Hyper‐reflective dots in optical coherence tomography imaging and inflammation markers in diabetic retinopathy

Abstract

The aim of this study is to correlate small dot hyper‐reflective foci (HRF) observed in spectral domain optical coherence tomography (SD‐OCT) scans of an animal model of hyperglycaemia with focal electroretinography (fERG) response and immunolabelling of retinal markers. The eyes of an animal model of hyperglycaemia showing signs of diabetic retinopathy (DR) were imaged using SD‐OCT. Areas showing dot HRF were further evaluated using fERG. Retinal areas enclosing the HRF were dissected and serially sectioned, stained and labelled for glial fibrillary acidic protein (GFAP) and a microglial marker (Iba‐1). Small dot HRF were frequently seen in OCT scans in all retinal quadrants in the inner nuclear layer or outer nuclear layer in the DR rat model. Retinal function in the HRF and adjacent areas was reduced compared with normal control rats. Microglial activation was detected by Iba‐1 labelling and retinal stress identified by GFAP expression in Müller cells observed in discrete areas around small dot HRF. Small dot HRF seen in OCT images of the retina are associated with a local microglial response. This study provides the first evidence of dot HRF correlating with microglial activation, which may allow clinicians to better evaluate the microglia‐mediated inflammatory component of progressive diseases showing HRF.

Proliferative gliosis, a rare finding following multilayered inverted internal limiting membrane flap technique for concurrent macular hole and retinal detachment: Case series

“…Moreover, hyperreflective foci observed in our patient's OCT may confirm the presence of activated macrophages and microglia, as suggested by several studies. 20 …”

Hyper-reflective foci changes in RRMS under natalizumab therapy

“…The evaluation of microglia activity in vivo is limited by the expansive and complex methodology (i.e., PET-MRI) needed ( 18 , 19 ). Recently, OCT was demonstrated to be able to identify HRF, nodules of activated microglia, in the inner retina, ( 6 ). In previous studies, we investigated the association of HRF with inflammatory parameters and found a strong correlation with cortical demyelination ( 8 ).…”

“…Optical Coherence Tomography (OCT) allows to study in vivo retinal microglia activation ( 6 ). Indeed, it has been recently demonstrated in an animal model of diabetes that focal Blood-Retina-Barrier (BRB) damage strongly associate with retinal microglia proliferation, and the histologically defined pattern corresponded to the hyper-reflective foci (HRF) observed by OCT ( 6 ). Thus, HRF has been proposed as in-vivo biomarker of microglia proliferation.…”