Multimodal Approaches for the Analysis of Retinal Functional Disorders―Focusing on Retinal Detachment.

Abstract

Microstructural and functional restoration of the retina after reattaching a retinal detachment were assessed by electroretinography (ERG), optical coherence tomography (OCT), adaptive optics (AO) fundus imaging, and laser speckle flowgraphy (LSFG). As a representative study, an intentional retinal detachment created during macular translocation surgery by a 360° retinotomy, reducing the cone ERGs by 12% was compared to the preoperation values. Six months after successful reattachment surgery, the amplitudes of the a- and b-waves of the focal macular ERGs (FMERGs) elicited by a 15° spot recovered to 66% and 74%, respectively, of that of the fellow eyes. The increase in the amplitudes of the b-waves was significantly correlated with the increase in the length of the cone interdigitation zone (CIZ) and the size of the outer photoreceptor area after the surgery. These results indicate that, after surgical repair of a fovea-off rhegmatogenous retinal detachmen t (RRD), recovery of the inner as well as the outer segments of the photoreceptors was essential for the recovery of the FMERGs. We also examined the recovery of macular function after the resolution of central serous chorioretinopathy (CSC). The results showed that the pattern of recovery of the FMERGs after resolution of subretinal fluid (SRF) in CSC was different from that after successful surgery for fovea-off RRD. OCT examinations showed a gradual restoration of the foveal photoreceptors after reattachment up to one year in RRD with foveal detachment before surgery. The improvement in the best-corrected visual acuity (BCVA) was significantly correlated with the thickness of the ellipsoid zone-RPE. Multiple regression analyses showed that the presence of a foveal bulge was the only significant independent predictor of the BCVA. We present our AO findings on the morphology of the nerve fiber layer, cone photoreceptors and retinal vascular walls in healthy eyes. We also present our AO findings in cases of occult macular dystrophy, autosomal recessive bestrophinopathy, acute zonal occult outer retinopathy, macular hypoplasia and the neovascular vessels in eyes with diabetic retinopathy. We first analyzed our data on the relationship between FMERGs and cone densities. An AO fundus camera was used to evaluate the cone mosaic, and the cone packing density at 2° from the fovea in healthy eyes. We performed FMERG using a 15° stimulus spot. The amplitudes and implicit times of the a-wave, b-wave, and the oscillatory potentials (OPs) were measured, and the relationships between the cone packing densities, the amplitudes and implicit times of these components were analyzed. The results showed that the mean cone packing density 2° from the fovea was significantly and positively correlated with the amplitudes of the a-wave, b-wave and the OPs. However, the density was not significantly correlated with the implicit times of each component. We examined the changes in the cone packing density and the recovery of the outer retina after scleral buckling surgery for RRD in the images obtained by an AO fundus camera. It was not possible to obtain quality images of the cone mosaics to calculate the cone packing density before surgery. However, that was possible after surgery, and the cone packing density was significantly improved at 12 months post-surgery compared to 6 months post-surgery. However, the cone packing density at 12 months post-surgery (13005±1656 cells/mm2) was significantly lower than the density of the fellow eyes (21157±517 cells/mm2). The OCT images at 2° from the fovea showed that the thickness of the CIZ had recovered to that of the fellow eyes, and the increase of the cone packing density was significantly correlated with the increase in the thickness of the CIZ-RPE. We also present our findings on the retinal blood flow in eyes with a RRD measured by LSFG. Our results show that the retinal blood flow on the optic nerve head was reduced in eyes with RRD, and it recovered following successful RRD repair by vitrectomy. The choroidal blood flow did not change significantly following segmental scleral bucking surgery although the subfoveal choroidal thickness increased temporally. Lumen diameter was determined by LSFG and AO. Eyes that underwent vitrectomy became more myopic earlier than the control eyes due to the development of nuclear cataracts. The preoperative diagnosis of RRD was the only significant risk factor for a higher intraocular pressure long after surgery. To try and further improve visual function, we examined the process of RRD repair with an intraoperative OCT equipped with an operating microscope. We noted that some of the SRF remained at the fovea postoperatively and had a triangular shape. We describe the development of our original 23 G- and 25 G-intraoperative fiber OCT probe. We show the structure of the probe, the results of animal experiments, and the clinical experiences using this intraoperative fiber OCT probe. We also present the results of our molecular biological studies designed to determine the pathological mechanism of retinal diseases and to develop new therapies. We found that IL-1β activated NLRP3 in the macrophages that had migrated into the subretinal space after a retinal detachment in a mouse model. It was also found that photoreceptor death after a retinal detachment could be suppressed by the inhibition of IL-1β. Furthermore, we found that the level of IL-1β was elevated in the SRF of patients with a RRD. To prevent the pathological changes of proliferative vitreoretinopathy (PVR) after a retinal detachment, we determined the specific microRNAs in the vitreous and SRF of patients with a retinal detachment. We evaluated the effect of the specific microRNAs on the RPE. MicroRNA PCR array detected hsa-miR-148a-3p only in the vitreous fluid and SRF with higher levels in the SRF in patients with a retinal detachment but not in the vitreous of patients with macular holes and vitreomacular traction syndrome. Next, we examined the role of hsa-miR-148a-3p in the pathogenesis of PVR by using RPE cells in culture. RPE cells overexpressing hsa-miR-148a-3p had an increase in the expression of αSMA, a marker of epithelial-mesenchymal transition (EMT) and increased ability to migrate. These observations indicate that retinal detachment-specific microRNA, hsa-miR-148a-3p, plays an important role in EMT of RPE cells. We also determined that Caveolin-1 is highly expressed in proliferative membranes of eyes with PVR, and it suppressed EMT of RPE cells. This indicates that Caveolin-1 might be a potential therapeutic target preventing proliferative membrane development in PVR.