Spectral domain optical coherence tomography based imaging biomarkers for diabetic retinopathy

OCT biomarkers as predictors of visual improvement in diabetic macular edema eyes receiving dexamethasone implants

BACKGROUND

Several optical coherence tomography (OCT) biomarkers have been proposed as predictors for functional and anatomical outcomes in Diabetic Macular Edema (DME). This study aims to examine the impact of these OCT features on the visual acuity improvement of patients with DME after long-acting Dexamethasone intravitreal implants (DEX-I) injection. Furthermore, the safety and impact of DEX-I on clinical parameters, including intraocular pressure (IOP) were assessed.

METHODS

In this retrospective observational study, we reviewed the medical records of naïve and non-naïve eyes with DME who received at least one DEX-I. The primary endpoint was visual acuity improvement of ≥ 5 ETDRS letters at 1 month and 4 months after treatment. Secondary outcomes were the changes in OCT biomarkers and the impact of DEX-I on IOP at 1 and 4 months of follow-up. Linear panel regression analysis was used to test for differences in central subfield thickness (CST) over time and it was stratified according to biomarkers at baseline. Finally, a logistic regression analysis was used to identify factors predicting visual improvement at 1 and 4 months.

RESULTS

We included 33 eyes of which 63.6% were at an advanced stage of DME. Overall, CST, cube average thickness (CAT), cube volume (CV), and intraretinal cystoid spaces > 200 μm (ICS) decreased following DEX-I injection (p < 0.001). Additionally, a thicker CST at baseline was observed in eyes with better visual improvement at one month (p = 0.048). After logistic regression analysis, CST was retained as the only predictor for visual improvement at one month (p = 0.044). Furthermore, panel regression analysis identified a relation between subfoveal neuroretinal detachment (SND) at baseline and CST increase at four months. Lastly, only 15.2% of the eyes necessitated topical medication for IOP reduction, with no differences observed when stratifying between naïve and non-naïve eyes.

CONCLUSION

Our analyses suggest that a ticker baseline CST may serve as a positive predictor of early visual improvement and SND presence at baseline may be a negative prognostic factor for CST increase 4 months after DEX-I injection. Other well-known biomarkers, such as disorganization of the inner retinal layers (DRIL) and hyperreflective foci (HF), did not demonstrate prognostic value on visual outcomes, at least within the first four months following the injection.

Inhibiting MiR-34α reduces retinal cell apoptosis and downstream NF-κB pathway in diabetic retinopathy rats through regulating HMGB1 expression

BACKGROUND

This is a research aimed to study the effect of micro ribonucleic acid (miR)-34α on the retinal cell apoptosis in diabetic retinopathy (DR) rats and its key molecular mechanism.

METHODS

Sprague-Dawley rats were randomly divided into healthy group (H group, N.=5), diabetes group (D group, N.=5), diabetes + negative control transfection group (N group, N.=5) and diabetes + miR-34α inhibitor transfection group (M group, N.=5). The rat model of diabetes was established via intraperitoneal injection of 2% streptozotocin solution (60 mg/kg). After 72 h, the urine glucose and blood glucose were detected, and the urine glucose above 3+ and the blood glucose concentration >16.7 mmol/L indicated the successful modeling. After the rats were normally fed for 4 months, the changes in expression of miR-34α in retinal tissues were detected via reverse transcription-polymerase chain reaction (RT-PCR), the pathological changes in retinal tissues were observed via hematoxylin-eosin (HE) staining, and the retinal cell apoptosis was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Moreover, the changes in the number of cells containing active caspase-3 in retinal tissues were determined through immunohistochemistry, and the changes in expressions of caspase-3, high mobility group box 1 (HMGB1) and nuclear factor-κB (NF-κB) in retinal tissues were determined through Western blotting.

RESULTS

Compared with those in H group, the cell density declined, and the cells were arranged disorderly with swelling in each retinal layer, the expression of miR-34α in retinal tissues was increased, the retinal cell apoptosis was enhanced, the number of cells containing active caspase-3 in retinal tissues rose, and the expressions of caspase-3, HMGB1 and NF-κB in retinal tissues were increased in D group, N group and M group (P<0.05). Compared with those in D group and N group, the cell density rose, and the cells were arranged less disorderly with milder swelling in each retinal layer, the expression of miR-34α in retinal tissues declined, the retinal cell apoptosis was weakened, the number of cells containing active caspase-3 in retinal tissues was decreased, and the expressions of caspase-3, HMGB1 and NF-κB in retinal tissues were reduced in M group (P<0.05).

CONCLUSIONS

Inhibiting miR-34α reduces the retinal cell apoptosis in DR rats through regulating the HMGB1 expression and downstream NF-κB pathway.

Interleaved Optical Coherence Tomography: Clinical and Laboratory Biomarkers in Patients with Diabetic Macular Edema

(1) Background: The global burden of diabetes mellitus (DM) has been estimated to reach 600 million patients worldwide by 2040. Approximately 200 million people will develop diabetic retinopathy within this time frame. Diabetic macular edema (DME) is a severe, vision-threatening complication that can develop at any stage of diabetic retinopathy, and it represents the main cause of vision loss in patients with DM. Its harmful consequences on visual function could be prevented with timely recognition and treatment. (2) Methods: This study assessed the clinical (demographic characteristics, diabetic evolution, and systemic vascular complications); laboratory (glycated hemoglobin, metabolic parameters, capillary oxygen saturation, and renal function); ophthalmologic exam; and spectral-domain optical coherence tomography (SD–OCT) (macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, temporal inner, inferior outer, superior outer, nasal outer, and temporal outer thicknesses, disruption of the ellipsoid zone, and disruption of the inner retinal layers (DRIL) parameters in three groups of individuals: healthy controls (HC), patients with DME and type 1 DM (T1DM—group A), and patients with DME and type 2 DM (T2DM—group B) to identify novel correlations between them that would open a path to new pathogenetic hypotheses and, implicitly, to the identification of new therapeutic methods, as part of a tailored treatment within the concept of precision medicine. (3) Results: The duration of DM was significantly longer in group A as compared with group B, as were the prevalence of smoking and systemic vascular complications. Capillary oxygen saturation and estimated glomerular filtration rates were significantly lower, and serum creatinine levels were significantly higher in group A as compared to group B. Regarding the OCT findings, DME had a predominantly eccentric pattern, and the right eye was more severely affected in both groups of patients. Significantly higher values were obtained in group B as compared to group A for the following OCT biomarkers: macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, inferior outer and nasal outer thickness. The disruption of the ellipsoid zone was significantly more prevalent within group A, whereas the overall disruption of the retinal inner layers (DRIL) was identified significantly more frequently in group B. (4) Conclusions: Whereas systemic and laboratory biomarkers were more severely affected in patients with DME and T1DM, the OCT quantitative biomarkers revealed significantly higher values in patients with DME and T2DM.

Early Diagnosis of Multiple Sclerosis Using Swept-Source Optical Coherence Tomography and Convolutional Neural Networks Trained with Data Augmentation

BACKGROUND

The aim of this paper is to implement a system to facilitate the diagnosis of multiple sclerosis (MS) in its initial stages. It does so using a convolutional neural network (CNN) to classify images captured with swept-source optical coherence tomography (SS-OCT).

METHODS

SS-OCT images from 48 control subjects and 48 recently diagnosed MS patients have been used. These images show the thicknesses (45 × 60 points) of the following structures: complete retina, retinal nerve fiber layer, two ganglion cell layers (GCL+, GCL++) and choroid. The Cohen distance is used to identify the structures and the regions within them with greatest discriminant capacity. The original database of OCT images is augmented by a deep convolutional generative adversarial network to expand the CNN's training set.

RESULTS

The retinal structures with greatest discriminant capacity are the GCL++ (44.99% of image points), complete retina (26.71%) and GCL+ (22.93%). Thresholding these images and using them as inputs to a CNN comprising two convolution modules and one classification module obtains sensitivity = specificity = 1.0.

CONCLUSIONS

Feature pre-selection and the use of a convolutional neural network may be a promising, nonharmful, low-cost, easy-to-perform and effective means of assisting the early diagnosis of MS based on SS-OCT thickness data.

COVID-19: more than a respiratory virus, an optical coherence tomography study

Purpose

The purpose of this study is to investigate anatomic and morphologic features of inner and outer retinal layers in patients recovered from COVID-19 with Spectral Domain Optical Coherence Tomography (SD-OCT), whether correlate with any symptoms during disease process.

Methods

32 patients recovered from COVID-19 and age- and gender-matched 36 healthy controls were included in this cross-sectional study. Ganglion cell-inner plexiform layer, macular and peripapiller retinal nerve fiber layer (RNFL), inner nuclear layer (INL), outer nuclear layer (ONL), outer plexiform layer (OPL) and the outer retinal hyperreflective bands including external limiting membrane (ELM), ellipsoid zone (EZ) and interdigitation zone (IZ) were examined with SD-OCT. The differences of each retinal layers thickness among subgroup analysis of ocular pain and headache were also compared.

Results

Macular RNFL of inner and outer nasal and outer inferior quadrants were thinner in COVID-19 patients compared to healthy control group (p = 0.046, p = 0.014 and p = 0.016, respectively). Thinning in outer superior quadrant of GCIPL and INL quadrants were detected in patients with headache (p = 0.026 and p = 0.01). Superonasal and inferotemporal sectors of pRNFL were thinner in patients with ocular pain compared to patients without ocular pain (p = 0.024 and p = 0.015). Integrity of EZ, ELM and IZ was evaluated as continuous line and protected on each OCT scans.

Conclusion

The study demonstrated convincing evidence that SARS-CoV-2 can affect the inner and outer retinal layers, with subclinical localized alterations, particularly in patients with headache and ocular pain symptoms during COVID-19 period.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10792-021-01952-5.

Increased serum cortisol is associated with alterations in cross-sectional and topographic OCT parameters in diabetic retinopathy: a preliminary study

PURPOSE

Cortisol, a steroid hormone, plays an essential role in metabolic processes of diabetes mellitus. This study for the first time evaluated the association of serum cortisol with spectral domain optical coherence tomography (SD-OCT)-based cross-sectional and topographic parameters with severity of diabetic retinopathy (DR).

METHODS

A tertiary care center-based preliminary study was undertaken. Fourteen consecutive cases of DR and fifteen healthy controls were included. Cases were graded according to ETDRS classification: non-proliferative DR (NPDR, n = 8) and proliferative DR (PDR, n = 6). All study subjects underwent complete ophthalmological evaluation. Serum cortisol was analyzed using chemiluminescence microparticle assay method. Central subfield thickness (CST), cube average thickness (CAT), cube volume (CV), retinal nerve fiber layer (RNFL) thickness, disorganization of inner retinal layers (DRIL), grade of retinal photoreceptor ellipsoid zone (EZ) disruption and grade of retinal pigment epithelium (RPE) alterations were evaluated using SD-OCT. Statistical analysis was done using ANOVA and Pearson's correlation analysis.

RESULTS

Mean serum cortisol levels (µg/dL) were NPDR = 11.59 ± 0.42, PDR = 14.50 ± 0.26 and controls = 8.22 ± 0.77. With increasing severity of DR, mean CST, CAT, CV showed positive correlation, whereas mean RNFL thickness showed negative correlation with serum cortisol levels (p < 0.01). DRIL, EZ disruption and RPE alterations showed positive correlation with serum cortisol levels (p < 0.001).

CONCLUSION

Serum cortisol levels are significantly associated with severity of DR and correlate positively with CST, CAT, CV, DRIL, EZ disruption and RPE alterations and negatively with RNFL thickness.

Optical Coherence Tomography (Angiography) Biomarkers in the Assessment and Monitoring of Diabetic Macular Edema

Retinopathy is one of the most severe diabetes-related complications, and macular edema is the major cause of central vision loss in patients with diabetes mellitus. Significant progress has been made in recent years in optical coherence tomography and angiography technology. At the same time, various parameters have been attributed the role of biomarkers creating the frame for new monitoring and treatment strategies and offering new insights into the pathogenesis of diabetic retinopathy and diabetic macular edema. In this review, we gathered the results of studies that investigated various specific OCT (angiography) parameters in diabetic macular edema, such as central subfoveal thickness (CST), cube average thickness (CAT), cube volume (CV), choroidal thickness (CT), retinal nerve fiber layer (RNFL), retinal thickness at the fovea (RTF), subfoveal choroidal thickness (SFCT), central macular thickness (CMT), choroidal vascularity index (CVI), total macular volume (TMV), central choroid thickness (CCT), photoreceptor outer segment (PROS), perfused capillary density (PCD), foveal avascular zone (FAZ), subfoveal neuroretinal detachment (SND), hyperreflective foci (HF), disorganization of the inner retinal layers (DRIL), ellipsoid zone (EZ), inner segment/outer segment (IS/OS) junctions, vascular density (VD), deep capillary plexus (DCP), and superficial capillary plexus (SCP), in order to provide a synthesis of biomarkers that are currently used for the early diagnosis, assessment, monitoring, and outlining of prognosis.