The Relationship Between Retinal Vessel Oxygenation and Spatial Distribution of Retinal Nonperfusion in Retinal Vascular Diseases

Deep Capillary Plexus as Biomarker of Peripheral Capillary Nonperfusion in Central Retinal Vein Occlusion

Purpose

To identify the vascular biomarkers of peripheral capillary nonperfusion in patients affected by naive central retinal vein occlusion (CRVO), and to analyze their changes over the follow-up.

Study Design

Consecutive prospective case series with a planned follow-up of 2 years.

Participants

Thirty-five patients affected by CRVO and 35 healthy gender- and age-matched subjects were enrolled in the study.

Methods

Ophthalmic examination included best corrected visual acuity (BCVA), ultrawidefield fluorescein angiography (UWFFA), OCT, and OCT angiography (OCTA).

Main Outcome Measures

Vessel density (VD) at the superficial capillary plexus and deep capillary plexus (DCP) were calculated on OCTA images. The ischemic index (ISI) was calculated on UWFFA.

Results

The mean baseline ISI was 37%, increasing to 40% at the end of the follow-up, whereas it was 4.9% in the patients' fellow eyes and 4.5% in the control group with no change over the follow-up. OCT angiography revealed VD reduction in the DCP, considering both 3 × 3 mm and 12 × 12 mm scans. The correlation analyses revealed that DCP VD was the only parameter showing a statistically significant correlation with the foveal avascular zone (FAZ) area, BCVA, and ISI.

Conclusions

Deep capillary plexus VD impairment is detectable in all CRVO cases, variably involving both the central retina (with enlarged FAZ) and the periphery (with VD reduction in the peripheral retina). The severity of DCP VD reduction has correlates with various clinical markers. Deep capillary plexus VD may represent a crucial biomarker to characterize CRVO, and further studies are necessary to identify the cutoff thresholds for the different clinical manifestations.

Advances in Retinal Oximetry

Similar to other organs, the retina relies on tightly regulated perfusion and oxygenation. Previous studies have demonstrated that retinal blood flow is affected in a variety of eye and systemic diseases, including diabetic retinopathy, age-related macular degeneration, and glaucoma. Although measurement of peripheral oxygen saturation has become a standard clinical measurement through the development of pulse oximetry, developing a noninvasive technique to measure retinal oxygen saturation has proven challenging, and retinal oximetry technology currently remains inadequate for reliable clinical use. Here, we review current strategies and approaches, as well as several newer technologies in development, and discuss the future of retinal oximetry.

Retinal nonperfusion in optical coherence tomography angiography

BACKGROUND

Retinal nonperfusion (NP) is a biomarker for assessment of the severity of diabetic retinopathy and retinal vein occlusion. However, various conditions mimic the retinal NP flow void signals that are observed in optical coherence tomography angiography (OCTA).

METHODS

In this review, the possible mechanisms for these similar void flow signals in OCTA were summarized, and the discrepancies between the evaluations of retinal NP with fluorescein angiography and OCTA were also investigated and evaluated in terms of size and morphology.

RESULTS AND CONCLUSION

Vascular occlusion, resulting in retinal ischemia, leads to a flow void signal, indicating retinal NP in OCTA images. In addition, displacement of retinal vessels secondary to cystoid macular edema presents a false NP signal and produces a flow void signal similar to that of retinal NP in OCTA. Finally, various pathological conditions can coexist in the same retinal disease, with one of these factors playing a major role. Understanding the various causes of retinal NP in OCTA will be beneficial in conducting appropriate pathological investigations and making appropriate treatment and management choices.