In Vivo Laser Confocal Microscopy of Keratic Precipitates Is a Useful Tool in Differencing Specific Uveitis Diagnosis as Well As Active From Inactive Uveitis

Abstract

Purpose: : A hallmark of active intraocular inflammation is keratic precipitates (KP). Although the appearance of KP can provide diagnostic information, slit-lamp exam (SLE) can categorize KP to a very limited extent. The Heidelberg Retinal Tomograph II with the Rostock Corneal Module attachment (HRT-RCM) (Heidelberg Engineering, Germany) is a new generation confocal laser scanning microscope allowing images with much more cellular detail.

Methods: : Prospective, multicenter study. IRB aproved. Data collected: uveitis phenotype, degree of activity at the time of scanning, and type of KPs on SLE (granulomatous, fine, medium or stellate). Scanning with the HRT-RCM on first and subsequent visits. Grading of the images by set criteria of 8 KP types by two independent, masked graders. Statistical evaluation, including Κ values for interobserver agreement.

Results: : A total of 120 eyes from 110 subjects, with 145 eyes scanned on all time-points together were included.17 subjects with infectious cause, herpetic (N=13), Toxoplasmosis (N=2), Syphilis and Tuberculosis (N=1 each). Of the remaining 94 subjects the most common type was Fuchs Heterochromic Cyclitis (FHC) (N=27), followed by idiopathic (N=15) and sarcoidosis-related (N=13). 70 eyes had active disease and 75 were considered inactive at the different time-points.SLE: The majority of eyes (N=98) had only one KP type seen, with a median of 1 KP type per eye (range 1-3).HRT-RCM: the majority had more than 2 KP types (N=88), with up to 7 KP types detected, with a median of 3 KP types per eye.Agreement between the two masked graders was high, average Κ value across all 8 KP types was 0.71.Both stellate and cruciform KP were significantly associated with a diagnosis of FHC (p<0.05). In contrast, no specific KP type was found to be associated with infective vs. non-infective uveitis diagnoses. Nodular and granular KPs were found to be significantly associated with active uveitis, while inkblot KP were significantly associated with inactive uveitis (p < 0.05).

Conclusions: : Laser confocal microscopy of KPs in uveitis holds promise as a diagnostic tool, differentiating specific uveitis forms and distinguishing active from inactive uveitis.

Keywords: uveitis-clinical/animal model • microscopy: confocal/tunneling • inflammation