Eye Culturing for Drainage

Indications for Culturing

The American Academy of Ophthalmology recommends obtaining corneal cultures before initiating antimicrobial therapy if the eye drainage is associated with a central or large corneal infiltrate (≥2 mm), significant stromal involvement, anterior chamber cells, or any sight-threatening features 1
Mandatory culturing indications include central corneal infiltrate within 3 mm of corneal center AND ≥2 mm in size, presence of ≥1+ cells in the anterior chamber, stromal melting or significant stromal involvement, multiple corneal infiltrates or ≥2 adjacent lesions, history of corneal surgery, and atypical features suggesting fungal, amoebic, or mycobacterial infection 1, 2

The American Academy of Ophthalmology recommends using proparacaine 0.5% as topical anesthetic, and avoiding tetracaine due to antimicrobial effects that interfere with culture results 1
Avoid anesthetics with preservatives to improve culture yield, and obtain scrapings from the base or periphery of the infected area using sterile blade, platinum spatula, or jeweler's forceps 1, 2
Do not collect only purulent material, as this yields inadequate results, and consider using nylon-tipped flocked swab, which has similar culture-positivity rates and is more cost-effective 2, 5

Inoculate directly onto appropriate culture media to maximize yield, and if direct inoculation is not feasible, place in transport media (modified Amies medium or thioglycolate broth-moistened swab) 2, 5
Immediately incubate or promptly deliver to laboratory, and adding liquid culture media increases bacterial isolation compared to solid media alone 2, 5

Perform Gram stain and Giemsa stain for large, central, or sight-threatening infiltrates, and add potassium hydroxide, Calcofluor white, and acid-fast stains for post-surgical infiltrates 1

Do not perform aqueous or vitreous taps for hypopyon in bacterial keratitis unless high suspicion of endophthalmitis, as hypopyon is usually sterile 2
Recognize that cornea specialists correctly differentiate bacterial from fungal keratitis in fewer than 70% of cases by clinical appearance alone, highlighting the critical importance of cultures for proper pathogen identification 1, 2