Longitudinal Changes of Geographic Retinal Darkening in a Cohort of Ebola Survivors

Abstract

Purpose : Little is known regarding the longitudinal retinal sequelae in Ebola virus disease (EVD) survivors. An Ebola-specific retinal lesion and associated areas of geographic retinal darkening (GRD) were observed amongst EVD survivors in a previous case-control study. GRD, also known as dark-without-pressure are little understood but lesional OCT correlates to retinal ellipsoid layer hyporeflectivity. We performed an observational study in a cohort of EVD survivors to observe for longitudinal changes.

Methods : 137 Ebola survivors were invited for ophthalmic examination including widefield retinal imaging (Optos® Daytona, Dunfermline, UK) in Freetown, Sierra Leone. Median age was 31 (IQR 23.5-39). M:F ratio::1:0.78. Median time from Ebola treatment unit discharge to ophthalmic review was 479 days (range 97-977 days). Patients with identified GRD and/or Ebola retinal lesions were invited for examinations between January and November 2016.

Results : 95 presumed Ebola-specific retinal lesions were identified in 12.4% (17/137) of survivors. Mean number of lesions per eye was 3.9 (range 1-24, SD 5.19). All were systemically well and visually asymptomatic. 84.2% of these had a circumferential dark retinal halo. 18.8% (12/137) of survivors had areas of GRD (33.3% bilateral). Four patterns were identified (Figure 1): a) mid-peripheral (MP) (N=5), b) circumferential inline with the retinal arcade (CA) (N=3), c) distinct peripheral margin with circumferential posterior pole border (N=4), d) distinct peripheral margin with no posterior pole border (N=5). Mean period of review was 210 days (range 62-290, SD 77.3). All MP GRD areas showed recession over time, one of which developed perivascular infiltrates which resolved without treatment. All CA areas showed evidence of expansion. 66.7% had co-existent white-without-pressure.

Conclusions : We provide the first evidence of GRD in EVD survivors and propose a classification scheme based on imaging appearance. We found examples of GRD expanding and receding over time. The ellipsoid layer anatomically correlates to a high density of retinal mitochondria. Changes in mitochondrial refractivity have been shown to equate to enzymatic activity. Hypo-reflectivity of this layer, seen in GRD may therefore indicate visualisation of a viral effect upon retinal mitochondrial metabolic state. These findings may have systemic parallels in relation to Post-Ebola syndrome.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.