Coffee Grain–Shaped Structures At Corneal Confocal Microscopy: A Predictor of Amebic Keratitis

Abstract

 

Purpose:

 

To describe a corneal confocal microscopy finding and its similarity to in vitro observation of Acanthamoeba sp.

 

Methods:

 

Confocal microscopy was performed with Confoscan 2.0 (Nidek,Gamagori, Japan) in patients whose Acanthamoeba cultures of corneal scrapings were positive. Biomicroscopy was used to identify the infiltrated regions of the cornea to be undegone confocal examination. Soy agar plates with trophozoytes and cysts of Acanthamoeba sp overlay was held vertically and examined with the same device in order to provide image control.

 

Results:

 

During confocal microscopy evaluation of the acanthamoeba laid soy plates, hyper–reflective, round structures with its center split into two parts reseambling a coffee grain were. Such structures were among others which showed a whole hyper–reflective center. Important to note that a thick, double wall was observed surrounding the cysts content. Other interesting feature was the tendency of the cysts to gather into groups. In the study group, four patients with culture confirmed infectious keratitis showed identical structures during the examination. Coffee grain –shaped structures were evident.

 

Conclusions:

 

Identification of coffee grain opacities during confocal microscopy in patients with infectious keratitis should be regarded as a possible sign of amebic keratitis.  

 

Keywords: Acanthamoeba • microscopy: confocal/tunneling • keratitis