In a new study employing optical coherence tomography (OCT) imaging, researchers at the University of Liverpool (England) have identified the specific characteristics of retinal lesions caused by the Ebola virus, which provide further clues as to how the virus travels to the retina and causes damage.
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In a 2016 study, a research team led by Paul Steptoe compared eye examinations of Ebola survivors in Sierra Leone and a control population. A total of 82 Ebola survivors who had previously reported ocular symptoms and 105 unaffected controls from civilian and military personnel underwent ophthalmic examination, including widefield retinal imaging. The team identified a unique retinal scar in 15% of Ebola survivors who reported eye symptoms after recovering.
In the team's latest study, the researchers used OCT (which is noninvasive) to image the retinas of the survivors with this Ebola retinal scar. These images provide a high-resolution, cross-sectional view of the retina and help to demonstrate that within these Ebola retinal scars, there are multiple, microscopic focal areas of damage to the retinal layers corresponding to the photoreceptors with a collapse of the overlying retinal structures. This pattern of scarring supports a theory that the virus travels along neuronal structures within the retina.
The researchers also identified areas of abnormal retina surrounding the Ebola retinal scars in 89% of cases. The affected areas appear darker than the normal retina and occur because of a change in the reflectance of a layer of the retinal layer called the ellipsoid zone, which contains a high concentration of mitochondria (the structures that create energy to run the cell).
Steptoe says that the recent finding implies that the virus may be causing a wider effect to the surrounding retinal cells beyond the boundary of the scars. In the cases the research team identified, the position of the scars did not involve the part of the retina responsible for fine central vision, but in survivors where scars are close to this area, they have detected permanent visual field defects.
Full details of the work appear in JAMA Ophthalmology.