Migration of an outer retinal element in a healthy child fol
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Non-invasive retinal imaging techniques have reached cellular resolution,1,2 but the natural contrast in the retina is limited. Specific cells are therefore difficult to identify on the images, and there are no artificial markers that can be applied in vivo to enhance their visualization. The term “longitudinal multimodal imaging“ to describe repeated short-term follow-up imaging with multiple modalities for the purpose of detecting and tracking diminutive retinal changes over time.

Case report

A 7-year old girl in good health underwent a routine eye examination and screening for refractive anomaly. The girl was found to be emmetropic and to have uncorrected visual acuity of 20/20 in both eyes. By OCT examination one of multiple, densely spaced B-scans of the upper macula showed an isolated hyperreflective element of 15 μm axial extent at the level of the outer limiting membrane. On the accompanying infrared cSLO fundus image, this element was correlated with a small isolated hyporeflective spot of 30 μm in diameter . Color fundus photography showed this as a faint dark spot without a halo which did not resemble a hemorrhage or pigment. Additional two similar spots were identified in the macula on the cSLO image. One of them were covered by the OCT scan where it had the same characteristics on the B-scan. Because of the unknown nature of these findings, longitudinal examinations of the first mentioned element were made at days 8, 16, 25, 33, and 52 after the initial visit. Follow-up OCT was made as a block of multiple, densely spaced B-scans in high-resolution with an averaging of 70 scans per line. The corresponding photoreceptor area was imaged with en face reflectance AO.

At presentation the hyperreflective element on the OCT B-scan was accompanied by an umbra of 45 μm constricted to the myoid, ellipsoid, and outer segment layer 3 whereas the more posterior layers were unaffected. This limited shadow could be explained by the entry pupil of the OCT device being much larger than the element in the retina. Restitutions of the outer limiting membrane and the ellipsoid zone were seen at days 8 and 16, respectively, when the element was most notable on OCT for its umbra. It remained clearly visible up to day 25 on cSLO and AO despite its gradually diminishing extent on the B-scan . At day 33 there was no trace of the element on the OCT B-scan while there was still a small spot on cSLO and a slight defect on the AO image. Full restitution of the photoreceptor mosaic was seen on AO on day 52. The rate of migration was estimated as 1.2 μm per day by dividing the total length of the element and its umbra, 60 μm, by 52 days.

This case report presents an incidental, unique observation where an isolated, cell-sized element was seen to move through the retina in a healthy child using these techniques. Introduction of the term “longitudinal multimodal imaging“ was done to describe repeated short-term follow-up imaging with multiple modalities for the purpose of detecting and tracking diminutive retinal changes over time.

Source: https://www.sciencedirect.com/science/article/pii/S2451993620300281
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