2023 FDA Science Forum
Cobalt rapidly changes photoreceptor outer segment structure in optical coherence tomography images of the rabbit retina.
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Contributing OfficeCenter for Devices and Radiological Health
Abstract
Purpose: Cobalt-containing metal hip implants can, in rare, cases cause retinopathy. Previous retinal ganglion cell studies in rabbit showed cobalt (1mM) resulted in a rapid loss of the light response. Here we used optical coherence tomography (OCT) M-scans to study the effect of cobalt on the photoreceptor structure in the ex-vivo rabbit retina. Methods: We studied the effects of cobalt using a retinal eyecup preparation, time lapse OCT, and New Zealand white rabbits. The retina was superfused with an oxygenated Ames Ringer on a modified Leica MP multiphoton microscope stage . Time-lapse cross-sectional B-scan images of the rabbit retina were taken at 15 sec intervals. After a control period, cobalt (8-1000μM) was bath applied to the retina for 10min, and then washed out. Select retina were processed for histology. Using OCT M-scans, temporal changes in the dimensions of the retinal structures affected by cobalt were examined and quantified. Results: We studied how cobalt affected the retinal thickness in OCT M-scans. In the control condition, OCT M-scans showed there was little change in the retinal thickness to sham applications of Ringer’s solution (n=5). In contrast, application of 1mM cobalt caused a rapid shrinkage in the retinal thickness averaging -3.3±1.9 μm (n=7) (p<0.01, 1-tailed T-test). In the presence of 1mM cobalt, the width of the retinal pigment epithelium to inner segment (IS) line declined an average of -2.0± 1.2 μm n=7.mean.s.d. (P< 0.01 1-tailed T-test). This suggested a large effect of 1mM cobalt was on the photoreceptor outer segments. In addition, there was reduction in the peak intensity of the IS line of 9± 4.5 AU (SEM) in 1mM cobalt, n=7. No retinal shrinkage was seen in cobalt at doses of 40μM, however there were effects on the photoreceptor IS and outer segment lines in OCT M-scans. Conclusions: We found cobalt caused rapid changes in the structure of the rabbit retinal tissue. At (0.2-1.0 mM), cobalt caused a retinal shrinkage which was largely due to a reduction in the photoreceptor outer segment width and a disruption of the photoreceptor tips in the OCT image.
