Right now, people affected by retinal vein occlusion (RVO) are typically prescribed injections of a vascular endothelial growth factor inhibitor (anti-VEGF) into their eye.

Experiments on mice conducted by researchers at Columbia University and Sanford Burnham Prebys Medical Discovery Institute in the US suggest this uncomfortable and slightly scary treatment could one day be replaced with eye drops.

RVO occurs when a vein in the eye's retina gets blocked, leading to swelling, inflammation, damage to the retina, and even vision loss, depending on the severity of the problem.

Anti-VEGF injections have been shown to reduce swelling and improve vision. Not only does it require a thin hypodermic to be inserted into the eye to work, however, the injections aren't always effective at treating RVO.

The daunting prospect of an eye injection tends to mean people put off treatment too, which can mean the problem then gets worse.

Mouse eye scan
Lab mice were treated to develop retinal vein occlusion. (Avrutsky et al., Frontiers in Neuroscience, 2023)

In the laboratory tests, eye drops containing an experimental drug were found to be twice as effective in mice as standard anti-VEGF injections when it came to reducing RVO swelling and improving blood flow in the retina. What's more, unlike injections, the eye drops protected against vision loss by preventing the photoreceptors in the eye from deteriorating.

The eye drops contained a compound called Pen1-XBir3, previously found to block the enzyme caspase-9. This enzyme triggers cell death, and is known to be overactive in blood vessels damaged by RVO.

"We think the eye drops improve the health of blood vessels in the retina, which then decreases the toxic signaling that damages the retina's neurons and leads to vision loss," says neurovascular biologist Maria Avrutsky from Columbia University.

It's a very promising result, though clearly this needs to be tested out in people now that we know how well it works in mice. Human clinical trials are planned, and the researchers say other treatments could be developed using the same compound.

Our eyes are one of the most delicate and important parts of our bodies, and any damage can severely impact the quality of someone's life. The good news is we're seeing regular advancements made in the treatment of eye conditions, like the one reported here – whether it's eye drops to counter aging or growing entirely new retinas.

"There's an opportunity to help more people with this disease that is a leading cause of blindness worldwide," says Columbia University cell biologist Carol Troy.

"Finding the root cause of RVO is the holy grail, but if we can at least provide better symptomatic relief that doesn't distress patients, it would be a really good start."

The research has been published in Frontiers in Neuroscience.