In vivo confocal microscopy of corneal microscopic foreign bodies in horses.

Objective: To describe in vivo corneal confocal microscopy of horses with microscopic corneal foreign bodies and to correlate findings with clinical, cytological, and histopathologic evaluations of clinical cases and foreign body morphologies observed in vitro with the confocal microscope.

Animal Studied: Five horses with microscopic corneal foreign bodies.

Procedures: Sedated and anesthetized horses were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. Confocal microscopy images were compared with images from cytologic and histopathologic corneal samples. To establish microscopic morphologic features, confocal microscopy images of burdock pappus bristles and surgical glove powder were obtained by in vitro examination.

Results: Horses were examined by in vivo confocal microscopy to assist in identifying corneal opacities detected by slit-lamp biomicroscopy, to determine the etiology of clinically idiopathic keratitis, or to localize corneal opacities presumed to be foreign bodies for surgical planning. Corneal foreign bodies presumptively identified by confocal microscopy included burdock pappus bristles, other plant foreign materials, and surgical glove powder. The corneal foreign bodies appeared as moderately or hyper-reflective linear, circular, or oval structures by confocal microscopy and did not resemble any normal anatomic structures. The confocal microscopic identification of the foreign bodies was corroborated by cytologic and histopathologic findings in some horses. The in vivo confocal microscopic appearance of the foreign bodies was consistent with morphologies observed during examination of foreign bodies in vitro.

Conclusions: In vivo corneal confocal microscopy provides a noninvasive method for the detection, characterization, and localization of microscopic foreign bodies in the equine cornea.