Objective measurement of vitreous inflammation using optical coherence tomography

Abstract

Purpose: To obtain measurements of vitreous signal intensity from optical coherence tomography (OCT) image sets in patients with uveitis, with the aim of developing an objective, quantitative marker of inflammatory activity in patients with this disease.

Design: Retrospective, observational case-control series.

Participants: Thirty patients (30 eyes) with vitreous haze secondary to intermediate, posterior, or panuveitis; 12 patients (12 eyes) with uveitis but without evidence of vitreous haze; and 18 patients (18 eyes) without intraocular inflammation or vitreoretinal disease.

Methods: Clinical and demographic characteristics were recorded, including visual acuity (VA), diagnosis, and anatomic type of uveitis. In each eye, the anterior chamber (AC) was graded for cellular activity and flare according to standardized protocols. The presence and severity of vitreous haze were classified according to the National Eye Institute system. Spectral-domain OCT images were analyzed using custom software. This software provided an "absolute" measurement of vitreous signal intensity, which was then compared with that of the retinal pigment epithelium (RPE), generating an optical density ratio with arbitrary units ("VIT/RPE-Relative Intensity").

Main outcome measures: Correlation between clinical vitreous haze scores and OCT-derived measurements of vitreous signal intensity.

Results: The VIT/RPE-Relative Intensity was significantly higher in uveitic eyes with known vitreous haze (0.150) than in uveitic eyes without haze or in healthy controls (0.0767, P = 0.0001). The VIT/RPE-Relative Intensity showed a significant, positive correlation with clinical vitreous haze scores (r = 0.566, P = 0.0001). Other ocular characteristics significantly associated with VIT/RPE-Relative Intensity included VA (r = 0.573, P = 0.0001), AC cells (r = 0.613, P = 0.0001), and AC flare (r = 0.385, P = 0.003). Measurement of VIT/RPE-Relative Intensity showed a good degree of intergrader reproducibility (95% limits of agreement, -0.019 to 0.016).

Conclusions: These results provide preliminary evidence that OCT-derived measurements of vitreous signal intensity may be useful as an outcome measure in patients with uveitis. If validated in future studies, such measures may serve as an objective, quantitative disease activity end point, with the potential to improve the "signal:noise" ratio of clinical trials in this area, thus enabling smaller studies for the same power. The incorporation of automated vitreous analysis in commercial OCT systems may, in turn, facilitate monitoring and re-treatment of patients with uveitis in clinical practice.