory for the results.
Complications of corneal scrapings
- May lead to permanent damage to the corneal epithelium adhesion complex and therefore affect prognosis,
- Scleral extension of the infection,
- Residual corneal scarring,
- Corneal perforation,
How long does corneal scraping takes to heal?
The healing of scraping is unpredictable or we can say is totally based upon the degree of lesion. The healing is based upon how big the scrape is and how severe the infection is.
(Note: All the complications are rare and exceptions)