Taking a corneal scrape
1. Liaise with microbiology staff and Request an urgent Gram stain.
2. Warm refrigerated media to room temperature.
3. Instil topical Anaesthetic.
4. Explain the procedure.
5. At the slit lamp, use a Kimura spatula, or 20-gauge needle to remove superficial debris from the ulcer, and then scrape the edges and base.
6. Streak material onto two glass slides for Gram and Giemsa staining (or other preferred stain). Air dry and label with pencil.
7. Take additional scrapes, one for each culture medium. Streak material onto agar plates without breaking the surface. Flame the blade and cool for 20 seconds between scrapes, or select a fresh needle.
8. Plate onto blood agar, chocolate agar, and Sabouraud’s agar.
9. If acanthamoeba is suspected, streak onto the centre of a non- nutrient agar plate.
10. Tape covers onto the plates to prevent evaporation.
11. Culture contact lenses, cases, and solutions. Document that the patient understands these will be destroyed in the process.
12. Label all material, and transport immediately to the laboratory.
13. Cultures may be positive in 24 hours, but can take up to 3 weeks for fungi, acanthamoeba, or anaerobes.
Taking a corneal scrape power point presentations :
Corneal Ulcer
1. CORNEAL ULCER PRESENTED BY- Captain Ayinun Nahar Trainee in Ophthalmology Armed Forces Medical Institute
2. Definition Corneal ulcer : Refers to corneal tissue excavation associated with an epithelial defect, usually with infiltration and necrosis.
3. Histology of Cornea
4. Classification Corneal ulcers can be classified in three ways : 1. On the basis of aetiology 2. On the basis of location of ulcer 3. On the basis of involvement of the corneal layers
5. Classification a. Infective: – Bacterial – Viral – Fungal – Protozoal b. Non-infective/sterile : – Neuroparalytic – Neurotrophic – Corneal ulcer due to Vit A deficiency – Mooren ulcer 1. On the basis of aetiology –
6. Classification 2. On the basis of location of ulcer- Central Paracentral Peripheral
7. Classification Deep 3. On the basis of involvement of the corneal layers- Superficial
8. Predisposing Factors • Ocular trauma • Dry eye • Chronic dacryocystitis • Exophthalmos • Xerophthalmia • Entropion • Trichiasis • Contact lens wear • Prolong use of local steroids Local Factors :
9. Predisposing Factors • Systemic Factors : – Malnutrition – DM – Alcoholism – Drug addiction – Malignancy – Immunosuppressive drugs
10. Predisposing Factors Contact lens users are predisposed to corneal ulcer. Causes : • Negligence • Prolonged period of time • Cleaning with tap water • Contamination
11. Infective Corneal Ulcer • Compromised ocular defence • Sight threatening condition • Ocular emergency
12. Ocular defence mechanism • Corneal epithelium- mechanical barrier • Conjunctiva- cellular & chemical components • Tear film- biological protective system Major components of ocular defence system
13. Barriers of microbial infection
14. Causative Organisms
15. Pathogenesis Corneal abrasion Microbes adhere , clone and invade to stromal lamellae,release toxins & lytic enzymes Host response PMNs at the site of defect from tears & limbal vessels release of cytokines & interleukins progressive invasion of cornea & increase in size of ulcer Phagocytosis Release of free radicals, proteolytic enzymes Necrosis & sloughing of epithelium, Bowman’s membrane & stroma A saucer shaped defect with projecting walls above the normal surface due to swelling of tissue resulting from fluid imbibition by corneal stroma with grey zone of infiltration
Taking a corneal scrape videos:
Corneal scrape
Taking a corneal scrape
