Imaging evidence of diabetic choroidopathy in vivo: angiographic pathoanatomy and choroidal-enhanced depth imaging

Diabetic uveopathy

Diabetes can involve several ocular structures -- including the cornea, lens, and retina -- and cause vascular and neural changes in these tissues. Although retinopathy is the most common ocular complication of diabetes, uveopathy can also be observed. This includes vascular, neural, muscular, and basement membrane changes. The main clinical manifestations of diabetic uveopathy are anterior uveitis and abnormal pupillary dynamics. Fluorescein angiography, optical coherence tomography, and optical coherence tomography angiography are ideal for the imaging of vascular changes of the iris and choroid, while dynamic pupillometry is a simple screening tool to detect neuropathy. Additionally, ultrasound biomicroscopy can provide clear images of the ciliary body. Iris abnormalities, primarily angiopathy and neuropathy, can appear as alterations in vascular diameter, neovascularization, and abnormal pupillary dynamics. Choroidal abnormalities primarily affect blood vessels, including alterations in vascular diameter, microaneurysm formation, and neovascularization. The abnormal manifestations in the ciliary body include a decrease in vessel count, alterations in their diameter, isolated angiomatous dilatation, and diffuse thickening of the basal membrane of the pigment epithelium.

Evaluation of Choroidal Structures in Children with Newly Diagnosed Type-1 Diabetes Mellitus

Objectives

The objective of this study was to evaluate the subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) in children with newly diagnosed type 1 diabetes mellitus (T1DM).

Methods

A total of 80 children (40 with T1DM and 40 healthy controls) were included in this cross-sectional study. Enhanced depth imaging optical coherence tomography (EDI-OCT) images of all participants were analyzed. The SFCT, total choroidal area (TCA), luminal area (LA), stromal area (SA), and CVI measurements were obtained from EDI-OCT images and compared between groups. The effects of HbA1c, fasting plasma glucose, and axial length measurements on choroidal measurements were investigated.

Results

There was no significant difference between the groups according to TCA (0.84 [0.57-1.26] vs. 0.88 [0.65-1.16] mm2, p=0.745), LA (0.55 [0.41-0.79] vs. 0.59 [0.43-0.74] mm2, p=0.745), SA (0.27 [0.15-0.47] vs. 0.28 [0.15-0.47] mm2, p=0.935), and CVI (68.03 [66.5-70.5] vs. 67.75 [66.2-69.5] %, p=0.794), respectively. However, T1DM patients had thinner SFCT compared to control subjects (309.0 [327-489] and 398.5 [219-491], p<0.044). No correlation was found between HbA1c, fasting plasma glucose, axial length measurements, and SFCT, TCA, LA, SA, or CVI.

Conclusion

Children with newly diagnosed T1DM have thinner SCFT in comparison to healthy children, however, no significant difference in CVI was observed between the groups. Long-term follow-up should be used to confirm the impact of the DM duration on CVI.

Optical coherence tomography angiography of the retina and choroid in systemic diseases

Optical coherence tomography angiography (OCTA) has transformed ocular vascular imaging, revealing microvascular changes linked to various systemic diseases. This review explores its applications in diabetes, hypertension, cardiovascular diseases, and neurodegenerative diseases. While OCTA provides a valuable window into the body's microvasculature, interpreting the findings can be complex. Additionally, challenges exist due to the relative non-specificity of its findings where changes observed in OCTA might not be unique to a specific disease, variations between OCTA machines, the lack of a standardized normative database for comparison, and potential image artifacts. Despite these limitations, OCTA holds immense potential for the future. The review highlights promising advancements like quantitative analysis of OCTA images, integration of artificial intelligence for faster and more accurate interpretation, and multi-modal imaging combining OCTA with other techniques for a more comprehensive characterization of the ocular vasculature. Furthermore, OCTA's potential future role in personalized medicine, enabling tailored treatment plans based on individual OCTA findings, community screening programs for early disease detection, and longitudinal studies tracking disease progression over time is also discussed. In conclusion, OCTA presents a significant opportunity to improve our understanding and management of systemic diseases. Addressing current limitations and pursuing these exciting future directions can solidify OCTA as an indispensable tool for diagnosis, monitoring disease progression, and potentially guiding treatment decisions across various systemic health conditions.

Short-term Effects of Intravitreal Dexamethasone Implant on Choroidal Structure in Eyes with Refractory Diabetic Macular Edema

Objectives

The objective of the study was to evaluate choroidal structural changes after intravitreal dexamethasone implant (IDI) in eyes with diabetic macular edema (DME) refractory to antivascular endothelial growth factor (VEGF) therapy.

Methods

Twenty-three eyes of 14 patients with DME refractory to anti-VEGF therapy were included in this retrospective study. Detailed ophthalmological examinations were recorded, and optical coherence tomography images were obtained before and 3 months after IDI. Choroidal images were binarized into the luminal area and total choroidal area. Subfoveal choroidal thickness and choroidal vascularity index (CVI) were calculated.

Results

The mean best-corrected visual acuity (BCVA) and central macular thickness (CMT) were improved significantly (from 0.94 to 0.81 LogMAR, p=0.02, and from 464 to 371 μ, p=0.01, respectively) after IDI. There were no significant changes in both SCFT and CVI at the end of the follow-up period (from 446.3 to 428.8 μ, p=0.51 and from 63.1 to 63.7 p=0.35, respectively).

Conclusion

IDI in eyes with DME refractory to anti-VEGF therapy improves BCVA and CMT but has no significant effect on SCFT and CVI in the short term.

The Role of Diabetic Choroidopathy in the Pathogenesis and Progression of Diabetic Retinopathy

Diabetic choroidopathy was first described on histopathological specimens of diabetic eyes. This alteration was characterized by the accumulation of PAS-positive material within the intracapillary stroma. Inflammation and polymorphonuclear neutrophils (PMNs) activation are crucial elements in choriocapillaris impairment. The evidence of diabetic choroidopathy in vivo was confirmed with multimodal imaging, which provides key quantitative and qualitative features to characterize the choroidal involvement. The choroid can be virtually affected in each vascular layer, from Haller's layer to the choriocapillaris. However, the damage on the outer retina and photoreceptor cells is essentially driven by a choriocapillaris deficiency, which can be assessed through optical coherence tomography angiography (OCTA). The identification of characteristic features of diabetic choroidopathy can be significant for understanding the potential pathogenic and prognostic implications in diabetic retinopathy.

Pathological Neurovascular Unit Mapping onto Multimodal Imaging in Diabetic Macular Edema

Diabetic retinopathy is a form of diabetic microangiopathy, and vascular hyperpermeability in the macula leads to retinal thickening and concomitant reduction of visual acuity in diabetic macular edema (DME). In this review, we discuss multimodal fundus imaging, comparing the pathogenesis and interventions. Clinicians diagnose DME using two major criteria, clinically significant macular edema by fundus examination and center-involving diabetic macular edema using optical coherence tomography (OCT), to determine the appropriate treatment. In addition to fundus photography, fluorescein angiography (FA) is a classical modality to evaluate morphological and functional changes in retinal capillaries, e.g., microaneurysms, capillary nonperfusion, and fluorescein leakage. Recently, optical coherence tomography angiography (OCTA) has allowed us to evaluate the three-dimensional structure of the retinal vasculature and newly demonstrated that lamellar capillary nonperfusion in the deep layer is associated with retinal edema. The clinical application of OCT has accelerated our understanding of various neuronal damages in DME. Retinal thickness measured by OCT enables us to quantitatively assess therapeutic effects. Sectional OCT images depict the deformation of neural tissues, e.g., cystoid macular edema, serous retinal detachment, and sponge-like retinal swelling. The disorganization of retinal inner layers (DRIL) and foveal photoreceptor damage, biomarkers of neurodegeneration, are associated with visual impairment. Fundus autofluorescence derives from the retinal pigment epithelium (RPE) and its qualitative and quantitative changes suggest that the RPE damage contributes to the neuronal changes in DME. These clinical findings on multimodal imaging help to elucidate the pathology in the neurovascular units and lead to the next generation of clinical and translational research in DME.

Advances in application of swept-source optical coherence tomography angiography in diagnosis and treatment of diabetic retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of global blinding. More attention should be paid to the diagnosis, treatment and prognosis of DR. Swept-source optical coherence tomography angiography (SS-OCTA) is a novel imaging technique presented in recent years. It can accurately present the various levels of the retina, choriocapillaris, macula, and the optic papillary microcirculation, which is new to the diagnosis and prognosis of DR. However, SS-OCTA is limited by poor fixation or severe media clouding and is susceptible to motion artefacts and segmentation errors. Future limitations need to be addressed and large prospective trials conducted to refine the relevance of SS-OCTA to DR. The present study reviews the advances in clinical application of SS-OCTA in diagnosis, treatment and prognosis of DR.

Rates of Choroidal and Neurodegenerative Changes Over Time in Diabetic Patients Without Retinopathy: A 3-Year Prospective Study

PURPOSE

To evaluate the longitudinal changes of retinal neurodegeneration and choroidal thickness in diabetic patients with and without diabetic retinopathy (DR).

DESIGN

Prospective observational cohort study.

METHODS

This prospective observational cohort study recruited type 2 diabetic patients from a community registry in Guangzhou. All participants underwent annual ocular examinations via swept-source optical coherence tomography that obtained choroid thickness (CT), retinal thickness (RT), and ganglion cell-inner plexiform layer (GC-IPL) thickness. The changes in GC-IPL, CT, and RT between patients who developed incident DR (IDR) or remained non-DR (NDR) were compared during a 3-year follow-up.

RESULTS

Among 924 patients, 159 (17.2%) patients developed IDR within the 3-year follow-up. A reduction in GC-IPL, RT, and CT was observed in NDR and IDR; however, CT thinning in patients with IDR was significantly accelerated, with an average CT reduction of -6.98 (95% CI: -8.26, -5.71) μm/y in patients with IDR and -3.98 (95% CI: -4.60, -3.36) μm/y in NDR patients (P < .001). Reductions in average GC-IPL thickness over 3 years were -0.97 (95% CI: -1.24, -0.70) μm/y in patients with IDR and -0.76 (95% CI: -0.82, -0.70) μm/y in NDR patients (P = .025). After adjusting for confounding factors, the average CT and GC-IPL thinning were significantly faster in patients with IDR compared with those who remained NDR by 2.09 μm/y (95% CI: 1.01, 3.16; P = .004) and -0.29 μm/y (95% CI: -0.49, -0.09; P = .004), respectively. The RT in the IDR group increased, whereas the RT in the NDR group decreased over time, with the adjusted difference of 2.09 μm/y (95% CI: 1.01, 3.16; P < .001) for central field RT.

CONCLUSIONS

The rate of retinal neurodegeneration and CT thinning were significantly different between the eyes that developed IDR and remained NDR during the 3-year follow-up, but both groups observed thickness reduction. This indicates that GC-IPL and CTs may decrease before the clinical manifestations of DR.

Parapapillary Choroidal Microvasculature Predicts Diabetic Retinopathy Progression and Diabetic Macular Edema Development: A Three-Year Prospective Study

PURPOSE

To determine the predictive value of the microcirculation of the optic nerve head by swept-source optical coherence tomography angiography for identifying individuals with high risk of diabetic retinopathy (DR) progression and diabetic macular edema (DME) development.

DESIGN

Prospective observational cohort study.

METHODS

A total of 946 patients (1879 eyes) with type 2 diabetes mellitus were recruited who had no DR or mild nonproliferative DR at baseline, and no DME. All subjects underwent 3 × 3 mm swept-source optical coherence tomography angiography centered on the optic nerve head to generate angiograms in 4 layers: radial peripapillary plexus, superficial retinal capillary plexus (SCP), deep retinal capillary plexus, and choriocapillaris (CC). The CC flow deficit percentage (CC FD%), vessel density (VD), and perfusion density (PD) were quantified.

RESULTS

During the 3 consecutive years of follow-up, 312 eyes (16.60%) experienced DR progression and 115 eyes (6.12%) developed DME. The DR progression was related to a lower VD of the SCP (relative risk per standard deviation decrease, 95% confidence interval): 1.30, 1.14-1.48; P < .001), a lower PD of the SCP (1.41, 1.24-1.60; P < .001), a lower VD of the radial peripapillary plexus (1.23, 1.08-1.40; P = .002), and an elevated CC FD% (1.62, 1.40-1.88; P < .001). The DME occurrence was associated with a lower VD of SCP (1.35, 1.09-1.66; P = .005), a lower PD of SCP (1.29, 1.05-1.59; P = .016), and a higher CC FD% (1.29, 1.03-1.61; P < .001). The CC FD% significantly improved the predictive power, with the increase of the C-statistic for DR progression and DME occurrence by 3.83% (P = .002) and 5.24% (P < .001), respectively.

CONCLUSIONS

This study provides the first longitudinal evidence suggesting that peripapillary CC FD% can improve the prediction of DR progression and DME development beyond traditional risk factors.

Influence of Intravitreal Therapy on Choroidal Thickness in Patients with Diabetic Macular Edema

OBJECTIVE

This study aimed to analyze the variation in subfoveal choroidal thickness (SFCT) and its relationship with the variation in central macular thickness (CME) in response to intravitreal therapy with an antiangiogenic (anti-VEGF) drug or corticosteroid in type 2 diabetic patients with diabetic macular edema (DME).

MATERIAL AND METHODS

This retrospective study included 70 eyes of 35 patients: 26 eyes received 4-5 intravitreal injections of aflibercept, 26 eyes were treated with a single intravitreal implant injection of dexamethasone, and 18 eyes without DME did not receive intravitreal therapy. SPECTRALIS® optical coherence tomography (OCT) (Heidelberg Engineering, Heidelberg, Germany) was used to measure the SFCT and CME before and at the end of the follow-up period.

RESULTS

The mean reductions in CME were 18.8 +/- 14.7% (aflibercept) and 29.7 +/- 16.9% (dexamethasone). The mean reductions in SFCT were 13.8 +/- 13.1% (aflibercept) and 19.5 +/- 9.6% (dexamethasone). The lowering effects of both parameters were significantly greater in the group treated with the dexamethasone implant (p = 0.022 and p = 0.046 for CMT and SFCT, respectively). Both therapies significantly decreased both CME and SFCT, independent of factors such as age, sex, previous intravitreal therapy, antidiabetic treatment, and the time of diabetes progression. There were no changes in the mean values of CME and SFCT in the untreated eyes.

CONCLUSIONS

SFCT significantly decreased in response to intravitreal therapy with anti-VEGF or corticosteroids, irrespective of age, sex, previous intravitreal therapy, antidiabetic treatment, and the time of diabetes progression. There was a correlation between the changes in CME and SFCT after intravitreal therapy with aflibercept or dexamethasone implantation. SFCT was not a good predictor of the CME response but could be used to monitor the response to treatment. Local intravitreal therapy only affected the treated eye.

Imaging-based Assessment of Choriocapillaris: A Comprehensive Review

PURPOSE

Over the past two decades, advancements in imaging modalities have significantly evolved the diagnosis and management of retinal diseases. Through these novel platforms, we have developed a deeper understanding of the anatomy of the choroidal vasculature and the choriocapillaris. The recently developed tools such as optical coherence tomography (OCT) and OCT angiography (OCTA) have helped elucidate the pathological mechanisms of several posterior segment diseases. In this review, we have explained the anatomy of the choriocapillaris and its close relationship to the outer retina and retinal pigment epithelium.

METHODS

A comprehensive search of medical literature was performed through the Medline/PubMed database using search terms: choriocapillaris, choroid, quantification, biomarkers, diabetic retinopathy, age-related macular degeneration, choroidal blood flow, mean blur rate, flow deficit, optical coherence tomography, optical coherence tomography angiography, fluorescein angiography, indocyanine green angiography, OCTA, Doppler imaging, uveitis, choroiditis, white dot syndrome, tubercular serpiginous-like choroiditis, choroidal granuloma, pachychoroid, toxoplasmosis, central serous chorioretinopathy, multifocal choroiditis, choroidal neovascularization, choroidal thickness, choroidal vascularity index, choroidal vascular density, and choroidal blood supply. The search terms were used either independently or combined with choriocapillaris/choroid.

RESULTS

The imaging techniques which are used to qualitatively and quantitatively analyze choriocapillaris are described. The pathological alterations in the choriocapillaris in an array of conditions such as diabetes mellitus, age-related macular degeneration, pachychoroid spectrum of diseases, and inflammatory disorders have been comprehensively reviewed. The future directions in the study of choriocapillaris have also been discussed.

CONCLUSION

The development of imaging tools such as OCT and OCTA has dramatically improved the assessment of choriocapillaris in health and disease. The choriocapillaris can be delineated from the stromal choroid using the OCT and quantified by manual or automated methods. However, these techniques have inherent limitations due to the lack of an anatomical distinction between the choriocapillaris and the stromal choroid, which can be overcome with the use of predefined segmentation slabs on OCT and OCTA. These segmentation slabs help in standardizing the choriocapillaris imaging and obtain repeatable measurements in various conditions such as diabetic retinopathy, age-related macular degeneration, pachychoroid spectrum, and ocular inflammations. Additionally, Doppler imaging has also been effectively used to evaluate the choroidal blood flow and quantifying the choriocapillaris and establishing its role in the pathogenesis of various retinochoroidal diseases. As tremendous technological advancements such as wide-field and ultra-wide field imaging take place, there will be a significant improvement in the ease and accuracy of quantifying the choriocapillaris.

Choroidal Assessment in Patients with Type 2 Diabetes Mellitus and Non-Proliferative Diabetic Retinopathy by Swept-Source Ocular Coherence Tomography and Image Binarization

Background and Objectives: The aim of this study was to evaluate choroidal structure and vascularity indices in patients with non-proliferative diabetic retinopathy (NPDR). Materials and Methods: Sixty-three eyes from sixty-three patients were evaluated: 21 from healthy subjects, 20 with diabetes mellitus (DM) and no diabetic retinopathy (DR), and 22 with DM and non-proliferative diabetic retinopathy without diabetic macular edema (DME). Each patient underwent ocular examination, macular swept-source ocular coherence tomography (SS-OCT) imaging, glycemic control, and systemic high blood pressure (HBP) evaluation. Subfoveal choroidal thickness (SF-CT) was manually assessed on a line scan. Line scan OCT images were exported to ImageJ program. The areas under a 1.5, 3 and 6 mm horizontal line centered on the fovea were assessed by converting the OCT images to binary images, and total choroidal area (TCA), luminal area (LA), stromal area (SA), LA:SA ratio, and choroidal vascularity index (CVI) were evaluated. SF-CT and choroidal parameters were compared between groups, and correlations with ocular and systemic factors were analyzed. Results: SF-CT, TCA, LA, and SA were similar between groups. CVIs were significantly different between groups for all three studied areas (CVI-1.5: 66.21% vs. 66.06% vs. 63.74%, p = 0.003; CVI-3: 65.88% vs. 66.46% vs. 63.79%, p = 0.008; CVI-6: 64.79% vs. 65.40% vs. 63.61%, p = 0.032). NPDR patients had significantly lower CVIs compared to DM patients (p < 0.05). No association of choroidal parameters with glycemic control, DM duration and HBP was found significant (p < 0.05). Conclusions: Choroidal assessment by SS-OCT and image binarization in healthy subjects, subjects with DM without DR, and subjects with DM and NPDR indicated that CVI changes were identifiable and significant in early DR. The lack of association with ocular and systemic factors suggest that CVIs are reliable assessment parameters of choroidal vascular structure.

Diabetic macular ischaemia- a new therapeutic target?

Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.

Retinal Vascularization Abnormalities Studied by Optical Coherence Tomography Angiography (OCTA) in Type 2 Diabetic Patients with Moderate Diabetic Retinopathy

Diabetic retinopathy (DR) is the most severe and frequent retinal vascular disease that causes significant visual loss on a global scale. The purpose of our study was to evaluate retinal vascularization in the superficial capillary plexus (SCP), the deep capillary plexus (DCP) and the choriocapillaris (CC) and changes in the foveal avascular zone (FAZ) by optical tomography angiography (OCTA) in patients with type 2 diabetes mellitus (DM2) with moderate DR but without diabetic macular oedema (DME). Fifty-four eyes of DM2 with moderate DR (level 43 in the ETDRS scale) and without DME and 73 age-matched healthy eyes were evaluated using OCTA with swept-source (SS)-OCT to measure microvascularization changes in SCP, DCP, CC and the FAZ. The mean ages were 64.06 ± 11.98 and 60.79 ± 8.62 years in the DM2 and control groups, respectively. Visual acuity (VA) was lower in the DM2 patients (p = 0.001), OCTA showed changes in the SCP with a significant diminution in the vascular density and the FAZ area was significantly higher compared to healthy controls, with p < 0.001 at the SCP level. The most prevalent anatomical alterations were peripheral disruption in the SCP (83.3%), microaneurysms (MA) in the SCP and in the DCP (79.6% and 79.6%, respectively) and flow changes in the DCP (81.5%). A significant positive correlation was observed between the DM2 duration and the FAZ area in the SCP (0.304 with p = 0.025). A significant negative correlation was also found between age and CC central perfusion (p < 0.001). In summary, a decrease in the vascular density in DM2 patients with moderate DR without DME was observed, especially at the retinal SPC level. Furthermore, it was found that the FAZ was increased in the DM2 group in both retinal plexuses and was greater in the SCP group.

The role of inflammation and neurodegeneration in diabetic macular edema

The pathogenesis of diabetic macular edema (DME) is complex. Persistently high blood glucose activates multiple cellular pathways and induces inflammation, oxidation stress, and vascular dysfunction. Retinal ganglion cells, macroglial and microglial cells, endothelial cells, pericytes, and retinal pigment epithelium cells are involved. Neurodegeneration, characterized by dysfunction or apoptotic loss of retinal neurons, occurs early and independently from the vascular alterations. Despite the increasing knowledge on the pathways involved in DME, only limited therapeutic strategies are available. Besides antiangiogenic drugs and intravitreal corticosteroids, alternative therapeutic options tackling inflammation, oxidative stress, and neurodegeneration have been considered, but none of them has been currently approved.

Latent Diabetic Macular Edema in Chinese Diabetic Retinopathy Patients

Purpose: To compare the detection rates of optical coherence tomography (OCT) and fluorescein angiography (FA) in a diabetic macular edema (DME) and the severity of diabetic retinopathy in both color fundus images (CFI) and FA, and to investigate the predictive factors in macular leakages in FA.

Methods: This was a retrospective study, and a total of 132 eyes of 77 patients with diabetic retinopathy were enrolled. Macular OCT, FA, and CFI were reviewed and measured. Central foveal thickness was also measured.

Results: The severity of diabetic retinopathy in FA was significantly higher than that in CFI (p < 0.001). OCT detected 26 eyes with DMEs, which included the following: 13 eyes with cystoid macular edemas; 13 eyes with serous retinal detachments; 11 eyes with diffuse retinal thickening; 4 eyes with vitreomacular interface abnormalities. In contrast, 72 out of 132 eyes (54.5%) showed macular leakages in FA, which was significantly higher than that detected by OCT (p < 0.001). Compared with FA, the sensitivity and the specificity of OCT in detecting DMEs were 30.6 and 93.3%, respectively. However, central foveal thickness was not significantly different between the patients with non-clinically significant macular edema (CSME, 253.1 ± 26.95 μm) and slight CSME (270.9 ± 37.11 μm, p = 0.204). The mean central foveal thickness in diabetic macular edema (FA) eyes was 271.8 ± 66.02 μm, which was significantly higher than that (253. ± 25.21 μm) in non-DME (FA) eyes (p = 0.039). The central foveal thickness in DME (FA) eyes was significantly lower than that in eyes with DME (OCT) (p = 0.014). After adjusting for age and sex, a logistic regression analysis showed that the classification of diabetic retinopathy in FA was positively associated with macular leakage in FA (p < 0.001).

Conclusions: The severity of diabetic retinopathy is underestimated in CFI compared with that in FA. FA can detect latent DMEs, which appeared normal on OCT. The central foveal thickness is not a sensitive parameter for detecting latent DMEs.

Choroidal vascular structures in diabetic patients: a meta-analysis

PURPOSE

Choroidal vascular structures are likely to be affected in diabetic patients. The aim of this study was to conduct a meta-analysis of choroidal vascular structures in diabetic eyes with no diabetic retinopathy (NDR) and healthy control eyes, which was systematically evaluated by various factors involving the measurements.

METHODS

This study identified clinical data from publications in PubMed and web of science until May 2020. Independent retrospective or prospective clinical studies comparing NDR and healthy control eyes regarding choroidal vascular structures were extracted. Five related studies were enrolled, cumulating in a total of 282 diabetic eyes and 511 control eyes examined in this study. Heterogeneity was statistically quantified by I2 statistics, and meta-analysis was performed using a random effects model. This study included 2 different algorisms of binarization determining the ratio of luminal areas in total choroidal areas, both of which were consolidated and called "choroidal vascular ratio."

RESULTS

Meta-analysis clearly showed that the choroidal vascular ratio was significantly lower in NDR eyes than in healthy control eyes (weighted mean difference =  - 2.16; 95%CI: - 3.19 to - 1.13; P < 0.005). Similar results were obtained in sub-analysis based on adjustment of serum HbA1c levels and duration of diabetes.

CONCLUSIONS

The choroidal vascular ratio of NDR eyes was significantly lower than that of healthy control eyes. The ratio might contribute to a better understanding of the pathophysiology involved in the development of diabetic retinopathy, although there was some heterogeneity in primary analysis studies.

Photoreceptor cells and RPE contribute to the development of diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.

CHANGES IN SUBFOVEAL CHOROIDAL THICKNESS AFTER INTRAVITREAL DEXAMETHASONE IMPLANT THERAPY FOR DIABETIC MACULAR EDEMA

PURPOSE

To investigate changes in subfoveal choroidal thickness (SFCT) and their relationship with best-corrected visual acuity and optical coherence tomography parameters after intravitreal dexamethasone implant injection for diabetic macular edema.

METHODS

Eighty-one eyes treated with dexamethasone implant injection for diabetic macular edema were evaluated for best-corrected visual acuity, central macular thickness, SFCT, and optical coherence tomography parameters at baseline and Weeks 7 and 14.

RESULTS

The mean baseline SFCT significantly decreased at Weeks 7 (P < 0.001) and 14 (P < 0.001). At Week 7, each 1-µm reduction in central macular thickness and five Early Treatment Diabetic Retinopathy Study letters (-0.1 logarithm of the minimal angle of resolution) improvement were associated with SFCT reductions of 0.09 (P = 0.002) and 3.91 (P = 0.044) µm, respectively. At Week 14, each 1-µm reduction in central macular thickness was associated with a 0.14-µm reduction in SFCT (P < 0.001). Eyes with good functional and anatomical responses exhibited significantly greater SFCT reductions. Subretinal fluid resulted in greater SFCT changes (P = 0.039) and better best-corrected visual acuity (P = 0.033) at Week 7. A continuous ellipsoid zone/interdigitation zone layer was associated with a smaller mean SFCT at Week 7 (P = 0.002) and better best-corrected visual acuity at Weeks 7 and 14 (both, P < 0.001).

CONCLUSION

Changes in SFCT after dexamethasone implant injection therapy for diabetic macular edema may predict anatomical and functional outcomes and correlate with optical coherence tomography features that are known as predictors of treatment response.

Neurovascular unit in diabetic retinopathy: pathophysiological roles and potential therapeutical targets

Diabetic retinopathy (DR), one of the common complications of diabetes, is the leading cause of visual loss in working-age individuals in many industrialized countries. It has been traditionally regarded as a purely microvascular disease in the retina. However, an increasing number of studies have shown that DR is a complex neurovascular disorder that affects not only vascular structure but also neural tissue of the retina. Deterioration of neural retina could precede microvascular abnormalities in the DR, leading to microvascular changes. Furthermore, disruption of interactions among neurons, vascular cells, glia and local immune cells, which collectively form the neurovascular unit, is considered to be associated with the progression of DR early on in the disease. Therefore, it makes sense to develop new therapeutic strategies to prevent or reverse retinal neurodegeneration, neuroinflammation and impaired cell-cell interactions of the neurovascular unit in early stage DR. Here, we present current perspectives on the pathophysiology of DR as a neurovascular disease, especially at the early stage. Potential novel treatments for preventing or reversing neurovascular injuries in DR are discussed as well.

Quantitative assessment of vascular density in diabetic retinopathy subtypes with optical coherence tomography angiography

Background

Quantitative assessment of vascular density (VD) of retinal and choriocapillaris (CC) in various stages of diabetic retinopathy (DR) using spectral domain optical coherence tomography angiography (SD OCTA).

Methods

188 eyes of 97 participants were recruited in this cross-sectional study. The macular OCTA (3x3mm) scan was performed and the computer algorithm assessed VD at the level of superficial capillary plexus (SCP), deep capillary plexus (DCP) and CC.

Results

All measured parameters were decreased in retinal VD at the more extreme stages of DR, with the exception of SCP foveal VD. There was a constant pattern of decrease in VD of CC from normal cases to cases of NDR and NPDR and then a slight increase occurred in the PDR stage but never touching the normal quantities. Age, fasting blood sugar, and years of diabetes mellitus were correlated with reduced VD in different segments. Multivariate linear regression analysis showed that best-corrected visual acuity (BCVA) was positively correlated with parafoveal VD at SCP and VD of foveal area at CC. VD of all subfields of macular area except foveal DCP VD showed reduced levels in diabetic macular edema (DME) patients compared to those without DME.

Conclusions

The findings of the study endorse retina VD changes as a potential biomarker for DR development before retinopathy becomes clinically evident. It seems that parafoveal VD of SCP and foveal VD of CC are good biomarkers to predict VA in the diabetic patients.

Analysis of the Choroid and Its Relationship with the Outer Retina in Patients with Diabetes Mellitus Using Binarization Techniques Based on Spectral-Domain Optical Coherence Tomography

(1) Background: We aimed to reveal the relationship between the choroid and the outer retina with optical coherence tomography (OCT) in patients with diabetes mellitus (DM) with mild or no diabetic retinopathy (DR) in order to find early biomarkers for progressing retinopathy. (2) Methods: We performed a prospective study including 61 eyes of patients with type 1 or type 2 DM and 36 eyes of healthy controls. All subjects were imaged with Spectralis OCT. The choroid was assesseed using enhanced depth imaging OCT (EDI-OCT). Binarization of subfoveal choroidal images was done with public domain software, ImageJ (version 1.53a; National Institutes of Health, Bethesda, Maryland, USA). (3) Results: Luminal area, stromal area and total choroidal area were significantly decreased in diabetic patients compared to control: 0.23 ± 0.07 vs. 0.28 ± 0.08, p = 0.012; 0.08 ± 0.03 vs. 0.10 ± 0.04, p = 0.026; 0.31 ± 0.09 vs. 0.38 ± 0.11, p = 0.008. The thickness of retinal pigment epithelium (RPE) correlated positively with the choroidal vascularity index (CVI). The correlations between outer nuclear layer (ONL), photoreceptors (PR) and foveal choroidal thickness (FChT) were moderately negative. (4) Conclusion: Thicker RPE and a thinner PR layer may be assigned the role of early biomarkers signaling the conversion time to progressing retinopathy.

Choroidal Vascularity Index in Patients with Type-1 Diabetes Mellitus without Diabetic Retinopathy

Purpose: This study aims to assess choroidal vascularity index (CVI) and choroidal thickness (CT) in patients diagnosed with type 1 diabetes mellitus (DM) and compare them with healthy control subjects.Methods: This retrospective and cross-sectional study includes 43 patients diagnosed with type 1 DM and 43 healthy age/gender-matched subjects as the control group. Enhanced depth imaging optical coherence tomography (EDI-OCT; Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany) images of all participants were analyzed. CT measurements of five different points (subfoveal, 500 µm temporal, 1500 µm temporal, 500 µm nasal, and 1500 µm nasal to the fovea) were obtained. Choroid images were divided into luminal (LA) and stromal areas (SA) determined by image binarization method. Choroidal vascularity index (CVI) was defined as the ratio of LA to total choroid area (TCA). The effects of age, HbA1c, fasting plasma glucose, duration of DM, mean blood pressure, intraocular pressure, and axial length measurements on CVI were investigated.Results: There was no significant difference between any of the CT measurements of the groups (all p > .05). There was no significant difference between the groups according to TCA (0.82 ± 0.24 vs. 0.80 ± 0.19; p = .065), LA (0.54 ± 0.17 vs. 0.55 ± 0.16; p = .123) and SA (0.28 ± 0.06 vs. 0.25 ± 0.07; p = .068). However, patients had significantly lower CVI compared to control subjects (66.07 ± 3.19 vs. 68.89 ± 2.85, p < .001). Univariate linear regression model revealed that there was a negative correlation between disease duration and CVI (standardized beta coefficient: -0.416, p = .006).Conclusion: According to our findings, reduced CVI may indicate subclinical dysfunction in choroid of patients with type 1 DM.

Evaluation of the inner choroid using OCT angiography

The advent of optical coherence tomography angiography (OCTA) has allowed a qualitative and quantitative analysis of the retinal vasculature and the choriocapillaris. With the use of OCTA, several studies evaluated the changes in the choriocapillaris showing how this vascular structure plays a significant role in the pathogenesis of different conditions. This article reviews the current methods of analysis of the choriocapillaris and the relevant findings in different chorioretinal diseases.

Choroidal Changes in Diabetic Patients With Different Stages of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the long-term microvascular complications of diabetes mellitus (DM) and is considered a leading cause of vision loss worldwide. Chronic hyperglycemia can cause microvascular abnormalities to the retina and the choroid as well. The vascular tissue of the choroid supplies blood to the outer retina, photoreceptors, and retinal pigment epithelium. It plays an important role in the metabolic exchange of the retina. Many experimental studies reported that choroidal pathology in diabetic patients might play a role in developing DR. Choroidal thickness (CT) can reflect changes in the vasculature of the choroid and can be used to assess the vascularity of the choroid itself. CT differs between healthy and diseased states of the eye as well as with the aging process. This means that thinner or thicker choroid may indicate an ocular disease. Choroidal vascularity index (CVI) is also used as a marker for choroidal vascularity assessment and indirectly measures choroidal vascularity quantitatively. Many studies have been conducted to evaluate the choroid in many different ocular diseases. However, the results regarding CT in DM, especially in patients with DR, are various as thickened, thinned, or no changes. Thus, the status of the choroid in patients with DM with or without DR remains controversial between researchers. In this systematic review, we reviewed 18 articles that were done to investigate the relationship between structural choroidal changes in diabetic patients with different stages of DR, focusing on CT, CVI, and some other parameters evaluating choroidal changes.

Diabetic macular edema with pachychoroid features

Background

To investigate the clinical features of diabetic macular edema (DME) in eyes with pachychoroid phenotypes using multimodal retinal imaging.

Methods

We retrospectively reviewed 210 eyes from 210 DME patients and analyzed the clinical and imaging parameters, including visual acuity, central macular thickness (CMT), subfoveal choroidal thickness (SFCT) and neural retina layer thickness (NRT). The DME eyes were divided into two groups: group 1 (80 eyes with submacular detachment [SMD]) and group 2 (130 eyes without SMD). The clinical and imaging parameters of 285 eyes from 285 diabetic patients without DME were collected as a control group.

Results

DME eyes with pachychoroid phenotypes were more frequent in group 1 than in group 2 (53 eyes [66.25%] and 53 eyes [40.77%], respectively, P < 0.001). Pachychoroid phenotypes were identified in 108 (37.90%) of the control eyes. CMT and NRT were greater in group 1 than in group 2. In group 1, 37 eyes had SMD combined with focal edema, and 43 eyes had SMD combined with diffuse-type edema. No significant difference in pachychoroid phenotypes was found between the focal and diffuse types (26 [70.27%] and 27 [62.79%], respectively, P = 0.481). In group 2, 70 eyes had focal-type edema, and 60 eyes had diffuse-type edema. No significant difference in the frequency of pachychoroid phenotypes was found (32 [45.71%] and 21 [35.00%], respectively, P = 0.215). Interestingly, among the 70 eyes with focal edema in group 2, 13 (40.6%) and 5 (13.2%) eyes with and without pachychoroid phenotypes showed no definite microaneurysms, respectively.

Conclusion

SMD and focal edema without definite microaneurysms may be clinical manifestations of DME with pachychoroid phenotypes and possibly related to choroidal circulation disturbance in DME.

Choroid structure analysis following initiation of hemodialysis by using swept-source optical coherence tomography in patients with and without diabetes

We aimed to evaluate choroid structural changes using swept-source optical coherence tomography (SS-OCT) following hemodialysis initiation in diabetic and nondiabetic patients with end-stage kidney disease (ESKD). In this multicenter, prospective, cross-sectional study, diabetic (DM group; 30 eyes; 16 patients) and nondiabetic patients (NDM group; 30 eyes; 15 patients) with ESKD were evaluated after hemodialysis initiation. SS-OCT findings were analyzed using a manual delineation technique and binarization method before the first and last hemodialysis sessions, conducted approximately 2 weeks apart. Subfoveal choroidal thickness changes and mean large choroidal vessel layer thickness were significantly greater in the DM group (−13.3% ± 2.5% and −14.5% ± 5.2%, respectively) than the NDM group (−9.5% ± 3.1% and −9.2% ± 3.4%, respectively; p = 0.049 and p = 0.02, respectively). Binarized SS-OCT analysis revealed that the mean subfoveal choroidal area was significantly larger in the DM group (−21.9% ± 6.5%) than the NDM group (−17.2% ± 5.9%; p = 0.032). The change ratio in mean luminal area values was significantly greater in the DM group (−27.7% ± 8.7%) than the NDM group (−17.7% ± 5.8%; p = 0.007). The DM group exhibited substantial changes in the choroidal layer, possibly reflecting choroidal vascular disorders caused by diabetes.

Functional correlation between choroidal and retinal vascularity in low-grade diabetic retinopathy

AIMS

To perform an automated functional assessment of retinal and choroidal microvasculature in eyes with low-grade diabetic retinopathy (DR) using optical coherence tomography angiography (OCT-A) and to identify potential perfusion changes in case of early vascular damage.

METHODS

This is an observational, case-control study of consecutive diabetic patients with level 20 DR severity scale score and age-matched healthy subjects. A prototypal OCT-angiography was used to obtain the OCT-angiograms of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris (CC) layer. A validated automated microstructural analysis provided data on SCP, DCP and CC vascular perfusion density (VPD). A comparative assessment between different vascular layers and different groups was performed.

RESULTS

Twenty-nine diabetic patients (7 females, 24%) and 20 healthy controls were enrolled. VPD values were significantly lower in the DCP (25.1% vs. 26.5%; p = 0.04) and CC (71.2% vs. 86.6%; p = 0.0001) of diabetic patients compared with controls. A statistically significant negative linear correlation was reported between CC VPD and DCP VPD in diabetic patients; at the reverse, a positive linear correlation between the same parameters was noticed in controls.

CONCLUSION

Retinal and choroidal vascular networks, although distinct entities, seem functionally interconnected: varying the degree of perfusion may be a mutual compensatory mechanism in response to an ischemic injury.

Microvascular Changes in the Choriocapillaris of Diabetic Patients Without Retinopathy Investigated by Swept-Source OCT Angiography

Purpose

To investigate the microvascular changes in macular retina and choriocapillaris (CC) in diabetic eyes without retinopathy using swept-source optical coherence tomography angiography (SS-OCTA).

Methods

A commercial SS-OCTA system was used to collect 6 × 6-mm macular scans from patients. Three depth-resolved retinal slabs and a CC slab were segmented by a validated semiautomated algorithm. Retinal vessel area density, vessel skeleton density, and nonperfusion area were calculated on segmented retinal slabs. Foveal avascular zone was automatically measured based on en face image of the whole retinal layer. For CC quantification, the percentage of flow deficits (FD%) and the flow deficit (FD) sizes were measured. 

Results

Sixteen eyes from 16 diabetic patients without clinically detectable retinopathy and 16 eyes from 16 age-matched nondiabetic controls were included. There was no significant difference between the two groups in all retinal vessel quantitative parameters (all P > 0.05). However, the mean FD% and mean FD sizes were significantly increased in CC in the central 1.0-mm disk (P = 0.011 and P = 0.017, respectively), the central 1.5-mm rim (P = 0.003 and P = 0.009, respectively), the central 2.5-mm rim (P = 0.018 and P = 0.020, respectively), and the entire 5.0-mm disk (P = 0.009 and P = 0.008, respectively) in diabetic eyes compared with controls.

Conclusions

CC perfusion in the macula is decreased in diabetic patients without retinopathy as compared to age-matched normal controls. Decreased CC perfusion in the macula may be an early indicator of otherwise clinically undetectable diabetic vasculopathy.

Optical Coherence Tomography Angiography in Diabetes and Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes mellitus that disrupts the retinal microvasculature and is a leading cause of vision loss globally. Recently, optical coherence tomography angiography (OCTA) has been developed to image the retinal microvasculature, by generating 3-dimensional images based on the motion contrast of circulating blood cells. OCTA offers numerous benefits over traditional fluorescein angiography in visualizing the retinal vasculature in that it is non-invasive and safer; while its depth-resolved ability makes it possible to visualize the finer capillaries of the retinal capillary plexuses and choriocapillaris. High-quality OCTA images have also enabled the visualization of features associated with DR, including microaneurysms and neovascularization and the quantification of alterations in retinal capillary and choriocapillaris, thereby suggesting a promising role for OCTA as an objective technology for accurate DR classification. Of interest is the potential of OCTA to examine the effect of DR on individual retinal layers, and to detect DR even before it is clinically detectable on fundus examination. We will focus the review on the clinical applicability of OCTA derived quantitative metrics that appear to be clinically relevant to the diagnosis, classification, and management of patients with diabetes or DR. Future studies with longitudinal design of multiethnic multicenter populations, as well as the inclusion of pertinent systemic information that may affect vascular changes, will improve our understanding on the benefit of OCTA biomarkers in the detection and progression of DR.

Choroidal Thickness After Dexamethasone Implant or Aflibercept in Patients with Diabetic Macular Edema Persistent to Ranibizumab

Purpose: This study aims to compare subfoveal choroidal thicknesses (SFCTs) after intravitreal dexamethasone (IVD) or intravitreal aflibercept (IVA) treatment in patients with persistent diabetic macular edema (DME) unresponsive to intravitreal ranibizumab (IVR). Methods: The study consisted of patients with DME unresponsive to IVR treatment in which 37 were administered 1 dose IVD (group A) and 34 patients who were administered 3 doses of IVA (group B), as well as 35 healthy individuals (group C). Detailed ophthalmological examination and optical coherence tomography parameters of group A and group B, including central retinal thickness and SFCT, were retrospectively evaluated before and after treatment. Results from preinjection, and 1, 2, and 3 months after injection were analyzed. Results of group A and group B were compared within themselves and also compared with group C. Results: SFCT measurements were compared within group A and group B (1 = preinjection; 2 = 1 month postinjection; 3 = 2 months postinjection; 4 = 3 months postinjection). There was significant thinning in SFCT between 1-2, 1-3, 1-4, 2-3, 2-4, and 3-4 time intervals within both group A and group B (both P < 0.001). Comparison of SFCT measurements showed preinjection, 1-, and 2-month values of group A were significantly thicker than those of group C (P < 0.001), whereas there was no significant difference between 3-month values (P = 0.09). Preinjection, 1-, and 2-month values of group B were significantly thicker than those of group C (P < 0.001), whereas there was no significant difference between 3-month values (P = 0.06). Conclusions: Three month follow-up showed thinning in SFCT measurements in patients with persistent DME unresponsive to IVR who were applied IVD or IVA treatment.

Choroidal Thickness and Urinary Albumin Excretion in Type 2 Diabetic Patients without Retinopathy

The role of retinal vasculature's dysfunction in the physiopathology of Diabetic Retinopathy (DR) has been extensively described. Recently, the existence of a diabetic choroidal vasculopathy has been proposed. The purpose of this study was to compare choroidal thickness (CT) in nondiabetic patients and in type 2 diabetic patients without retinopathy, using EDI SD-OCT. Additionally, considering the diabetic patient group, compare CT in patients with and without microalbuminuria. This retrospective study selected patients sent from primary health-care centers as part of the national screening of diabetic retinopathy. Inclusion criteria were diagnosis of type 2 diabetes mellitus, absence of diabetic retinopathy, and a 24 hours urinary albumin measurement in the last 3 months at the primary health-care center. Nondiabetic patients were selected from a database in the ophthalmology department, and only healthy patients were included. At the screening visit, all patients performed a complete ophthalmologic examination by the same examiner. All eyes were examined with SD- OCT, and all scans were performed in the EDI mode. Measurements were made at three points: subfoveal, 1500 μm temporally and nasally to the foveal center. We included 110 eyes of 110 diabetic patients without diabetic retinopathy and 30 eyes of 30 healthy controls. Mean subfoveal CT was greater in diabetic patients without retinopathy (with normoalbuminuria or microalbuminuria) when compared with nondiabetic patients (p < 0.05). In diabetic patients without retinopathy, the subfoveal and temporal choroid was thicker among patients with microalbuminuria when compared with those of normoalbuminuric patients (p < 0.05). The subfoveal and temporal choroid was thicker among diabetic patients with microalbuminuria compared with nondiabetic patients. (p < 0.05). This study suggests that choroidal changes are present in type 2 diabetic patients even before the clinical development of retinopathy.

Topographic analysis of macular choriocapillaris flow deficits in diabetic retinopathy using swept-source optical coherence tomography angiography

Background

The purpose of this study was to investigate the association between diabetic retinopathy (DR) severity and macular choriocapillaris (CC) flow deficit percentage (FD %) in different macular regions using swept-source optical coherence tomography angiography (SS-OCTA).

Methods

Diabetic patients with SS-OCTA images were graded by severity and retrospectively assessed. CC FD % was calculated in four different regions of the OCTA image: inner, middle, outer, and full-field region. The generalized estimating equations (GEE) approach for clustered eye data was used to determine effect size and significance of age and disease severity on FD % for each region.

Results

160 eyes from 90 total diabetic patients met inclusion criteria. Out of 90 patients, 33 had no DR, 17 had mild nonproliferative DR (NPDR), 8 had moderate NPDR, 10 had severe NPDR and 22 had proliferative DR. Age and DR severity had a significant positive association with FD % for each region studied with a greater effect in the two centermost regions. The increase in flow deficit percentage per year of age by region was: inner 0.12 (p < 0.001), middle 0.09 (p < 0.001), outer 0.05 (p < 0.001, full-field 0.06 (p < 0.001). The increase in flow deficit percentage per increase in diabetic retinopathy severity stage by region was: inner 0.65 (p < 0.0087), middle 0.56 (p < 0.0012), outer 0.33 (p < 0.045), full-field 0.36 (p < 0.018).

Conclusions

Topographic analysis of the CC FD % in diabetic eyes suggests that CC flow impairment corresponds to DR severity, with all studied regions of the CC significantly affected. There was greater regional impairment due to age and disease severity in the inner and middle regions.

QUANTITATIVE AND QUALITATIVE ANALYSIS OF THE THREE CAPILLARY PLEXUSES AND CHORIOCAPILLARIS IN PATIENTS WITH TYPE 1 AND TYPE 2 DIABETES MELLITUS WITHOUT CLINICAL SIGNS OF DIABETIC RETINOPATHY: A Prospective Pilot Study

PURPOSE

To separately evaluate the three retinal capillary plexuses and the choriocapillaris in patients with diabetes mellitus (DM) Type 1 and Type 2, without clinical signs of diabetic retinopathy.

METHODS

The study was prospective and cross-sectional. Only patients with age ≤55 years were included. We used a swept-source optical coherence tomography angiography device (Triton; Topcon, Tokyo, Japan) to obtain both quantitative and qualitative analysis of the retinal capillary plexuses (superficial capillary plexus; middle capillary plexus; and deep capillary plexus) and the choriocapillaris.

RESULTS

We included 17 patients with DM Type 1 (age 34.52 ± 11.05 years, 29 eyes), 17 patients with DM Type 2 (age 48.76 ± 3.26 years, 32 eyes), and 23 healthy control subjects (age 41.82 ± 8.97 years, 43 eyes). When compared with controls, vessel density in the central 1 mm was reduced in both DM Type 1 and DM Type 2 groups in the superficial capillary plexus (P = 0.05 and P = 0.02, respectively), and in DM Type 2 in the deep capillary plexus (P = 0.03). Foveal avascular zone was increased in the middle capillary plexus and deep capillary plexus of DM Type 2 group compared with controls (P = 0.03 and P = 0.02, respectively). Choriocapillary voids were more frequent in DM Type 1 and DM Type 2 compared with controls (P = 0.003 and P < 0.001, respectively).

CONCLUSION

Microvascular modifications are present in the three retinal capillary plexuses and the choriocapillaris in both DM Type 1 and DM Type 2 even in the absence of clinical signs of diabetic retinopathy.

Clinical and angiographic characterization of choroidal neovascularization in diabetic retinopathy

BACKGROUND

To report the clinical and angiographic characteristics of choroidal neovascularization in patients with diabetic retinopathy.

METHODS

Patients of type 2 diabetes mellitus with presence of choroidal neovascularization in at least one eye were retrospectively analyzed. The study eyes were divided into three groups based on presence (active or scarred) or absence of choroidal neovascularization (fellow eyes). Imaging characteristics of active choroidal neovascularization were recorded using optical coherence tomography, fluorescein, and indocyanine angiography. Central macular thickness, subfoveal choroidal thickness, and large choroidal vessel layer thickness were compared at baseline and final visit.

RESULTS

Our study reports the prevalence rate of choroidal neovascularization in eyes with diabetic retinopathy (0.27%; 36 out of 13,382 eyes). A total of 64 eyes of 32 patients (age, mean ± standard deviation: 68.5 ± 9.3 years) with baseline visual acuity of 0.69 ± 0.69 logarithm of minimum angle of resolution (Snellen equivalent 20/100) were included. Nonproliferative diabetic retinopathy (57 eyes) comprised the majority followed by proliferative diabetic retinopathy (7 eyes). Eyes with choroidal neovascularization (36, 56.25%) included both active (25) and scarred (11) choroidal neovascularization, with bilateral choroidal neovascularization in 4 patients. Type 1 choroidal neovascularization was the most common subtype of choroidal neovascularization on optical coherence tomography. Common etiologies for active choroidal neovascularization included age-related macular degeneration (3; 12%), myopia (1; 4%), and inflammatory choroidal neovascularization secondary to chorioretinitis (1; 4%). In the remaining 20 eyes, choroidal neovascularization formation was primarily due to diabetic choroidopathy.

CONCLUSION

The prevalence of choroidal neovascularization in eyes with diabetic retinopathy is very low, with a lower prevalence of age-related macular degeneration. Diabetic choroidopathy plays a significant role in formation of choroidal neovascularization in eyes with diabetic retinopathy.

SIGNIFICANT REDUCTION OF BOTH PERIPAPILLARY AND SUBFOVEAL CHOROIDAL THICKNESS AFTER PANRETINAL PHOTOCOAGULATION IN PATIENTS WITH TYPE 2 DIABETES

PURPOSE

To evaluate changes in peripapillary choroidal thickness (PCT) and subfoveal choroidal thickness (SFCT) after panretinal photocoagulation (PRP) for diabetic retinopathy.

METHODS

This retrospective interventional study included 59 treatment-naive eyes of 33 patients who underwent PRP and completed ≥12 months of follow-up. Peripapillary choroidal thickness and SFCT were measured at baseline and 1, 3, 6, and 12 months post-PRP. Differences between baseline and 12 months (ΔSFCT and ΔPCT) and percentage changes (ΔSFCT or ΔPCT/baseline × 100%) were determined.

RESULTS

Mean SFCT was 287.7 ± 76.7 μm (139.0-469.0 μm) at baseline and 225.8 ± 62.0 μm (102.5-379.5 μm) 12 months post-PRP (P < 0.001). Mean PCT was 161.2 ± 16.5 μm (75.3-308.1 μm) at baseline and 128.4 ± 41.8 μm (73.0-212.9 μm) 12 months post-PRP (P < 0.001). ΔSFCT was -61.3 ± 28.7 μm (-139.5 to -17.0 μm), and %SFCT was 21.2 ± 7.2% (6.8% to 36.1%). ΔPCT was -36.4 ± 23.2 μm (-149.1 to 5.4 μm), and %PCT was 22.4 ± 12.0% (2.5% to 62.6%). Diabetic retinopathy severity was the only factor significantly correlated with %SFCT (β = 0.500, P = 0.004) and %PCT (β = 0.152, P = 0.024).

CONCLUSION

Both PCT and SFCT reduced significantly after PRP. Diabetic retinopathy severity was significantly correlated with post-PRP changes of peripapillary and SFCT.

Subfoveal choroidal thickness in diabetic macular edema

Purpose: To evaluate subfoveal choroidal thickness (SFCT) in eyes with diabetic macular edema (DME) using spectral domain OCT (SD-OCT). Materials and methods: Ninety eyes were divided into three equal groups: group A, non-proliferative diabetic retinopathy (NPDR) with no DME; group B, NPDR having DME; and group C, non-diabetic patients. The central subfield retinal thickness (CSRT) and SFCT were measured using spectral domain OCT. Results: There was a moderate negative correlation between age and SFCT in group B (r=-0.455, P=0.012). We found no significant correlation between best corrected visual acuity (BCVA) and SFCT in all groups (for groups A, B, and C, respectively: r=0.189, P=0.316; r=-0.195, P=0.302; and r=-0.181, P=0.337). There was no significant correlation between duration of diabetes and SFCT (r=-0.118, P=0.534 and r=-0.136, P=0.475 for groups A and B, respectively). The CSRT was 229.13±16.2, 336.4±74.85, and 223.13±16.9 µm in groups A, B, and C, respectively. The mean SFCT was 260.6±49.2, 259±50.8, and 252±50 µm in groups A, B, and C, respectively. We found no significant correlation between CSRT and SFCT in all groups (for groups A, B, and C, respectively: r=-0.049, P=0.796, r=0.239, P=0.204, r=-0.021, P=0.914). There was no significant difference in SFCT between group B (DME) on one hand and groups A and C on the other hand (P=0.9 and 0.59, respectively). Conclusion: There is no significant correlation between CSRT and SFCT in DME. Choroidal thickness assessment is not an indicator of the severity of DME and cannot be used as a monitor of its progression.

Repeatability and reproducibility of retinal and choroidal thickness measurements in Diabetic Macular Edema using Swept-source Optical Coherence Tomography

Purpose

To evaluate the repeatability and reproducibility of retinal and choroidal thickness measured with Swept source Optical Coherence Tomography (SS-OCT) in eyes with Diabetic Macular Edema (DME).

Methods

42 DME eyes were imaged using SS-OCT standard Macular scanning protocols. Retinal and choroidal thickness were measured in the Total macular circle (TMC) and foveal central subfield (FCS) using device-integrated specific software. The coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were determined as a measure of repeatability and relative reliability within graders. Reproducibility was assessed using Bland-Altman plots and 95% limits of agreement (LoA) were determined as a measure of interobserver variability.

Results

Intragrader CR of retinal and choroidal thickness were 8.37 and 12.20 microns for TMC and 22.24 and 32.40 microns for FCS, and intergrader 95% LoA were 7.37–8.69 and -27.2–27.71 microns for TMC and -34.21–41.93 and -30.46–24.84 for FCS, respectively. Retinal and choroidal thickness showed very good intraobserver reliability for both TMC and FCS (ICC 0.99, LoA 0.98–0.99 in all cases). Intraobserver and interobserver variability for retinal and choroidal thickness was not significantly different for TMC (p = 0.98 and p = 0.90, p = 0.98 and p = 0.91) or FCS (p = 0.97 and p = 0.85, p = 0.78 and p = 0.73), respectively.

Conclusions

Retinal and choroidal thickness in DME eyes can be quantified with good reliability, repeatability and reproducibility using new OCT devices that incorporate swept source technology. The technical advantages of this technology may provide new insights in the understanding of the choroidal changes related with DME.

Choriocapillaris and retinal vascular plexus density of diabetic eyes using split-spectrum amplitude decorrelation spectral-domain optical coherence tomography angiography

BACKGROUND/AIMS

Split-spectrum amplitude decorrelation angiography for spectral-domain optical coherence tomography has enabled detailed, non-invasive assessment of vascular flow. This study evaluates choriocapillaris and retinal capillary perfusion density (CPD) in diabetic eyes using optical coherence tomography angiography (OCTA).

METHODS

Records of 136 eyes that underwent OCTA imaging at a single institution were reviewed. Eyes were grouped as non-diabetic controls (37 eyes), patients with diabetes mellitus (DM) without diabetic retinopathy (DM without DR, 31 eyes), non-proliferative diabetic retinopathy (NPDR, 41 eyes) and proliferative diabetic retinopathy (PDR, 27 eyes). Quantitative CPD analyses were performed on OCTA images for assessing perfusion density of the choriocapillaris and retinal plexus for all patients and compared between groups.

RESULTS

Eyes with NPDR and PDR showed significantly decreased choriocapillaris CPD compared with controls, while DM eyes without DR did not show significant change. Choriocapillaris whole-image CPD was decreased by 8.3% in eyes with NPDR (p<0.01) and decreased by 7.1% in eyes with PDR (p<0.01). Choriocapillaris parafoveal CPD was decreased by 8.9% in eyes with NPDR (p<0.01) and decreased by 8.2% in eyes with PDR (p<0.01). Compared with controls, only eyes with PDR showed significantly decreased retinal CPD, as well as significantly increased foveal avascular zone (FAZ) area. In those patients, retinal whole-image CPD was decreased by 9.7% (p<0.01), retinal foveal CPD was decreased by 20.5% (p<0.01) and retinal parafoveal CPD was decreased by 11.4% (p<0.01). FAZ area was increased by 50.9% (p<0.01).

CONCLUSIONS

Choriocapillaris and retinal CPD are reduced in diabetic retinopathy, while FAZ area is increased in eyes with PDR. Vascular changes captured by new imaging modalities can further characterise diabetic choroidopathy.

Choroidal microvascular proliferation secondary to diabetes mellitus

Diabetes is a common endocrine disorder associated with peripheral microvascular diseases such as proliferative retinal microangiopathy (or diabetic retinopathy), which may lead to blindness. Unfortunately, diabetic microvascular abnormalities in the choroid are underestimated in clinical practice. Recent literature has revealed that the severity of diabetic retinopathy is aggravated by choroidopathy resulting from hyperglycemia. Here, we introduce a case of diabetic retinopathy with choroidal neovascularization membrane but without signs of retinal microvascular proliferation or drusen. We investigated the pathogenesis of choroidal microvascular proliferation secondary to diabetes. We postulate that choroidal neovascularization is an intraocular microvascular complication of diabetes mellitus. Intravitreal anti-vascular endothelial growth factor therapy may be a treatment option for microvascular proliferation in both retina and choroids.

Assessment of Global and Local Alterations in Retinal Layer Thickness in Ins2 (Akita) Diabetic Mice by Spectral Domain Optical Coherence Tomography

PURPOSE/AIM

The Ins2 (Akita) mouse is a spontaneous diabetic mouse model with a heterozygous mutation in the insulin 2 gene that results in sustained hyperglycemia. The purpose of the study was to assess global and local retinal layer thickness alterations in Akita mice by analysis of spectral domain optical coherence tomography (SD-OCT) images.

MATERIALS AND METHODS

SD-OCT imaging was performed in Akita and wild-type mice at 12 and 24 weeks of age. Inner retinal thickness (IRT), outer retinal thickness (ORT), total retinal thickness (TRT), and photoreceptor outer segment length (OSL) were measured. Mean global thickness values were compared between Akita and wild-type mice. Local thickness variations in Akita mice were assessed based on normative values in wild-type mice.

RESULTS

Akita mice had higher blood glucose levels and lower body weights (p < 0.001). On average, IRT, ORT, and TRT were approximately 2% lower in Akita mice than in wild-type mice (p ≤ 0.02). In Akita mice, the percent difference between retinal areas with thickness below and above normative values for IRT, ORT, and TRT was 22%, 32%, and 38%, respectively.

CONCLUSIONS

These findings support the use of the Akita mouse model to study the retinal neurodegenerative effects of hyperglycemia.

CHOROIDAL THICKNESS IN DIABETIC RETINOPATHY ASSESSED WITH SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To compare the choroidal thickness (CT) of diabetic eyes (different stages of disease) with controls, using swept-source optical coherence tomography.

METHODS

A multicenter, prospective, cross-sectional study of diabetic and nondiabetic subjects using swept-source optical coherence tomography imaging. Choroidal thickness maps, according to the nine Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, were obtained using automated software. Mean CT was calculated as the mean value within the ETDRS grid, and central CT as the mean in the central 1 mm. Diabetic eyes were divided into four groups: no diabetic retinopathy (No DR), nonproliferative DR (NPDR), NPDR with diabetic macular edema (NPDR + DME), and proliferative DR (PDR). Multilevel mixed linear models were performed for analyses.

RESULTS

The authors included 50 control and 160 diabetic eyes (n = 27 No DR, n = 51 NPDR, n = 61 NPDR + DME, and n = 21 PDR). Mean CT (ß = -42.9, P = 0.022) and central CT (ß = -50.2, P = 0.013) were statistically significantly thinner in PDR eyes compared with controls, even after adjusting for confounding factors. Controlling for age, DR eyes presented a significantly decreased central CT than diabetic eyes without retinopathy (β = -36.2, P = 0.009).

CONCLUSION

Swept-source optical coherence tomography demonstrates a significant reduction of CT in PDR compared with controls. In the foveal region, the choroid appears to be thinner in DR eyes than in diabetic eyes without retinopathy.

Diabetic Choroidopathy: Choroidal Vascular Density and Volume in Diabetic Retinopathy With Swept-Source Optical Coherence Tomography

PURPOSE

To compare choroidal vascular density (CVD) and volume (CVV) in diabetic eyes and controls, using en face swept-source optical coherence tomography (SS-OCT).

DESIGN

Prospective cross-sectional study.

METHODS

Setting: Multicenter.

PATIENT POPULATION

Total of 143 diabetic eyes-27 with no diabetic retinopathy (DR), 47 with nonproliferative DR (NPDR), 51 with NPDR and diabetic macular edema (DME), and 18 with proliferative DR (PDR)-and 64 age-matched nondiabetic control eyes.

OBSERVATION PROCEDURES

Complete ophthalmologic examination and SS-OCT imaging. En face SS-OCT images of the choroidal vasculature were binarized.

MAIN OUTCOME MEASURES

CVD, calculated as the percent area occupied by choroidal vessels in the central macular region (6-mm-diameter circle centered on the fovea), and throughout the posterior pole (12 × 9 mm). The central macular CVV was calculated by multiplying the average CVD by macular area and choroidal thickness (obtained with SS-OCT automated software). Multilevel mixed linear models were performed for analyses.

RESULTS

Compared to controls (0.31 ± 0.07), central macular CVD was significantly decreased by 9% in eyes with NPDR + DME (0.28 ± 0.06; ß = -0.03, P = .02) and by 15% in PDR (0.26 ± 0.05; ß = -0.04, P = .01). The central macular CVV was significantly decreased by 19% in eyes with PDR (0.020 ± 0.005 mm3, ß = -0.01, P = .01) compared to controls (0.025 ± 0.01 mm3).

CONCLUSIONS

Choroidal vascular density and volume are significantly reduced in more advanced stages of diabetic retinopathy. New imaging modalities should allow further exploration of the contributions of choroidal vessel disease to diabetic eye disease pathogenesis, prognosis, and treatment response.

Quantifying Microvascular Abnormalities With Increasing Severity of Diabetic Retinopathy Using Optical Coherence Tomography Angiography

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.

Diabetic choroidopathy

Early histopathological studies of diabetic choroids demonstrated loss of choriocapillaris (CC), tortuous blood vessels, microaneurysms, drusenoid deposits on Bruchs membrane, and choroidal neovascularization. The preponderance of histopathological changes were at and beyond equator. Studies from my lab suggest that diabetic choroidopathy is an inflammatory disease in that leukocyte adhesion molecules are elevated in the choroidal vasculature and polymorphonuclear neutrophils are often associated with sites of vascular loss. Modern imaging techniques demonstrate that blood flow is reduced in subfoveal choroidal vasculature. Angiography has shown areas of hypofluorescence and late filling that probably represent areas of vascular loss and/or compromise. Perhaps, as a result of vascular insufficiency, the choroid appears to thin in DC unless macular edema is present. Enhanced depth imaging (EDI-SD) OCT and swept source (SS) OCT have documented the tortuosity and loss in intermediate and large blood vessels in Sattler's and Haller's layer seen previously with histological techniques. The risk factors for DC include diabetic retinopathy, degree of diabetic control, and the treatment regimen. In the future, OCT angiography could be used to document loss of CC. Because most of the measurement and imaging are in the posterior pole, the severity of DC may be underappreciated in the published accounts of DC assessed with imaging techniques. However, it is now possible to document DC and quantify these changes clinically. This suggests that DC should be evaluated in future clinical trials of drugs targeting DR because vascular changes similar to those in DR are occurring in DC.

Diabetic Macular Edema With and Without Subfoveal Neuroretinal Detachment: Two Different Morphologic and Functional Entities

PURPOSE

To assess specific morphologic and functional characteristics in eyes with diabetic macular edema (DME) with subfoveal neuroretinal detachment (SND+) vs DME without SND (SND-).

DESIGN

Cross-sectional, prospective, comparative case series.

METHODS

Seventy-two patients (72 eyes: 22 eyes SND+ and 50 eyes SND-) with treatment-naïve, center-involving DME were evaluated. Data gathering included fundus color photographs, fluorescein angiography, spectral-domain optical coherence tomography (SD-OCT), best-corrected visual acuity (BCVA), and microperimetry. The following parameters were evaluated with SD-OCT: central macular thickness (CMT [including SND]); central retinal thickness (CRT [excluding SND]); choroidal thickness (CT); nasal and temporal retinal thickness (RT) at 500 μm and 1500 μm from the fovea; the number of hyperreflective retinal spots (HRS) in the central 3000 μm; and the presence of SND and integrity of the external limiting membrane (ELM). Retinal sensitivity (RS) was evaluated within 4 degrees and 12 degrees of the fovea. Correlation among CT, RS, and HRS in patients with and without SND was determined.

RESULTS

CMT (P = .032), temporal RT at 1500 μm (P = .03), mean CT (P = .009), and mean number of HRS (P = .0001) were all higher in SND+ vs SND- eyes. CRT, BCVA, HbA1c, and prevalence of systemic arterial hypertension were not different between the 2 groups. RS within 4 degrees (P = .002) and 12 degrees (P = .015) was lower in SND+ vs SND- eyes. SND correlated significantly with disruption of the ELM (54.55% vs 24%, P = .01) and lower RS. A direct correlation was found between the number of HRS, presence of SND, CT, and RS within 12 degrees in SND- eyes, and an inverse correlation was found between CT and RS within 12degrees in SND+ eyes.

CONCLUSIONS

These data may improve characterization of DME in eyes with SND. DME with SND correlates with greater CT, more HRS, disruption of the ELM, and significant macular functional impairment (RS decrease) vs SND-.

Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema

Diabetic macular oedema (DMO) is the leading cause of vision loss in the working-age population. Blood-retinal barrier (BRB) dysfunction in diabetic retinopathy (DR), mainly at the level of the retinal vessels, has long been related with leakage and fluid accumulation, leading to macular oedema. However, the nourishment of the macula is provided by the choroid and a diabetic choroidopathy has been described. Therefore, there has been a growing interest in studying the role of the choroid in the pathophysiology of DR and DMO, mainly by optical coherence tomography (OCT). Nevertheless, there are conflicting results in the different studies. We summarize the results from the available studies, describe the limitations and confounding factors and discuss future procedures to avoid bias.

Diabetic retinopathy: current understanding, mechanisms, and treatment strategies

Diabetic retinopathy (DR) causes significant visual loss on a global scale. Treatments for the vision-threatening complications of diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) have greatly improved over the past decade. However, additional therapeutic options are needed that take into account pathology associated with vascular, glial, and neuronal components of the diabetic retina. Recent work indicates that diabetes markedly impacts the retinal neurovascular unit and its interdependent vascular, neuronal, glial, and immune cells. This knowledge is leading to identification of new targets and therapeutic strategies for preventing or reversing retinal neuronal dysfunction, vascular leakage, ischemia, and pathologic angiogenesis. These advances, together with approaches embracing the potential of preventative or regenerative medicine, could provide the means to better manage DR, including treatment at earlier stages and more precise tailoring of treatments based on individual patient variations.

The pathology associated with diabetic retinopathy

This review summarizes the pathological features of diabetic retinopathy. The lesions occurring in the diabetic retina have been described over many decades using descriptive and experimental approaches based on clinical studies on patients, human post-mortem material, animal models and various in vitro systems. We have also accumulated a wealth of knowledge about basic molecular mechanisms and key pathogenic processes that drive these abnormalities in diabetic retina. Despite these advances, there are still limited therapeutic options for diabetic retinopathy with those currently available only addressing late-stage disease. With a particular focus on the earlier stages of diabetes, there is growing appreciation the complex neuronal, glial and microvascular abnormalities which progressively disrupt retinal function. This is especially true from the perspective of the neurovascular unit during health and disease. Based on a strong appreciation of cellular and molecular pathology that underpins diabetic retinopathy, further advances are anticipated as we drive towards development of efficacious therapeutic options that can address all stages of disease.

ULTRAHIGH SPEED SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF RETINAL AND CHORIOCAPILLARIS ALTERATIONS IN DIABETIC PATIENTS WITH AND WITHOUT RETINOPATHY

PURPOSE

To investigate the utility of ultrahigh speed, swept source optical coherence tomography angiography in visualizing retinal microvascular and choriocapillaris (CC) changes in diabetic patients.

METHODS

The study was prospective and cross-sectional. A 1,050 nm wavelength, 400 kHz A-scan rate swept source optical coherence tomography prototype was used to perform volumetric optical coherence tomography angiography of the retinal and CC vasculatures in diabetic patients and normal subjects. Sixty-three eyes from 32 normal subjects, 9 eyes from 7 patients with proliferative diabetic retinopathy, 29 eyes from 16 patients with nonproliferative diabetic retinopathy, and 51 eyes from 28 diabetic patients without retinopathy were imaged.

RESULTS

Retinal and CC microvascular abnormalities were observed in all stages of diabetic retinopathy. In nonproliferative diabetic retinopathy and proliferative diabetic retinopathy, optical coherence tomography angiography visualized a variety of vascular abnormalities, including clustered capillaries, dilated capillary segments, tortuous capillaries, regions of capillary dropout, reduced capillary density, abnormal capillary loops, and foveal avascular zone enlargement. In proliferative diabetic retinopathy, retinal neovascularization above the inner limiting membrane was visualized. Regions of CC flow impairment in patients with proliferative diabetic retinopathy and nonproliferative diabetic retinopathy were also observed. In 18 of the 51 of eyes from diabetic patients without retinopathy, retinal mircrovascular abnormalities were observed and CC flow impairment was found in 24 of the 51 diabetic eyes without retinopathy.

CONCLUSION

The ability of optical coherence tomography angiography to visualize retinal and CC microvascular abnormalities suggests it may be a useful tool for understanding pathogenesis, evaluating treatment response, and earlier detection of vascular abnormalities in patients with diabetes.