Morphological Implications of Vascular Structures Not Visualized on Optical Coherence Tomography Angiography in Retinal Vein Occlusion

Role of optical coherence tomography angiography in the evaluation of peripheral ischemia in retinal vein occlusion

In the last decade, optical coherence tomography angiography (OCTA) has become part of the clinical management of retinal vein occlusion (RVO), proving in itself a useful technique for both the prediction of visual acuity (VA) outcomes and the risk of complications. In fact, OCTA has been proven a valid imaging technique in detailed assessment of foveal and parafoveal microvascular status in both acute and chronic RVO. Quantitative OCTA data have shown a significant correlation not only with final VA but also with the extension of peripheral ischemia, which represents a major risk factor for macular edema recurrence and neovascularization onset. Finally, wide-field OCTA represents a promising noninvasive technique for the assessment of peripheral ischemia. The aim of this review is to report the main literature findings about microvascular changes and clinical applications of OCTA in the context of RVO-induced peripheral ischemia.

Optical coherence tomography angiography as predictor of visual outcomes in retinal vein occlusion treated with antiangiogenic therapy

PURPOSE

Evaluate optical coherence tomography angiography (OCT-A) features in retinal vein occlusions (RVO) associated with visual outcomes after anti-VEGF.

METHODS

Analytical observational study performed in eyes with macular edema secondary to RVO treated with anti-VEGF, with at least 6 months of follow-up. Bradley et al. classification of macular ischemia was used. Logistic regression analysis was used to investigate associations between final best-corrected visual acuity (BCVA) and OCT-A.

RESULTS

A total of 62 eyes, 61 subjects, mean age of 70 ± 12,6 years were included. Median follow up time 21,2 months (IQR 24.8), 53,2% had central retinal vein occlusion (CRVO) and 46,8% branch retinal vein occlusion (BRVO). Median BCVA pre-treatment was 0,84 logMAR (IQR 0,83) and post-treatment 0,47 logMAR (IQR 0,52). BCVA improved at the end of follow-up (p = 0,01), as well as central retinal thickness (CRT) (p = 0,02). Regarding capillary densities (CD), there was a decrease for both plexus, Superficial CD (p = 0,01) and Deep CD (p = 0,01), being more involved the superficial plexus. The lower the capillary density in both plexus, the worse BCVA, Superficial CD (r - 0,27, p = 0,03) and Deep CD (r - 0,29, p = 0,02). Media FAZ pre-treatment was 0,30 mm2 (IQR 0,23), with enlargement to 0,37 mm2 (IQR 0,32) (p = 0,01) post-treatment. Preservation of External Limiting Membrane/ Ellipsoid Zone (ELM/EZ) was seen in 60% of subjects (n = 37). The majority had grade 3 macular ischemia. Variables that best explain visual results were, baseline visual acuity (p = 0,01), pre-treatment CRT (p = 0,02) and pretreatment foveal superficial CD (p = 0,02).

CONCLUSIONS

Variables that best explain final vision after anti-VEGF were baseline visual acuity, CRT and foveal superficial CD.

Collateral Vessel Development in Central and Branch Retinal Vein Occlusions Are Associated With Worse Visual and Anatomic Outcomes

Purpose

The purpose of this study was to investigate the effects of the extension of collateral vessels on the outcomes of eyes affected by central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO).

Methods

The study was designed as a cross-sectional case series. Patients affected by CRVO and BRVO were progressively recruited, along with an age- and sex-matched control group of healthy subjects. Structural optical coherence tomography (OCT) and OCT angiography (OCTA; 4.5 × 4.5 mm and 9.0 × 9.0 mm acquisitions) were performed on all participants in order to assess the relationship between the presence of collateral vessels and final anatomical outcomes - central macular thickness (CMT), foveal avascular zone - and functional outcomes - best corrected visual acuity (BCVA).

Results

Fifty-six eyes affected by CRVO and 47 eyes affected by BRVO were included. Baseline LogMAR BCVA was 0.41 ± 0.33 LogMAR in CRVO, and 0.39 ± 0.25 LogMAR in BRVO (P < 0.01), improving to 0.20 ± 0.26 LogMAR in CRVO (P < 0.01), and 0.19 ± 0.22 LogMAR in BRVO (P < 0.01). Baseline CMT was 511 ± 214 µm in CRVO and 482 ± 178 µm in BRVO (P > 0.05), decreasing to 328 ± 105 µm (P < 0.01) and 321 ± 78 µm in CRVO and BRVO, respectively (P < 0.01). Collateral vessels were detected in 16 of 56 eyes (29%) in CRVO and in 47 of 47 eyes (100%) in BRVO. Their extension was correlated with worse anatomic and visual outcomes. Remarkably, no correlation was found with peripheral capillary nonperfusion and vessel density impairment.

Conclusions

The present study demonstrates that collateral vessel extension is associated with worse anatomic and functional outcomes in patients affected by CRVO and BRVO.

Evaluation of Microvascular Structure Changes after Conbercept Treatment on Macular Edema Secondary to Retinal Vein Occlusion

Aims

To confirm the therapeutic efficacy of conbercept for the treatment of macular edema (ME) secondary to retinal vein occlusion (RVO) by using optical coherence tomography angiography (OCTA) and to find out the differences in therapeutic efficacy between ischemic and nonischemic retinal vein occlusion (iRVO or non-iRVO) after conbercept treatment.

Methods

In this prospective, randomized, and comparative study, 60 unilateral eyes suffered from RVO combined with macular edema were included and fellow eye as controls. After an initial intravitreal injection of conbercept (IVIC), a pro re nata (PRN) strategy was adopted, and the follow-up time was 6 months. The foveal avascular zone (FAZ), vascular density of superficial capillary plexus (SCP), and vascular density of deep retinal capillary plexus (DCP), nonperfused areas (NPAs) were evaluated with OCTA on baseline and after treatment.

Results

The mean intravitreal injection number was 2.9 ± 0.89 times during six months in iRVO patients and 2.1 ± 0.86 times in non-iRVO patients, with statistically significant difference (p < 0.05). On baseline, central macular thickness (CMT) and FAZ were significantly thickened and enlarged compared to those of healthy fellow eyes; the vascular density of SCP and DCP were significantly decreased, and the differences were statistically significant (p < 0.05). Compared to baseline, after treatment, the best-corrected visual acuity (BCVA) was improved in either iRVO or non-iRVO (−0.601 ± 0.387, −0.241 ± 0.341 logMAR, p < 0.05). In iRVO, the improvement was more substantial than that of the non-iRVO group. FAZ in the non-iRVO group had significantly decreased compared to that in iRVO group (−0.044 ± 0.040 versus 0.014 ± 0.043 mm², p < 0.05). CMT, the vascular density of SCP, and DCP had no significant difference.

Conclusions

The changes of microvascular structure can be quantitatively evaluated by using OCTA for the patients with RVO. Conbercept had a significant effect on treatment of RVO with macular edema. A more profound effect was achieved in the iRVO group on visual improvement and FAZ reduction in the non-iRVO group after conbercept treatment.

Exploring the relationship between collaterals and vessel density in retinal vein occlusions using optical coherence tomography angiography

Purpose

To characterize the types of collaterals in eyes with retinal vein occlusion (RVO) and further investigate their correlations with vessel densities of the superficial (SCP) and the deep capillary plexus (DCP) using optical coherence tomography angiography (OCTA).

Methods

This cross-sectional study included 25 eyes of 23 patients with RVO. 3 x 3 mm² OCTA macular scans were used to quantify the parafoveal vessel density (VD) of the SCP and DCP, and to classify the collaterals into one of four types (true superficial, true deep, superficial diving, and foveal collateral). Generalized estimating equation (GEE) regression analysis was performed to identify significant associations between parafoveal VD and collaterals. We further compared parafoveal VD between subgroups classified by the presence of specific collateral types based on the results of a clustering algorithm.

Results

16 of 25 eyes (64%) developed collaterals. Of the 43 collateral vessels analyzed, 12/19 (63%) true superficial collaterals developed in eyes with central RVO, while all 10 superficial diving collaterals (100%) developed in eyes with branch RVO. Located exclusively in the SCP, true superficial collaterals were all arteriovenous (A-V), while diving collaterals were all veno-venular (V-V). We found a significant negative correlation between SCP VD and the total number of collaterals (P < 0.001) for the entire study cohort. Furthermore, BRVO eyes that developed superficial diving collaterals and CRVO eyes that developed true superficial collaterals demonstrated significantly lower SCP VD (P-value = 0.014) and DCP VD (P-value = 0.030), respectively, as compared to the eyes without collaterals in the respective RVO group.

Conclusion

Our data shows that decreased capillary perfusion in RVO is associated with the development of collaterals, while the RVO type largely dictates the type of collateral that ultimately develops.

The anti-inflammatory and anti-oxidative effects of conbercept in treatment of macular edema secondary to retinal vein occlusion

To investigate the effects of conbercept on inflammatory and oxidative response in macular edema secondary to retinal vein occlusion (RVO-ME). Retinal microvasculature were detected by optical coherence tomographic angiography (OCTA). The inflammation related factors including prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), prostaglandin F2a (PGF2a), intercellular cell adhesion molecule-1 (ICAM-1) and macrophage inflammatory protein-1 (MIP-1) were determined in human and mice with RVO-ME. OCTA images showed that capillary non-perfusion, enlargement of the foveal avascular zone, telangiectatic vessels and some forms of intraretinal edema in RVO-ME and all these were alleviated by conbercept treatment. PGE1, PGE2, PGF2a, ICAM-1 and MIP-1 in aqueous fluid extracted from RVO-ME patients was significantly increased compared with non-RVO subjects, intravitreal injection of conbercept partly reduced ICAM-1 and MIP-1 levels but not PGE1, PGE2 and PGF2a. The glutathione level was reduced in aqueous fluid extracted from RVO-ME patients but was restored after conbercept treatment. The inflammation, angiogenesis and ROS generation was increased in RVO-ME mice, conbercept partly inhibited these effects. Mechanistically, conbercept inhibited vascular endothelial growth factor (VEGF), ICAM-1, MIP-1, NOX-1 and NOX-4 protein expressions, but not PGE1, PGE2 and PGF2a expressions. Conbercept alleviates RVO-ME through inhibiting inflammation, angiogenesis and oxidative responses. These findings further reveals the molecular mechanism of conbercept for treatment of RVO-ME.