Quantitative Parameters from OCT Angiography in Patients with Diabetic Retinopathy and in Those with Only Peripheral Retinopathy Compared with Control Participants

The relationship between ON-OFF function and OCT structural and angiographic parameters in early diabetic retinal disease

PURPOSE

This study measured associations between ON and OFF functional indicators and structural optical coherence tomography (OCT) and OCT angiography (OCTA) markers in diabetic retinal disease.

METHODS

Fifty-four participants with type 1 or type 2 diabetes (mean age = 34.1 years; range 18-60) and 48 age-matched controls (mean age = 35.4 years, range 18-59) underwent visual psychophysical testing, OCT and OCTA retinal imaging. Psychophysical tasks measuring (A) contrast increment and decrement sensitivity and (B) response times to increment and decrement targets were assessed as surrogate measures of ON and OFF retinal ganglion cell function.

RESULTS

The group with diabetes had worse foveal contrast increment and decrement thresholds (p = 0.04) and were slower to search for increment and decrement targets relative to controls (p = 0.009). Individuals with diabetes had a less circular foveal avascular zone (FAZ) (p < 0.001) but did not differ from controls in foveal vessel density and FAZ area. Functional and structural outcome measures related to the peripheral retina were also comparable between those with and without diabetes. Functional responses to increments and decrements were not significantly correlated with FAZ circularity or vessel density in individuals with diabetes.

CONCLUSIONS

Diabetic retinal disease results in impaired performance on measures of inferred ON and OFF pathway function in addition to vascular deficits measurable with OCTA. Future longitudinal studies may determine the temporal relationship between these deficits, and whether they predict future diabetic retinopathy.

Sequence and Detectability of Changes in Macular Ganglion Cell Layer Thickness and Perfusion Density in Early Glaucoma

Purpose

To investigate whether macular perfusion density (PD) changes measured over time by optical coherence tomography angiography (OCTA) are detectable before progressive macular ganglion cell layer (GCL) thinning in early glaucoma.

Methods

This prospective longitudinal cohort study involved patients with early open-angle glaucoma and healthy subjects imaged by OCT and OCTA every 4 months. GCL thickness and macular PD were evaluated in 16 tiles in the macula. We estimated baseline percentage losses of GCL thickness or macular PD in glaucoma patients with age-corrected normative values derived from the healthy subjects. Additionally, the threshold slope separating glaucoma patients from healthy subjects with 90% specificity was used to determine the number of patients with steeper slopes than the threshold slope.

Results

Eighty patients with glaucoma and 42 healthy subjects were included. In eight tiles (50%), patients with a significant macular PD slope had a significantly greater baseline percentage loss of GCL thickness relative to macular PD compared to patients without a significant macular PD slope. Furthermore, in 15 tiles (94%), a greater baseline percentage loss of GCL thickness relative to PD was significantly correlated with faster PD slopes. In contrast, only one tile (6%) showed these significant trends for GCL slopes. The number of patients with faster GCL slopes than threshold slopes was significantly larger than patients with faster PD slopes in 12 tiles (75%).

Conclusions

A decrease in GCL thickness precedes a measurable decrease in macular PD. Early glaucomatous progression is more frequently detectable with changes in GCL thickness compared to macular PD.

The Framework of Quantifying Biomarkers of OCT and OCTA Images in Retinal Diseases

Despite the significant advancements facilitated by previous research in introducing a plethora of retinal biomarkers, there is a lack of research addressing the clinical need for quantifying different biomarkers and prioritizing their importance for guiding clinical decision making in the context of retinal diseases. To address this issue, our study introduces a novel framework for quantifying biomarkers derived from optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) images in retinal diseases. We extract 452 feature parameters from five feature types, including local binary patterns (LBP) features of OCT and OCTA, capillary and large vessel features, and the foveal avascular zone (FAZ) feature. Leveraging this extensive feature set, we construct a classification model using a statistically relevant p value for feature selection to predict retinal diseases. We obtain a high accuracy of 0.912 and F1-score of 0.906 in the task of disease classification using this framework. We find that OCT and OCTA's LBP features provide a significant contribution of 77.12% to the significance of biomarkers in predicting retinal diseases, suggesting their potential as latent indicators for clinical diagnosis. This study employs a quantitative analysis framework to identify potential biomarkers for retinal diseases in OCT and OCTA images. Our findings suggest that LBP parameters, skewness and kurtosis values of capillary, the maximum, mean, median, and standard deviation of large vessel, as well as the eccentricity, compactness, flatness, and anisotropy index of FAZ, may serve as significant indicators of retinal conditions.

Optical coherence tomography angiography suggests choriocapillaris perfusion deficit as etiology of acute macular neuroretinopathy

PURPOSE

Acute macular neuroretinopathy (AMN) can cause sudden-onset and permanent scotoma in healthy young patients. Analysis of optical coherence tomography (OCT) and OCT angiography (OCTA) of AMN patients may provide insights into disease mechanism.

METHODS

We conducted a retrospective study of consecutive SARS-Cov-2-related AMN patients that presented in our clinic between Jan 1st, 2022, and April 30th, 2023, within 30 days of symptom onset. Retinal vessel area density (VAD) of AMN lesions in OCTA was quantified and compared to an adjacent tissue control (ATC). This quantification was performed for the superficial vascular plexus (SVP), the intermediate capillary plexus (ICP), the deep capillary plexus (DCP), the choriocapillaris (CC), and choroid. Furthermore, en face OCT images were analyzed.

RESULTS

Nine AMN patients were identified, 6 of these (4 female, 2 male, average age 25 years) fulfilled the inclusion criteria and were included into this study. Average time from symptom onset to OCTA was 14.3 days. No VAD differences between AMN and adjacent tissue were found in either retinal layer (SVP, ICP, DCP). In contrast, VAD in CC was reduced by 27% against the ATC (p = 0.007) and choroidal VAD was reduced by 41% (p = 0.017). Further analysis of en face OCT could show that the pathognomonic infrared hyporeflectivity in AMN is caused by photoreceptor alterations rather than changes in the inner retinal layers.

CONCLUSIONS

Our data suggests that a perfusion deficit in the choroidal layers is responsible for AMN rather than in the DCP, which is the predominant hypothesis in current literature.

THE EFFECT OF INCREASING ACQUISITION SPEED ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IMAGES: A Qualitative and Quantitative Analysis

PURPOSE

To evaluate the effect of two different A-scan rates on qualitative and quantitative parameters on optical coherence tomography angiography images in a clinical setting.

METHODS

Subjects undergoing a comprehensive ophthalmic examination were scheduled for optical coherence tomography angiography imaging using a new SPECTRALIS device allowing for 85 and 125 kHz scan rate. Consecutive registered 20° × 20° optical coherence tomography angiography images using both speeds were acquired using the follow-up tool. The acquisition time and the quality values of each scan were extracted and analyzed. The image quality was also graded in pairs by two independent graders.

RESULTS

Two-hundred and one eyes of 128 consecutive patients (67 males, 52.3%) were included. Mean acquisition time significantly decreased from 56.92 ± 24.6 seconds on the 85 kHz images to 39.39 ± 15.5 seconds on the 125 kHz images (P < 0.001). The percentage change in acquisition time showed a mean decrease of 28.47%. Mean Q value significantly decreased from 32.97 ± 2.8 dB on the 85 kHz images to 31.43 ± 2.6 dB on the 125 kHz images (P < 0.001). Overall, 92.5% of images were graded as equal or better at 125 kHz A-scan rate.

CONCLUSION

The use of optical coherence tomography angiography in daily clinical practice may require higher A-scan rates for an optimal workflow. Increased speed may also reduce image sensitivity and thus image quality could be compromised. In this study, 125 kHz scan rate using SPECTRALIS showed significant benefit with reduction on the acquisition time and no clinically significant differences on image quality analysis. Further studies evaluating qualitative and quantitative data in specific retinal conditions and using other devices are required to confirm these results.