Bacterial Conjunctivitis (Pink Eye) Workup

Updated: Feb 07, 2023
  • Author: Karen K Yeung, OD, FAAO; Chief Editor: Andrew A Dahl, MD, FACS  more...
  • Print

Approach Considerations

A medical and detailed ocular history includes questions about the onset and duration of the red eye, the quality and quantity of discharge, presence or absence of pain, photophobia, trauma, blurry vision, foreign body sensation, ocular itch, contact lens use, history of previous ocular infections, and current and recent medication use. An eye evaluation should be performed with particular attention to reductions in best corrected vision in either eye, gross evaluation of lid margins and both bulbar and tarsal conjunctivae (presence or absence of a ciliary flush), any ocular discharge, pupillary reactions, any pain with eye movements, slit lamp biomicroscope evaluation of the cornea (with adjunctive fluorescein stain), IOP, and anterior chamber flare or cell. If only one eye has bacterial conjunctivitis, examine the unaffected eye first to prevent cross-infection.

Many astute eye-care providers use a long-wooded cotton-tipped applicator while examining patients. Thus, the ocular tissues are never touched by the examiner’s fingers. This approach can markedly reduce the potential for cross-contamination between eyes, as well as transmission to the examining physician and subsequent patients.

Traditional teaching suggests that significant eye pain, loss of vision, and photophobia are indications of serious eye disease. Anisocoria and ocular pain during pupillary constriction (even during a pencil push-up test) can also indicate serious eye diseases. [7] However, note that the absence of photophobia and anisocoria does not rule out the possibility of such serious diseases. Conversely, complete redness of the conjunctiva obscuring the tarsal vessels, purulent discharge, matting of both eyes in the morning, and onset during winter or spring all increase the probability of bacterial conjunctivitis. [7] If the patient has symptoms of itchy eyes and recurrent conjunctivitis, bacterial conjunctivitis is unlikely. [23] Dense deep-red to violaceous coloring of the conjunctiva that does not blanche with topical sympathomimetics (eg, phenylephrine 2.5%) indicates scleritis in the context of significant pain.

Conjunctival scrapings and cultures are frequently obtained in severe bacterial conjunctivitis or if there is corneal involvement, especially when the central cornea is affected, multiple keratitis lesions are present, any corneal ulcer is 2 mm or larger in diameter, or antibacterial therapy is ineffective. Gram staining and cultures should be grown in blood agar, chocolate agar, Sabouraud dextrose agar, and thioglycollate broth.

Imaging studies do not play a significant role in the workup of bacterial conjunctivitis unless an underlying condition is suspected. For example, MRA, CT scan, and orbital color Doppler may play a role in a suspected cavernous sinus fistula. Orbital CT scan may be indicated to rule out an orbital abscess or pansinusitis, when the conjunctivitis is coincident to orbital cellulitis.

Certain procedures may address a known or suspected underlying cause for conjunctivitis or conditions that mimic it. Removal of offending lashes with epilation forceps or by electrolysis may be indicated for trichiasis. Nasolacrimal duct irrigation may be attempted to see if an obstruction that predisposes to infection is present. An obstruction should be suspected in chronic and intermittent purulent conjunctivitis. Eversion of the eyelid at the slit lamp is indicated when a foreign body is suspected.


Conjunctival Scrapings and Cultures

Conjunctival scrapings can be performed with topical anesthetic and gentle use of a platinum spatula or similar blunt metallic object. This should precede antibiotic therapy. Gram stain is useful to identify bacterial characteristics. Giemsa stain is helpful to screen for intracellular inclusion bodies of Chlamydia. Cultures can be completed for viral, chlamydial and bacterial agents. If testing for N gonorrhoeae, specific procedures should be followed to optimize the yield. The anesthetic agent should be preservative-free, in order to limit false-negative culture results (Tetracaine, Alcon).Fungal culture is usually unnecessary, except in the setting of a corneal ulcer or in the case of known contamination of a specific contact lens solution, such as occurred in the contamination epidemic of early 2006. [24]

Additionally, the nature of the inflammatory reaction is reflected in the cellular response. Lymphocytes predominate in viral infections, neutrophils in bacterial infections and eosinophils in allergic reactions.