The Stalagmite Sign: A Novel OCT-IR Biomarker for Peripheral Infectious Retinitis.

Abstract

To define and evaluate the Stalagmite Sign, a multimodal pattern of multifocal, elongated, elevated, hyperreflective preretinal deposits on spectral-domain optical coherence tomography (SD-OCT) corresponding to discrete nodular paravascular hyporeflective lesions on co-registered near-infrared (IR) reflectance imaging, as a diagnostic biomarker for infectious peripheral retinitis in patients with posterior uveitis. Multicenter retrospective case series with diagnostic accuracy analysis. Forty-six eyes (44 patients) with the Stalagmite Sign, evaluated at tertiary uveitis referral centers between January 2024 and December 2025. For diagnostic accuracy analysis, 360 sign-negative comparator eyes were added (148 infectious, 212 non-infectious posterior uveitis), total: 406 eyes. A 2 × 2 contingency table was constructed using confirmed etiology as the reference standard, and diagnostic accuracy metrics were calculated with Wilson score 95% confidence intervals. Clinical features, intraocular polymerase chain reaction (PCR) results, and visual outcomes were assessed. Sensitivity, specificity, positive predictive value, and positive likelihood ratio (LR+) of the Stalagmite Sign for the diagnosis of infectious peripheral retinitis; intraocular PCR positivity rate; deposit resolution following antimicrobial therapy; and best-corrected visual acuity (BCVA) outcomes. An infectious etiology was confirmed in 44 (95.7%) of 46 sign-positive eyes: toxoplasmosis (32, 69.6%), herpetic retinitis (7, 15.2%), ocular syphilis (3, 6.5%), and fungal endophthalmitis (2, 4.3%). Peripheral retinitis was identified in 35 (76.1%) eyes; posterior pole retinitis in only 8 (17.4%). Two cases were non-infectious, presenting with deposits following silicone-oil removal, with spontaneous resolution. Specificity was 99.1% (95% CI 96.7-99.7%), positive predictive value 95.7% (95% CI 85.5-98.8%), and LR+ 24.5; sensitivity was 22.9% (95% CI 17.5-29.4%). PCR was positive in all 18 eyes. Deposits resolved within 3 months of antimicrobial therapy. Mean logMAR BCVA improved from 0.64 ± 0.40 to 0.43 ± 0.45 over 9.7 months mean follow-up (Friedman test, p < 0.001). The Stalagmite Sign is a high-specificity OCT-IR biomarker (99.1%, LR+ 24.5) for infectious peripheral retinitis, whose recognition should prompt comprehensive peripheral retinal evaluation, intraocular PCR, and antimicrobial therapy, while withholding corticosteroid monotherapy to prevent fulminant retinal necrosis. PCR is especially recommended in diagnostically uncertain cases, as a positive result is highly likely in the presence of the Stalagmite Sign.