Morphometry of the normal retinal periarteral capillary-free zone and changes during severe nonproliferative diabetic retinopathy

Microbiome and Retinal Vascular Diseases

The gut microbiome consists of more than a thousand different microbes and their associated genes and microbial metabolites. It influences various host metabolic pathways and is therefore important for homeostasis. In recent years, its influence on health and disease has been extensively researched. Dysbiosis, or imbalance in the gut microbiome, is associated with several diseases. Consequent chronic inflammation may lead to or promote inflammatory bowel disease, obesity, diabetes mellitus, atherosclerosis, alcoholic and non-alcoholic liver disease, cirrhosis, hepatocellular carcinoma, and other diseases. The pathogenesis of the three most common retinal vascular diseases, diabetic retinopathy, retinal vein occlusion, and retinal artery occlusion, may also be influenced by an altered microbiome and associated risk factors such as diabetes mellitus, atherosclerosis, hypertension, and obesity. Direct cause-effect relationships remain less well understood. A potential prevention or treatment modality for these diseases could be targeting and modulating the individual's gut microbiome.

Wide-field swept-source OCT angiography of the periarterial capillary-free zone before and after anti-VEGF therapy for branch retinal vein occlusion

BACKGROUND

The aim of the study was to investigate the changes in the periarterial capillary-free zone (paCFZ) after anti-vascular endothelial growth factor (VEGF) therapy in patients with branch retinal vein occlusion (BRVO) by wide-field swept-source optical coherence tomography angiography (SS-OCTA) and assess their associations with clinical outcomes.

METHODS

In this retrospective observational study of 54 treatment-naïve BRVO patients with macular edema, we reviewed the findings of 12 × 12 mm² SS-OCTA at baseline, 3, 6, and 12 months after intravitreal ranibizumab injections. The paCFZ and major retinal artery areas were measured on SS-OCTA images. The paCFZ area to artery area (P/A) ratio was calculated.

RESULTS

The paCFZ areas and P/A ratios of first- and second-order arteries were significantly greater in BRVO eyes than in contralateral eyes (all P < 0.01), but there were no differences in the first- and second-order artery areas (P = 0.20 and 0.25, respectively). The paCFZ areas and P/A ratios decreased significantly at 3, 6, and 12 months after anti-VEGF therapy (all P < 0.01). The baseline P/A ratio was significantly correlated with the baseline best-corrected visual acuity (BCVA), central retinal thickness, and their improvements at 3, 6, and 12 months (all P < 0.05). Baseline BCVA and P/A ratios of first- and second-order arteries were independently associated with the final BCVA in multivariate linear regression.

CONCLUSIONS

Wide-field SS-OCTA shows that anti-VEGF therapy can lead to a significant improvement in the paCFZ parameters in BRVO. Smaller baseline P/A ratios on SS-OCTA tend to predict better visual outcomes at 12 months after anti-VEGF therapy.

Wide-Field Swept-Source Optical Coherence Tomography Angiography Analysis of the Periarterial Capillary-Free Zone in Branch Retinal Vein Occlusion

Purpose

To investigate the characteristics of the retinal periarterial capillary-free zone (paCFZ) with wide-field swept-source optical coherence tomography angiography (SS-OCTA) in eyes with branch retinal vein occlusion (BRVO).

Methods

Seventy treatment-naïve eyes with BRVO and 35 healthy eyes were included. The paCFZ areas, artery calibers, and areas of the major arteries in the unaffected quadrants of BRVO eyes were measured in 12 × 12-mm SS-OCTA images and compared with those of the contralateral eyes and healthy eyes. Other multimodal imaging data were collected.

Results

There were no significant differences in the unaffected artery caliber or area among the three groups (all P > 0.05). The unaffected paCFZ areas and the ratios of the unaffected paCFZ area to the counterpart artery area (paCFZ/artery area) of the major arteries were significantly larger than those in the contralateral or healthy eyes (all P < 0.05). Subgroup analysis revealed that the paCFZ/artery area value differed significantly between ischemic and nonischemic BRVO eyes (P < 0.01). The paCFZ/artery area value was positively correlated with logMAR best-corrected visual acuity, symptom duration, central macular thickness, and retinal nonperfusion area in BRVO.

Conclusions

Quantitative SS-OCTA measurements confirmed enlarged paCFZs along the unaffected major retinal arteries in BRVO eyes. The paCFZ parameters were correlated with symptom duration, retinal ischemia, and visual function.

Translational Relevance

Retinal periarterial capillary-free zones in BRVO can be non-invasively measured by SS-OCTA, assisting in clinically identifying retinal ischemia and evaluating visual function.

Retinal Nonperfusion Relationship to Arteries or Veins Observed on Widefield Optical Coherence Tomography Angiography in Diabetic Retinopathy

Purpose

To evaluate whether retinal capillary nonperfusion is found predominantly adjacent to arteries or veins in eyes with diabetic retinopathy (DR).

Methods

Sixty-three eyes from 44 patients with proliferative DR (PDR) or non-PDR (NPDR) were included. Images (12 × 12-mm) foveal-centered optical coherence tomography (OCT) angiography (OCTA) images were taken using the Zeiss Plex Elite 9000. In 37 eyes, widefield montages with five fixation points were also obtained. A semiautomatic algorithm that detects nonperfusion in full-retina OCT slabs was developed, and the percentages of capillary nonperfusion within the total image area were calculated. Retinal arteries and veins were manually traced. Based on the shortest distance, nonperfusion pixels were labeled as either arterial-side or venous-side. Arterial-adjacent and venous-adjacent nonperfusion and the A/V ratio (arterial-adjacent nonperfusion divided by venous-adjacent nonperfusion) were quantified.

Results

Twenty-two eyes with moderate NPDR, 16 eyes with severe NPDR, and 25 eyes with PDR were scanned. Total nonperfusion area in PDR (median: 8.93%) was greater than in moderate NPDR (3.49%, P < 0.01). Arterial-adjacent nonperfusion was greater than venous-adjacent nonperfusion for all stages of DR (P < 0.001). The median A/V ratios were 1.93 in moderate NPDR, 1.84 in severe NPDR, and 1.78 in PDR. The A/V ratio was negatively correlated with the total nonperfusion area (r = −0.600, P < 0.0001). The results from the widefield montages showed similar patterns.

Conclusions

OCTA images with arteries and veins traced allowed us to estimate the nonperfusion distribution. In DR, smaller nonperfusion tends to be arterial-adjacent, while larger nonperfusion tends toward veins.