Shigeta Arichika

Correlation between thickening of the inner and outer retina and visual acuity in patients with epiretinal membrane.

Purpose: The purpose of this study was to examine the relationship between thickening of the inner and outer retinal layers and visual acuity in patients with idiopathic epiretinal membrane. Methods: We examined 30 eyes of 30 patients and 25 eyes of 25 healthy volunteers as age-matched normal control subjects. The inner (between the vitreoretinal interface and the outer border of inner plexiform layer), outer, and full retinal thickness at the fovea, parafovea, and perifovea were measured using spectral-domain optical coherence tomography. Results: Thickening ratios of both the inner and outer retina were greater in the fovea than in the other macular regions (P < 0.0001). Inner foveal retinal thickening was significantly greater than outer foveal retinal thickening (P < 0.0001). However, outer retinal thickening in the fovea (r = 0.644, P < 0.001), parafovea (r = 0.616, P < 0.001), and perifovea (r = 0.410, P = 0.025) was significantly correlated with visual acuity; inner retinal thickening was not. Visual acuity tended to be worse, although not significantly so, in eyes with photoreceptor disruption. Conclusion: Epiretinal membrane-induced retinal damage associated with visual acuity seems to be located within the outer retina external to the inner plexiform layer.

Focal Choroidal Excavation in Eyes With Central Serous Chorioretinopathy

PURPOSE To study the prevalence and 3-dimensional (3-D) tomographic features of focal choroidal excavations in eyes with central serous chorioretinopathy (CSC) using swept-source optical coherence tomography (OCT). DESIGN Prospective, cross-sectional study. METHODS We examined 116 consecutive eyes with CSC with a prototype 3-D swept-source OCT. 3-D images of the shape of the macular area, covering 6 × 6 mm(2), were reconstructed by segmentation of the outer surface of the retinal pigment epithelium (RPE). RESULTS The 3-D swept-source OCT detected focal choroidal excavations in 9 eyes (7.8%). The 3-D scanning protocol, coupled with en face scans, allowed for clear visualization of the excavation morphology. In 5 eyes with focal excavations, unusual choroidal tissue was found beneath the excavation, bridging the bottom of the excavation and the outer choroidal boundary. Additionally, 3 of those 5 eyes showed a suprachoroidal space below the excavation, as if the outer choroidal boundary is pulled inward by this bridging tissue. The focal choroidal excavations were located within fluorescein leakage points and areas of choroidal hyperpermeability. Eyes with focal choroidal excavations were more myopic (-4.42 ± 2.92 diopters) than eyes without excavations (-0.27 ± 1.80 diopters, P = .001). Subfoveal choroidal thickness was significantly thinner (301.3 ± 60.1 μm) in eyes with focal excavations than in eyes without the excavations (376.6 ± 104.8 μm, P = .036). CONCLUSIONS Focal choroidal excavations were present in 7.8% of eyes with CSC. In these eyes, focal choroidal excavations may have formed from RPE retraction caused by focal scarring of choroidal connective tissue.

Retinal Hemorheologic Characterization of Early-Stage Diabetic Retinopathy Using Adaptive Optics Scanning Laser Ophthalmoscopy

PURPOSE Adaptive optics scanning laser ophthalmoscopy (AO-SLO) is a noninvasive technique that allows for the direct monitoring of erythrocyte aggregates in retinal capillaries. We analyzed the retinal hemorheologic characteristics in normal subjects, diabetic patients without diabetic retinopathy (NDR), and diabetic patients with nonproliferative diabetic retinopathy (NPDR), using spatiotemporal (ST) blood flow images to visualize blood corpuscle trajectory. METHODS AO-SLO images of the parafoveal capillary network were acquired for three groups: 20 healthy volunteers, 17 diabetic patients with NDR (8 type 1 and 9 type 2 patients), and 10 diabetic patients with NPDR (4 type 1 and 6 type 2). The erythrocyte aggregate velocity assigned to a relative cardiac cycle and the elongation rate of the erythrocyte aggregate were calculated. RESULTS Careful observation revealed that flow velocity fluctuations were found with higher frequency in diabetic patients than in normal subjects. The total average velocities were 1.26 ± 0.22 mm/s in the normal group, 1.31 ± 0.21 mm/s in the NDR group, and 1.63 ± 0.35 mm/s in the NPDR group. The average velocities of the NPDR group were higher than those in the normal (P = 0.001) and NDR (P = 0.009) groups. The average elongation rates of the 3 groups were 0.67 ± 0.20, 0.39 ± 0.19, and 0.33 ± 0.11, respectively. Elongation rate differed significantly between the normal and NDR (P = 0.003) groups as well as the normal and NPDR (P = 0.001) groups. CONCLUSIONS AO-SLO can be used to detect retinal hemorheologic changes in the early stages of diabetic retinopathy.

Retinal microstructural changes in eyes with resolved branch retinal vein occlusion: an adaptive optics scanning laser ophthalmoscopy study.

PURPOSE To assess macular photoreceptor abnormalities in eyes with resolved branch retinal vein occlusion (BRVO) using adaptive optics scanning laser ophthalmoscopy (AO-SLO). DESIGN Prospective observational cross-sectional case series. METHODS After complete resolution of macular edema and retinal hemorrhage, 21 eyes (21 patients) with BRVO underwent full ophthalmologic examination and imaging with optical coherence tomography (OCT) and a prototype AO-SLO system. Cone density and spatial mosaic organization were assessed using AO-SLO images. RESULTS Regular parafoveal cone mosaic patterns were clearly visualized with the prototype AO-SLO imaging system in the BRVO-unaffected side. However, in the side of the retina previously affected by the BRVO, cone mosaic patterns were disorganized and dark regions missing wave-guiding cones were apparent. Additionally, retinal capillaries were dilated, no longer had a uniform caliber, and had less direct paths through the retina. In the affected side, parafoveal cone density was significantly decreased, compared with the corresponding retinal area on the unaffected side (P < .001). Furthermore, the hexagonal Voronoi domain ratio and the nearest-neighbor distances were significantly lower than in the unaffected side (P < .05). These parameters were also correlated with photoreceptor layer integrity in the parafovea. CONCLUSIONS After BRVO-associated retinal hemorrhage and macular edema resolved, affected parafoveal cone density decreases and the cone mosaic spatial arrangement is disrupted, becoming more irregular. These cone microstructural abnormalities may extend to parafovea in the BRVO-unaffected side.

Association of focal choroidal excavation with age-related macular degeneration.

PURPOSE To study the prevalence, tomographic features, and clinical characteristics of focal choroidal excavation (FCE) in eyes with exudative age-related macular degeneration (AMD). METHODS We examined 243 consecutive eyes with exudative AMD with a prototype swept-source optical coherence tomography (OCT) system. Three-dimensional images of the macular area, covering 6 × 6 mm(2), were reconstructed by segmentation of the outer surface of the retinal pigment epithelium. RESULTS Three-dimensional swept-source OCT revealed 15 excavations in 12 eyes (4.9%); 10 had a single excavation and 2 had multiple excavations (2 and 3 excavations, respectively). In multiaveraged scans, unusual choroidal tissue was found beneath 5 excavations, bridging the excavation with the outer choroidal boundary. Additionally, the suprachoroidal space was observed beneath 7 excavations-the outer choroidal boundary appeared to be pulled inward by this bridging tissue. In 9 excavations, color fundus photographs showed pigmentary disturbance. Fourteen excavations (93.3%) were located within or adjacent to the choroidal neovascularization area. Compared with eyes without FCE, in eyes with FCE, the mean age was significantly higher (P = 0.040) and mean visual acuity was significantly better (P = 0.014). In addition, polypoidal lesions were observed in 8 of 12 eyes with FCE, but they appeared to have a limited effect on either the rate of FCE (P = 0.44) or the clinical characteristics of the eyes. CONCLUSIONS While FCE may be partially related to the choroidal neovascularization associated with exudative AMD, other factors may also influence this association.

Adaptive Optics-Assisted Identification of Preferential Erythrocyte Aggregate Pathways in the Human Retinal Microvasculature

Purpose To characterize human parafoveal blood flow using adaptive optics scanning laser ophthalmoscopy (AO-SLO). Methods In 5 normal subjects, erythrocyte aggregate distributions were analyzed on 3 different days. Erythrocyte aggregates were described as a “dark tail” in AO-SLO. The characteristics of the pathways with dark tail flow in the parafovea were measured. Additionally, the tendency for dark tail flow before and after bifurcations was analyzed to study the blood flow in detail. Results Average velocity in parent vessels with dark tail flow was 1.30±0.27 mm/s. Average velocity in daughter vessels with dark tail flow was 1.12±0.25 mm/s, and the average velocity of plasma gaps in daughter vessels without dark tail flow was 0.64±0.11 mm/s. Downstream from the bifurcations, the velocity in vessels with dark tail flow was higher than that in those without it (p<0.001), and the branching angles of vessels with dark tail flow were smaller than those of vessels without it (p<0.001). Conclusions Images from the AO-SLO noninvasively revealed pathways with and without dark tail flow in the human parafovea. Pathways with dark tail flow in the daughter vessels generally had faster flow and smaller bifurcation angles than daughter vessels without dark tail flow. Thus, AO-SLO is an instructive tool for analyzing retinal microcirculatory hemodynamics.

Effects of age and blood pressure on the retinal arterial wall, analyzed using adaptive optics scanning laser ophthalmoscopy

The wall-to-lumen ratio (WLR) of the vasculature is a promising early marker of retinal microvascular changes. Recently, adaptive optics scanning laser ophthalmoscopy (AOSLO) enabled direct and noninvasive visualization of the arterial wall. Using AOSLO, we analyzed the correlation between age and WLR in 51 normal subjects. In addition, correlations between blood pressure and WLR were analyzed in 73 subjects (51 normal subjects and 22 hypertensive patients). WLR showed a strong correlation with age (r = 0.68, P < 0.0001), while outer diameter and inner diameter did not show significant correlation with age in the normal group (r = 0.13, P = 0.36 and r = −0.12, P = 0.41, respectively). In the normal and hypertensive groups, WLR showed a strong correlation with systolic and diastolic blood pressure (r = 0.60, P < 0.0001 and r = 0.65, P < 0.0001, respectively). In conclusion, AOSLO provided noninvasive and reproducible arterial measurements. WLR is an early marker of morphological changes in the retinal arteries due to age and blood pressure.

Potential Measurement Errors Due to Image Enlargement in Optical Coherence Tomography Imaging

The effect of interpolation and super-resolution (SR) algorithms on quantitative and qualitative assessments of enlarged optical coherence tomography (OCT) images was investigated in this report. Spectral-domain OCT images from 30 eyes in 30 consecutive patients with diabetic macular edema (DME) and 20 healthy eyes in 20 consecutive volunteers were analyzed. Original image (OR) resolution was reduced by a factor of four. Images were then magnified by a factor of four with and without application of one of the following algorithms: bilinear (BL), bicubic (BC), Lanczos3 (LA), and SR. Differences in peak signal-to-noise ratio (PSNR), retinal nerve fiber layer (RNFL) thickness, photoreceptor layer status, and parallelism (reflects the complexity of photoreceptor layer alterations) were analyzed in each image type. The order of PSNRs from highest to lowest was SR > LA > BC > BL > non-processed enlarged images (NONE). The PSNR was statistically different in all groups. The NONE, BC, and LA images resulted in significantly thicker RNFL measurements than the OR image. In eyes with DME, the photoreceptor layer, which was hardly identifiable in NONE images, became detectable with algorithm application. However, OCT photoreceptor parameters were still assessed as more undetectable than in OR images. Parallelism was not statistically different in OR and NONE images, but other image groups had significantly higher parallelism than OR images. Our results indicated that interpolation and SR algorithms increased OCT image resolution. However, qualitative and quantitative assessments were influenced by algorithm use. Additionally, each algorithm affected the assessments differently.

Image Quality Improvement in Adaptive Optics Scanning Laser Ophthalmoscopy Assisted Capillary Visualization Using B-spline-based Elastic Image Registration

Purpose To investigate the effect of B-spline-based elastic image registration on adaptive optics scanning laser ophthalmoscopy (AO-SLO)-assisted capillary visualization. Methods AO-SLO videos were acquired from parafoveal areas in the eyes of healthy subjects and patients with various diseases. After nonlinear image registration, the image quality of capillary images constructed from AO-SLO videos using motion contrast enhancement was compared before and after B-spline-based elastic (nonlinear) image registration performed using ImageJ. For objective comparison of image quality, contrast-to-noise ratios (CNRS) for vessel images were calculated. For subjective comparison, experienced ophthalmologists ranked images on a 5-point scale. Results All AO-SLO videos were successfully stabilized by elastic image registration. CNR was significantly higher in capillary images stabilized by elastic image registration than in those stabilized without registration. The average ratio of CNR in images with elastic image registration to CNR in images without elastic image registration was 2.10 ± 1.73, with no significant difference in the ratio between patients and healthy subjects. Improvement of image quality was also supported by expert comparison. Conclusions Use of B-spline-based elastic image registration in AO-SLO-assisted capillary visualization was effective for enhancing image quality both objectively and subjectively.

INFLUENCE OF VITRECTOMY SURGERY ON THE INTEGRITY OF OUTER RETINAL LAYERS IN DIABETIC MACULAR EDEMA.

Purpose: To investigate the influence of pars plana vitrectomy (PPV) on the integrity of photoreceptor layers in eyes with diabetic macular edema (DME) by using parallelism (a parameter that comprehensively reflects photoreceptor–retinal pigment epithelium [RPE] complex alterations) in spectral-domain optical coherence tomography (SD-OCT) imaging. Methods: A consecutive series of 64 eyes in 55 patients with diabetic macular edema who underwent pars plana vitrectomy were recruited into the study. Spectral-domain optical coherence tomography images were obtained preoperatively and 6 months after surgery. The morphologic features of the outer retinal layers were assessed quantitatively using parallelism and qualitatively by graders, including continuity of the external limiting membrane (ELM) line, continuity of the photoreceptor inner and outer segment (IS/OS) junction line, and the presence of hyperreflective foci in the outer retinal layers. The relationships between parallelism, visual acuity (VA), and photoreceptor layer status were evaluated. Results: After surgery, foveal thickness significantly decreased (P < 0.0001) and visual acuity improved (P < 0.0001) from baseline level. Postoperative parallelism (0.632 ± 0.137) was significantly higher than preoperative parallelism (0.531 ± 0.172) (P < 0.0001). A number of eyes with hyperreflective foci reduced after surgery, while separate evaluation of the inner and outer segment junction and external limiting membrane lines did not show significant changes. Moreover, preoperative and postoperative parallelism values showed significant correlations with postoperative visual acuity and serum lipid levels. Foveal thickness and logMAR visual acuity did not show significant correlations with any blood test data. Conclusion: Pars plana vitrectomy might be effective for resolution of hyperreflective foci in outer retinal layers. Parallelism is a potential marker for localization of hyperreflective foci and useful as a predictive factor for postoperative visual acuity.