Showing papers in "Investigative Ophthalmology & Visual Science in 2017"
TL;DR: Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR, and higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR.
Abstract: Purpose We quantified retinal and choriocapillaris microvascular changes in healthy control eyes and different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA). Methods This retrospective cross-sectional study included 137 eyes of 86 patients with different stages of DR and 44 eyes of 26 healthy age-matched controls. Participants were imaged with a commercial OCTA device (RTVue-XR Avanti). We analyzed the superficial (SCP) and deep (DCP) retinal capillary plexus, the full retina, and choriocapillaris for the following OCTA parameters: foveal avascular zone, vessel density, percent area of nonperfusion (PAN), and adjusted flow index (AFI). We adjusted for age, sex, and the correlation between eyes of the same study participant in our statistical models. Results All OCTA parameters showed a significant linear correlation with DR severity (P < 0.05) in the univariate models except for AFI measured in the SCP and these correlations remained significant after correcting for covariates. Compared to the other capillary layers, the AFI at the DCP decreased significantly with DR severity. When comparing individual disease severity groups as categories, eyes of subjects with diabetes without DR had significantly increased PAN and AFI in the SCP compared to healthy subjects (P < 0.05). Conclusions Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR. Higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR. The steep decline of blood flow in the DCP with increasing DR severity suggests that alterations at the DCP warrant further investigation.
259 citations
TL;DR: Superficial and deep retinal vessel density in parafovea of diabetic patients without diabetic retinopathy are both decreased compared to healthy subjects.
Abstract: Purpose To compare optical coherence tomography (OCT) angiographic parameters in retina and choriocapillaris between control subjects and diabetic patients without diabetic retinopathy (NDR). Correlations were studied between OCT angiography parameters, retinal structure parameters, and systemic characteristics in all subjects. Methods Sixty-two patients were included in the study: control subjects (n = 33) and patients with NDR (n = 29). Optical coherence topography angiographic parameters were as follows: vessel density (%) (in superficial, deep retinal vessel plexus and in choriocapillary layer) and foveal avascular zone (FAZ) area (mm2) in superficial and deep retinal vessel plexus of parafovea. Split-spectrum amplitude decorrelation angiography (SSADA) software algorithm was used for evaluation of vessel density and FAZ area (nonflow area tool). Spectral-domain OCT was used to assess full, inner, and outer retinal thickness and volume in parafovea. Results In superficial and deep retina, vessel densities in NDR (44.35% ± 13.31% and 31.03% ± 16.33%) were decreased as compared to control subjects (51.39% ± 13.05%, P = 0.04; and 41.53% ± 14.08%, P < 0.01). Foveal avascular zone in superficial retina of NDR patients (0.37 ± 0.11 mm2) was greater than in controls (0.31 ± 0.10 mm2, P = 0.02). Superficial vessel density significantly correlated with full retinal thickness and volume in parafovea (r = 0.43, P = 0.01; r = 0.43, P = 0.01) and with outer retinal volume in parafovea (r = 0.35, P < 0.05) of healthy subjects. Systolic blood pressure and ocular perfusion pressure significantly correlated with deep vessel density in NDR (r = -0.45, P = 0.02; r = -0.46, P = 0.01), but not in controls. Conclusions Superficial and deep retinal vessel density in parafovea of diabetic patients without diabetic retinopathy are both decreased compared to healthy subjects. The associations between vessel density with retinal tissue thickness and with subject's clinical characteristics differ between healthy subjects and patients with NDR.
249 citations
TL;DR: The density of the retinal capillary microvasculature is reduced and the area of flow deficit in the CC is increased in eyes with greater myopia, and the relevance of microvascular alterations in the setting of myopia warrants further study.
Abstract: Purpose To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using quantitative optical coherence tomography angiography (OCTA) analysis. Methods Macular OCTA images of 3 × 3 mm were obtained using the RTVue-XR Avanti with AngioVue. Quantitative measurements of the retinal capillary microvascular layers and the CC were analyzed using en face projection images. Vessel density and fractal dimension of the superficial and deep retinal capillary plexus, and area and density of flow reduction in the CC were analyzed, quantified, and compared with an age-matched control group. Results Fifty eyes with myopia and 34 age-matched healthy eyes were included in this study. The vessel density and the vessel branching complexity using fractal dimension of the retinal capillary microvasculature were significantly lower in myopic eyes (P < 0.001 and P = 0.001). The total number of flow voids in the CC was lower (108.93 vs. 138.63, P = 0.001) but the total and average flow void area was significantly higher (total area 3.715 ± 0.257 vs. 3.596 ± 0.194 mm2, P = 0.026; average area 0.044 ± 0.029 vs. 0.028 ± 0.010 mm2, P = 0.002) compared with the healthy control group. Average choroidal thickness was lower in the myopic group versus the normal control cohort (123.538 ± 73.477 vs. 246.97 ± 41.745 μm, P < 0.05) and significantly reduced in eyes with lacquer cracks (LC) compared with myopic eyes without LC formation (P = 0.003). There was no correlation between choroidal thickness and quantitative parameters of the CC in the myopic eyes. Conclusions The density of the retinal capillary microvasculature is reduced and the area of flow deficit in the CC is increased in eyes with greater myopia. The relevance of microvascular alterations in the setting of myopia warrants further study.
234 citations
TL;DR: Ocular biometry should be performed with OCTA to correct image magnification error induced by axial length variation, and caution is advised when interpreting interocular and interindividual comparisons of SRVD and FAZA derived from OCTA without image size correction.
Abstract: We examined the impact of axial length on superficial retinal vessel density (SRVD) and foveal avascular zone area (FAZA) measurement using optical coherence tomography angiography. The SRVD and FAZA were quantified before and after correction for magnification error associated with axial length variation. Although SRVD did not differ before and after correction for magnification error in the parafoveal region, change in foveal SRVD and FAZA were significant. This has implications for clinical trials outcome in diseased eyes where significant capillary dropout may occur in the parafovea.
209 citations
TL;DR: Cataract surgical rate and economic indicators are closely associated, indicating the strong influence of resource availability on healthcare delivery and it is important to be innovative in delivery of low-cost services and invest strategically in capacity development to meet cataract surgical need in low-resource settings.
Abstract: Purpose: Cataract is the leading cause of blindness and cataract surgical rate (CSR) is used as a proxy indicator of access to cataract services in a country. The aim of this study was to explore the associations between the CSR and the economic development of countries in terms of gross domestic product per capital (GDP/P) and gross national income per capita (GNI/P). Methods: We systematically searched OVID (Medline and Embase), Pubmed, Embase.com, ISI Web of Science, and Cochrane Library databases, and retrieved additional data from unpublished reports. Cataract surgical rates and economic indicators (GDP/P, GNI/P) were collected for each country from 2005 to 2014. Complete data were used for the 50 largest countries according to World Health Organization (WHO) population estimates. Linear correlations between GDP/P and CSR were calculated. Cataract surgical rate data over two periods were used for analysis: 2005 to 2009 and 2010 to 2014 (CSR in 2009 or nearest year, CSR in 2014 or nearest year). Results: Over the study period, CSR data were available for 152 countries across both time periods. Most of the CSR data were obtained from nongovernment organization (NGO) reports, including WHO reports. A good linear correlation between CSR and GDP/P was found overall, nearest to 2009 (β = 0.162, Linear: y = 0.162x + 282.242; R2 = 0.665, P < 0.001). Regression analysis of CSR nearest to 2014 produced similar findings, with significant correlations between CSR and GDP/P (Linear: y = 0.208x + 94.008; R2 = 0.785, P < 0.001). When using GNI/P as an economic indicator, similarly excellent lines of fit were obtained. After adjusting for time and country, CSR was significantly associated with GDP/P (Coefficient = 0.147, R2 = 0.759, P < 0.001), and GNI/P (Coefficient = 0.152, R2 = 0.757, P < 0.001). Most countries had an increase in CSRs over time, with the greatest increases observed for Iran and Argentina. Conclusion: Cataract surgical rate and economic indicators are closely associated, indicating the strong influence of resource availability on healthcare delivery. Considering this relationship, it is important to be innovative in delivery of low-cost services and invest strategically in capacity development to meet cataract surgical need in low-resource settings.
184 citations
TL;DR: The areas of CNV tended to be larger when imaged with SS-O CTA than with SD-OCTA, and this difference was greater for the 6 × 6-mm2 scans.
Abstract: Purpose The purpose of this study was to compare imaging of choroidal neovascularization (CNV) using swept-source (SS) and spectral-domain (SD) optical coherence tomography angiography (OCTA). Methods Optical coherence tomography angiography was performed using a 100-kHz SS-OCT instrument and a 68-kHz SD-OCTA instrument (Carl Zeiss Meditec, Inc.). Both 3 × 3- and 6 × 6-mm2 scans were obtained on both instruments. The 3 × 3-mm2 SS-OCTA scans consisted of 300 A-scans per B-scan at 300 B-scan positions, and the SD-OCTA scans consisted of 245 A-scans at 245 B-scan positions. The 6 × 6-mm2 SS-OCTA scans consisted of 420 A-scans per B-scan at 420 B-scan positions, and the SD-OCTA scans consisted of 350 A-scans and 350 B-scan positions. B-scans were repeated four times at each position in the 3 × 3-mm2 scans and twice in the 6 × 6-mm2 scans. Choroidal neovascularization was excluded if not fully contained within the 3 × 3-mm2 scans. The same algorithm was used to detect CNV on both instruments. Two graders outlined the CNV, and the lesion areas were compared between instruments. Results Twenty-seven consecutive eyes from 23 patients were analyzed. For the 3 × 3-mm2 scans, the mean lesion areas for the SS-OCTA and SD-OCTA instruments were 1.17 and 1.01 mm2, respectively (P = 0.047). For the 6 × 6-mm2 scans, the mean lesion areas for the SS-OCTA and SD-OCTA instruments were 1.24 and 0.74 mm2 (P = 0.003). Conclusions The areas of CNV tended to be larger when imaged with SS-OCTA than with SD-OCTA, and this difference was greater for the 6 × 6-mm2 scans.
161 citations
TL;DR: The measurement of the macular superficial vessel density had similar diagnostic accuracy to peripapillary RNFL and macular GCC thickness for differentiating between glaucomatous and healthy eyes.
Abstract: Purpose To quantitatively evaluate the superficial microvasculature in the macular and peripapillary areas in glaucomatous and healthy eyes using optical coherence tomography angiography (OCT-A). Methods We enrolled 26 eyes of medically managed primary open-angle glaucoma patients and 27 eyes of healthy subjects were enrolled in this prospective study. Measurements of OCT-A vessel density were acquired both in the macular and peripapillary areas. We compared vessel density values, the circumpapillary retinal nerve fiber layer (cpRNFL), the ganglion cell complex (GCC), and standard automated perimetry (SAP) parameters across study groups. Areas under the receiver operating characteristic (AUROC) curves were used to evaluate diagnostic accuracy. Quadratic regression models were used to determine the correlations between SAP severity and outcome measures. Results The whole image vessel density (wiVD) in glaucomatous eyes was lower than that in healthy eyes in the macular (38.5% ± 2.2% vs. 43.2% ± 2.3%, P < 0.001) and peripapillary areas (43.8% ± 5.7% vs. 53.3% ± 3.0%, P < 0.001). The circumpapillary vessel density (cpVD) was also lower in glaucomatous eyes (53.3% ± 7.0% vs. 61.5% ± 3.2%, P < 0.001). We found the AUROCs for discriminating between glaucomatous and healthy eyes were highest for cpRNFL (0.95) and GCC (0.95); followed by macular wiVD (0.94); peripapillary wiVD (0.93); and cpVD (0.89). The correlations between SAP severity were strongest with peripapillary wiVD (R2 = 0.58); followed by cpVD (R2 = 0.55); GCC (R2 = 0.51); cpRNFL (R2 = 0.42); and macular wiVD (R2 = 0.36). Conclusions Medically managed glaucomatous eyes show sparser superficial microvasculature in the macular area than do healthy eyes. The measurement of the macular superficial vessel density had similar diagnostic accuracy to peripapillary RNFL and macular GCC thickness for differentiating between glaucomatous and healthy eyes.
142 citations
TL;DR: In this pilot study, retinal capillary density and FAZ area remained statistically unchanged in the short-term after a single intravitreal injection of an anti-VEGF agent.
Abstract: Purpose To evaluate the changes in foveal avascular zone (FAZ) area and the retinal capillary density after a single intravitreal anti-VEGF injection for macular edema secondary to diabetic retinopathy or retinal vein occlusion. Methods In this prospective noncomparative case series, 18 eyes of 15 patients with diabetic macular edema (13 eyes) or macular edema secondary to central retinal vein occlusion (5 eyes) were included. Optical coherence tomography angiography (OCTA) images were obtained, and retinal capillary vessel density and FAZ area were measured in the foveal and parafoveal regions at the level of the superficial (SCP) and deep retinal capillary plexus (DCP) before and at the first visit after intravitreal injection. Results The mean interval between baseline and follow up OCTA was 32.5 ± 9.4 (range, 21-50) days. Foveal and parafoveal vessel density in the SCP and DCP were not significantly different before and after intravitreal injection (all P > 0.1), nor was FAZ area (P = 0.48 and P = 0.42, respectively). No significant difference was found between eyes with diabetic macular edema and those with retinal vein occlusion with respect to the mean change of vessel density and FAZ area (all P > 0.05). Conclusions In this pilot study, retinal capillary density and FAZ area remained statistically unchanged in the short-term after a single intravitreal injection of an anti-VEGF agent.
138 citations
TL;DR: Results demonstrate for the first time that ANRIL regulates VEGF expression and function in diabetic retinopathy and this regulation is mediated by p300, miR200b, and EZH2 of the PRC2 complex.
Abstract: Purpose Long noncoding RNAs (lncRNAs) previously thought to be "dark matter" of the genome, play key roles in various biological processes. The lncRNA ANRIL is located at a genetic susceptibility locus for coronary artery diseases and type 2 diabetes. We examined the role of ANRIL in diabetic retinopathy, through study of its regulation of VEGF both in vitro and in vivo. Methods Human retinal endothelial cells (HRECs) were subjected to incubation in high glucose to mimic diabetes. ANRIL expression was measured with or without small interfering RNA (siRNA) knockdown in HRECs. ANRIL knockout mice, with or without streptozotocin-induced diabetes, were also investigated. Cell and tissues were measured for VEGF mRNA and protein expression. Functional alterations in VEGF were determined through tube formation, cell proliferation, and retinal vascular permeability assays. Vascular endothelial growth factor regulation through ANRIL's interactions with polycomb repressive complex 2 (PRC2) components and p300 were studied thorough PRC2 blocker, siRNA, and RNA immunoprecipitation (RNA-IP) assays. Results High glucose and diabetes caused ANRIL upregulation in HRECs and in the retina. Glucose-mediated elevation of ANRIL, on silencing, prevented VEGF expression. Such regulation involved ANRIL-mediated control of the PRC2 components p300 and miR200b. Direct binding of ANRIL to p300 and enhancer of zeste homolog 2 (EZH2; a PRC2 component) were elevated following exposure to high glucose levels. Conclusions Our results demonstrate for the first time that ANRIL regulates VEGF expression and function in diabetic retinopathy. This regulation is mediated by p300, miR200b, and EZH2 of the PRC2 complex.
136 citations
TL;DR: RPE activation and migration comprise an important precursor to atrophy that can be observed at the cellular level in vivo via validated SDOCT, and are supported as intraretinal hyperreflective foci in spectral-domain optical coherence tomography (SDOCT).
Abstract: Purpose To summarize and contextualize recent histology and clinical imaging publications on retinal pigment epithelium (RPE) fate in advanced age-related macular degeneration (AMD); to support RPE activation and migration as important precursors to atrophy, manifest as intraretinal hyperreflective foci in spectral-domain optical coherence tomography (SDOCT) Methods The Project MACULA online resource for AMD histopathology was surveyed systematically to form a catalog of 15 phenotypes of RPE and RPE-derived cells and layer thicknesses in advanced disease Phenotypes were also sought in correlations with clinical longitudinal eye-tracked SDOCT and with ex vivo imaging-histopathology correlations in geographic atrophy (GA) and pigment epithelium detachments (PED) Results The morphology catalog suggested two main pathways of RPE fate: basolateral shedding of intracellular organelles (apparent apoptosis in situ) and activation with anterior migration Acquired vitelliform lesions may represent a third pathway Migrated cells are packed with RPE organelles and confirmed as hyperreflective on SDOCT RPE layer thickening due to cellular dysmorphia and thick basal laminar deposit is observed near the border of GA Drusenoid PED show a life cycle of slow growth and rapid collapse preceded by RPE layer disruption and anterior migration Conclusions RPE activation and migration comprise an important precursor to atrophy that can be observed at the cellular level in vivo via validated SDOCT Collapse of large drusen and drusenoid PED appears to occur when RPE death and migration prevent continued production of druse components Data implicate excessive diffusion distance from choriocapillaris in RPE death as well as support a potential benefit in targeting drusen in GA
134 citations
TL;DR: Structural damage is evident both in the peripapillary and in macular areas, and diagnostic abilities are excellent for structural variables, less so but still good for peripAPillary VD, and poor for macular VD.
Abstract: Purpose To evaluate macular and peripapillary vessel perfusion density (VD) in glaucoma suspects (GS) and glaucoma patients; to correlate ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) thicknesses with macular and peripapillary VD; and to evaluate the diagnostic accuracy of the structural and vascular parameters. Methods A consecutive series of GS, glaucoma patients, and healthy subjects was prospectively recruited from July 1, 2016, to January 31, 2017. All subjects underwent standard automated perimetry, spectral-domain optical coherence tomography (OCT), and 6 × 6-mm optical coherence tomography angiography (OCT-A) centered on the fovea and optic nerve. Results Forty controls, 40 GS, and 40 glaucoma patients were enrolled. Peripapillary RNFL, GCIPL, and macular RNFL thicknesses significantly decreased in the glaucoma group compared to controls and GS (P 0.05). At the peripapillary area, a correlation between RNFL thickness and VD was found; conversely, no statistically significant correlation was found between GCIPL thicknesses and macular VD (all P > 0.05) in all groups. Peripapillary RNFL and GCIPL showed higher diagnostic capacity compared to peripapillary and macular VDs. Conclusions Structural damage is evident both in the peripapillary and in macular areas. Vascular damage seems to be less prominent, as it was seen only for the glaucoma group and at the radial peripapillary plexus. Diagnostic abilities are excellent for structural variables, less so but still good for peripapillary VD, and poor for macular VD.
TL;DR: CircRNAs are involved in DR pathogenesis, and thus serve as potential biomarkers of DR diagnosis, and therefore serve as possible biomarkers in clinical samples.
Abstract: Purpose To reveal the expression profile and clinical significance of circular RNAs (circRNAs) in diabetic retinopathy (DR). Methods Circular RNA microarrays were performed to identify DR-related circRNAs. Gene ontology (GO) enrichment and KEGG analysis was performed to determine the biologic modules and signaling pathway. TargetScan and miRana program was used to predict circRNA/miRNA interaction. Quantitative PCR assays were performed to detect circRNA expression pattern in clinical samples. Ki67 staining, Transwell, tube formation, and spheroid sprouting assays were performed to investigate the role and mechanism of circRNA in endothelial angiogenic function. Results A total of 529 circRNAs were aberrantly expressed in diabetic retinas. The host genes of differentially expressed circRNAs were targeted to ATP binding (biologic process); extracellular exosome (cellular component); and intracellular signal transduction (molecular function). Circ_0005015 was verified to be upregulated in the plasma, vitreous sample, and fibrovascular membranes of DR patients. Circ_0005015 facilitated retinal endothelial angiogenic function via regulating endothelial cell proliferation, migration, and tube formation. Circ_0005015 acted as miR-519d-3p sponge to inhibit miR-519d-3p activity, leading to increased MMP-2, XIAP, and STAT3 expression. Conclusions circRNAs are involved in DR pathogenesis, and thus serve as potential biomarkers of DR diagnosis.
TL;DR: Intermediate AMD eyes of patients with neovascular AMD in the fellow eye have an increased average choriocapillaris signal void size compared to eyes without neov vascular AMD in a fellow eye, which may prove to be a useful parameter for evaluating eyes with AMD.
Abstract: Purpose The purpose of this study was to compare the choriocapillaris plexus in eyes with intermediate AMD (iAMD), with or without neovascular AMD in the fellow eye, using optical coherence tomography angiography (OCTA). Methods We collected data from 42 eyes with iAMD from 42 patients who had obtained OCTA. This cohort was divided into two subgroups according to the status of the fellow eye, yielding a group of 20 cases with bilateral intermediate AMD (bilateral iAMD group) and 22 cases with neovascular AMD in the fellow eye (unilateral iAMD group). An additional control group of 20 eyes from 20 healthy subjects was included for comparison. Main outcome measures were: (1) the percent of nondetectable perfused choriocapillaris area and (2) the average choriocapillaris signal void size. Results No differences in the percent of nondetectable perfused choriocapillaris area were found among the three groups (2.3 ± 1.4% in the unilateral iAMD group, 1.5 ± 0.9% in the bilateral iAMD group, and 1.7 ± 1.4% in the control group, respectively). The average choriocapillaris signal void size, however, was significantly increased in unilateral iAMD eyes (293.7 ± 71.2 μm2) compared to both bilateral iAMD (241.5 ± 51.6 μm2, P = 0.031) and control (212.7 ± 48.6 μm2, P = 0.001) eyes. Conclusions Intermediate AMD eyes of patients with neovascular AMD in the fellow eye have an increased average choriocapillaris signal void size compared to eyes without neovascular AMD in the fellow eye. If replicated in future studies, choriocapillaris signal void size may prove to be a useful parameter for evaluating eyes with AMD.
TL;DR: Novel PAR software may provide improved visualization of all three major parafoveal retinal capillary plexuses including the ICP, and vessel density decreased with increasing age while FAZ area increased with age.
Abstract: Purpose To identify and quantify the three distinct retinal capillary plexuses and the foveal avascular zone (FAZ) in healthy subjects according to age using optical coherence tomography angiography (OCTA) with novel projection artifact removal (PAR) software and improved segmentation. Methods All eyes in this cross-sectional study underwent OCTA imaging using RTVue XR Avanti with novel PAR AngioVue software. OCTA scans were analyzed and the three main parafoveal retinal capillary plexuses were segmented and vessel density and FAZ area were calculated. Results A total of 152 normal eyes from 95 subjects (39 males, 56 females, mean age 42 ± 25 years) were included. The mean vessel density was 15.48 ± 2.04 mm-1 in the superficial retinal capillary plexus (SCP), 15.28 ± 1.82 mm-1 in the intermediate retinal capillary plexus (ICP), and 16.33 ± 2.32 mm-1 in the deep retinal capillary plexus (DCP) for 3 × 3-mm OCTA images. Analysis of 3 × 3-mm scans yielded a mean FAZ area of 0.270 ± 0.101 mm2. The average reduction in vessel density per year of age with 3 × 3-mm OCTA scans was 0.04 mm-1 (0.22%) in the SCP, 0.05 mm-1 (0.27%) in the ICP, and 0.06 mm-1 (0.30%) in the DCP. The average increase in FAZ area per year of age was 0.0015 mm2 (0.72%). Conclusions Novel PAR software may provide improved visualization of all three major parafoveal retinal capillary plexuses including the ICP. Using this technology, SCP, ICP, and DCP vessel density decreased with increasing age while FAZ area increased with age.
TL;DR: A machine learning methodology to predict anti-VEGF treatment needs from OCT scans taken during treatment initiation is proposed and evaluated, an important step toward image-guided prediction of treatment intervals in the management of neovascular AMD.
Abstract: Purpose The purpose of this study was to predict low and high anti-VEGF injection requirements during a pro re nata (PRN) treatment, based on sets of optical coherence tomography (OCT) images acquired during the initiation phase in neovascular AMD. Methods Two-year clinical trial data of subjects receiving PRN ranibizumab according to protocol specified criteria in the HARBOR study after three initial monthly injections were included. OCT images were analyzed at baseline, month 1, and month 2. Quantitative spatio-temporal features computed from automated segmentation of retinal layers and fluid-filled regions were used to describe the macular microstructure. In addition, best-corrected visual acuity and demographic characteristics were included. Patients were grouped into low and high treatment categories based on first and third quartile, respectively. Random forest classification was used to learn and predict treatment categories and was evaluated with cross-validation. Results Of 317 evaluable subjects, 71 patients presented low (≤5), 176 medium, and 70 high (≥16) injection requirements during the PRN maintenance phase from month 3 to month 23. Classification of low and high treatment requirement subgroups demonstrated an area under the receiver operating characteristic curve of 0.7 and 0.77, respectively. The most relevant feature for prediction was subretinal fluid volume in the central 3 mm, with the highest predictive values at month 2. Conclusions We proposed and evaluated a machine learning methodology to predict anti-VEGF treatment needs from OCT scans taken during treatment initiation. The results of this pilot study are an important step toward image-guided prediction of treatment intervals in the management of neovascular AMD.
TL;DR: It is demonstrated that patients with DR have higher levels of both inflammatory cytokines and NTs in their vitreous, and Müller glia could be the potential source of NTs under inflammatory conditions to exert neuroprotection.
Abstract: Purpose To assess vitreous levels of inflammatory cytokines and neurotrophins (NTs) in diabetic retinopathy (DR) and elucidate their potential roles. Methods A prospective study was performed on 50 vitreous samples obtained from patients with DR (n = 22) and the nondiabetic controls (n = 28). All patients were candidates for vitrectomy. Inflammatory cytokine and NT levels were determined with ELISA. Potential source and role of NTs was determined by using human retinal Muller glia and mouse photoreceptor cells and challenging them with TNF-α or IL-1β, followed by detection of NTs and cell death. Results Vitreous NT levels of all DR patients were significantly higher than those of nondiabetic controls (nerve growth factor [NGF, P = 0.0001], brain-derived neurotrophic factor [BDNF, P = 0.009], neurotrophin-3 [NT-3, P < 0.0001], neurotrophin-4 [NT-4, P = 0.0001], ciliary neurotrophic factor [CNTF, P = 0.0001], and glial cell-derived neurotrophic factor [GDNF, P = 0.008]). Similarly, the levels of inflammatory mediators IL-1β (P < 0.0001), IL-6 (P = 0.0005), IL-8 (P < 0.0001), and TNF-α (P < 0.0001) were also higher in eyes with DR. Interestingly, inflammatory cytokine and NT levels, particularly TNF-α (P < 0.05), IL-8 (P < 0.004), NT-3 (P = 0.012), NGF (P = 0.04), GDNF (P = 0.005), and CNTF (P = 0.002), were higher in eyes with nonproliferative diabetic retinopathy (NPDR) than in eyes with active proliferative diabetic retinopathy (PDR). Cytokine stimulation of Muller glia resulted in production of NTs, and GDNF treatment reduced photoreceptor cell death in response to inflammation and oxidative stress. Conclusions Together, our study demonstrated that patients with DR have higher levels of both inflammatory cytokines and NTs in their vitreous. Muller glia could be the potential source of NTs under inflammatory conditions to exert neuroprotection.
TL;DR: The aim of the workshop was to assemble stakeholders from academic and regulatory spheres to discuss clinical data on potential primary and secondary clinical trial endpoints; patient stratification for disease monitoring, interventions, and evaluation of treatment response; and identification of future research avenues.
Abstract: The Association for Research in Vision (ARVO), together with the Foundation Fighting Blindness (FFB), organized the National Eye Institute (NEI)–Food and Drug Administration (FDA) endpoints workshop on age-related macular degeneration (AMD) and inherited retinal diseases (IRD) on November 9, 2016. The public workshop convened basic researchers, clinicians, and regulatory authorities in an interactive forum to discuss the latest clinical findings on AMD and IRD with the goal of optimizing clinical trial design and developing trial endpoints. Specifically, the aim of the workshop was to assemble stakeholders from academic and regulatory spheres to discuss clinical data on potential primary and secondary clinical trial endpoints; patient stratification for disease monitoring, interventions, and evaluation of treatment response; and identification of future research avenues. The workshop was jointly organized by Dr. Frederick Ferris III, MD, Clinical Director at the NEI; Dr. Emily Chew, MD, Deputy Clinical Director at the NEI; Dr. Karl Csaky, MD, PhD, Managing Director and Head of Molecular Ophthalmology Laboratory at the Retina Foundation of the Southwest; Dr. Jacque L. Duncan, MD, Professor of Clinical Ophthalmology at the University of California, San Francisco; and Janet K. Cheetham, PharmD, from the FFB. The workshop format was a series of presentations followed by panel discussions, in which FDA representatives offered regulatory perspectives on potential endpoints for clinical trial design. The following key topics were discussed.
TL;DR: During macular hole closure, the ILM functioned as a scaffold for the proliferation and migration of Müller cells, and may promote Müller cell activation.
Abstract: Purpose To investigate the mechanism of macular hole (MH) closure following the inverted internal limiting membrane (ILM) technique. Methods We performed the inverted ILM flap surgical technique as an experimental MH model in monkeys, and investigated the process of MH closure immunohistochemically. We then investigated the effects of type IV collagen, fibronectin, and laminin, which are constituent proteins of the ILM, on the proliferation and migration of cultivated Muller cells (MIO-M1). We also investigated the expression of neurotrophic factors and basic fibroblast growth factor (bFGF) in human ILM and MIO-M1 cells, and the effect of MIO-M1 migration on the expression of these factors, via immunohistochemical staining and the real-time reverse transcription polymerase chain reaction. Results Ten days after inverted ILM flap surgery, the MH had closed and proliferating glial fibrillary acidic protein (GFAP)-positive cells surrounded the ILM. Type IV collagen, fibronectin, and laminin all enhanced the proliferation of MIO-M1 cells, and type IV collagen and fibronectin enhanced the migration of MIO-M1 cells. Neurotrophic factors and bFGF were present on the surface of the human ILM, and MIO-M1 cells produced these factors. Neurotrophic factors and bFGF were expressed to a significantly greater extent by migrating MIO-M1 cells than by these cells in their static state. Conclusions During MH closure, the ILM functioned as a scaffold for the proliferation and migration of Muller cells, and may promote Muller cell activation. Neurotrophic factors and bFGF produced by activated Muller cells and present on the surface of the ILM may contribute to MH closure.
TL;DR: A comprehensive sequence analysis in a large cohort of German STGD1 patients demonstrates a possible modifying effect of common sequence variants on ABCA4-associated disease and adds to the mutational spectrum of the ABCA 4 gene.
Abstract: Purpose Stargardt disease (STGD1) is an autosomal recessive retinopathy, caused by mutations in the retina-specific ATP-binding cassette transporter (ABCA4) gene. To establish the mutational spectrum and to assess effects of selected deep intronic and common genetic variants on disease, we performed a comprehensive sequence analysis in a large cohort of German STGD1 patients. Methods DNA samples of 335 STGD1 patients were analyzed for ABCA4 mutations in its 50 coding exons and adjacent intronic sequences by resequencing array technology or next generation sequencing (NGS). Parts of intron 30 and 36 were screened by Sanger chain-terminating dideoxynucleotide sequencing. An in vitro splicing assay was used to test selected variants for their splicing behavior. By logistic regression analysis we assessed the association of common ABCA4 alleles while a multivariate logistic regression model calculated a genetic risk score (GRS). Results Our analysis identified 148 pathogenic or likely pathogenic mutations, of which 48 constitute so far unpublished ABCA4-associated disease alleles. Four rare deep intronic variants were found once in 472 alleles analyzed. In addition, we identified six risk-modulating common variants. Genetic risk score estimates suggest that defined common ABCA4 variants influence disease risk in carriers of a single pathogenic ABCA4 allele. Conclusions Our study adds to the mutational spectrum of the ABCA4 gene. Moreover, in our cohort, deep intronic variants in intron 30 and 36 likely play no or only a minor role in disease pathology. Of note, our findings demonstrate a possible modifying effect of common sequence variants on ABCA4-associated disease.
TL;DR: During aging, decreases in retinal vessel density, inner retinal layer thickness, and venular BFV were evident and impacted each other as observed by simultaneous changes in multiple retinal components.
Abstract: Purpose To characterize age-related alterations in the retinal microcirculation, microvascular network, and microstructure in healthy subjects. Methods Seventy-four healthy subjects aged from 18 to 82 years were recruited and divided into four age groups (G1 with age <35 years, G2 with age 35 ∼ 49 years, G3 with age 50 ∼ 64 years, and G4 with age ≥65 years). Custom ultra-high resolution optical coherence tomography (UHR-OCT) was used to acquire six intraretinal layers of the macula. OCT angiography (OCTA) was used to image the retinal microvascular network. The retinal blood flow velocity (BFV) was measured using a Retinal Function Imager (RFI). Results Compared to G1, G2 had significant thinning of the retinal nerve fiber layer (RNFL) (P < 0.05), while G3 had thinning of the RNFL and ganglion cell and inner plexiform layer (GCIPL) (P < 0.05), in addition to thickening of the outer plexiform layer (OPL) and photoreceptor layer (PR) (P < 0.05). G4 had loss in retinal vessel density, thinning in RNFL and GCIPL, and decrease in venular BFV, in addition to thickening of the OPL and PR (P < 0.05). Age was negatively related to retinal vessel densities, the inner retinal layers, and venular BFV (P < 0.05). By contrast, age was positively related to OPL and PR (P < 0.05). Conclusions During aging, decreases in retinal vessel density, inner retinal layer thickness, and venular BFV were evident and impacted each other as observed by simultaneous changes in multiple retinal components.
TL;DR: Proinflammatory cytokines/chemokines play an essential role in the pathogenesis of DR and circulating biomarkers and retinal imaging aimed at assessing inflammation have emerged as useful tools for monitoring the onset and progression of DR.
Abstract: Purpose To review the usefulness of local and systemic inflammatory biomarkers of diabetic retinopathy (DR) to implement a more personalized treatment Methods An integrated research (from ophthalmologist and diabetologist point of view) of most significant literature on serum, vitreous, and aqueous humor (AH) biochemical biomarkers related to inflammation at early and advanced stages of DR (including diabetic macular edema [DME] and proliferative DR) was performed Moreover, novel imaging retinal biomarkers of local "inflammatory condition" were described Results Multiple inflammatory cytokines and chemokines are increased in DR in both serum as well as in the eye (vitreous and AH) Nevertheless, local rather than systemic production of proinflammatory cytokines seems more relevant in the pathogenesis of both DR and DME In the eye, retinal glia cells (macroglia and microglia) together with RPE are major sources of proinflammatory and angiogenic modulators Retinal imaging allows for noninvasive clinical evaluation of retinal inflammatory response induced by diabetes mellitus Conclusions Proinflammatory cytokines/chemokines play an essential role in the pathogenesis of DR Therefore, circulating biomarkers and retinal imaging aimed at assessing inflammation have emerged as useful tools for monitoring the onset and progression of DR In addition, "liquid biopsy" of AH seems a good option in patients with advanced stages of DR requiring intravitreous injections This strategy may permit us to implement a more personalized treatment with better visual function outcome Further evaluation and validation of circulating and local biomarkers, as well as multimodal imaging is needed to gain new insights into this issue
TL;DR: The findings suggest that age and sex collectively shape the conjunctival microbiome, and may change the immune homeostasis of the ocular surface through alterations of its commensal microbiome.
Abstract: Purpose A growing body of evidence suggests that the microbiome of the ocular surface confers potent immunoregulatory functions and has a key role in the physiologic maintenance of healthy eyes and in the pathogenesis of ocular diseases. Although the microbiome is known to be affected by age and sex, the influence of these factors on ocular surface microbiota in healthy adults remains largely unknown. Methods Ocular surface microbiome samples were obtained from the inferior bulbar conjunctiva of 48 young and 42 old adults at Zhongshan Ophthalmic Center. Using metagenomic shotgun sequencing, we characterized the sex- and age-differences in conjunctival microbiome profiles of healthy adults. Results Male and female groups differed only in the β diversity of bacterial communities, while there were significant differences in bacterial composition, metabolic functions, and the abundance of antibiotic resistance genes between young and old adult groups. Conclusions Our findings suggest that age and sex collectively shape the conjunctival microbiome, and may change the immune homeostasis of the ocular surface through alterations of its commensal microbiome.
TL;DR: To the authors' knowledge, this is the first evidence of a glymphatic pathway in the optic nerve, and this pathway may be highly relevant to optic nerve diseases, including glaucoma.
Abstract: Purpose The purpose of this study was to determine whether cerebrospinal fluid (CSF) enters the optic nerve via a glymphatic pathway and whether this entry is size-dependent. Methods Fluorescent dextran tracers (fluorescein isothiocyanate [FITC]) of four different sizes (10, 40, 70, and 500 kDa) and FITC-ovalbumin (45 kDa) were injected into the CSF of 15 adult mice. Tracer distribution in the orbital optic nerve at 1 hour after injection was assessed in tissue sections with confocal microscopy. Tracer distribution within the optic nerve was studied in relation to blood vessels and astrocytes identified by isolectin histochemistry and glial fibrillary acidic protein (GFAP) immunofluorescence, respectively. Aquaporin 4 (AQP4) immunostaining was performed to assess astrocytic endfeet in relation to CSF tracer. Results One hour following tracer injection into CSF, all tracer sizes (10-500 kDa) were noted in the subarachnoid space surrounding the orbital optic nerve. In all cases, 10 kDa (n = 4/4) and 40 kDa (n = 3/3) tracers were noted within the optic nerve, while 70-kDa tracer was occasionally noted (n = 1/4). Tracer found within the nerve was specifically localized between isolectin-labeled blood vessels and GFAP-positive astrocytes or AQP4-labeled astrocytic endfeet. The 500-kDa tracer was not detected within the optic nerve. Conclusions To our knowledge, this is the first evidence of a glymphatic pathway in the optic nerve. CSF enters the optic nerve via spaces surrounding blood vessels, bordered by astrocytic endfeet. CSF entry into paravascular spaces of the optic nerve is size-dependent, and this pathway may be highly relevant to optic nerve diseases, including glaucoma.
TL;DR: The data suggest that sub-RPE deposit formation is initiated, and probably regulated, by the RPE, as well as the loss of permeability of the Bruch's membrane and choriocapillaris complex associated with age and early AMD.
Abstract: PURPOSE: Extracellular deposits containing hydroxyapatite, lipids, proteins, and trace metals that form between the basal lamina of the RPE and the inner collagenous layer of Bruch's membrane are hallmarks of early AMD. We examined whether cultured RPE cells could produce extracellular deposits containing all of these molecular components.
METHODS: Retinal pigment epithelium cells isolated from freshly enucleated porcine eyes were cultured on Transwell membranes for up to 6 months. Deposit composition and structure were characterized using light, fluorescence, and electron microscopy; synchrotron x-ray diffraction and x-ray fluorescence; secondary ion mass spectroscopy; and immunohistochemistry.
RESULTS: Apparently functional primary RPE cells, when cultured on 10-μm-thick inserts with 0.4-μm-diameter pores, can produce sub-RPE deposits that contain hydroxyapatite, lipids, proteins, and trace elements, without outer segment supplementation, by 12 weeks.
CONCLUSIONS: The data suggest that sub-RPE deposit formation is initiated, and probably regulated, by the RPE, as well as the loss of permeability of the Bruch's membrane and choriocapillaris complex associated with age and early AMD. This cell culture model of early AMD lesions provides a novel system for testing new therapeutic interventions against sub-RPE deposit formation, an event occurring well in advance of the onset of vision loss.
TL;DR: On average, automated SS-OCTA measurements were larger than SD-O CTA measurements and consistent with the results from using hand-drawn measurements, which were in agreement with the hand- drawn measurements.
Abstract: Purpose To compare the lesion sizes of choroidal neovascularization (CNV) imaged with spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) and measured using an automated detection algorithm. Methods Patients diagnosed with CNV were imaged by SD-OCTA and SS-OCTA systems using 3 × 3-mm and 6 × 6-mm scans. The complex optical microangiography (OMAGC) algorithm was used to generate the OCTA images. Optical coherence tomography A datasets for imaging CNV were derived by segmenting from the outer retina to 8 μm below Bruch's membrane. An artifact removal algorithm was used to generate angiograms free of retinal vessel projection artifacts. An automated detection algorithm was developed to quantify the size of the CNV. Automated measurements were compared with manual measurements. Measurements from SD-OCTA and SS-OCTA instruments were compared as well. Results Twenty-seven eyes from 23 subjects diagnosed with CNV were analyzed. No significant differences were detected between manual and automatic measurements: SD-OCTA 3 × 3-mm (P = 0.61, paired t-test) and 6 × 6-mm (P = 0.09, paired t-test) scans and the SS-OCTA 3 × 3-mm (P = 0.41, paired t-test) and 6 × 6-mm (P = 0.16, paired t-test) scans. Bland-Altman analyses were performed to confirm the agreement between automatic and manual measurements. Mean lesion sizes were significantly larger for the SS-OCTA images compared with the SD-OCTA images: 3 × 3-mm scans (P = 0.011, paired sample t-test) and the 6 × 6-mm scans (P = 0.021, paired t-test). Conclusions The automated algorithm measurements of CNV were in agreement with the hand-drawn measurements. On average, automated SS-OCTA measurements were larger than SD-OCTA measurements and consistent with the results from using hand-drawn measurements.
TL;DR: The predictive model proposed in this study represents a promising step toward image-guided prediction of AMD progression and is expected to accelerate and contribute to the development of new therapeutics that delay the progression of AMD.
Abstract: Purpose To develop a data-driven interpretable predictive model of incoming drusen regression as a sign of disease activity and identify optical coherence tomography (OCT) biomarkers associated with its risk in intermediate age-related macular degeneration (AMD). Methods Patients with AMD were observed every 3 months, using Spectralis OCT imaging, for a minimum duration of 12 months and up to a period of 60 months. Segmentation of drusen and the overlying layers was obtained using a graph-theoretic method, and the hyperreflective foci were segmented using a voxel classification method. Automated image analysis steps were then applied to identify and characterize individual drusen at baseline, and their development was monitored at every follow-up visit. Finally, a machine learning method based on a sparse Cox proportional hazard regression was developed to estimate a risk score and predict the incoming regression of individual drusen. Results The predictive model was trained and evaluated on a longitudinal dataset of 61 eyes from 38 patients using cross-validation. The mean follow-up time was 37.8 ± 13.8 months. A total of 944 drusen were identified at baseline, out of which 249 (26%) regressed during follow-up. The prediction performance was evaluated as area under the curve (AUC) for different time periods. Prediction within the first 2 years achieved an AUC of 0.75. Conclusions The predictive model proposed in this study represents a promising step toward image-guided prediction of AMD progression. Machine learning is expected to accelerate and contribute to the development of new therapeutics that delay the progression of AMD.
TL;DR: A machine learning system capable of automatically grading OCT scans into AMD severity stages was developed and showed similar performance as human observers, which could increase the efficiency of large-scale AMD studies and pave the way for AMD screening using OCT.
Abstract: Purpose: To evaluate a machine learning algorithm that automatically grades age-related macular degeneration (AMD) severity stages from optical coherence tomography (OCT) scans. Methods: A total of 3265 OCT scans from 1016 patients with either no signs of AMD or with signs of early, intermediate, or advanced AMD were randomly selected from a large European multicenter database. A machine learning system was developed to automatically grade unseen OCT scans into different AMD severity stages without requiring retinal layer segmentation. The ability of the system to identify high-risk AMD stages and to assign the correct severity stage was determined by using receiver operator characteristic (ROC) analysis and Cohen's kappa statistics (kappa), respectively. The results were compared to those of two human observers. Reproducibility was assessed in an independent, publicly available data set of 384 OCT scans. Results: The system achieved an area under the ROC curve of 0.980 with a sensitivity of 98.2% at a specificity of 91.2%. This compares favorably with the performance of human observers who achieved sensitivities of 97.0% and 99.4% at specificities of 89.7% and 87.2%, respectively. A good level of agreement with the reference was obtained (kappa = 0.713) and was in concordance with the human observers (kappa = 0.775 and kappa = 0.755, respectively). Conclusions: A machine learning system capable of automatically grading OCT scans into AMD severity stages was developed and showed similar performance as human observers. The proposed automatic system allows for a quick and reliable grading of large quantities of OCT scans, which could increase the efficiency of large-scale AMD studies and pave the way for AMD screening using OCT.
TL;DR: This study provided the first evidence of TSG-6 secreted by MSCs promoting corneal epithelial wound healing in diabetic mice through activating cornean epithelial stem/progenitor cells and accelerating M2 macrophage polarization.
Abstract: Purpose To explore the role and mechanism of bone marrow-derived mesenchymal stem cells (BM-MSCs) in corneal epithelial wound healing in type 1 diabetic mice. Methods Diabetic mice were treated with subconjunctival injections of BM-MSCs or recombinant tumor necrosis factor-α-stimulated gene/protein-6 (TSG-6). The corneal epithelial wound healing rate was examined by fluorescein staining. The mRNA and protein expression levels of TSG-6 were measured by quantitative RT-PCR and Western blot. The infiltrations of leukocytes and macrophages were analyzed by flow cytometry and immunofluoresence staining. The effect of TSG-6 was further evaluated in cultured limbal epithelial stem/progenitor cells, macrophages, and diabetic mice by short hairpin RNA (shRNA) knockdown. Results Local MSC transplantation significantly promoted diabetic corneal epithelial wound healing, accompanied by elevated corneal TSG-6 expression, increased corneal epithelial cell proliferation, and attenuated inflammatory response. Moreover, in cultured human limbal epithelial stem/progenitor cells, TSG-6 enhanced the colony-forming efficiency, stimulated mitogenic proliferation, and upregulated the expression level of ΔNp63. Furthermore, in diabetic mouse cornea and in vitro macrophage culture, TSG-6 alleviated leukocyte infiltration and promoted the polarization of recruited macrophages to anti-inflammatory M2 phenotypes with increased phagocytotic capacity. In addition, the promotion of epithelial stem/progenitor cell activation and macrophage polarization by MSC transplantation was largely abrogated by shRNA knockdown of TSG-6. Conclusions This study provided the first evidence of TSG-6 secreted by MSCs promoting corneal epithelial wound healing in diabetic mice through activating corneal epithelial stem/progenitor cells and accelerating M2 macrophage polarization.
TL;DR: The relationships between CNFA and other clinical measures of disease support its use as a surrogate endpoints for disease modification, pain severity, and functional capacity to assess potential disease modifying therapies for neuropathy.
Abstract: Purpose Sarcoidosis frequently is complicated by small nerve fiber loss (SNFL), which can be quantified using corneal confocal microscopy (CCM). Prior studies suggest that the innate repair receptor agonist cibinetide reverses corneal nerve loss. This phase 2b, 28-day, randomized trial of 64 subjects with sarcoid-associated SNFL and neuropathic pain assessed the effect of cibinetide on corneal nerve fiber area (CNFA) and regenerating intraepidermal fibers (GAP-43+) as surrogate endpoints for disease modification, pain severity, and functional capacity (6-minute walk test [6MWT]). Methods Cibinetide (1, 4, or 8 mg/day) was compared to placebo. The primary study endpoint was a change in CNFA at 28 days. Results The placebo-corrected mean change from baseline CNFA (μm2) at day 28 was 109 (95% confidence interval [CI], -429, 647), 697 (159, 1236; P = 0.012), and 431 (-130, 992) in the 1, 4, and 8 mg groups, respectively. Intraepidermal GAP-43+ fibers increased in the 4 mg group (P = 0.035). Further, changes in CNFA correlated with changes in GAP-43+ (ρ = 0.575; P = 0.025) and 6MWT (ρ = 0.645; P = 0.009). Pain improved significantly in all groups, with subjects having moderate-severe pain reporting a clinically meaningful placebo-corrected decrease in pain intensity in the 4 mg group (P = 0.157). Conclusions Cibinetide significantly increased small nerve fiber abundance in the cornea and skin, consistent with a disease modifying effect. The relationships between CNFA and other clinical measures of disease support its use as a surrogate endpoint to assess potential disease modifying therapies for neuropathy.
TL;DR: Fractal dimension based on OCT-A has the potential to quantitatively characterize retinal microvascular changes in the early stage of DM and could be an early indicator of microvasculature changes associated with retinopathy in type 2 diabetic patients.
Abstract: Purpose To determine the ability of fractal dimension to detect early changes in the retinal microvascular network imaged by optical coherence tomography angiography (OCT-A) in type 2 diabetic patients. Methods Sixty-seven patients with type 2 diabetic mellitus (DM) (48 with no diabetic retinopathy [DR], 19 with minimal DR) and 40 control subjects. Macular OCT-A images of the superficial and deep retinal capillary layers in a 2.5-mm diameter concentric annular zone (excluding the foveal avascular zone) were subdivided into six annular rings and four quadrants. A custom automated algorithm was developed to quantify the complexity and density of the two retinal capillary layers by fractal analysis. Results Compared to controls, the fractal dimensional parameter (Dbox) of the two retinal capillary layers in most regions was significantly lower in diabetic patients with minimal DR (P 0.05). Based on the receiver operating characteristic curve analysis, the Dbox values for the deep retinal capillary layer had the highest index to discriminate diabetic patients with and without minimal DR from controls. Conclusions Fractal dimension based on OCT-A has the potential to quantitatively characterize retinal microvascular changes in the early stage of DM. Changes in the fractal dimension in the deep retinal capillary layer could be an early indicator of microvasculature changes associated with retinopathy in type 2 diabetic patients.