October 2018

RETINA

Emerging research on Ebola’s effect on the retina


by Liz Hillman EyeWorld Senior Staff Writer






Series of OCT sections of Ebola retinal lesions demonstrating varying severity A to C. The white triangles indicate an area of perilesional dark without pressure.
Source: CC-BY License. © 2018 Steptoe PJ et al. JAMA Ophthalmology

Widefield fundus image demonstrating multifocal Ebola retinal lesions. The white triangles indicate the border of an extensive area of dark without pressure.

Ebola retinal lesions demonstrating characteristic sharp angulations
Source (all): CC-BY License. © 2018 Steptoe PJ et al. JAMA Ophthalmology

 

Study analyzes retinal lesions that seem to be unique in Ebola survivors

Though Ebola virus disease has remained largely out of mainstream media headlines since the historic outbreak in West Africa from 2014–2016, ongoing research about the disease has continued, including about its ocular effects.
The largest study of Ebola survivors, published in 2016, detailed persistent conditions experienced by an estimated 17,000 survivors. From an ocular standpoint, these predominately included uveitis and conjunctivitis.1 A more recent study sought to differentiate Ebola retinal lesions from other retinal pathologies in West Africa.2
“Differentiating what is due to Ebola 1 year after the infection and what is more likely secondary to other more common retinal infections in West Africa, such as toxoplasmosis chorioretinitis, is challenging,” said Paul Steptoe, MD, Institute of Translational Medicine, University of Liverpool, Liverpool, U.K., the study’s lead author. He added, however, that “without the ability to identify what specific ophthalmic sequelae are most likely as a consequence of Ebola virus infection, as opposed to other retinal infections, further research would have no basis.”
Furthermore, Dr. Steptoe said, “[U]nderstanding the specific ocular effects of Ebola virus infection enables us to understand the visual burden of this disease. This information is useful in aiding the planning of ophthalmic care required for future epidemics and if any long-term management or intervention is required. Secondly, analyzing Ebola retinal lesions, utilizing modern imaging techniques, provides an opportunity to gain insights into the pathophysiological mechanism of the virus within the retina in a noninvasive manner.”
That said, Dr. Steptoe and coinvestigators, who were affiliated with University of Liverpool, the 34 Military Hospital, and Connaught Hospital, Freetown, Sierra Leone, originally began a case-controlled study, which characterized and compared retinal findings based on ultra-widefield retinal imaging of Ebola survivors compared to local controls.3 According to Dr. Steptoe, the prevalence of retinal scarring was about 20% in both groups, but a certain retinal lesion was only identified in Ebola survivors.
It is this specific type of scarring, being the one characteristic lesion only seen in Ebola survivors and not the control population in that study, that was analyzed in the latest paper. Fourteen survivors of Ebola virus disease were identified to have this type of retinal lesion (141 lesions identified in 22 of 27 eyes of the group). The retinas and lesions were evaluated with ultra-widefield scanning laser ophthalmoscopy, fundus autofluorescence, swept-source OCT, Humphrey visual field analysis, and spatial analysis.
According to the study results, the lesions were mainly “nonpigmented with a pale-gray appearance.” OCT imaging, which was obtained on 41 of the lesions, showed “V-shaped hyperreflectivity of the outer nuclear layer overlying discontinuities of the ellipsoid zone and interdigitation zone in the smaller lesions,” Steptoe et al. wrote.
Larger lesions appeared to collapse retinal layers and resulted in loss of retinal thickness, and while lesion shape varied, one characteristic was sharp angulations, frequently seen in lesions around the posterior pole.
“Perilesional areas of dark without pressure (thinned ellipsoid zone hyporeflectivity) accompanied 125 of the 141 lesions (88.7%) to varying extents,” Steptoe et al. wrote.
Dr. Steptoe described all of these features as “fascinating.” The cause for the sharp angulations, Dr. Steptoe said, was hypothesized to be secondary to the tight triangular packing of the retinal cone mosaic. Peripapillary lesions with a curvilinear appearance, which resembled the angulations of the retinal nerve fiber layer at the optic nerve, were also observed, Dr. Steptoe said.
“The lesions appear to be confined to the retinal structure and are commonly surrounded by areas of dark without pressure of varying size,” he continued. “In some cases, these areas are confined to the margin of the lesion but were observed to involve 360 degrees of the retina in some cases.”
Why do some survivors of Ebola virus disease develop retinal lesions while others don’t, even if they present with other ocular conditions, such as anterior or intermediate uveitis? Dr. Steptoe said this question remains unresolved.
“It may be due to differences in viral load among individuals or differences in host response to the virus,” he said.
According to the study authors, the importance of these findings has yet to be determined, and follow-up research is ongoing.
“These findings suggest that survivors of [Ebola virus disease] in future outbreaks would benefit from ophthalmologic evaluation, including via OCT analysis of visual field assessment,” Steptoe et al. wrote.

References

1. Mattia JG, et al. Early clinical sequelae of Ebola virus disease in Sierra Leone: a cross-sectional study. Lancet Infect Dis. 2016;16:331–8.
2. Steptoe PJ, et al. Multimodal imaging and spatial analysis of Ebola retinal lesions in 14 survivors of Ebola virus disease. JAMA Ophthalmol. 2018;136:689–693.
3. Steptoe PJ, et al. Novel retinal lesion in Ebola survivors, Sierra Leone, 2016. Emerg Infect Dis. 2017;23:1102–1109.

Editors’ note: Dr. Steptoe has no financial interests related to his comments.

Contact information

Steptoe
: psteptoe@liverpool.ac.uk

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