CORRELATION BETWEEN CYSTOID SPACES IN CHRONIC DIABETIC MACULAR EDEMA AND CAPILLARY NONPERFUSION DETECTED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

Changes in Retinal Microvasculature and Visual Acuity After Antivascular Endothelial Growth Factor Therapy in Retinal Vein Occlusion

Purpose

To investigate the changes in the retinal microvasculature during the course of anti-VEGF therapy in eyes with macular edema due to retinal vein occlusion (RVO) and their association with visual outcomes.

Methods

The vessel density (VD) and foveal avascular zone (FAZ) area in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were quantitatively measured by optical coherence tomography angiography (OCTA) in 48 consecutive eyes with RVO before and 1, 3, 6, 9, and 12 months after anti-VEGF therapy. Anti-VEGF therapy was performed either with ranibizumab or aflibercept following a pro re nata (PRN) regimen. The correlation between post-treatment best-corrected visual acuity (BCVA) and changes in the retinal microvasculature evaluated by OCTA were assessed.

Results

The BCVA improved significantly at 12 months (P < 0.001). Better BCVA at 12 months was significantly associated with a better VD in the SCP and DCP both at baseline (R2 = 0.524, P < 0.001 and R2 = 0.457, P < 0.001, respectively) and at 12 months (R2 = 0.521, P < 0.001 and R2 = 0.662, P < 0.001, respectively). Overall, both VD and FAZ did not change significantly during the 12 months. However, the progression of nonperfusion was observed in the SCP in 6 (13%) eyes and in the DCP in 10 (21%) eyes. The number of macular edema recurrence was significantly associated with a decrease in the VD (P = 0.006 [SCP] and P < 0.001 [DCP]) and less visual gain (P = 0.02) after treatment.

Conclusions

Anti-VEGF therapy maintains retinal perfusion in most patients with RVO. Preserving retinal perfusion is crucial for better visual outcomes.

Implication of Deep-Vascular-Layer Alteration Detected by Optical Coherence Tomography Angiography for the Pathogenesis of Diabetic Retinopathy

The aim of this narrative mini review is to analyze optical coherence tomography angiography (OCTA) parameters from reports that involved both superficial and deep vascular layers in patients with diabetes and to assess their relevance for the pathogenesis of diabetic retinopathy (DR). Papers published from January 2015 to August 2018 describing the use of OCTA in diabetes were identified and reviewed through a Medline/PubMed search. OCTA studies suggest that parameters are altered in patients with diabetes in all retinal vascular layers. From all included studies that evaluated both the superficial and the deep vascular layer, a number of studies suggested that the deep vascular layer was affected at an earlier stage of DR. OCTA parameter alterations were more prominent in the deep vascular layer than in the superficial vascular layer in patients with DR, and deep-vascular-layer alterations were most evident in patients with diabetic macular edema. Regarding that retinal venules originate from the deep vascular layer of the retina, alteration of OCTA parameters at the deep vascular layer in diabetic patients may imply a predominant affection of the venous side of the retinal vascular system in the pathogenesis of DR.

The diagnostic value of optical coherence tomography angiography in diabetic retinopathy: a systematic review

PURPOSE

Diabetic retinopathy (DR) is one of the leading causes of blindness worldwide. Accurate investigative tools are essential for the early diagnosis and monitoring of the disease. Optical coherence tomography angiography (OCTA) is a recently developed technology that enables visualisation of the retinal microvasculature.

METHODS

A systematic review of the literature was performed to examine the diagnostic use of OCTA in DR to date. Medline, EMBASE, and Cochrane databases were searched to find relevant studies. Sixty-one original studies were selected for the review.

RESULTS AND DISCUSSION

OCTA has demonstrated the ability to identify microvascular features of DR such as microaneurysms, neovascularisation, and capillary non-perfusion. Furthermore, OCTA is enabling quantitative evaluation of the microvasculature of diabetic eyes. It has demonstrated the ability to detect early microvascular changes, in eyes with or without clinically evident DR. It has also been shown to detect progressive changes in the foveal avascular zone, and vascular perfusion density, with worsening severity of disease. It provides three-dimensional visualisation of the individual retinal vascular networks and is thereby enhancing our understanding of the role of the deeper vasculature in the pathogenesis of diabetic retinopathy and maculopathy.

CONCLUSION

However, limitations exist with current OCTA technology, in respect to the small field of view, image quality, projection artefact, and inaccuracies in analysis of the deeper vascular layers. While questions remain regarding its practical applicability in its present form, with continuing development and improvement of the technology, the diagnostic value of OCTA in diabetic retinopathy is likely to become evident.

Optical Coherence Tomography Angiography in Intermediate Uveitis

PURPOSE

To investigate the involvement of the retinal and choriocapillaris microvasculature in intermediate uveitis on optical coherence tomography angiography (OCT-A).

DESIGN

Case-control study.

METHODS

Patients and age-matched controls were imaged with swept-source OCT-A. Using ImageJ, superficial and deep retinal vasculature were semi-automatically analyzed for vessel (VD) and skeleton density (SD), vessel diameter index (VDI), and fractal dimension (FD). Choriocapillaris layer was automatically graded for mean signal intensity, signal intensity standard deviation, kurtosis of signal intensity distribution, and flow signal voids.

RESULTS

Twenty-nine intermediate uveitis eyes and 30 control eyes were included. Both superficial and deep retinal layers showed significant reduction in all OCT-A parameters (eg, superficial retinal layer: 0.31 vs 0.40 VD, 5.6e^-8 vs 6.4e^-8 SD, 5.4e⁶ vs 6.1e⁶ VDI, and 1.78 vs 1.79 FD, respectively, all P < .05). At the choriocapillaris layer a greater heterogeneity of perfusion with a shift toward a higher proportion of large confluent flow signal voids was present. Also in the absence of macular edema OCT-A parameters were reduced when compared with healthy controls (all parameters except for VDI in the superficial retinal layer and the choriocapillaris kurtosis and flow signal void analyses).

CONCLUSIONS

In intermediate uveitis, reduced vascular density and complexity in superficial as well as deep retinal layers and altered choriocapillaris perfusion are present. Moreover, these findings indicate impairment of the macular microvasculature even in the absence of macular edema. The results of our study may aid in the diagnosis as well as the monitoring of intermediate uveitis.

THE RELATIONSHIP BETWEEN FOVEAL AVASCULAR ZONE AREA, VESSEL DENSITY, AND CYSTOID CHANGES IN DIABETIC RETINOPATHY: AN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY STUDY

PURPOSE

To measure the foveal avascular zone (FAZ) areas and vessel densities of patients with diabetic retinopathy and to study their relationship with diabetic cystoid changes and retinal thickness.

METHODS

Prospective case series of 51 eyes of 31 patients with diabetic retinopathy. The eyes were grouped based on the presence or absence of cystoid edema and evaluated using optical coherence tomography angiography. The FAZ areas and vessel density were compared.

RESULTS

The FAZ area at the superficial capillary plexus level was equal between the eyes with and without cystoid edema. Vessel density did not differ as well. There was no correlation with retinal thickness. In eyes with cystoid changes, FAZ area changes at the deep capillary plexus level were difficult to interpret.

CONCLUSION

The FAZ area and vessel density at the superficial capillary plexus level are reproducible and independent of the presence of cystoid edema.

New insights into diabetic retinopathy by OCT angiography

Diabetic retinopathy (DR) is one of the most common diabetic complications, which has become a leading cause for vision loss, mainly because of macular edema and vitreous hemorrhage. Optical coherence tomography (OCT) angiography is a novel technique to visualize vascular changes including microaneurysm, non-perfusion area, intraretinal microvascular abnormalities, and neovascularization. Recently, it is possible to quantify vascular density, foveal avascular zone area, non-perfusion area objectively using OCT angiography. In addition, OCT angiography also provides an alternative method to evaluate the effect of anti-vascular endothelial growth factor (VEGF) treatments by providing high resolution images of macular microcirculatory abnormalities. Thus OCT angiography is an effective method to investigate the vascular changes of the disease, and can also be potentially applied in the diagnosis, treatment, and follow up of DR.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

Clinical applications of optical coherence tomography angiography: What we have learnt in the first 3 years

A review of the literature from 2014 to 2016 was conducted, focusing on the results of optical coherence tomography angiography in different chorioretinal diseases. In only 3 years, optical coherence tomography angiography has been shown to be an effective tool for diagnosing choroidal neovascularization complicating age-related macular degeneration, pathologic myopia, and inflammatory conditions. The technique has sometimes been considered superior to conventional multimodal imaging, for example, in choroidal neovascularization associated with chronic central serous chorioretinopathy or multifocal choroiditis. In retinal vascular diseases, optical coherence tomography angiography has helped to understand the condition described as paracentral acute middle maculopathy and has been considered highly effective for the analysis of retinal vascular macular changes secondary to retinal vein occlusion or macular telangiectasia. Changes in the foveal avascular zone, also reported in diabetic maculopathy, have been shown to occur before any angiographic signs. A reduction in capillary vascular density has been reported in the fovea of eyes with malignant melanoma, but not in eyes with choroidal nevus. However, optical coherence tomography angiography is a recent technique that probably needs refinements and further studies. Nevertheless, the first 3 years of optical coherence tomography angiography use suggest its clinical relevance and useful applications in daily clinical practice.

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.

OCT angiography and visible-light OCT in diabetic retinopathy

In recent years, advances in optical coherence tomography (OCT) techniques have increased our understanding of diabetic retinopathy, an important microvascular complication of diabetes. OCT angiography is a non-invasive method that visualizes the retinal vasculature by detecting motion contrast from flowing blood. Visible-light OCT shows promise as a novel technique for quantifying retinal hypoxia by measuring the retinal oxygen delivery and metabolic rates. In this article, we discuss recent insights provided by these techniques into the vascular pathophysiology of diabetic retinopathy. The next milestones for these modalities are large multicenter studies to establish consensus on the most reliable and consistent outcome parameters to study diabetic retinopathy.

En Face Doppler Optical Coherence Tomography Measurement of Total Retinal Blood Flow in Diabetic Retinopathy and Diabetic Macular Edema

Importance

Alterations in ocular blood flow play an important role in the pathogenesis and progression of diabetic retinopathy (DR). However, the measurement of retinal blood flow in clinical studies has been challenging. En face Doppler optical coherence tomography (OCT) provides an effective method for measuring total retinal blood flow (TRBF) in the clinic.

Objective

To investigate TRBF in eyes with DR of varying severity, with or without diabetic macular edema (DME), using en face Doppler OCT.

Design, Setting, and Participants

This was a cross-sectional study conducted from May 23, 2014, to January 11, 2016, which analyzed 41 eyes with DR from 31 diabetic patients, 20 eyes without DR from 11 diabetic patients, and 16 eyes from 12 healthy age-matched controls, all at the New England Eye Center in Boston, Massachusetts.

Main Outcomes and Measures

Participants were imaged with a high-speed, swept-source OCT prototype at 1050-nm wavelength using repeated en face Doppler OCT raster scans, comprising 600 × 80 axial scans and covering a 1.5 × 2-mm2 area centered at the optic disc. The TRBF was automatically calculated using custom Matlab software.

Results

This study included 41 eyes with DR from 31 diabetic patients (mean [SD] age, 62.8 [13.4] years; 12 were female patients), 20 eyes without DR from 11 diabetic patients (mean [SD] age, 58.8 [10.1] years; 5 were female patients), and 16 eyes from 12 healthy age-matched controls (mean [SD] age, 57.9 [8.1] years; 8 were female participants). The mean (SD) TRBF was 28.0 (8.5) µL/min in the eyes with DME, 48.8 (13.4) µL/min in the eyes with DR but without DME, 40.1 (7.7) µL/min in the diabetic eyes without retinopathy, and 44.4 (8.3) µL/min in age-matched healthy eyes. A difference in TRBF between the eyes with DME that were treated and the eyes with DME that were not treated was not identified. The TRBF was consistently low in the eyes with DME regardless of DR severity. The eyes with moderate nonproliferative DR but without DME exhibited a wide range of TRBF from 31.1 to 75.0 µL/min, with the distribution being highly skewed.

Conclusions and Relevance

High-speed en face Doppler OCT can measure TRBF in healthy and diabetic eyes. Diabetic eyes with DME exhibited lower TRBF than healthy eyes (P ≤ .001). Further longitudinal studies of TRBF in eyes with DR would be helpful to determine whether reduced TRBF is a risk factor for DME.

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.