Outbreak of Rift Valley Fever Retinitis in Rwanda: Novel Imaging Findings and Response to Treatment with Corticosteroids.

Purpose: To describe the clinical and epidemiological characteristics of the first epidemic of Rift Valley Fever retinitis in Rwanda and to report novel imaging findings and a possible role for corticosteroids.

Methods: Retrospective analysis of all patients who presented with presumed Rift Valley Fever retinitis at the Rwanda Charity Eye Hospital over a period of 4 months in 2022. Multimodal images are reviewed including optical coherence tomography, fluorescein angiography, color, infrared, red-free, and autofluorescence photography.

Results: The newly identified arciform hyporeflective pattern on infrared imaging was present in 100% of patients. Out of 9 patients treated with oral corticosteroids, 7 (78%) experienced a visual acuity increase of at least 0.2 during follow-up, in comparison to only 4 (28%) out of 14 of untreated patients. Out of four patients treated with a subtenon corticosteroid injection, only one (25%) reached this threshold. Post-hoc pairwise comparison with Bonferroni correction revealed a significant difference in average visual acuity improvement ( = 0.034) between patients receiving oral corticosteroids (0.35 ± 0.07) versus no treatment (0.11 ± 0.04).

Conclusion: The identified arciform hyporeflective pattern on infrared imaging appears to be characteristic of Rift Valley Fever retinitis and should be known to clinicians working in endemic regions. Compared to a historical cohort and to untreated patients in this non-randomized study, there appears to be a benefit of treatment with oral corticosteroids.