Keratic Precipitates: The Underutilized Diagnostic Clue.

The morphology of keratic precipitates (KPs) may yield important diagnostic clues. However, KPs have not been described in a standardized manner and the traditional classification of granulomatous or non-granulomatous KPs is not helpful in differentiating infectious from noninfectious uveitis. A granulomatous uveitis may initially appear non-granulomatous. We suggest three ways to examine KPs that may aid in differentiating the infectious from noninfectious etiologies. The first method is the in vivo confocal microscopy (IVCM) description and classification of KPs, in which the "non-granulomatous" subset of dendritiform and infiltrative KPs should be differentiated from smooth-rounded KPs and globular KPs which are "granulomatous." The second and third clues are the distribution and color of the KPs. KPs that extend beyond the midline may suggest an infective cause, and fresh pigmented KPs suggest a viral cause. Careful examination of the KPs may immediately reveal the clues to the diagnosis, minimizing unnecessary tests and costs.