Three-dimensional segmentation and reconstruction of the retinal vasculature from spectral-domain optical coherence tomography

Retinal OCT-Derived Texture Features as Potential Biomarkers for Early Diagnosis and Progression of Diabetic Retinopathy

Purpose

Diabetic retinopathy (DR) is usually diagnosed many years after diabetes onset. Indeed, an early diagnosis of DR remains a notable challenge, and, thus, developing novel approaches for earlier disease detection is of utmost importance. We aim to explore the potential of texture analysis of optical coherence tomography (OCT) retinal images in detecting retinal changes in streptozotocin (STZ)-induced diabetic animals at "silent" disease stages when early retinal molecular and cellular changes that cannot be clinically detectable are already occurring.

Methods

Volume OCT scans and electroretinograms were acquired before and 1, 2, and 4 weeks after diabetes induction. Automated OCT image segmentation was performed, followed by retinal thickness and texture analysis. Blood-retinal barrier breakdown, glial reactivity, and neuroinflammation were also assessed.

Results

Type 1 diabetes induced significant early changes in several texture metrics. At week 4 of diabetes, autocorrelation, correlation, homogeneity, information measure of correlation II (IMCII), inverse difference moment normalized (IDN), inverse difference normalized (INN), and sum average texture metrics decreased in all retinal layers. Similar effects were observed for correlation, homogeneity, IMCII, IDN, and INN at week 2. Moreover, the values of those seven-texture metrics described above decreased throughout the disease progression. In diabetic animals, subtle retinal thinning and impaired retinal function were detected, as well as an increase in the number of Iba1-positive cells (microglia/macrophages) and a subtle decrease in the tight junction protein immunoreactivity, which did not induce any physiologically relevant effect on the blood-retinal barrier.

Conclusions

The effects of diabetes on the retina can be spotted through retinal texture analysis in the early stages of the disease. Changes in retinal texture are concomitant with biological retinal changes, thus unlocking the potential of texture analysis for the early diagnosis of DR. However, this requires to be proven in clinical studies.

Evaluation of the effect of fluorescein angiography on retinal vessel diameter: an optical coherence tomography study

PURPOSE

To evaluate the effect of fluorescein angiography on retinal vessel diameter with Optical Coherence Tomography (OCT).

METHODS

In this cross-sectional study, a total of 81 eyes of 81 patients who were performed fluorescein angiography (FA) procedure were included. Retinal vessels were examined with the Spectral-domain OCT at baseline and immediately after FA procedure. A cube scan consisting of seven horizontal scans were placed at the inferior border of the disk to include the inferior temporal retinal vessels. Vessels diameters were measured at five measurement points (480-1440 μm inferiorly from the optic disk border).

RESULTS

The mean age of the study subjects was 58.02 ± 14.1 years. At baseline, the mean diameter of the retinal artery was 120.16 ± 24.56 µm and of the vein 157.94 ± 32.34 µm at the measurement point of 480 μm, with a gradual decrease to 114.91 ± 25.59 and 152.17 ± 28.17 µm, respectively, at 1440 μm. After FA procedure, the mean diameter of the retinal artery was 122.85 ± 26.35 and of the vein 158.30 ± 32.21 µm at the measurement point of 480 μm, with a gradual decrease to 115.22 ± 22.91 and 151.94 ± 28.93 µm, respectively, at 1440 μm. There were no statistical differences for either of these comparisons at any of the points of both artery and vein measurements.

CONCLUSION

There was not any clinically significant change in retinal artery diameter such as a dilatatory response after FA procedure in patients with hypertension, diabetes, and age-related macular degeneration (AMD).

In vivo imaging of retinal hemodynamics with OCT angiography and Doppler OCT

Retinal hemodynamics is important for early diagnosis and precise monitoring in retinal vascular diseases. We propose a novel method for measuring absolute retinal blood flow in vivo using the combined techniques of optical coherence tomography (OCT) angiography and Doppler OCT. Doppler values can be corrected by Doppler angles extracted from OCT angiography images. A three-dimensional (3D) segmentation algorithm based on dynamic programming was developed to extract the 3D boundaries of optic disc vessels, and Doppler angles were calculated from 3D vessel geometry. The accuracy of blood flow from the Doppler OCT was validated using a flow phantom. The feasibility of the method was tested on a subject in vivo. The pulsatile retinal blood flow and the parameters for retinal hemodynamics were successfully obtained.