Collateral blood vessels forming in an eye with BRVO, visualized as glowing pathways.

Can Collateral Vessels Save Your Sight? Understanding BRVO and Ocular Angiography

Soraya Malik in Health & Wellness December 2025 • 4 min read.

"Optical coherence tomography angiography (OCTA) is revolutionizing how we detect and manage branch retinal vein occlusion (BRVO). Learn how these vessels affect your vision!"

Macular edema, the swelling of the macula, is a major cause of vision loss in people with branch retinal vein occlusion (BRVO). BRVO occurs when a vein in the retina, the light-sensitive tissue at the back of your eye, becomes blocked. This blockage leads to increased pressure, causing fluid and blood to leak into the macula, which is responsible for sharp, central vision.

In the aftermath of BRVO, your eye attempts to compensate. Tiny, new blood vessels called collateral vessels may form to bypass the blockage. Doctors have long debated whether these vessels help or hinder recovery. Some believe they relieve pressure and reduce swelling, while others suspect they contribute to persistent leakage and further complications.

Traditional methods like funduscopy and fluorescein angiography (FA) have limitations in visualizing these delicate vessels. However, optical coherence tomography angiography (OCTA) offers a non-invasive way to see these vessels in detail. This article will help you to understand how OCTA is changing the way we understand and manage BRVO.

Decoding Collateral Vessels: What OCTA Reveals About BRVO

Collateral blood vessels forming in an eye with BRVO, visualized as glowing pathways.

A recent study published in the British Journal of Ophthalmology investigated the role of collateral vessels in eyes with BRVO using OCTA. Researchers at Nagoya City University in Japan followed 28 patients with BRVO and macular edema, monitoring the presence and characteristics of collateral vessels over six months. The results shed light on when these vessels form, their impact on macular edema, and their relationship to visual outcomes.

The key finding was that collateral vessels were present in the vast majority of eyes (82%) at the beginning of the study. This suggests that these vessels develop rapidly in response to the initial blockage. Here are other important aspects of the findings:

Location Matters: Collateral vessels tended to form in the temporal region of the macula, either alone or in combination with the nasal region.
BRVO Subtype Influence: Major BRVO, involving a larger vein branch, and ischemic BRVO, characterized by poor blood flow, were more likely to have collateral vessels.
Leakage Concerns: About one-third of the collateral vessels showed signs of leakage, often associated with the presence of microaneurysms (tiny bulges in the vessel walls).
Impact on Macular Edema: Eyes with collateral vessels tended to experience faster resolution of macular edema, and a greater reduction in central retinal thickness (CRT), a measure of swelling.

While the presence of collateral vessels didn't directly translate to better visual acuity, the study highlights their association with reduced macular edema. However, it also raises concerns about the potential for leakage from these vessels, particularly when microaneurysms are present.

Protecting Your Vision: What This Means for BRVO Management

The information highlights the complex role of collateral vessels in BRVO. While they may aid in reducing macular edema, they can also contribute to leakage and further complications. OCTA is playing a crucial role in helping doctors visualize these vessels and make informed decisions about treatment strategies. Regular eye exams, prompt diagnosis, and personalized treatment plans are essential for managing BRVO and preserving your vision.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1136/bjophthalmol-2018-313322, Alternate LINK

Title: Collateral Vessels On Optical Coherence Tomography Angiography In Eyes With Branch Retinal Vein Occlusion

Subject: Cellular and Molecular Neuroscience

Journal: British Journal of Ophthalmology

Publisher: BMJ

Authors: Norihiro Suzuki, Yoshio Hirano, Taneto Tomiyasu, Ryo Kurobe, Yusuke Yasuda, Yuya Esaki, Tsutomu Yasukawa, Munenori Yoshida, Yuichiro Ogura

Published: 2018-11-22

Everything You Need To Know

What is Branch Retinal Vein Occlusion (BRVO), and how does it affect vision?

Branch Retinal Vein Occlusion (BRVO) occurs when a vein in the retina, the light-sensitive tissue at the back of the eye, becomes blocked. This blockage leads to increased pressure, causing fluid and blood to leak into the macula, which is responsible for sharp, central vision. This leakage results in macular edema, the swelling of the macula, a major cause of vision loss for people with BRVO. If the macular edema isn't addressed, it can severely impair central vision, making it difficult to see fine details or perform tasks that require clear vision. The location of the blockage within the retinal vein network impacts the severity of the vision loss, with blockages closer to the macula often causing more significant problems.

How does Optical Coherence Tomography Angiography (OCTA) help in understanding BRVO?

Optical Coherence Tomography Angiography (OCTA) is a non-invasive imaging technique that provides detailed visualization of the blood vessels in the retina. It allows doctors to see the delicate collateral vessels that form in response to BRVO. Unlike traditional methods like funduscopy and fluorescein angiography (FA), OCTA can visualize these vessels in detail, helping doctors assess their presence, location, and characteristics. This is crucial because the behavior of collateral vessels, specifically their potential to leak or aid in reducing macular edema, impacts treatment decisions and prognosis. By using OCTA, doctors gain a better understanding of how BRVO affects the eye and can make more informed decisions about treatment strategies.

What are collateral vessels, and what role do they play in BRVO?

Collateral vessels are tiny, new blood vessels that form in the eye as a compensatory response to a blockage, such as in Branch Retinal Vein Occlusion (BRVO). Their role is to bypass the blockage and potentially relieve pressure and reduce swelling. However, they can also contribute to further complications. A recent study using Optical Coherence Tomography Angiography (OCTA) found that collateral vessels were present in the majority of eyes with BRVO. While these vessels may help reduce macular edema, they can also be prone to leakage, especially when microaneurysms (tiny bulges in the vessel walls) are present. This leakage can worsen the condition and negatively impact visual outcomes. The overall effect of collateral vessels on visual recovery is complex and depends on their characteristics and behavior.

How do collateral vessels influence macular edema and visual outcomes in BRVO?

Collateral vessels' impact on macular edema and visual outcomes in Branch Retinal Vein Occlusion (BRVO) is complex. The study found that the presence of collateral vessels was associated with faster resolution of macular edema and a greater reduction in central retinal thickness (CRT), a measure of swelling. This suggests that collateral vessels may help in reducing swelling. However, about one-third of the collateral vessels showed signs of leakage, often associated with microaneurysms. While the presence of collateral vessels didn't directly translate to better visual acuity, the study highlights their association with reduced macular edema. The overall impact underscores the need for careful monitoring using techniques such as Optical Coherence Tomography Angiography (OCTA) to assess the behavior of these vessels.

What does the information about collateral vessels mean for the management of BRVO?

The information about collateral vessels highlights the complex role they play in Branch Retinal Vein Occlusion (BRVO) and underscores the importance of Optical Coherence Tomography Angiography (OCTA) in managing the condition. While these vessels may aid in reducing macular edema, they can also contribute to leakage and further complications. The findings suggest that regular eye exams, prompt diagnosis, and personalized treatment plans are essential for managing BRVO and preserving vision. OCTA helps doctors visualize these vessels and make informed decisions about treatment strategies, balancing the potential benefits of collateral vessels in reducing macular edema with the risks of leakage and further complications. This nuanced understanding of collateral vessels allows for more effective and targeted interventions.