Can optical coherence tomography replace fluorescein angiography in detection of ischemic diabetic maculopathy?

Interocular Symmetry of Choroidal Parameters in Patients with Diabetic Retinopathy with and without Diabetic Macular Edema

This study focuses on the interocular comparison of choroidal parameters in diabetic patients with diabetic retinopathy (DR) with and without diabetic macular edema (DME), as well as in patients with unilateral DME (present in only one eye). The aim of this study was to determine the symmetry in order to obtain better insights into the pathophysiology of diabetic choroidopathy. This retrospective single-center cross-sectional study included 170 eyes from 85 patients (61 with DR and 24 controls), divided into subgroups depending on the presence of DME. The patients underwent fluorescein angiography and spectral domain optical coherence tomography examination, and the analysis included various choroidal parameters: choroidal thickness, volume, and the choroidal vascularity index (CVI). In terms of the choroidal thickness, one eye of a patient with DR, regardless of the presence, absence, or unilaterality of DME, may be treated as representative for that patient. CVI proved symmetrical for controls and patients with DR without DME. However, there was some asymmetry of CVI in patients with bilateral or unilateral DME. There was no straightforward relationship between choroidopathy and DME. Other mechanisms were also involved in the pathogenesis.

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”.

Correlation between Choroidal Vascularity Index and Outer Retina in Patients with Diabetic Retinopathy

The choroid supplies blood to the outer retina. We quantified outer retinal and choroidal parameters to understand better the pathogenesis of diabetic retinopathy (DR) and diabetic macular edema (DME). The retrospective cross-sectional single-center study included 210 eyes from 139 diabetic patients and 76 eyes from 52 healthy controls. Spectral-domain optical coherence tomography (OCT) was carried out with a Spectralis HRA + OCT imaging device. The outer retinal layer (ORL), outer nuclear layer (ONL), and choroidal thicknesses were assessed along with the choroidal vascularity index (CVI). The presence of DR, whether with DME or without, was associated with choroidal thinning (p < 0.001). Compared with the controls, patients with DR without DME presented with lower ORL and ONL thickness (p < 0.001), whereas those with DR and DME had higher values of both parameters (p < 0.001). Significant correlations between outer retinal and choroidal parameters were found only in patients with DR without DME (ORL with choroidal thickness: p = 0.003, rho = 0.34; ORL with CVI: p < 0.001, rho = 0.49, ONL with CVI: p < 0.027, rho = 0.25). No correlations between choroidal and outer retinal parameters were observed in the controls and patients with DR and concomitant DME. Aside from diabetic choroidopathy, other pathogenic mechanisms seem to predominate in the latter group.

Quantitative Assessment of Choroidal Parameters in Patients with Various Types of Diabetic Macular Oedema: A Single-Centre Cross-Sectional Analysis

Simple Summary

Choroidopathy is one of the components in the pathogenesis of diabetic macular oedema (DME). This study investigated the optical coherence tomography-based choroidal parameters: thickness, volume, choroidal vascularity index (CVI), luminal area (LA), stromal area (SA), and total choroidal area (TCA) in relation to the presence and type of DME (cystoid, diffuse, and with subretinal fluid). Diabetic choroidopathy seems to play a role in the development of DME but is less likely involved in the pathogenesis of specific types thereof.

Abstract

Diabetic macular oedema (DME) is an outcome of multiple, complex and not fully understood mechanisms. The aim of this study was to define the role of choroidopathy in the pathogenesis of various DME types. The retrospective cross-sectional single-centre study included 140 eyes from 105 patients with DME and 76 eyes from 52 non-diabetic controls. The eyes were stratified according to the type of DME: cystoid, diffuse, and with subretinal fluid. Optical coherence tomography-based choroidal parameters: thickness, volume, choroidal vascularity index (CVI), luminal area (LA), stromal area (SA), and total choroidal area (TCA) were compared. Eyes with DME, regardless of the type thereof, had lower choroidal thickness, volume, and CVI values than the controls. Further, the eyes with some specific DME types differed significantly from the controls in terms of LA and SA. While the eyes with various DME types did not differ significantly in terms of their choroidal thickness, volume and CVI, some between-group differences were found in LA, SA and TCA. Diabetic choroidopathy seems to play a role in the development of DME but is less likely involved in the pathogenesis of specific types thereof.

Recurrent monocular exudative retinal detachment as the first manifestation of squamous cell lung cancer: A case report

RATIONALE

In this report, we present an extremely rare case of recurrent monocular exudative retinal detachment without concomitant ocular metastases. This turned out to be the first symptom of squamous cell lung cancer.

PATIENT CONCERNS

A 63-year-old woman was referred to our ophthalmology clinic by her primary care physician with a complaint of deteriorating vision in her right eye that had started four months prior, without concomitant pain.

DIAGNOSES

We observed a detachment in the lower part of the retina during her ophthalmoscopy. We did not find any tears, holes, or degenerative changes in the periphery of the retina of the right eye during the surgery. In addition, plaques, tumor masses, and metastases were absent. Therefore, we diagnosed her with unilateral paraneoplastic exudative retinal detachment. Imaging tests performed before surgery revealed perihilar density with a visible air bronchogram in the middle field of the left lung. This turned out to be squamous cell carcinoma.

INTERVENTIONS

Patient underwent pars plana vitrectomy and routine laboratory and imaging tests before the procedure that utilized 20-gauge instrumentation. The subretinal fluid and was drained and a tamponade using Densiron (Fluoron Co, Neu-Ulm, Germany) was applied. After ophthalmic treatment, patient underwent complex oncological treatment based on chemotherapy and radiotherapy.

OUTCOMES

Despite the application of heavy silicone oil (Densiron) into the vitreous chamber, we observed a recurrence of retinal detachment in the right eye during the follow-up visit, 13 months after the first ophthalmic surgery. Following subsequent pars plana vitrectomy, the Densiron and subretinal membranes were removed. Despite oncological treatment, the patient died, twenty months after the appearance of the first ocular symptoms.

LESSONS

Exudative retinal detachment without tumor metastasis to the eyeball can be one of the first signs of lung cancer in rare cases. Multidisciplinary care and imaging methods with greater accuracy will provide comprehensive care to the patients. It will not only facilitate timely detection and treatment of lung tumors but also for a plethora of oncological diseases.

Foveal Avascular Zone Does Not Correspond to Choroidal Characteristics in Patients with Diabetic Retinopathy: A Single-Center Cross-Sectional Analysis

PURPOSE

The aim of the study was to compare two non-overlapping blood supply systems of the retina to obtain a better insight into the relation between diabetic macular retinopathy and choroidopathy. Specifically, the study focused on the relationships between (1) retinal vascular changes around the fovea in fluorescein angiography (FA) and (2) choroidal thickness, volume and other parameters assessed by optical coherence tomography (OCT).

PATIENTS AND METHODS

The retrospective cross-sectional single-center study included 210 eyes from 152 patients with diabetic retinopathy (mean age 60.7±12.4 years, 49.3% of women; foveal avascular zone [FAZ] outline: 44.3% grade ≤2, 55.7% grade ≥3). The outline of FAZ, a measure of capillary loss due to ischemic processes, was analyzed on FA according to the Early Treatment Diabetic Retinopathy Study Research Group (ETDRS) standards. The eyes were stratified according to the FAZ outline and size and the presence of clinically significant diabetic macular edema (CSME). Then, resultant groups were compared in terms of the spectral domain OCT parameters: choroidal thickness and volume (within ETDRS subfields), luminal, stromal and total choroidal areas and choroidal vascularity index (based on the foveal scan). Statistical analysis was based on univariate models with the choroidal parameters as independent variables, and age, sex, panretinal photocoagulation, the severity of diabetic retinopathy and CSME as covariates.

RESULTS

No significant relationships were found between the FAZ outline and area and choroidal characteristics of patients with diabetic retinopathy. In patients without CSME, no correlation was observed between the FAZ area and choroidal characteristics. In patients with CSME, no correlation was found between the FAZ area and choroidal characteristics other than the choroidal vascularity index.

CONCLUSION

In patients with diabetic retinopathy, damage to the macular retinal vasculature (FAZ) does not seem to be associated with changes in the choroidal vasculature, and these two processes appear to occur independently.

Comparison of foveal avascular zone and retinal vascular density in healthy Chinese and Caucasian adults

PURPOSE

The aim of this study was to measure and compare the retinal vascular parameters and foveal avascular zone (FAZ) in Chinese and Caucasian populations by using optical coherence tomography angiography (OCT-A).

METHODS

Fifty-one eyes of Han Chinese and 43 eyes of Caucasians were retrospectively included in our study. The measurements were acquired using Zeiss Cirrus 5000, with the same software version 10 in Poland and China.

RESULTS

The size of the FAZ was 0.33 ± 0.012 and 0.28 ± 0.014 mm² (p = 0.0289) and the diameter was 2.43 ± 0.06 and 2.18 ± 0.07 mm (p = 0.0057) for Chinese and Caucasian populations, respectively. However, no differences were observed in circularities between the populations. The full Early Treatment of Diabetic Retinopathy Study (ETDRS) vessel length density was significantly different for Chinese (17.05 ± 0.24 mm/mm² ) and Caucasian (16.08 ± 0.43 mm/mm² ) populations. In addition, the outer ETDRS vessel length density was significantly different for Chinese (16.43 ± 0.42 mm/mm² ) and Caucasian (17.47 ± 0.24 mm/mm² ) populations, but the central 7.33 ± 1.68 versus 9.32 ± 1.54 mm/mm² for the Caucasian and Chinese and inner 16.14 ± 0.52 for Caucasian and 16.93 ± 0.27 mm/mm² for Chinese subjects density was not. A significant yet weak positive correlation between FAZ and vessel density was observed (r = 0.216). Furthermore, no significant intersexual differences were observed in study parameters.

CONCLUSION

The Chinese population had larger FAZ with higher vessel length density in the superficial layers of the retina than the Caucasian population.

Evaluation of the correlation between quantitative measurement of the foveal avascular zone and retinal vessel density and outer retinal disruptions in diabetic patients

Background/aim

The aim of the current study was to evaluate the correlation between the integrity of the outer retinal layers on optical coherence tomography (OCT) and objective parameters of retinal microvascular perfusion on optical coherence tomography angiography (OCTA).

Materials and methods

A total of 105 eyes of 54 diabetic patients were included in the study. Integrity of the outer retinal layers including the external limiting membrane (ELM), ellipsoid zone (EZ), and interdigitation zone (IZ) was assessed by spectral-domain optical coherence tomography. The foveal avascular zone (FAZ) area and vessel density (VD) measurements in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in all the Early Treatment Diabetic Retinopathy Study (ETDRS) sectors were evaluated by OCTA. Associations between the quantitative measurement of the FAZ and retinal VD measurements and outer retinal disruptions were evaluated.

Results

The FAZ area was correlated with outer retinal layer disruption both in the superficial plexus (r = 0.244, 0.228, 0.212, P = 0.013, 0.02, 0.031 for the ELM, EZ, and IZ, respectively) and the deep capillary plexus (r = 0.298, 0.234, 0.197, P = 0.002, 0.019, 0.048 for the ELM, EZ, and IZ, respectively). A significant relationship was also found between the VD measurements in the SCP and DCP in ETDRS sectors and the outer retinal layers disruption.

Conclusion

The results of the current study show a significant relationship between the quantitative OCTA parameters and the integrity of the outer retinal layers. This finding reveals a correlation between retinal capillary nonperfusion and outer retinal disruption in eyes with diabetic retinopathy.

Within-subject assessment of foveal avascular zone enlargement in different stages of diabetic retinopathy using en face OCT reflectance and OCT angiography

Enlargement of the foveal avascular zone (FAZ) due to progressive capillary nonperfusion is associated with visual deterioration in patients with diabetic retinopathy. The FAZ area has long been considered an important clinical marker of advancing retinopathy. However, a large body of literature shows that the FAZ area varies considerably in healthy eyes, resulting in substantial overlap between controls and diabetics, thus reducing its discriminatory value. In this study, within-subject FAZ area enlargement was obtained by the comparison of the structural FAZ area to the functional FAZ area using simultaneously-acquired, corresponding en face OCT reflectance and OCT angiography images. Our study suggests that en face OCT reflectance images provide useful anatomic baselines of structural FAZ morphology prior to the onset of disease. Measurements of within-subject FAZ area enlargement appear to be a more sensitive method for identifying the onset of diabetic retinopathy as compared to using OCT angiographic measurements of FAZ alone.

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.

Optical coherence tomography angiography in pseudophakic cystoid macular oedema compared to diabetic macular oedema: qualitative and quantitative evaluation of retinal vasculature

AIMS

To describe optical coherence tomography angiography (OCT-A) abnormalities of patients with pseudophakic cystoid macular oedema (PCMO) before and after pharmacological resolution, compared with diabetic macular oedema (DMO) and normal eyes.

METHODS

In this retrospective, observational study, 44 eyes (30 patients) were included: 15 eyes (15 patients) affected by PCMO; 14 healthy fellow eyes used as negative control group; 15 eyes (15 age-matched and sex-matched patients) with DMO used as positive control group. All patients underwent a complete ophthalmological examination at baseline, including OCT-A scans of the macula through AngioPlex CIRRUS-5000 (Carl Zeiss Meditec, Dublin, USA). Patients with PCMO and DMO were re-evaluated after the pharmacological resolution of cystoid macular oedema (CMO).

RESULTS

Disruption of parafoveal capillary arcade and cystoid spaces in deep capillary plexus (DCP) were frequent in patients with PCMO and DMO (73% and 100%, 87% and 100%). Capillary abnormalities and non-perfusion greyish areas in DCP were more frequent in DMO (P<0.001 and P=0.014). Patients with PCMO showed a larger foveal avascular zone area in DCP at baseline (P<0.001), which significantly reduced after treatment (P=0.001). Vessel density of full-thickness retina and DCP was reduced in patients with PCMO (P=0.022 and P=0.001), and no changes were observed after treatment. Interestingly, DCP appeared less represented in patients with DMO than PCMO subjects (P=0.001).

CONCLUSIONS

Patients with PCMO have an impairment of mainly DCP, partially reversible after treatment. Furthermore, we disclosed that different alterations of the retinal vasculature characterise CMO derived from two different diseases, namely PCMO and DMO, and this could be due to their distinct pathophysiology.

Select Features of Diabetic Retinopathy on Swept-Source Optical Coherence Tomographic Angiography Compared With Fluorescein Angiography and Normal Eyes

IMPORTANCE

Optical coherence tomographic angiography (OCTA) is a recently developed noninvasive imaging technique that can visualize the retinal and choroidal microvasculature without the injection of exogenous dyes.

OBJECTIVE

To evaluate the potential clinical utility of OCTA using a prototype swept-source OCT (SS-OCT) device and compare it with fluorescein angiography (FA) for analysis of the retinal microvasculature in diabetic retinopathy.

DESIGN, SETTING, AND PARTICIPANTS

Prospective, observational cross-sectional study conducted at a tertiary care academic retina practice from November 2013 through November 2014. A cohort of diabetic and normal control eyes were imaged with a prototype SS-OCT system. The stage of diabetic retinopathy was determined by clinical examination. Imaging was performed using angiographic 3 × 3-mm and 6 × 6-mm SS-OCT scans to generate 3-dimensional en-face OCT angiograms for each eye. Two trained Boston Image Reading Center readers reviewed and graded FA and OCTA images independently.

MAIN OUTCOMES AND MEASURES

The size of the foveal nonflow zone and the perifoveal intercapillary area on OCTA were measured in both normal and diabetic eyes using Boston Image Reading Center image analysis software.

RESULTS

The study included 30 patients with diabetes (mean [SD] age, 55.7 [10] years) and 6 control individuals (mean [SD] age, 55.1 [6.4] years). A total of 43 diabetic and 11 normal control eyes were evaluated with OCTA. Fluorescein angiography was performed in 17 of 43 diabetic eyes within 8 weeks of the OCTA. Optical coherence tomographic angiography was able to identify a mean (SD) of 6.4 (4.0) microaneurysms (95% CI, 4.4-8.5), while FA identified a mean (SD) of 10 (6.9) microaneurysms (95% CI, 6.4-13.5). The exact intraretinal depth of microaneurysms on OCTA was localized in all cases (100%). The sensitivity of OCTA in detecting microaneuryms when compared with FA was 85% (95% CI, 53-97), while the specificity was 75% (95% CI, 21-98). The positive predictive value and the negative predictive value were 91% (95% CI, 59-99) and 60% (95% CI, 17-92), respectively.

CONCLUSIONS AND RELEVANCE

Optical coherence tomographic angiography enables noninvasive visualization of macular microvascular pathology in eyes with diabetic retinopathy. It identified fewer microaneurysms than FA, but located their exact intraretinal depth. Optical coherence tomographic angiography also allowed the precise and reproducible delineation of the foveal nonflow zone and perifoveal intercapillary area. Evaluation of OCTA may be of clinical utility in the evaluation and grading of diabetic eye disease.

Spectral Domain Optical Coherence Tomography Features and Classification Systems for Diabetic Macular Edema: A Review

Spectral domain optical coherence tomography (SD-OCT) is fast becoming the current standard of care for the detection and assessment of diabetic macular edema. With the application of SD-OCT for imaging of retinal microstructure and measurement of retinal thickness, new information regarding disease characteristics has been gathered, which was unrecognized previously. Retinal thickness measurements on SD-OCT have also been used for deciding the management and monitoring of the disease. Since its development, OCT has enhanced the understanding of retinal anatomical changes in diabetic retinopathy. Several authors have used SD-OCT to classify diabetic macular edema with the purpose of correlating the pathophysiology with disease severity. The classification systems have helped monitor the treatment efficacy and provide prognostic information on the treatment outcome. The following review article summarizes these classifications.

En face Integrated Central Avascular Zone (EFICAZ): a noninvasive tool for correlating morphological and functional damage in central diabetic macular edema

BACKGROUND

As numerous factors account for diabetic maculopathy, retinal thickness alone is poorly correlated to visual function in diabetic macular edema. En face optical coherence tomography (OCT) enables assessing retinal changes at specific layers. By averaging several planes, overall changes can be better appreciated.

METHODS

Retrospective analysis of a consecutive group of 16 patients (30 eyes) with diabetic macular edema in at least one eye, was compared to a control group of 17 healthy subjects (34 eyes). Healthy volunteers and diabetic patients being seen as part of their regular care underwent swept source OCT fundus imaging. En face Integrated Central Avascular Zone (EFICAZ) was manually determined and measured on images obtained by swept-source optical coherence tomography (OCT). EFICAZ was then compared between both populations and, for diabetic patients, correlated with best corrected visual acuity, as measured by the Snellen chart.

RESULTS

In healthy subjects, a moderate correlation was found between age and EFICAZ (Pearson's coefficient = 0.45, P = 0.01). In age-matched populations (mean age of 63 ± 3.8 years for eight healthy subjects and 62.7 ± 8.9 years for diabetic patients; P = 0.9), EFICAZ was significantly higher in diabetic than non-diabetic eyes (2.92 ± 1.10 mm² versus 1.86 ± 0.53 mm²; P < 0.01). In diabetic patients, correlation between the size of EFICAZ and visual acuity (Pearson's correlation coefficient = -0 .72, P < 0.001) was stronger than between OCT measured central subfield retinal thickness and visual acuity (Pearson's correlation coefficient = -0.02, N.S).

CONCLUSIONS

EFICAZ increases with age in normal subjects. It is significantly larger in diabetic than in non-diabetic subjects. It offers a better way to determine visual acuity than OCT measurement of central retinal thickness. This new approach, which takes into account several factors involved in diabetic maculopathy, could be useful in monitoring response to therapy. It can easily be combined with other modalities.

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.

Association of Diabetic Macular Nonperfusion With Outer Retinal Disruption on Optical Coherence Tomography

IMPORTANCE

Diabetic macular nonperfusion leads to decreased perifoveal capillary blood flow, which in turn causes chronic ischemia of the retinal tissue. Using point-to-point correlation between spectral-domain optical coherence tomography (SD-OCT) and nonperfusion on fluorescein angiography, we observed that retinal capillary nonperfusion is associated with photoreceptor compromise on OCT. This study highlights a new concept of a possible contribution of the retinal deep capillary plexus to photoreceptor compromise in diabetic retinopathy in the absence of diabetic macular edema.

OBJECTIVE

To report outer retinal structural changes associated with enlargement of the foveal avascular zone and/or capillary nonperfusion in the macular area of diabetic patients.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective observational cross-sectional study in 9 patients who were diagnosed as having diabetic retinopathy without diabetic macular edema and underwent fluorescein angiography and SD-OCT for diabetic retinopathy from July 8, 2014, to December 1, 2014, at a tertiary academic referral center. This analysis was conducted between December 2, 2014, and January 31, 2015.

MAIN OUTCOMES AND MEASURES

Outer retinal changes on SD-OCT in areas of macular ischemia.

RESULTS

The study included 13 eyes of 9 diabetic patients (4 men and 5 women aged 34-58 years) with a mean duration of diabetes mellitus of 14.5 years. Nine eyes showed outer retinal disruption revealed by SD-OCT that colocalized to areas of enlargement of the foveal avascular zone and macular capillary nonperfusion. Four fellow eyes with normal foveal avascular zones did not show any retinal changes on SD-OCT.

CONCLUSIONS AND RELEVANCE

Macular ischemia in diabetic patients can be associated with photoreceptor compromise. The presence of disruption of the photoreceptors on OCT in diabetic patients can be a manifestation of underlying capillary nonperfusion in eyes without diabetic macular edema. Ischemia at the deep capillary plexus may play an important role in these outer retinal changes.

Application of different imaging modalities for diagnosis of Diabetic Macular Edema: A review

Diabetic Macular Edema (DME) is caused by accumulation of extracellular fluid from hyperpermeable capillaries within the macula. DME is one of the leading causes of blindness among Diabetes Mellitus (DM) patients. Early detection followed by laser photocoagulation can save the visual loss. This review discusses various imaging modalities viz. biomicroscopy, Fluorescein Angiography (FA), Optical Coherence Tomography (OCT) and colour fundus photographs used for diagnosis of DME. Various automated DME grading systems using retinal fundus images, associated retinal image processing techniques for fovea, exudate detection and segmentation are presented. We have also compared various imaging modalities and automated screening methods used for DME grading. The reviewed literature indicates that FA and OCT identify DME related changes accurately. FA is an invasive method, which uses fluorescein dye, and OCT is an expensive imaging method compared to fundus photographs. Moreover, using fundus images DME can be identified and automated. DME grading algorithms can be implemented for telescreening. Hence, fundus imaging based DME grading is more suitable and affordable method compared to biomicroscopy, FA, and OCT modalities.

Optical coherence tomography angiography of the foveal avascular zone in diabetic retinopathy

Purpose

To analyze foveal avascular zone (FAZ) dimensions and symmetry in patients with diabetic retinopathy (DR) compared to healthy controls using optical coherence tomography angiography (OCT angiography).

Methods

OCT angiography was performed via an Avanti® RTVue 100 XR OCT system (Optovue, Inc., Fremont, CA, USA) in patients with diabetes mellitus (DM) and healthy adults. A frame centered on the fovea was used for FAZ measurements. The borders of the superficial vascular layer were defined as 3 μm below the internal limiting membrane (ILM) and 15 μm below the inner plexiform layer (IPL), and for the deep vascular layer as15 μm and 70 μm below the IPL, respectively. Angles of maximum FAZ diameter were measured in all eyes by two graders.

Results

In healthy eyes (N = 25), the FAZ surrounding vascular arcades were intact, showing a vertical or horizontal oval symmetrical formation with a maximum diameter usually on the horizontal or vertical axis. Diabetic eyes (N = 29) presented with disintegrity of the vascular arcades, resulting in an enlarged FAZ. In the superficial layer, the mean horizontal FAZ diameter was significantly larger in the DR group (753 μm ±272 μm) than in the control group (573 μm ±177 μm, p = 0.029). The difference was even more pronounced in the deep layer, with a mean value of 659 μm ±194 μm in the control group and 1009 μm ±342 μm in the DR group (p = 0.001). Furthermore, in the superficial layer, the angle of the maximum FAZ diameter was 0° (±15°) or 90° (±15°) in 72.0 % of healthy eyes. In eyes with DR, the angle was 0° (±15°) or 90° (±15°) in only 6.9 % of cases, due to the irregular configuration of the FAZ.

Conclusions

OCT angiography is capable of imaging retinal vasculature without dye injection. Our data suggest that it can detect disintegrity of the vascular arcades surrounding the FAZ, thus differentiating DM from healthy eyes. Vascular abnormalities were more pronounced in the deep vascular layer.

Updates in the management of diabetic macular edema

Diabetes mellitus is a chronic disease which has multiple effects on different end-organs, including the retina. In this paper, we discuss updates on diabetic macular edema (DME) and the management options. The underlying pathology of DME is the leakage of exudates from retinal microaneurysms, which trigger subsequent inflammatory reactions. Both clinical and imaging techniques are useful in diagnosing, classifying, and gauging the severity of DME. We performed a comprehensive literature search using the keywords "diabetes," "macula edema," "epidemiology," "pathogenesis," "optical coherence tomography," "intravitreal injections," "systemic treatment," "hypertension," "hyperlipidemia," "anemia," and "renal disease" and collated a total of 47 relevant articles published in English language. The main modalities of treatment currently in use comprise laser photocoagulation, intravitreal pharmacological and selected systemic pharmacological options. In addition, we mention some novel therapies that show promise in treating DME. We also review systemic factors associated with exacerbation or improvement in DME.