Objective Quantification of Anterior Chamber Inflammation: Measuring Cells and Flare by Anterior Segment Optical Coherence Tomography

Purpose: To assess the ability of swept-source (SS) optical coherence tomography (OCT) of the anterior segment (AS) to measure anterior chamber (AC) inflammation (both flare and cells) objectively. To compare OCT-derived inflammatory indices with standard techniques. Design: Prospective evaluation of a diagnostic test. Participants: Patients diagnosed with anterior uveitis (active or inactive) and controls. Methods: Participants underwent an AC inflammation evaluation including: clinical cell and flare grading and laser flare photometry (LFP). Uveitis patients were divided into active or inactive uveitis status according to clinical grading. Anterior segment SS-OCT scans were obtained for each participant. Tomographic images were analyzed to count the AC cells, and to calculate to absolute measurements of aqueous signal intensity. The absolute values were compared with the signal measured by the scan outside the eye, generating an optical density ratio (aqueous-to-air relative intensity [ARI] index). Correlations between OCT-derived AC inflammatory indexes and LFP, clinical grading, participant category (active or inactive uveitis, control), age, gender, and central corneal thickness (CCT) were assessed. Main outcome measures: Correlation between OCT-derived AC inflammatory indexes (ARI index and AC cells on OCT) and standard clinical techniques (LFP, clinical cell grading). Results: Two hundred thirty-seven eyes (70 active uveitis, 97 inactive uveitis, and 70 controls) were included. Anterior chamber cells count on OCT did not differ between inactive uveitis and controls, but was significantly higher in active uveitis compared to the other categories (both P < 0.0001). All groups had different LFP (all P < 0.0001). Active uveitis had significantly higher ARI index compared with inactive uveitis and controls (both P < 0.0001). Interobserver agreement (intraclass correlation coefficient) for ARI index was 0.78. The ARI index correlated positively with age (P = 0.043) and negatively with CCT (P = 0.006). The ARI index correlated with LFP in the active uveitis group (P < 0.0001), but not in the others. Anterior chamber cells on OCT increased among all cell clinical grades (P < 0.0001). The ARI index increased among all flare clinical grades (P < 0.005). Conclusions: Anterior segment SS-OCT could be used for a comprehensive assessment of AC inflammation, providing objective measurements of inflammatory cells and aqueous flare.