In-vivo Laser Confocal Microscopy of Keratic Precipitates in Patients With Uveitis Using the HRT II Rostock Cornea Module

Abstract

Purpose:: Imaging of keratic precipitates (KPs) in ocular inflammatory diseases has been previously described but was limited to a white light tandem scanning microscope. Our preliminary results using the Heidelberg Confocal Laser Microscope (HRT II), which provides greater resolution, have been previously presented. In this present study, we examined KPs in a greater number and variety of ocular inflammatory diseases with longitudinal follow up.

Methods:: Patients with uveitis who attended either the Casey Eye Institute or the Interdisciplinary Uveitis Center in Heidelberg (N=71) were scanned using the HRT II with the Rostock Cornea Module attachment at a depth of 450-650 µm from the corneal epithelium and a minimum area of coverage of 4mm². Images were taken at presentation and on follow-up. The majority (N=59) had non-infectious uveitis, with the main subsets being Fuchs heterochromic cyclitis (N=11), multiple sclerosis (N=5), sarcoidosis (N=6) and HLA-B27 associated uveitis (N=10). Sixteen of these had active uveitis at the time of the initial scan, with follow up scans performed in 11. Twelve patients had infectious uveitis: VZV (N=3), HSV (N=7), Toxoplasmosis (N=1) and Tuberculosis (N=1). Eight had follow up scans. All images were graded by two graders, where KPs were classified according to strict morphologic criteria.

Results:: Greater than one type of KPs were seen in the same eye at the same time point in the majority of subjects (N=46). Those with active uveitis were more likely to have varied KPs than those with quiescent disease (58% vs. 44%). Subjects with granulomatous KPs on slitlamp examination were also more likely to have varied KPs on confocal microscopy than those with fine KP. Dendritiform KPs were more common in those with non-infective uveitis than with infective uveitis. Those with HLA B27 uveitis were again noted to have a unique KP morphology. KP morphology was also noted to change over time.

Conclusions:: The image quality with the laser confocal microscope allows greater detail of KPs to be seen, with more than one morphological type now being observed in the same eye at the same time point in a larger number of subjects than previously. Confocal microscopy appears to be useful in the diagnosis of specific subtypes of uveitis, such as HLA B27 associated disease.

Keywords: microscopy: confocal/tunneling • imaging/image analysis: clinical • inflammation