Anti-Hexokinase 1 Antibody as a Novel Serum Biomarker of a Subgroup of Diabetic Macular Edema.

Diabetic retinopathy (DR) induces the breakdown of the blood-retinal barrier and promotes neuroinflammation, although autoimmune responses to sequestered retinal antigens remain poorly understood. In this study, we investigated the autoantibodies for retinal antigens in sera from diabetic macular edema (DME) patients. Screening by immunoblotting demonstrated that IgG from 7 of 10 DME sera samples reacted to an ~102-kDa autoantigen from porcine retinas. Immunoprecipitation with autoantibodies from DME sera and subsequent mass spectrometry enabled us to identify hexokinase 1 as an autoantigen reactive to IgG from DME sera. IgG in 7 of 10 DME sera partially colocalized to hexokinase 1 in the outer plexiform layer of rodent retinas. Quantitative analyses using enzyme-linked immunosorbent assays revealed that the serum titers of this autoantibody were significantly higher in the DME sera than those in the sera from diabetic patients without DME, and 20 (24.1%) of the 83 DME serum samples had higher IgG titers than the cutoff value (mean + 2 standard deviations of the sera from diabetic patients without DR). Multivariate logistic regression analysis confirmed that the higher titer of anti-hexokinase 1 IgG was clinically feasible for the diagnosis of DME. These data identify anti-hexokinase 1 antibody as a serum biomarker of a subset of DME.

Anti-Fumarase Antibody as a Predictor of Functional Efficacy of Anti-VEGF Therapy for Diabetic Macular Edema.

Purpose: To evaluate whether baseline titers of anti-fumarase antibody are associated with visual prognosis after anti-VEGF treatment for diabetic macular edema (DME). Methods: In this retrospective study, we investigated 52 eyes of 52 DME patients who received intravitreal injections of anti-VEGF drugs (ranibizumab or aflibercept) after blood sampling at baseline. Optical coherence tomography (OCT) images were obtained at every monthly visit. The serum titer of anti-fumarase antibody at baseline was measured using ELISA. We evaluated the relationship between the titer of anti-fumarase antibody at baseline and visual acuity (VA) improvement at 12 months. Results: The serum titer of anti-fumarase IgG was related to the logMAR visual acuity (VA; R = 0.329, P = 0.017) and the disrupted ellipsoid zone (EZ; R = 0.364, P = 0.008) at baseline. The titer of this autoantibody was not associated with logMAR VA (R = -0.007, P = 0.980) but was associated with VA improvement (R = 0.465, P < 0.001) at 12 months upon anti-VEGF treatment. The transverse length of the disrupted EZ line was shortened at 12 months (P < 0.001), and restoration of the EZ line was correlated to the autoantibody titer (R = 0.396, P = 0.004) compared with the decrease in central subfield (CSF) thickness. Multivariate analysis showed that pretreatment logMAR VA (ß = 0.296, P = 0.045) and the autoantibody titer (ß = 0.328, P = 0.017) were associated with VA improvement after anti-VEGF treatment. In contrast, the titer was not associated with logMAR VA at 12 months. Conclusions: Anti-fumarase antibody is a novel serum biomarker predicting better functional efficacy of anti-VEGF treatment for DME.

Anti-fumarase antibody promotes the dropout of photoreceptor inner and outer segments in diabetic macular oedema.

AIMS/HYPOTHESIS: In diabetic macular oedema (DMO), blood components passing through the disrupted blood-retinal barrier cause neuroinflammation, but the mechanism by which autoantibodies induce neuroglial dysfunction is unknown. The aim of this study was to identify a novel autoantibody and to evaluate its pathological effects on clinically relevant photoreceptor injuries. METHODS: Biochemical purification and subsequent peptide fingerprinting were applied to identify autoantigens. The titres of autoantibodies in DMO sera were quantified and their associations with clinical variables were evaluated. Two animal models (i.e. passive transfer of autoantibodies and active immunisation) were characterised with respect to autoimmune mechanisms underlying photoreceptor injuries. RESULTS: After screening serum IgG from individuals with DMO, fumarase, a Krebs cycle enzyme expressed in inner segments, was identified as an autoantigen. Serum levels of anti-fumarase IgG in participants with DMO were higher than those in diabetic participants without DMO (p < 0.001) and were related to photoreceptor damage and visual dysfunction. Passively transferred fumarase IgG from DMO sera in concert with complement impaired the function and structure of rodent photoreceptors. This was consistent with complement activation in the damaged photoreceptors of mice immunised with fumarase. Fumarase was recruited to the cell surface by complement and reacted to this autoantibody. Subsequently, combined administration of anti-fumarase antibody and complement elicited mitochondrial disruption and caspase-3 activation. CONCLUSIONS/INTERPRETATION: This study has identified anti-fumarase antibody as a serum biomarker and demonstrates that the generation of this autoantibody might be a pathological mechanism of autoimmune photoreceptor injuries in DMO.

Granular lesions of short-wavelength and near-infrared autofluorescence in diabetic macular oedema.

OBJECTIVES: To document and characterise hyper- and hypo-reflective lesions, which we describe as 'granular' on short-wavelength autofluorescence (SW-AF) and near-infrared (NIR)-AF images in diabetic macular oedema (DMO). METHODS: Consecutive 103 eyes of 78 patients suffering from centre-involving DMO were reviewed retrospectively. Mosaics of hyper- and hypo-fluorescent dots on both SW-AF and NIR-AF signals were delineated and defined as granular lesions in the macula. We evaluated the association of such lesions with the logarithm of the minimum angle of resolution visual acuity (logMAR VA) and spectral-domain optical coherence tomography (SD-OCT) images. RESULTS: Diffuse mosaics of hyper- and hypo-fluorescent dots were delineated in 36 and 45 eyes on SW-AF and NIR-AF images, respectively, and both AF images defined granular lesions in 33 eyes. These lesions were delineated in both the fovea and extrafoveal areas on NIR-AF images but were limited to the parafoveal and perifoveal subfields on SW-AF images. There was a significant difference in logMAR VA between eyes with and without granular lesions (0.358 ± 0.269 vs. 0.185 ± 0.234; P = 0.001). Granular lesions were associated with the mosaic pattern on NIR-AF images (P < 0.001) but not with other parameters on SW-AF and NIR-AF images. The retinal thickness in the central subfield was greater in eyes with granular lesions (538.0 ± 163.6 µm vs. 448.8 ± 120.2 µm; P = 0.003). Granular lesions were associated with ELM disruption and hyper-reflective foci in the outer retinal layers (P = 0.004 and P = 0.037, respectively). CONCLUSIONS: Granular lesions defined on both SW-AF and NIR-AF images were related to retinal oedema with photoreceptor damage and concomitant VA reduction in DMO.

Association between characteristics of foveal cystoid spaces and short-term responsiveness to ranibizumab for diabetic macular edema.

PURPOSE: To investigate the association between the characteristics of foveal cystoid spaces and short-term responsiveness to ranibizumab treatment for diabetic macular edema (DME) at 3 months from the initial injection. METHODS: We retrospectively reviewed 66 eyes of 61 patients with center-involved DME who received three consecutive ranibizumab injections and following as-needed administrations. We evaluated the relationship between visual improvement at 3 months and the preoperative optical coherence tomography (OCT) parameters including hyperreflective foci, heterogeneous OCT reflectivity, mean levels of OCT reflectivity and height of foveal cystoid spaces. RESULTS: Twenty-three eyes without preoperative hyperreflective foci in the foveal cystoid spaces had significantly greater improvement in the logarithm of the minimum angle of resolution visual acuity (logMAR VA) at 3 months than 43 eyes with foci (P = 0.006). That was similar to the greater reduction in CSF thickness in eyes without lesions after treatment at the same time point (P < 0.001). VA improvement at 3 months was not associated with the height (R = 0.215, P = 0.083) or the reflectivity levels (R = -0.079, P = 0.538) of foveal cystoid spaces. There were no differences in VA changes between eyes with and without heterogeneous reflectivity in foveal cystoid spaces (P = 0.297). Multivariate analyses showed that logMAR VA and the absence of hyperreflective foci in foveal cystoid spaces were associated with VA improvement at 3 months. CONCLUSION: Hyperreflective foci in foveal cystoid spaces at baseline predict poorer short-term responsiveness to ranibizumab injections for DME.

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.

Diabetic Neuroglial Changes in the Superficial and Deep Nonperfused Areas on Optical Coherence Tomography Angiography.

Purpose: To evaluate the relationship between lamellar capillary nonperfusion on optical coherence tomography angiography (OCTA) images and neuroglial changes on structural optical coherence tomography (OCT) images in diabetic retinopathy (DR). Methods: We retrospectively reviewed 101 consecutive eyes of 69 patients with DR. OCTA and OCT images within a 3 × 3-mm square centered on the fovea were acquired simultaneously. The nonperfused areas (NPAs) in the superficial capillary layer (sNPA) (from the nerve fiber layer [NFL] to the inner plexiform layer [IPL]), the deep layer (dNPA) (corresponding mainly to the inner nuclear layer [INL]), or both layers (bNPA) were measured individually along 10 transverse lines. The corresponding lamellar neuroglial changes also were evaluated on OCT images. Results: The transverse lengths of the sNPA, dNPA, and bNPA were 2.34% (interquartile range, 0.81-5.55), 0.61% (0-1.99), and 5.96% (4.02-10.88), respectively. The length of the sNPA was correlated significantly with the lengths of no boundary between the NFL and ganglion cell layer (GCL)/IPL and the spots with inverted OCT reflectivity in the sNPA. The transverse length of the dNPA was associated with the length of cystoid spaces in the INL or Henle's fiber layer (HFL) in the dNPA. There was a significant correlation between the transverse lengths of the bNPA and no boundary between the NFL and GCL/IPL within the bNPA. Conclusions: Systematic evaluation of the OCTA-OCT association showed structural changes in the neuroglial tissues corresponding to the lamellar NPAs and suggested the feasibility of layer-by-layer evaluation of the capillary nonperfusion in DR.

Clinical relevance of reduced decorrelation signals in the diabetic inner choroid on optical coherence tomography angiography.

Diabetes induces lesions of the retinal and choroidal capillaries, which promote the pathogenesis of diabetic retinopathy (DR). The decorrelation signals in optical coherence tomography angiography (OCTA) represent the blood flow and vascular structure, and three-dimensional OCTA images enable individual capillary layers to be evaluated separately. The current study documented that en-face OCTA images revealed spots of flow void in the choriocapillaris layer in eyes with DR. Quantitative investigation demonstrated that non-flow areas within the central subfield (CSF) increased in eyes with more severe DR grades. The non-flow areas in the choriocapillaris layer were also associated with poorer visual acuity (VA) in all 108 eyes. A modest correlation was noted between the areas of flow void and poorer VA in 69 eyes without DME, whereas the non-flow areas were not related to VA or to CSF thickness measured by OCT in 39 eyes with DME. In 12 eyes with ischemic maculopathy, the choriocapillaris layer beneath the disrupted ellipsoid zone of the photoreceptor (EZ) had greater areas of flow void than did the area beneath an intact EZ. These data suggested that disrupted choroidal circulation has clinical relevance and contributes to the pathogenesis of DR.

Relation between macular morphology and treatment frequency during twelve months with ranibizumab for diabetic macular edema.

PURPOSE: To investigate whether baseline optical coherence tomography (OCT) parameters can predict the treatment frequency of intravitreal ranibizumab (IVR) injections during the first year in patients with diabetic macular edema (DME) treated with pro re nata (PRN) IVR injections. METHODS: We retrospectively reviewed 68 eyes of 63 patients with center-involved DME who received IVR injections for 12 months or longer according to three monthly IVR injections followed by the PRN dosing. We measured the mean retinal thicknesses in the individual subfields of the Early Treatment Diabetic Retinopathy Study grid and evaluated the qualitative and quantitative parameters on OCT sectional images. We investigated the relationship between these OCT parameters at baseline and the number of IVR injections during the 12-month follow-up. RESULTS: Three loading doses were administered to 10 eyes; four to seven annualized IVR injections were administered to 34 eyes. The number of eyes that received IVR injections decreased gradually until month 6 and was almost constant from months 7 to 11. No relationships were seen between the treatment frequency and baseline systemic factors and the ophthalmic examination findings. Univariate analyses showed that the number of IVR injections during the first year was associated with the mean retinal thickness in the individual subfields and the transverse length of the disrupted external limiting membrane (ELM) and ellipsoid zone of the photoreceptors. Multivariate analysis showed a significant association with the thickness in the inferior subfield alone. The treatment frequency during the 12-month follow-up was not correlated with improved visual acuity but was associated with the decrease in the central subfield thickness and disrupted ELM. CONCLUSION: The retinal thickness in the inferior subfield predicts the treatment frequency during the first year in eyes with DME treated with PRN IVR injections.

Restoration of foveal photoreceptors after intravitreal ranibizumab injections for diabetic macular edema.

Anti-vascular endothelial growth factor drugs are the first-line treatment for diabetic macular edema (DME), although the mechanism of the visual acuity (VA) improvement remains largely unknown. The association between photoreceptor damage and visual impairment encouraged us to retrospectively investigate the changes in the foveal photoreceptors in the external limiting membrane (ELM) and ellipsoid zone (EZ) on spectral-domain optical coherence tomography (SD-OCT) images in 62 eyes with DME treated with intravitreal ranibizumab (IVR) injections. The transverse lengths of the disrupted EZ and ELM were shortened significantly (P < 0.001 and P = 0.044, respectively) at 12 months. The qualitative investigation also showed restoration of the EZ and ELM lines on SD-OCT images. The EZ at 12 months lengthened in 34 of 38 eyes with discontinuous EZ and was preserved in 16 of 21 eyes with complete EZ at baseline. VA improvement was positively correlated with shortening of the disrupted EZ at 12 months (ρ = 0.463, P < 0.001), whereas the decrease in central subfield thickness was associated with neither VA improvement nor changes in EZ status (ρ = 0.215, P = 0.093 and (ρ = 0.209, P = 0.103, respectively). These data suggested that photoreceptor restoration contributes to VA improvement after pro re nata treatment with IVR injections for DME independent of resolved retinal thickening.

White Dots as a Novel Marker of Diabetic Retinopathy Severity in Ultrawide Field Imaging.

PURPOSE: To characterize white dots in diabetic retinopathy (DR) and their association with disease severity using ultra-wide-field scanning laser ophthalmoscopy. METHODS: We randomly selected 125 eyes of 77 patients (25 eyes from individual categories of the international classification of DR severity) for which ultrawide field photographs were obtained. We characterized white dots, which were delineated by higher signal levels on green but not red laser images, and evaluated the relationship between the number of white dots and the international severity scale of DR. RESULTS: Most white dots were located in nonperfused areas, and the number of total white dots was significantly correlated to that of dots in nonperfused areas. White dots corresponded to microaneurysms around the boundary between nonperfused areas and perfused areas or unknown lesions in nonperfused areas. Eyes with DR had significantly more white dots than those with no apparent retinopathy. The numbers of white dots in moderate nonproliferative diabetic retinopathy (NPDR) or more severe grades were significantly higher than in mild NPDR. The area under the receiver operating characteristics curve (AROC) analyses demonstrated that the number of white dots had the significance in the diagnosis of DR (0.908-0.986) and moderate NPDR or more severe grades (0.888-0.974). CONCLUSIONS: These data suggest the clinical relevance of white dots seen on ultrawide field images in the diagnosis of the severity of DR.

In Vivo Choroidal Vascular Lesions in Diabetes on Swept-Source Optical Coherence Tomography.

Diabetes induces microvascular diseases including diabetic retinopathy and choroidopathy which reciprocally promote the pathogenesis, although optical coherence tomography images of diabetic choroidopathy remains to be documented. Here we evaluated the qualitative characteristics of choroidal vascular lesions in patients with diabetes and their association with diabetic retinopathy on swept-source optical coherence tomography (SS-OCT) images. We retrospectively reviewed 110 consecutive eyes of 110 patients with diabetes and 35 eyes of 35 healthy subjects for whom SS-OCT images (6x6-mm scans centered on the fovea) of sufficient quality were acquired. The curve of chorioretinal sections was flattened using Bruch's membrane as a reference surface, followed by generation of en-face images. We characterized choroidal vascular lesions and evaluated their association with the logarithm of the minimum angle of resolution visual acuity (logMAR VA), retinal and choroidal thicknesses, and diabetic retinopathy severity. En-face SS-OCT images showed unvisualized vessels in Sattler's layer in 33 eyes (30.0%). Focal narrowing was seen in choroidal vessels in Haller's layer in 56 eyes (50.9%). The choroidal vessels ended in the superficial or middle portion of Haller's layer, referred to as vascular stumps, in 20 eyes (18.2%). Diabetic eyes had these findings more frequently than nondiabetic eyes. The subfoveal choroid was thicker in eyes with focal vascular narrowing and vascular stumps than in eyes without such lesions. Vascular stumps in Haller's layer were significantly related to diabetic retinopathy severity, logMAR VA, and central retinal and choroidal thicknesses. These novel findings on SS-OCT images would promote the better understanding of complicated pathogenesis in diabetic retinopathy and choroidopathy.

Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography.

The decorrelation signals in optical coherence tomography angiography (OCTA) are derived from the flow of erythrocytes and concomitantly delineate the retinal vasculature. We compared the structural and functional characteristics of vascular lesions visualized in fluorescein angiography (FA), OCTA, and en-face OCT images in 53 eyes (28 patients) with diabetic retinopathy (DR). The foveal avascular zone (FAZ) areas in OCTA images in the superficial layer almost corresponded to those in FA images. The FAZ areas in the en-face OCT images in the superficial layer were smaller than those in the FA images and correlated with each other, which agreed with the finding that en-face OCT images often delineated the vascular structure in the nonperfused areas in FA images. Microaneurysms appeared as fusiform, saccular, or coiled capillaries in OCTA images and ringed, round, or oval hyperreflective lesions in en-face OCT images. OCTA and en-face OCT images detected 41.0 ± 16.1% and 40.1 ± 18.6%, respectively, of microaneurysms in FA images, although both depicted only 13.9 ± 16.4%. The number of microaneurysms in FA images was correlated with that in OCTA and en-face OCT images. Comparisons of these modalities showed the associations and dissociations between blood flow and vascular structures, which improves the understanding of the pathogenesis of DR.

Characterization of Inner Retinal Spots With Inverted Reflectivity on En Face Optical Coherence Tomography in Diabetic Retinopathy.

PURPOSE: The purpose of this study was to characterize inner retinal spots with inverted reflectivity on en face images of swept-source optical coherence tomography (SS-OCT) in diabetic retinopathy (DR). METHODS: We retrospectively reviewed seventy-five eyes of 75 patients with DR (15 eyes with individual grades of DR severity). We obtained three-dimensional images (6 × 6 mm) centered on the fovea, followed by the generation of en face images. We investigated the morphologic characteristics of spots with inverted reflectivity, which had lower reflectivity than the surrounding areas in the nerve fiber layer (NFL) and higher reflectivity in the ganglion cell layer (GCL). RESULTS: Thirty-seven of 45 eyes (82.2%) with moderate nonproliferative diabetic retinopathy (NPDR) or more severe grades were accompanied with well-defined spots with inverted reflectivity, whereas 30 eyes with no apparent retinopathy or mild NPDR had no such lesions. These spots had various shapes in the NFL and GCL on en face OCT images; the mean area was 0.126 ± 0.052 mm2 at the NFL level. In all 75 eyes, 153 of 184 spots (83.2%) were localized in the NFL and GCL, whereas 31 spots (16.8%) extended to retinal layers deeper than the GCL. One-hundred sixty-nine spots (91.8%) were not visible on color fundus photographs, and 15 spots (8.2%) were accompanied by whitish-yellow lesions in the corresponding areas. In 45 eyes for which fluorescein angiography images were obtained, mild hypofluorescence was seen in 156 spots (84.8%) and focal nonperfused areas in 17 spots (9.2%). CONCLUSIONS: En face images of SS-OCT showed spots with inverted reflectivity in the NFL and GCL in DR.

Enhanced-Resolution Optical Coherence Tomography Imaging.

PURPOSE: The effect of the enhanced-resolution imaging (ERI) technique on optical coherence tomography (OCT) images was evaluated. METHODS: A total of 5 healthy subjects and 20 patients diagnosed with various eye diseases were recruited into the study. ERI, a novel image processing technique, was accomplished by using super-resolution technology, and was assessed by objectively and subjectively comparing the image quality among three different image groups: images enlarged without bicubic interpolation (NONE), with bicubic interpolation (IP), and with ERI. RESULTS: ERI showed a higher ratio of the detailed variance to the background variance than NONE, whereas no significant difference was detected between NONE and IP. The mean opinion score of 5 experienced retinal specialists for ERI was significantly higher than that for IP. CONCLUSIONS: ERI generated a sharper image and clearly visualized small objects. Additionally, it is effective in enhancing OCT image quality.

Macular morphologic findings on optical coherence tomography after microincision vitrectomy for proliferative diabetic retinopathy.

PURPOSE: To investigate macular morphology on spectral-domain optical coherence tomography (SD-OCT) images after microincision vitrectomy for vitreous hemorrhage associated with proliferative diabetic retinopathy (PDR). METHODS: In this retrospective case series, 69 eyes (57 consecutive patients) that underwent 23-gauge microincision vitrectomy for vitreous hemorrhage due to PDR were investigated. Qualitative and quantitative characteristics on SD-OCT images [central retinal thickness, external limiting membrane (ELM), and the ellipsoid zone, epiretinal membranes involving the fovea, and hyperreflective foci at the fovea] were assessed 6 months postoperatively. Their association with the logarithm of the minimum angle of resolution visual acuity (logMAR VA) was evaluated. RESULTS: The ELM was disrupted in 15 and the ellipsoid zone in 27 eyes, and associated significantly (P < 0.001, for both comparisons) with poor visual outcomes 6 months postoperatively. Hyperreflective foci in the outer retinal layers were associated with either a disrupted ELM or ellipsoid zone and poor prognoses (P < 0.001, for all comparisons). The accumulation of hyperreflective foci at the fovea in five eyes was correlated significantly (P < 0.001) with poorer logMAR VA. Twenty-nine eyes had center-involved diabetic macular edema 6 months postoperatively, whereas the central thickness was not correlated with the logMAR VA (R = -0.148, P = 0.224). Eight eyes with either epiretinal membrane on SD-OCT images had greater central thickness (P = 0.003), although there were no differences in the logMAR VA between eyes with and without it (P = 0.648). CONCLUSIONS: Foveal photoreceptor damage is associated with poor visual outcomes after microincision vitrectomy for vitreous hemorrhage due to PDR.

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.

Disorganized retinal lamellar structures in nonperfused areas of diabetic retinopathy.

PURPOSE: To investigate morphologic changes on spectral-domain optical coherence tomography (SD-OCT) images in nonperfused areas (NPAs) in diabetic retinopathy (DR). METHODS: One hundred eight consecutive eyes of 80 patients with diabetic ischemic maculopathy were retrospectively reviewed. The boundary between the nerve fiber layer (NFL) and the ganglion cell layer (GCL)/inner plexiform layer (IPL) and the status of Henle's layer were characterized on the vertical sectional images of SD-OCT. These findings were compared with the NPAs on the FA images and the logMAR visual acuity (VA). RESULTS: The SD-OCT images showed that most areas of capillary nonperfusion had an indistinct boundary between the NFL and GCL/IPL in DR, regardless of high or moderate OCT reflectivity. The total transverse length of the NPAs was correlated positively with that of the areas with no boundary between these layers in all 108 eyes (R = 0.860, P < 0.001). Sixty-four eyes that had center-involved diabetic macular edema (DME) also had a significant association between them (R = 0.764, P < 0.001), and the most significant correlation was seen in eyes without DME (R = 0.955, P < 0.001). The macular transverse length of the areas with no boundary between the NFL and GCL/IPL was associated modestly with the logMAR VA (R = 0.334, P < 0.001). The indistinct Henle's layer on SD-OCT images often was delineated specifically in the NPAs rather than in the perfused areas. CONCLUSIONS: Nonperfused areas were associated significantly with the absence of a boundary between the NFL and GCL/IPL on SD-OCT images in DR.

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.

Parallelism for quantitative image analysis of photoreceptor-retinal pigment epithelium complex alterations in diabetic macular edema.

PURPOSE: To propose a new method to quantitatively and comprehensively evaluate photoreceptor-RPE complex alterations on spectral-domain optical coherence tomography (SD-OCT) imaging in eyes with diabetic macular edema (DME). METHODS: Spectral-domain OCT images from a consecutive series of 90 eyes in 79 patients with DME and 30 healthy eyes in 30 volunteers were analyzed retrospectively. The subfoveal area covering the photoreceptor layers was skeletonized and the orientation of the segmented lines was termed "parallelism," which reflects image complexity. Photoreceptor layer status at the fovea was categorized by graders, including continuity of the external limiting membrane (ELM) line, inner segment ellipsoid line, and the presence of hyperreflective foci in the outer retinal layers. The relationships among parallelism, visual acuity, and photoreceptor layer status were evaluated. RESULTS: Parallelism was significantly lower in eyes with DME than in normal eyes (P < 0.0001), and correlated strongly with visual acuity in eyes with DME (R = -0.592; P < 0.0001). Eyes with an intact inner segment ellipsoid line or ELM line had significantly better visual acuity (VA) and higher parallelism than eyes with a discontinuous or absent inner segment ellipsoid line or ELM line. Parallelism was significantly higher (P < 0.0001) and logMAR VA significantly better (P < 0.0001) in the group without hyperreflective foci in the outer retinal layers than in the group with hyperreflective foci in the outer retinal layers. CONCLUSIONS: Parallelism has the potential to reflect structural changes of the photoreceptor layers in DME.