New insights into the pathoanatomy of diabetic macular edema: angiographic patterns and optical coherence tomography

A Novel Effect of Microaneurysms and Retinal Cysts on Capillary Perfusion in Diabetic Macular Edema: A Multimodal Imaging Study

Background/Objectives: The aim of this study was to investigate the potential contribution of microaneurysms (MAs) and retinal cysts to the pathogenesis of macular non-perfusion in patients with diabetic macular edema (DME) using multimodal imaging. Methods: In this cross-sectional study, 42 eyes with DME were analyzed using color fundus photography, fluorescein angiography (FA) and optical coherence tomography (OCT). Macular non-perfusion within the central 3000 µm was categorized by location and extent into foveal avascular zone enlargement (FAZE), focal non-perfusion (FNP) and diffuse non-perfusion (DNP). A custom-developed software was used to assess the colocalization of retinal cysts on OCT with areas of non-perfusion on the corresponding FA images. Also, the presence of leaky MAs adjacent to retinal cysts on FA was verified. Results: Colocalization between retinal cysts and non-perfusion was observed in 32 of 42 (76%) eyes: 19 of 23 (83%) eyes with FAZE and 13 of 16 (81%) eyes with FAZE+FNP. No cysts colocalization was found in all three eyes (100%) presenting with DNP. None of the eyes presented with FNP alone. In the remaining seven eyes (four eyes with FAZE and three eyes with FAZE+FNP), no colocalization was noticed. At least one leaky MA adjacent to retinal cysts was identified in all eyes presented with colocalization. Conclusions: Retinal cysts may contribute to the development of limited non-perfusion in DME. Leaky MAs appear to be the primary source of cyst formation, which may lead to localized capillary occlusion in the macula.

Ultrastructural imaging biomarkers in diabetic macular edema: A major review

Diabetic macular edema (DME) is a vision-threatening complication of diabetic retinopathy and causes significant morbidity in patients. Anti-vascular endothelial growth factor (VEGF) agents are the mainstay of treatment for DME, with steroid implants being used for the treatment of anti-VEGF resistant eyes. Over the years, several classification systems have been devised to describe the patterns of DME using optical coherence tomography (OCT). With the advent of effective treatments, it has become imperative that imaging cues are not merely used for classifying the disease but also as biomarkers for prognostication of disease activity and treatment response. In this aspect, newer imaging findings such as hyperreflective dots, photoreceptor integrity, and disorganization of retinal inner layers have been characterized in detail by several authors. Macular perfusion analysis using OCT angiography is the latest in the armamentarium for imaging DME. In this narrative review, we have summarized all relevant literature related to the ultrastructural imaging-based biomarkers of DME and their correlation to treatment.

Endpoints for clinical trials in ophthalmology

With the identification of novel targets, the number of interventional clinical trials in ophthalmology has increased. Visual acuity has for a long time been considered the gold standard endpoint for clinical trials, but in the recent years it became evident that other endpoints are required for many indications including geographic atrophy and inherited retinal disease. In glaucoma the currently available drugs were approved based on their IOP lowering capacity. Some recent findings do, however, indicate that at the same level of IOP reduction, not all drugs have the same effect on visual field progression. For neuroprotection trials in glaucoma, novel surrogate endpoints are required, which may either include functional or structural parameters or a combination of both. A number of potential surrogate endpoints for ophthalmology clinical trials have been identified, but their validation is complicated and requires solid scientific evidence. In this article we summarize candidates for clinical endpoints in ophthalmology with a focus on retinal disease and glaucoma. Functional and structural biomarkers, as well as quality of life measures are discussed, and their potential to serve as endpoints in pivotal trials is critically evaluated.

The Role of Laser Photocoagulation in Treating Diabetic Macular Edema in the Era of Intravitreal Drug Administration: A Descriptive Review

Background and Objectives: This study aimed to elucidate the role of laser photocoagulation therapy in the treatment of diabetic macular edema (DME) as an alternative to, or in conjunction with, the first-line treatment, anti-vascular endothelial growth factor (VEGF). Materials and Methods: A comprehensive literature search to identify studies that evaluated the efficacy of laser photocoagulation therapy in the management of DME was performed. The relevant findings of the efficacy of focal/grid laser therapy from data in randomized, controlled trials were synthesized, and the potential of new laser technologies, such as navigated laser systems, pattern scan lasers, and subthreshold lasers, was explored. The usefulness of multimodal imaging-guided laser therapy was also evaluated, with a focus on the potential contribution to anti-VEGF therapy. Results: Focal laser photocoagulation targeting microaneurysms remains an effective therapeutic approach to chronic refractory edema, despite the widespread use of anti-VEGF therapy. To achieve the best possible treatment outcomes, precise identification of microaneurysms is essential. This requires the use of multimodal imaging-guided, highly accurate, minimally invasive coagulation techniques. Subthreshold laser therapy can also reduce the frequency of anti-VEGF injections and minimize treatment burden. Conclusions: Further studies are needed to determine the optimal timing and settings for laser photocoagulation therapy and the potential of new laser technologies in the management of DME. Nevertheless, laser photocoagulation therapy plays an important role in the management of DME, in conjunction with anti-VEGF therapy.

HENLE FIBER LAYER THICKNESS AND AREA MEASUREMENT IN TYPE 2 DIABETES MELLITUS WITH AND WITHOUT RETINOPATHY USING A MODIFIED DIRECTIONAL OPTICAL COHERENCE TOMOGRAPHY STRATEGY

PURPOSE

To investigate the thicknesses and areas of Henle fiber layer (HFL), outer nuclear layer, and outer plexiform layer in the eyes of patients with diabetes with no diabetic retinopathy, in eyes with nonproliferative diabetic retinopathy without diabetic macular edema, and in healthy eyes using a modified directional optical coherence tomography strategy.

METHODS

In this prospective study, the no diabetic retinopathy group included 79 participants, the nonproliferative diabetic retinopathy group comprised 68 participants, and the control group had 58 participants. Thicknesses and areas of Henle fiber layer, outer nuclear layer, and outer plexiform layer were measured on a horizontal single optical coherence tomography scan centered on the fovea using directional optical coherence tomography.

RESULTS

The foveal, parafoveal, and total HFL were significantly thinner in the nonproliferative diabetic retinopathy group than in the no diabetic retinopathy group and the control group (all P < 0.05). The no diabetic retinopathy group had significantly thinner foveal HFL thickness and area compared with the control group (all P < 0.05). The nonproliferative diabetic retinopathy group had significantly thicker outer nuclear layer thickness and area in all regions than the other groups (all P < 0.05). The outer plexiform layer measurements did not differ between the groups (all P > 0.05).

CONCLUSION

Directional optical coherence tomography provides isolated thickness and area measurement of HFL. In patients with diabetes, the HFL is thinner, and HFL thinning begins before the presence of diabetic retinopathy.

Bridging the resources gap: deep learning for fluorescein angiography and optical coherence tomography macular thickness map image translation

Background

To assess the ability of the pix2pix generative adversarial network (pix2pix GAN) to synthesize clinically useful optical coherence tomography (OCT) color-coded macular thickness maps based on a modest-sized original fluorescein angiography (FA) dataset and the reverse, to be used as a plausible alternative to either imaging technique in patients with diabetic macular edema (DME).

Methods

Original images of 1,195 eyes of 708 nonconsecutive diabetic patients with or without DME were retrospectively analyzed. OCT macular thickness maps and corresponding FA images were preprocessed for use in training and testing the proposed pix2pix GAN. The best quality synthesized images using the test set were selected based on the Fréchet inception distance score, and their quality was studied subjectively by image readers and objectively by calculating the peak signal-to-noise ratio, structural similarity index, and Hamming distance. We also used original and synthesized images in a trained deep convolutional neural network (DCNN) to plot the difference between synthesized images and their ground-truth analogues and calculate the learned perceptual image patch similarity metric.

Results

The pix2pix GAN-synthesized images showed plausible subjectively and objectively assessed quality, which can provide a clinically useful alternative to either image modality.

Conclusion

Using the pix2pix GAN to synthesize mutually dependent OCT color-coded macular thickness maps or FA images can overcome issues related to machine unavailability or clinical situations that preclude the performance of either imaging technique.

Trial registration

ClinicalTrials.gov Identifier: NCT05105620, November 2021. “Retrospectively registered”.

The Role of Intravitreal Corticosteroids in the Treatment of DME: Predictive OCT Biomarkers

This work aims to summarize predictive biomarkers to guide treatment choice in DME. Intravitreal anti-VEGF is considered the gold standard treatment for centers involving DME, while intravitreal steroid treatment has been established as a second-line treatment in DME. However, more than 1/3 of the patients do not adequately respond to anti-VEGF treatment despite up to 4-weekly injections. Not surprisingly, insufficient response to anti-VEGF therapy has been linked to low-normal VEGF levels in the serum and aqueous humor. These patients may well benefit from an early switch to intravitreal steroid treatment. In these patients, morphological biomarkers visible in OCT may predict treatment response and guide treatment decisions. Namely, the presence of a large amount of retinal and choroidal hyperreflective foci, disruption of the outer retinal layers and other signs of chronicity such as intraretinal cysts extending into the outer retina and a lower choroidal vascular index are all signs suggestive of a favorable treatment response of steroids compared to anti-VEGF. This paper summarizes predictive biomarkers in DME in order to assist individual treatment decisions in DME. These markers will help to identify DME patients who may benefit from primary dexamethasone treatment or an early switch.

Direct Photocoagulation for Treating Microaneurysms with Hyperreflective Ring in Eyes with Refractory Macular Edema Associated with Branch Retinal Vein Occlusion

Microaneurysms (MAs) with hyperreflective rings are sometimes detected in eyes with refractory macular edema (ME) associated with branch retinal vein occlusion (BRVO) for more than 12 months after onset when examined using optical coherence tomography (OCT). We proposed that these MAs could result in refractory ME secondary to BRVO and hypothesized that OCT-guided direct photocoagulation of MAs could result in a reduction in refractory ME. Eleven eyes (from eleven different patients) with refractory ME associated with BRVO for more than 12 months following initial treatment were included. The mean number of MAs in each eye at baseline was 3.5 ± 2.0 (range, 1–8). The mean central subfield thickness, central macular volume, and parafoveal macular volume significantly decreased 6 months following initial direct photocoagulation when compared with those at baseline (baseline = 378.7 ± 61.8 μm, post-treatment = 304.2 ± 66.7 μm, p = 0.0005; baseline = 0.3 ± 0.049 mm³, post-treatment = 0.24 ± 0.053 mm³, p = 0.001; and baseline = 2.5 ± 0.14 mm³, post-treatment = 2.28 ± 0.15 mm³, p = 0.001, respectively). Moreover, the mean best-corrected visual acuity significantly improved 6 months following initial direct photocoagulation when compared with that at baseline (baseline = 0.096 ± 0.2 logarithm of the minimum angle of resolution (logMAR), post-treatment = 0.0077 ± 0.14 logMAR, p = 0.031). Direct photocoagulation could be suggested as a treatment option for refractory ME associated with BRVO in MAs with a hyperreflective ring on OCT.

Optical Coherence Tomography Angiography in Diabetic Patients: A Systematic Review

Background: Diabetic retinopathy (DR) is the leading cause of legal blindness in the working population in developed countries. Optical coherence tomography (OCT) angiography (OCTA) has risen as an essential tool in the diagnosis and control of diabetic patients, with and without DR, allowing visualisation of the retinal and choroidal microvasculature, their qualitative and quantitative changes, the progression of vascular disease, quantification of ischaemic areas, and the detection of preclinical changes. The aim of this article is to analyse the current applications of OCTA and provide an updated overview of them in the evaluation of DR. Methods: A systematic literature search was performed in PubMed and Embase, including the keywords “OCTA” OR “OCT angiography” OR “optical coherence tomography angiography” AND “diabetes” OR “diabetes mellitus” OR “diabetic retinopathy” OR “diabetic maculopathy” OR “diabetic macular oedema” OR “diabetic macular ischaemia”. Of the 1456 studies initially identified, 107 studies were screened after duplication, and those articles that did not meet the selection criteria were removed. Finally, after looking for missing data, we included 135 studies in this review. Results: We present the common and distinctive findings in the analysed papers after the literature search including the diagnostic use of OCTA in diabetes mellitus (DM) patients. We describe previous findings in retinal vascularization, including microaneurysms, foveal avascular zone (FAZ) changes in both size and morphology, changes in vascular perfusion, the appearance of retinal microvascular abnormalities or new vessels, and diabetic macular oedema (DME) and the use of deep learning technology applied to this disease. Conclusion: OCTA findings enable the diagnosis and follow-up of DM patients, including those with no detectable lesions with other devices. The evaluation of retinal and choroidal plexuses using OCTA is a fundamental tool for the diagnosis and prognosis of DR.

Indicators of Visual Prognosis in Diabetic Macular Oedema

Diabetic macular oedema (DMO) is an important cause of moderate vision loss in people with diabetes. Advances in imaging technology have shown that a significant proportion of patients with DMO respond sub-optimally to existing treatment options. Identifying associations and predictors of response before treatment is initiated may help in explaining visual prognosis to patients and aid the development of personalized treatment strategies. Imaging features, such as central subfoveal thickness, photoreceptor integrity, disorganization of retinal inner layers, choroidal changes, and macular perfusion, have been reported to be prognostic factors of visual acuity (VA) in DMO. In this review we evaluated each risk factor to understand their relative importance in visual prognostication of DMO eyes post-treatment. Although individually, some of these factors may not be significant predictors, in combination they may form phenotypes that can inform visual prognosis. Stratification based on these phenotypes needs to be developed to progress to personalized medicine for DMO.

Increased expression of Protein S in eyes with diabetic retinopathy and diabetic macular edema

Protein S (PS) is a multifunctional glycoprotein that ameliorates the detrimental effects of diabetes mellitus (DM). The aim of this study was to evaluate the distribution of PS in diabetic retinopathy (DR) and diabetic macular edema (DME). This was a study of 50 eyes with DM (37 with DME, 6 with proliferative DR, and 7 with no DR) and 19 eyes without DM. The level of PS was measured by enzyme immunoassay and was compared between eyes with or without DM, with or without DME, and with severe DME (≥ 350 μm) or mild DME (< 350 μm). We also performed immunohistopathologic evaluations of post-mortem eyes and the cystoid lesions excised during surgery. The aqueous free PS was significantly higher with DM (7.9 ± 1.2 ng/ml, P < 0.01) than without DM (6.1 ± 0.7). The aqueous free PS was significantly elevated with DME (8.2 ± 1.2, P < 0.05) compared to proliferative DR (7.0 ± 1.0) and no DR (7.0 ± 0.7). Eyes with severe DME had significantly higher aqueous free PS than mild DME (8.5 ± 1.3 vs. 7.7 ± 1.0, P < 0.05). Immunohistochemistry showed PS in the outer plexiform layer of the retina and cystoid lesion. The higher expression of PS with DR and DME suggests that PS is involved in their pathogenesis.

En face image-based classification of diabetic macular edema using swept source optical coherence tomography

This retrospective study was performed to classify diabetic macular edema (DME) based on the localization and area of the fluid and to investigate the relationship of the classification with visual acuity (VA). The fluid was visualized using en face optical coherence tomography (OCT) images constructed using swept-source OCT. A total of 128 eyes with DME were included. The retina was segmented into: Segment 1, mainly comprising the inner nuclear layer and outer plexiform layer, including Henle’s fiber layer; and Segment 2, mainly comprising the outer nuclear layer. DME was classified as: foveal cystoid space at Segment 1 and no fluid at Segment 2 (n = 24), parafoveal cystoid space at Segment 1 and no fluid at Segment 2 (n = 25), parafoveal cystoid space at Segment 1 and diffuse fluid at Segment 2 (n = 16), diffuse fluid at both segments (n = 37), and diffuse fluid at both segments with subretinal fluid (n = 26). Eyes with diffuse fluid at Segment 2 showed significantly poorer VA, higher ellipsoid zone disruption rates, and greater central subfield thickness than did those without fluid at Segment 2 (P < 0.001 for all). These results indicate the importance of the localization and area of the fluid for VA in DME.

Long-term full-field and multifocal electroretinographic changes after treatment with ranibizumab in patients with diabetic macular edema

PURPOSE

To investigate changes in macular and panretinal neuroretinal functions by electroretinographic examinations in eyes with diabetic macular edema (DME) treated with intravitreal ranibizumab.

MATERIAL AND METHODS

Sixty-four patients with DME were included in this prospective study. Patients were treated with ranibizumab injection according to the PRN regimen for over 12 months. Before treatment, all patients underwent fundus fluorescein angiography, optical coherence tomography (OCT), best-corrected visual acuity (BCVA) assessment, full-field (ff-ERG), and multifocal electroretinography (mf-ERG). In monthly visits, BCVA and OCT were performed. Besides, mf-ERG recordings were obtained at months 3, 6, 9, and 12, and ff-ERG was performed at month 12.

RESULTS

Fifty-eight patients completed the study. The mean age was 61.1 ± 8.5 (39-80) years. The mean number of injections was 6.19 ± 1.9. The decimal BCVA improved from 0.30 to 0.45 during the 12-month follow-up (p < 0.05). Macular thickness decreased from 413.5 μm to 329.5 μm (p < 0.05). The mf-ERG recordings in the central macular region showed improvements N1 and P1 amplitudes at months 9 and 12. There was a positive correlation between the baseline central (p < 001; r: - 0.378 and p < 0.05; r:-0.335, respectively), the second ring (p < 0.05; r: - 0.260 and p < 0.05; r: - 0.270, respectively) P1- and N1-wave amplitudes, and the BCVA at month 12. Full-field ERG recordings showed that peripheral neuroretinal responses were maintained or improved at month 12. Statistically significant improvements in BCVA and macular thickness were observed at all follow-up visits.

CONCLUSION

Multifocal electroretinographic recording started to improve 6 months after the beginning of intravitreal ranibizumab treatment in eyes with DME. This improvement was significant at months 9 and 12. A significant improvement in ff-ERG was observed at month 12.

Evaluation of morphological characteristics of diabetic macular edema in patients with non-proliferative versus proliferative diabetic retinopathy: a spectral-domain optical coherence tomography study

PURPOSE

To evaluate the morphological characteristics in patients with diabetic macular edema (DME), either with co-existent non-proliferative diabetic retinopathy (NPDR) or with PDR.

METHODS

Retrospective study includes 138 treatment naïve patients with DME, either with NPDR (n = 96) or in combination with PDR (n = 42). All patients underwent best corrected visual acuity (BCVA) measurement, spectral domain-optical coherence tomography (SD-OCT) and fluorescein angiography, while demographic characteristics were also recorded. Specific clinical and morphological characteristics were analyzed and compared between the two groups.

RESULTS

Patients with DME and PDR presented higher central retinal thickness and mixed type of edema, with predominantly cystoid component and large cysts, extending in the foveal, peri- and para-foveal area, compared to patients with DME and NPDR. The presence of non-perfusion areas in patients with DME and PDR led to additional ellipsoid zone and external limiting membrane disruption in a higher percentage, accompanied with worse visual acuity compared to patients with DME and NPDR. Patients with DME and PDR had also higher vitreomacular traction percentage and higher HbA1c levels than those with DME and NPDR.

CONCLUSION

Variations in morphological characteristics of DME on SD-OCT existed between patients with NPDR and those with PDR. These differences may explain the alterations in visual acuity and prognosis.

Development of a 1-year risk-prediction nomogram for good functional response with anti-VEGF agents in naive diabetic macular oedema

PURPOSE

To develop a risk-prediction nomogram based on baseline variables for good functional response during the 1st year of treatment with anti-VEGF agents in naive diabetic macular oedema (DME).

METHODS

This retrospective study included patients presenting naive-DME treated with anti-VEGF therapy at Dijon University Hospital (France) between 1 February 2012 and 31 March 2015 (derivation cohort). We studied baseline variables that had significant associations with a good functional response to anti-VEGF agents during the 1st year of treatment. We used a program to generate a nomogram based on a binary logistic regression predictive model. Then, this nomogram was tested on data from a separate cohort of naive-DME patients from a multicenter study involving 20 French ophthalmologic centres between January 2014 and June 2015 (validation cohort).

RESULTS

Age, baseline BCVA and ellipsoid zone integrity on spectral-domain optical coherence tomography (SD-OCT) are functional prognostic factors and were used to build a nomogram. The nomogram showed excellent discrimination for good functional responders (area under the curve (AUC) = 0.906, 95% confidence interval (95% CI) = [0.849-0.964], p = 0.004). The discriminative power of this nomogram was tested on the validation cohort data, demonstrating good discrimination of good functional responders (AUC = 0.942, 95% CI = [0.898-0.986], p < 0.001).

CONCLUSION

This nomogram provides a useful estimation of a good functional response in naive-DME patients treated with anti-VEGF agents.

The Effect of Anti-Vascular Endothelial Growth Factor on Retinal Microvascular Changes in Diabetic Macular Edema Using Swept-Source Optical Coherence Tomography Angiography

Purpose

This study evaluates the effect of anti-vascular endothelial growth factor (anti-VEGF) therapy on microaneurysm changes and foveal avascular zone (FAZ) using optical coherence tomography angiography (OCTA) in patients with diabetic macular edema (DME).

Design

Prospective observational study.

Materials and Methods

This study involved patients with DME undergoing anti-VEGF treatment (aflibercept, ranibizumab, and bevacizumab). Macula OCTA images were obtained before (visit 0) and 1 month after (visit 1) anti-VEGF injection. Microaneurysm counts were performed, and the FAZ was evaluated in the superficial capillary plexus (SCP) and deep capillary plexus (DCP). The differences in microaneurysms, FAZ, and clinical correlations were analyzed.

Results

A total of 152 eyes were analyzed. The patients' mean age was 59 years. Bevacizumab was used in 69.7%, ranibizumab in 15.1%, and aflibercept in 15.1%. There was a significant reduction in the FAZ in the SCP and DCP between visits 0 and 1. All anti-VEGF medications reduced the number of microaneurysms (p<0.01). After treatment, changes in the FAZ in SCP and DCP corresponded with changes in visual acuity (p<0.01).

Conclusion

Microaneurysms as detected by OCTA might serve as a biomarker for a clinical response to anti-VEGF treatment in the short term. The FAZ might also predict visual acuity improvement after anti-VEGF injection.

Trial Registration

Thai Clinical Trials Registry (TCTR20161010005).

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.

Evaluation of different Swept'Source optical coherence tomography angiography (SS-OCTA) slabs for the detection of features of diabetic retinopathy

PURPOSE

To compare different Swept-Source optical coherence tomography angiography (SS-OCTA) slabs for the detection of features of diabetic retinopathy (DR), to find the most suitable slab for grading.

METHODS

Retrospective cross-sectional study. Consecutive patients with DR were evaluated using SS-OCTA. The central 12 × 12 mm scan was used to generate the retinal, superficial and deep slab. The grading results of the slabs were then compared to determine if one specific slab is superior to detect respective features.

RESULTS

A total of 348 eyes (190 patients; mean age 58.1 ± 14.5 years) were graded for features of DR. The retinal slab detected most frequently MAs and IRMAs, however with no significant difference compared to the superficial slab (p = 0.93 and p = 0.93, respectively). Small capillary dropout was most frequently found on the superficial slab, but there was no significant difference compared with the retinal (p = 0.78) and deep slab (p = 0.45). The only statistically significant difference was found for large capillary dropout, where the retinal and superficial slab showed a higher detection rate compared with the deep slab (p ≤ 0.0001 and p = 0.001, respectively).

CONCLUSIONS

The superficial and retinal slabs are equally suitable for grading with no statistically significant difference in the detection rate of the diabetic features examined.

Differentiation of Underlying Pathologies of Macular Edema Using Spectral Domain Optical Coherence Tomography (SD-OCT)

Purpose: To describe the morphological characteristics of macular edema (ME) of different origins using spectral domain optical coherence tomography (SD-OCT). Methods: This article summarizes and highlights key morphologic findings, based on published articles, describing the characteristic presentations of ME of different origins using SD-OCT. The following pathologies were included: uveitic macular edema, pseudophakic cystoid macular edema (PCME), diabetic macular edema (DME), macular edema secondary to central or branch retinal vein occlusion (CRVO/BRVO), microcystic macular edema (MME), ME associated with epiretinal membrane (ERM), and retinitis pigmentosa (RP). Conclusions: Macular edema of different origins show characteristic patterns that are often indicative of the underlying cause and pathology. Thus, trained algorithms may in the future be able to automatically differentiate underlying causes and support clinical diagnosis. Knowledge of different appearances support the clinical diagnosis and can lead to improved and more targeted treatment of ME.

The impact of ganglion cell layer cysts in diabetic macular oedema treated with anti-vascular endothelial growth factor

PURPOSE

To investigate the prevalence and impact of ganglion cell layer cysts (GCLC) in patients with diabetic macular oedema (DME) under continuous anti-vascular endothelial growth factor (VEGF) therapy.

METHODS

The clinical findings and spectral domain optical coherence devices of baseline visits and follow-up after 12-24 and 36 months of DME patients under continuous anti-VEGF therapy were retrospectively collected and analysed for the impact of GCLC cysts. Previously established prognostic parameters were also assessed.

RESULTS

A total of 110 eyes of 110 DME patients (mean age 64 ± 10 years) were included. At baseline, 17% eyes had GCLC. With GCLC, the best-corrected visual acuity (BCVA) improvement was in mean 8.4 ± 2.4 Early-Treatment-Diabetic-Retinopathy-Study (ETDRS) letters less over the course of 36 months compared to the group lacking GCLC (p = 0.0009). Eyes with GCLC showed 68 ± 23.4 μm less central retinal thickness (CRT) decrease than eyes lacking GCLC (p < 0.0001). In the linear mixed effect models including external limiting membrane disruption, disintegration of inner retinal layer and epiretinal membrane, GCLC remained a statistical significant factor for the outcome parameter CRT, but missed statistical significance for BCVA.

CONCLUSION

Ganglion cell layer cysts (GCLC) seem to impact outcome in DME in patients receiving long-term treatment. This prognostic factor warrants further evaluation in the context of already well-established outcome parameters.

The effect of image quality on the reliability of OCT angiography measurements in patients with diabetes

Background

This study aimed to determine the relationship between image quality and measurement repeatability of optical coherence tomography angiography (OCTA) parameters in patients with non-proliferative diabetic retinopathy.

Methods

A total of 100 eyes of 50 patients were included in the study. Three OCTA images were obtained consecutively during one session of imaging in all patients using the RTVue AngioVue OCTA device. We applied the signal strength index (SSI) provided by the RTVue system to define scan quality. Superficial vessel density (VD) in the central 3 × 3 mm macular and in the perifoveal region, as well as foveal avascular zone (FAZ) area were evaluated by the AngioAnalytics software for each scan from three consecutive measurements, whereby measurement repeatability of the OCTA parameters were calculated. The effect of SSI value on OCTA parameters, as well as on measurement errors was assessed.

Results

Values of SSI ranged from 30 to 85 with an overall mean of 61.79 ± 10.38. Mean SSI values showed significant positive correlation with the mean retinal capillary vessel density values, but not with non-flow area. Repeatability of OCTA parameters was generally improved with higher SSI values. We calculated a mean correction factor of 0.22% (95% CI 0.20–0.24 µm; p < 0.001) for VD at the 3 × 3 mm macular scan, 0.23% (95% CI 0.21–0.26%; p < 0.001) for perifoveal VD and − 0.001 mm² (95% CI − 0.001 to 0.002; p = 0.001) for the non-flow area for each unit increase in SSI for the comparison of images with different SSI values.

Conclusions

The influence of image quality on OCTA metrics should be considered for image comparisons during follow-up to avoid misinterpretation of small changes in OCTA parameters in patients with diabetes.

Imaging and Biomarkers in Diabetic Macular Edema and Diabetic Retinopathy

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is the leading cause of acquired vision loss in adults across the globe. Early identification and treatment of patients with DR is paramount for vision preservation. The aim of this review paper is to outline current and new imaging techniques and biomarkers that are valuable for clinical diagnosis and management of DR.

RECENT FINDINGS

Ultrawide field imaging and automated deep learning algorithms are recent advancements on traditional fundus photography and fluorescein angiography. Optical coherence tomography (OCT) and OCT angiography are techniques that image retinal anatomy and vasculature and OCT is routinely used to monitor response to treatment. Many circulating, vitreous, and genetic biomarkers have been studied to facilitate disease detection and development of new treatments. Recent advancements in retinal imaging and identification of promising new biomarkers for DR have the potential to increase detection, risk stratification, and treatment for patients with DR.

Correlation of retinal layer changes with vision gain in diabetic macular edema during conbercept treatment

Backgrounds

To assess the changes in individual retinal layer thickness and visual function associated with gains in visual acuity after an intravitreal conbercept injection in the diabetic macular edema (DME) on spectral domain optical coherence tomography (SD-OCT) and microperimetry during 1-year follow-up.

Methods

Retrospective observational study. Twenty patients with clinically significant DME in the study eye were imaged by SD-OCT every 3 months and MP1 microperimeter in the third month while receiving anti-vascular endothelial growth factor (VEGF) (conbercept) treatment. In each patient, seven retinal layers were segmented in 98 scans covering a 6 mm × 6 mm area of the macula at baseline and during 1 year of treatment. An automatic, full-threshold microperimetry of the central field (10° × 10°, 40 stimulated points) with the MP1 microperimeter. Thickness and microperimetry changes were quantitatively measured and evaluated for their correlation with increases in visual acuity.

Results

Although thicknesses of the inner nuclear layer (INL) and the outer nuclear layer (ONL) were reduced the most after treatment (p < 0.05), decreases of the ganglion cell layer (GCL) (r = 0.591, p = 0.006) and inner plexiform layer (IPL) (r = 0.663, p = 0.001) in central subfield area was associated with best-corrected visual acuity (BCVA) gain, and had the best estimation of BCVA gain (adjust R² = 0.544). Mean macular sensitivity in the central subfield was also well correlated with BCVA gain (r = 0.531, p = 0.016).

Conclusions

Neural recovery occurred after the resolution of edema during conbercept treatment, due to the decreases in GCL and IPL associating with gains in vision and improved microperimetry.

Electronic supplementary material

The online version of this article (10.1186/s12886-019-1131-0) contains supplementary material, which is available to authorized users.

Multimodal OCT Reflectivity Analysis of the Cystoid Spaces in Cystoid Macular Edema

Purpose

To compare and evaluate images of macular cysts with different degrees of reflectivity (from gray to black signal) as observed in B scan spectral domain OCT (SDOCT) and EnFace OCT with decorrelation signal obtained with OCT-angiography (OCTA) in eyes with cystoid macular edema (CME) secondary to diabetic retinopathy (DR) and retinal vein occlusion (RVO).

Methods

Images from 3033 patients affected by CME secondary to diabetes or RVO examined OCTA (Optovue XR Avanti, Optovue, USA) at the University Eye Clinic of Créteil, Hôpital Intercommunal, France, and at the University Eye Clinic of Cagliari, “San Giovanni di Dio” Hospital, Italy, were retrospectively examined. The deep capillary plexus OCTA images and the corresponding EnFace OCT images, both acquired with the same automatic segmentation, had been overlapped to compose RGB color images as red and green channels, respectively, using ImageJ software (National Institutes of Health, Bethesda, MD). Afterward, linear regions of interest were traced on the color images to obtain the profiles of OCTA and EnFace gray values. Number of pixels, mean gray value and standard deviation of the area traced in OCT-A, and EnFace image were analyzed and statistically correlated. Data were exported to Excel to create the plots.

Results

94 patients with DME and 27 patients with RVO showed intraretinal macular cystoid spaces with similar homogeneous, gray-looking content; 73 patients with DME and 113 patients with RVO showed macular cystoid spaces with homogeneous, black-looking content, as observed at SD-OCT, EnFace and OCTA scans. Interestingly, the limits of macular cystoid spaces were clearly detectable with OCTA. The analysis of red and green profiles demonstrated a clearly visible overlap between average OCTA and EnFace signal observed around cystoid spaces that could be attributed to a relationship between the dynamic vascularization and the structural density of the tissue.

Conclusions

This is the first investigation that characterizes and correlates OCTA and EnFace signals on images of macular cystoid spaces in DR and RVO. The low intensity OCTA signals observed inside cystoid spaces raise a relevant question about their nature, as to whether they are due to the presence of corpusculated material pouring out from bloodocular-barrier or they should be considered OCTA artifacts.

Visualizing Structure and Vascular Interactions: Macular Nonperfusion in Three Capillary Plexuses

BACKGROUND AND OBJECTIVE

To assess the relationship between retinal vascular and structural changes in the superficial, middle, and deep capillary plexuses (SCP, MCP, DCP) using optical coherence tomography angiography (OCTA) and en face OCT.

PATIENTS AND METHODS

Patients with diabetic retinopathy were imaged using the Cirrus HD-OCT with AngioPlex. Using manual segmentation of the retinal layers, the authors compared OCTA to en face OCT images to examine corresponding patterns in each of the three capillary plexuses.

RESULTS

Areas of decreased perfusion and capillary dropout on OCTA were found to be associated with three corresponding lesions on en face OCT: hyporeflectivity, cystic edema, and hard exudates. Vascular changes in individual capillary plexuses corresponded with structural changes in their respective perfused retinal layers.

CONCLUSIONS

Using manual segmentation on OCTA, the authors provide a framework to visualize the relationship between vascular pathology on OCTA and structural changes on en face OCT within specific capillary plexuses. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e182-e190.].

Three-dimensional analysis of morphologic changes and visual outcomes in diabetic macular edema

PURPOSE

To investigate the association of retinal fluid volume with the visual and anatomic outcomes of patients with diabetic macular edema (DME) after treatment with bevacizumab.

STUDY DESIGN

Retrospective observational study.

METHODS

We retrospectively analyzed 65 eyes of 58 DME patients treated with bevacizumab. The volumes of the inner intraretinal fluid (IRF) in the inner nuclear layer (INL), outer IRF in the outer plexiform layer (OPL)/outer nuclear layer (ONL), and subretinal fluid (SRF) were calculated. The correlations between the baseline fluid volumes and best-corrected visual acuity (BCVA), area of disorganization of the retinal inner layers (DRIL), disrupted external limiting membrane (ELM), and disrupted ellipsoid zone (EZ) at 12 months after treatment were assessed.

RESULTS

The baseline volume of the inner IRF correlated with poor BCVA at the final visit (r = 0.52, P < .001) whereas the baseline volume of the outer IRF and SRF volume did not show a significant correlation with BCVA at the final visit (P = .07 and P = .61, respectively). The improvement in BCVA correlated with the reduction in the baseline volume of the inner IRF and outer IRF (r = 0.25, P = .04 and r = 0.36, P = .003), but not with the SRF volume (P = .59). The baseline volume of the inner IRF correlated positively with the area of DRIL and the disrupted ELM at the final visit (r = 0.56, P < .001 and r = 0.25, P = .04, respectively). Such relationship remained in each quadrant of the macula (P < .005 for all quadrants).

CONCLUSION

The baseline volume of the inner IRF correlated with a poor visual outcome, an increased DRIL area, and a more disrupted ELM area in patients with DME after treatment with bevacizumab.

Role of Inflammation in Classification of Diabetic Macular Edema by Optical Coherence Tomography

Diabetic macular edema (DME) is the abnormal accumulation of fluid in the subretinal or intraretinal spaces in the macula in patients with diabetic retinopathy and leads to severely impaired central vision. Technical developments in retinal imaging systems have led to many advances in the study of DME. In particular, optical coherence tomography (OCT) can provide longitudinal and microstructural analysis of the macula. A comprehensive review was provided regarding the role of inflammation using OCT-based classification of DME and current and ongoing therapeutic approaches. In this review, we first describe the pathogenesis of DME, then discuss the classification of DME based on OCT findings and the association of different types of DME with inflammation, and finally describe current and ongoing therapeutic approaches using OCT-based classification of DME. Inflammation has an important role in the pathogenesis of DME, but its role appears to differ among the DME phenotypes, as determined by OCT. It is important to determine how the different DME subtypes respond to intravitreal injections of steroids, antivascular endothelial growth factor agents, and other drugs to improve prognosis and responsiveness to treatment.

Hyperreflective foci on optical coherence tomography associate with treatment outcome for anti-VEGF in patients with diabetic macular edema

Purpose

To investigate the relationship between baseline number of hyperreflective foci (HF) on spectral domain optical coherence tomography (SD-OCT) in patients with diabetic macular edema (DME), as well as the dynamics of HF during treatment with anti-vascular endothelial growth factor (VEGF), and treatment response.

Methods

We evaluated patients diagnosed with DME scheduled for treatment with intravitreal bevacizumab. Eyes were classified as adequate or insufficient treatment responders based on logMAR visual acuity improvement and central retinal thickness (CRT) decrease after three consecutive injections. Associations between number of HF at baseline and treatment response, the change in HF over the course of treatment, and the distribution of HF within the retinal layers were evaluated.

Results

In 54 eyes of 41 patients, mean number of HF and CRT decreased after intravitreal treatment with bevacizumab (p = 0.002 and p<0.001 respectively). Decrease in CRT after 3 months was independently associated with a higher number of HF at baseline (estimated effect -2.61, 95% CI [-4.42–-0.31], p = 0.006). Eyes with adequate treatment response presented with more HF at baseline (OR 1.106, 95% CI [1.012–1.210], p = 0.030) than eyes with insufficient treatment response. Most HF were located within the inner retinal layers, and decrease of HF was mostly due to a decrease of inner retinal HF.

Conclusions

In patients with DME treated with anti-VEGF, higher baseline numbers of HF have predictive value for treatment response in terms of visual acuity improvement and CRT decrease after 3 months. In addition, HF were responsive to anti-VEGF therapy.

Intrasession and Between-Visit Variability of Retinal Vessel Density Values Measured with OCT Angiography in Diabetic Patients

In clinical practice the measurement error of an instrument has special importance in analyzing and interpreting data, and acknowledging limitations. The purpose of this study was to evaluate intrasession and between-visit reproducibility of OCT angiography measurements in diabetic patients. A total of 54 eyes of 27 diabetic patients underwent OCT angiography imaging. Foveal avascular zone (FAZ) area and superficial retinal vessel density (VD) at 3 mm were calculated using the AngioAnalytics software. Three consecutive images were acquired at first visit and one image 1 month later. Intrasession and between-visit reproducibility of parameters were characterized by intraclass correlation coefficient (ICC), coefficient of variation (CV), and coefficient of repeatability (CR) values. We measured excellent (>0.90) ICC values both in intrasession and between-visit comparisons. CV was higher for the FAZ area compared to VD both in intrasession (7.79% vs. 2.87%) and in between-visit (12.33% vs. 2.95%) comparisons. Between-visit CR value for VD was 4.53% (95% CI: 3.72–5.79%). These data suggest that OCT angiography shows excellent repeatability in diabetic patients, indicating that this non-invasive technology might be suitable for longitudinal assessment of microvascular complications.

Suspended Scattering Particles in Motion: A Novel Feature of OCT Angiography in Exudative Maculopathies

OBJECTIVE

To characterize features of extra-vascular optical coherence tomography angiography (OCTA) signals corresponding to hyperreflective intraretinal fluid across various exudative maculopathies.

DESIGN

Multicenter, retrospective, observational study.

PARTICIPANTS

Eyes with various forms of exudative maculopathy including diabetic retinopathy (DR), retinal vein occlusion (RVO), and neovascular-age related macular degeneration (nvAMD).

METHODS

Patients with extra-vascular OCTA signal identified on en face OCTA images were included in this study. This signal was readily distinguishable from projection artifacts. The regions with the extra-vascular motion signal on OCTA were named "Suspended Scattering Particles in Motion (SSPiM)." Depth-encoded, color, en face OCTA images (3mm × 3mm) centered on the fovea and their corresponding structural OCT scans were used to quantify features of SSPiM and its corresponding hyperreflective fluid. Longitudinal data were collected when available.

MAIN OUTCOME MEASURES

Anatomic location, the association with hyperreflective material, changes in location and appearance of SSPiM over time, and replication of SSPiM OCTA signal in an in vitro phantom.

RESULTS

Seventy-six eyes in 62 patients with various forms of exudative maculopathy were evaluated; 60 eyes with DR, 9 eyes with RVO, and 5 eyes nvAMD, 1 eye with macroaneurysm, and 1 eye with radiation retinopathy. Intraretinal accumulations of fluid with increased OCT signal intensity corresponded to regions of SSPiM in several exudative maculopathies. An in vitro phantom model demonstrates that particulate matter in suspension can generate similar OCTA signal. SSPiM showed an anatomic preference for vascular-avascular junctions. The hyperreflective fluid corresponding to SSPiM appeared more frequently in Henle's fiber layer (HFL) than the inner nuclear layer (INL) and was highly associated with hyperreflective material (HRM) found bordering the fluid. In five of eight longitudinal cases, the resolution of SSPiM resulted in the formation of confluent HRM. Clinically, this appeared as hard exudate on funduscopic images.

CONCLUSIONS

Clinical data suggest that SSPiM is a novel imaging feature of retinal vascular diseases that was not appreciated prior to the use of OCTA. We characterized several novel features of SSPiM and demonstrated that at least in some cases it resolves with residual hard exudate.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Multiscale sensorless adaptive optics OCT angiography system for in vivo human retinal imaging

We present a multiscale sensorless adaptive optics (SAO) OCT system capable of imaging retinal structure and vasculature with various fields-of-view (FOV) and resolutions. Using a single deformable mirror and exploiting the polarization properties of light, the SAO-OCT-A was implemented in a compact and easy to operate system. With the ability to adjust the beam diameter at the pupil, retinal imaging was demonstrated at two different numerical apertures with the same system. The general morphological structure and retinal vasculature could be observed with a few tens of micrometer-scale lateral resolution with conventional OCT and OCT-A scanning protocols with a 1.7-mm-diameter beam incident at the pupil and a large FOV (15 deg× 15 deg). Changing the system to a higher numerical aperture with a 5.0-mm-diameter beam incident at the pupil and the SAO aberration correction, the FOV was reduced to 3 deg× 3 deg for fine detailed imaging of morphological structure and microvasculature such as the photoreceptor mosaic and capillaries. Multiscale functional SAO-OCT imaging was performed on four healthy subjects, demonstrating its functionality and potential for clinical utility.

CORRELATION BETWEEN SUBFOVEAL CHOROIDAL THICKNESS AND FOVEAL THICKNESS IN THALASSEMIC PATIENTS

PURPOSE

To assess the impact of two iron chelation modalities in thalassemic patients on foveal and subfoveal choroidal thickness.

METHODS

The study included 60 β-thalassemia major patients. They included 30 patients on oral deferasirox after a period of subcutaneous deferoxamine (Group 2) and 30 patients on subcutaneous deferoxamine (Group 3). Thirty age- and sex-matched healthy children were included as a control group (Group 1). All participants underwent a complete ophthalmologic evaluation and Spectral Domain Optical Coherence Tomography.

RESULTS

Age, gender, intraocular pressure, best-corrected visual acuity, and refraction were not statistically different between the three studied groups. Ferritin level, pretransfusion hemoglobin, serum iron, and duration of thalassemia were not statistically different between the two thalassemic groups. Foveal thickness in Group 1 (225.15 ± 17.35 μm) was statistically higher than in Group 2 (210.53 ± 21.73 μm) (P < 0.001) and Group 3 (200.15 ± 7.34 μm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P = 0.001). Subfoveal choroidal thickness in Group 1 (279.70 ± 32.54 μm) was statistically higher than in Group 2 (255.80 ± 19.20 μm) (P < 0.001) and Group 3 (248.28 ± 20.43 μm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P < 0.05).

CONCLUSION

Thalassemic patients can develop a significant decrease in foveal thickness because of the inevitable use of chelation therapy. Deferoxamine as a chelating agent can affect foveal thickness more than the oral form (deferasirox).

RETINAL LAYER RESPONSE TO RANIBIZUMAB DURING TREATMENT OF DIABETIC MACULAR EDEMA: Thinner is Not Always Better

PURPOSE

To identify individual retinal layer thickness changes associated with visual acuity gain in diabetic macular edema treated with ranibizumab using layer segmentation on high-resolution optical coherence tomography scans.

METHODS

Retrospective observational case series. Thirty-three treatment-naive eyes with diabetic macular edema were imaged by spectral domain optical coherence tomography at monthly visits while receiving intravitreal ranibizumab treatment as needed, guided by visual acuity. Thickness changes of individual layers after 1 year were quantitatively analyzed and correlated with visual acuity gain.

RESULTS

The mean best-corrected visual acuity improvement at 1 year was 6.2 (SEM ± 1.5) Early Treatment Diabetic Retinopathy Study letters, and central retinal thickness decreased by 66 ± 18 μm. In the central subfield, there was a significant decrease of thickness for all layers (P < 0.05) except the outer nuclear layer. Multiple linear regression analysis revealed that thickness decrease of the inner retina was associated with better visual acuity, whereas for the outer retina the opposite was true. The best estimate of final visual acuity (R = 0.817, P < 0.001) was obtained, by including baseline visual acuity and thickness change of the inner and outer plexiform layers in the model.

CONCLUSION

Whereas thickness decrease of the inner retina was positively associated with visual acuity gain, the opposite was found for the outer retina. This might be indirect evidence for recovery of the outer retina during ranibizumab treatment.

Evaluation of pseudophakic cystoid macular edema using optical coherence tomography angiography

Purpose:

To compare the optical coherence tomography angiography (OCT-A) findings of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in eyes with pseudophakic cystoid macular edema (PCME) with those of fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT) and to compare PCME vascular density values of the SCP and DCP with those of healthy eyes.

Methods:

In this retrospective observational study, 13 eyes (12 patients) with PCME underwent comprehensive ophthalmologic examinations including visual acuity, FA, SD-OCT, and OCT-A. The vascular density of the SCP and DCP were measured using AngioAnalytics software in all PCME eyes and compared with 46 healthy eyes of 25 subjects.

Results:

In patients with PCME, at the level of SCP, the mean vascular density in the whole en face image was 44.48 ± 3.61% while it was 50.27 ± 5.30% at the level of the DCP. In contrast, the vascular density in the whole en face image was 50.35 ± 3.22 at the level of SCP while it was 56.15 ± 3.28 at the level of DCP in 46 healthy eyes of 25 subjects. The vascular density of patients with PCME was significantly lower than in healthy subjects at the SCP (p<0.0001) and at the DCP (p<0.0001).

Conclusion:

We report the OCT-A appearance of PCME and vascular density map with values that can be easily interpreted for quantitative evaluation of retina perfusion status using OCT-A. This approach might be the first step in helping us fully understand the pathophysiologic mechanisms underlying PCME.

Optical Coherence Tomography Angiography of DME and Its Association with Anti-VEGF Treatment Response

PURPOSE

To investigate the structural integrity of the superficial capillary plexuses (SCPs) and deep capillary plexuses (DCPs) using optical coherence tomography (OCT) angiography (OCTA) in patients with diabetic macular edema (DME) and its association with the response to anti-vascular endothelial growth factor (VEGF) treatment.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

We included 51 DME eyes with a poor response to anti-VEGF agents and 32 age-matched DME eyes with a good response to anti-VEGF treatment, along with 20 fellow eyes without DME from the cases and controls.

METHODS

The medical records, including OCTA and spectral-domain OCT (SD OCT), were reviewed and compared between the groups. En face OCTA images of the SCP and DCP were obtained for each eye. An anti-VEGF responder was defined by a reduction of more than 50 μm in central retinal thickness after 3 consecutive anti-VEGF treatments. A poor responder was defined by a reduction of less than 50 μm or an increase in central retinal thickness after 3 monthly injections.

MAIN OUTCOME MEASURES

We measured the vascular density and foveal avascular zone (FAZ) area and counted the number of microaneurysms in each layer. The SD OCT images were compared with OCTA findings.

RESULTS

Compared with non-DME eyes, DME eyes had a lower vascular density (P < 0.001) and larger FAZ area (P < 0.001) in the DCP and more microaneurysms (P < 0.001) in both layers. Although there was no significant difference in the SCP between anti-VEGF responders and poor responders, poor responders tended to show greater damage and more microaneurysms in the DCP (P < 0.001) and a larger FAZ area (P < 0.001). The topographic location of the disrupted synaptic portion of the outer plexiform layer (OPL) in SD OCT exactly corresponded to the nonflow area of the DCP in OCTA.

CONCLUSIONS

Compared with DME eyes that responded to anti-VEGF treatment, poor responders show significant damage to the integrity of the DCP, but not the SCP. The degree of OPL disruption in SD OCT corresponds well with the extent of DCP loss in DME eyes. The extent of DCP loss and the corresponding OPL disruption could be useful predictors of responsiveness to anti-VEGF treatment.

Contemporary retinal imaging techniques in diabetic retinopathy: a review

Over the last decade, there has been an expansion of imaging modalities available to clinicians to diagnose and monitor the treatment and progression of diabetic retinopathy. Recently, advances in image technologies related to OCT and OCT angiography have enabled improved visualization and understanding of this disease. In this review, we will describe the use of imaging techniques such as colour fundus photography, fundus autofluorescence, fluorescein angiography, infrared reflectance imaging, OCT, OCT-Angiography and techniques in adaptive optics and hyperspectral imaging in the diagnosis and management of diabetic retinopathy.

Diabetic Macular Edema Pathophysiology: Vasogenic versus Inflammatory

Diabetic macular edema (DME) can cause blindness in diabetic patients suffering from diabetic retinopathy (DR). DM parameters controls (glycemia, arterial tension, and lipids) are the gold standard for preventing DR and DME. Although the vascular endothelial growth factor (VEGF) is known to play a role in the development of DME, the pathological processes leading to the onset of this disease are highly complex and the exact sequence in which they occur is still not completely understood. Angiogenesis and inflammation have been shown to be involved in the pathogenesis of this disease. However, it still remains to be clarified whether angiogenesis following VEGF overexpression is a cause or a consequence of inflammation. This paper provides a review of the data currently available, focusing on VEGF, angiogenesis, and inflammation. Our analysis suggests that angiogenesis and inflammation act interdependently during the development of DME. Knowledge of DME etiology seems to be important in treatments with anti-VEGF or anti-inflammatory drugs. Current diagnostic techniques do not permit us to differentiate between both etiologies. In the future, diagnosing the physiopathology of each patient with DME will help us to select the most effective drug.

The discrepancy between central foveal thickness and best corrected visual acuity in cystoid macular edema secondary to central retinal vein occlusion after intravitreal lucentis® injection

Cystoid macular edema is a common retinal disorder with the potential for significant vision-related morbidity, and intravitreal lucentis(®) injection is confirmed to be an effective therapy approach. In the present study, we investigated the discrepancy between central foveal thickness and best corrected visual acuity in such lesions and infered that intravitreal lucentis(®) injection may help the visual function, related to the renewal of cells.

Fluorescein angiography versus optical coherence tomography-guided planning for macular laser photocoagulation in diabetic macular edema

PURPOSE

To compare laser photocoagulation plans for diabetic macular edema (DME) using fluorescein angiography (FA) versus optical coherence tomography (OCT) thickness map superimposed on the retina.

METHODS

Fourteen eyes with DME undergoing navigated laser photocoagulation with navigated photocoagulator had FA taken using the same instrument. Optical coherence tomography central retinal thickness map was imported to the photocoagulator and with same magnification aligned onto the retina. Three retina specialists placed laser spot marks separately on FA and OCT image in a masked fashion. The spots placed by each physician were compared between FA and OCT and among physicians. The area of dye leakage on FA and increased central retinal thickness on OCT of the same eye were also compared.

RESULTS

The average number of spots using FA and OCT template was 36.64 and 40.61, respectively (P = 0.0201). The average area of dye leakage was 7.45 mm, whereas the average area of increased central retinal thickness on OCT of the same eye was 10.92 mm (P = 0.013).

CONCLUSION

There is variability in the treatment planning for macular photocoagulation with a tendency to place more spots when guided by OCT than by FA. Integration of OCT map aligned to the retina may have an impact on treatment plan once such information is available.

Optical coherence tomography-guided selective focal laser photocoagulation: a novel laser protocol for diabetic macular edema

BACKGROUND

To compare the anatomic and functional results between optical coherence tomography (OCT)-guided selective focal laser photocoagulation (OCT-laser) and conventional modified Early Treatment Diabetic Retinopathy Study (mETDRS) laser treatment for diabetic macular edema (DME).

METHODS

We analyzed treatment outcomes in 47 consecutive eyes treated with OCT-laser compared to 31 matched eyes treated with mETDRS. In the OCT-laser group, we identified 'significant actively-leaking microaneurysms on OCT' (SALMO) which are responsible for edema in OCT B-scan images, and thoroughly ablated them with photocoagulation. Best-corrected visual acuity (BCVA) and retinal thickness by OCT were compared at baseline and 12 months after treatment between two groups.

RESULTS

OCT-laser treatment resulted in significant improvements in BCVA, central subfield thickness (CST), and maximum retinal thickness (MRT) from baseline at 12 months from the time of therapy (+2.5 letter score, p = 0.04; -45.56 μm in CST, p < 0.001; -91.6 μm in MRT, p < 0.001). The mean number of treated 'SALMO' was 5.6 ± 4.0 (range 1-26), while the number of MAs in 'treatable lesions' by fluorescein angiography (FA) in the same eye was 16.3 ± 11.8 (range 2-42). There was no difference between OCT-laser and mETDRS groups in changes of these parameters from baseline at 12 months (p = 0.56, p = 0.89, p = 0.43 respectively). Fundus autofluorescence (FAF) and OCT revealed less tissue damage in OCT-laser-treated eyes, compared to eyes treated with mETDRS (p < 0.001).

CONCLUSIONS

OCT-laser shows similar anatomic and functional outcomes compared to conventional laser (modified ETDRS), with significantly less retinal damages.

Comparison of a MEMS-Based Handheld OCT Scanner With a Commercial Desktop OCT System for Retinal Evaluation

PURPOSE

The goal of this study was to evaluate the ability of our handheld optical coherence tomography (OCT) scanner to image the posterior and anterior structures of the human eye, and especially the individual layers of the retina, and to compare its diagnostic performance with that of a fixed desktop commercial ophthalmic OCT system.

METHODS

We compared the clinical imaging results of our handheld OCT with a leading commercial desktop ophthalmic system (RTVue) used in specialist offices. Six patients exhibiting diabetes-related retinal pathology had both eyes imaged with each OCT system.

RESULTS

In both sets of images, the structural irregularities of the retinal layers could be identified such as retinal edema and vitreomacular traction.

CONCLUSIONS

Our handheld OCT system can be used to identify relevant anatomical structures and pathologies in the eye, potentially enabling earlier screening, disease detection, and treatment. Images can be acquired quickly, with sufficient resolution and negligible motion artifacts that would normally limit its diagnostic use.

TRANSLATIONAL RELEVANCE

Following screening and early disease detection in primary care via our optimized handheld OCT system, patients can be referred to a specialist for treatment, preventing further disease progression. While many primary care physicians are adept at using the ophthalmoscope, they can definitely take advantage of more advanced technologies.

Allosteric regulation of pathologic angiogenesis: potential application for angiogenesis-related blindness

Angiogenesis-related blindness (ARB) includes age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity, all of which are based on pathologic angiogenesis. Current treatment options such as surgery, laser photocoagulation, and steroid have shown limitations because they do not directly resolve the pathologic events in the retina. Furthermore, recently approved and developed therapeutic drugs only focus on direct inhibition of growth factors and suppression of downstream signaling molecules of activated receptor proteins by orthosteric ligands. In this regard, allosteric regulation of receptors and ligands can be a valuable mechanism in the development of novel drugs for ARB. In this review, we briefly address the clinical significance of ARB for further discussion on allosteric regulation of pathologic angiogenesis for ARB. Interestingly, key molecules in the pathogenesis of ARB can be targets for allosteric regulation, sharing characteristics as allosteric proteins. With investigation of allostery by introducing well-established models for allosteric proteins and currently published novel allosteric modulators, we discuss the potential of allosteric regulation for ARB. In conclusion, we hope that allosteric regulation of pathologic angiogenesis in ARB can open new opportunities for drug development.

Risk factors associated with diabetic macular edema

Diabetic macular edema (DME) is the most common cause of vision loss in patients with type 1 and type 2 diabetes. Glycemic control, hypertension, and dyslipidemia are known to be important risks factors for DME. In addition, nephropathy, anemia, sleep apnea, glitazone usage, and pregnancy are also important modifiable risk factors. It is important for physicians of different subspecialties to work together and understand multiple aspects of DME and diabetic healthcare.