CBD, Eye Health, and Eyesight: What New Cannabidiol Research Reveals

For years, people have been turning to CBD for calm, balance, and day-to-day wellbeing. But as its popularity has grown, so has an interesting question: How does CBD affect vision?
It’s a topic that pops up regularly online - mostly because CBD is often lumped together with THC, even though the two compounds behave very differently in the body.

At Harmony, we keep a close eye on emerging research, especially studies that look at safety and real-world use. And recently, a group of researchers in Spain published the first randomised controlled trial examining exactly this: how CBD influences visual function and optical quality in the short term. Their findings offer helpful insight, particularly for people who use CBD and want reassurance about how it interacts with day-to-day tasks that rely heavily on vision.

This article breaks down that study. Whether you’re curious, cautious, or simply want to understand CBD more deeply, here’s what you need to know.

New CBD Research: Understanding How Cannabidiol May Affect the Eye, Eyesight, and Ocular Function

Scientific research often revolves around complex ideas, but the goal of this trial was refreshingly straightforward: Does CBD impair vision in the short term?
To test this, researchers at the University of Granada designed a rigorous experiment, the kind usually used in pharmaceutical research.

They recruited 30 adults - young, healthy, and occasional users of cannabis or CBD - and brought them into the lab for a series of four sessions. Each person was assessed under three conditions:

• Placebo (0% CBD)

• 15% CBD (16 mg)

• 30% CBD (32 mg)

The order was randomised so that no one, including the researchers conducting the tests, knew which session contained which dose. After inhaling the assigned concentration, participants completed a long list of tests measuring clarity of vision, depth perception, contrast sensitivity, night-vision disturbances, and more. These assessments were chosen because they represent the skills we depend on every day - reading signs, judging distance, navigating dim lighting, or noticing movement while driving.

The team also measured “optical quality,” a term that might sound intimidating but simply refers to how sharply an image is formed on the retina. The clearer the optical quality, the better the visual experience.

In other words, this was not a quick or casual glance at vision. It was a full, clinically structured assessment - exactly what has been missing in conversations about CBD and eyesight.

How CBD and Cannabis Compounds Work in the Body: Why People Ask About Eyesight

To understand why this question is so common, it helps to look at where the confusion comes from. Many people associate cannabis products with red eyes or altered vision, but these effects are linked to THC, the psychoactive compound in cannabis - not CBD.

CBD does not produce intoxication, nor does it bind to the same receptors that THC does. But because the two come from the same plant, people naturally wonder whether CBD may also influence eyesight or visual clarity. The truth is, before this study, the evidence was extremely limited.

What we did know is that the body’s endocannabinoid system - the network CBD interacts with - is involved in many processes, including some vision-related pathways. But involvement does not automatically mean impairment. Understanding the difference requires careful testing, which is where this study fills an important gap.

What This Eye Research Measured: CBD Use, Visual Function, Ocular Effects

Vision is more than how clearly you can read a chart. That’s why the research team evaluated multiple aspects of visual function, including:

• Static and dynamic visual acuity: How clearly you see objects that are still or moving.

• Contrast sensitivity: Your ability to see differences between light and dark - important in low-light environments.

• Motion detection: How well you notice movement around you, which matters for driving or sports.

• Depth perception: Your sense of distance and three-dimensional space.

• Glare and halos: Bright disturbances often noticed when driving at night.

• Optical quality: How sharply the eye forms an image, measured with specialised equipment.

They also assessed pupil size, because changes in pupil diameter can affect brightness, focus, and overall visual performance.

Together, these tests provide one of the most detailed examinations of CBD’s effects on vision ever conducted.

What the Study Suggests: CBD Use, Eye Conditions, and the Effects of Cannabidiol

After analysing the results across all three CBD concentrations, the researchers reached a clear conclusion:
Short-term CBD use did not impair any aspect of visual function.

Not clarity.
Not depth perception.
Not contrast sensitivity.
Not night-vision indicators.
Not optical quality.

This finding held true across every test, including the most sensitive ones that detect subtle changes undetectable to the naked eye. You can see this in the detailed results tables on pages 5–9 of the published study, where none of the values showed clinically significant deterioration under CBD conditions. 

It’s worth noting that before the trial began, many participants believed CBD might slightly affect their vision. But the objective measurements showed no such effect. What people expect and what the eyes actually do can be two different things, and the study helps separate perception from reality.

What These Findings Mean for Everyday Eye Use: How CBD May Affect Eyesight

Research papers can feel far removed from everyday life, so let’s bring the findings into the real world.

Imagine someone uses CBD to unwind in the evening. According to this study, their ability to:

• read a book,

• watch a film,

• recognise facial expressions,

• navigate a dimly lit room, or

• drive home

would not be impaired by CBD itself, at least in the short-term timeframe tested in the study.

Similarly, for those who use CBD during the day - for stress, balance, or general wellbeing - the results suggest that ordinary visual tasks remain stable.

These insights are particularly relevant for anyone who worries about whether CBD could blur vision, reduce focus, or interfere with everyday responsibilities. While this study does not make long-term claims, it does provide reassuring evidence that short-term CBD exposure did not diminish visual performance.

Why Cannabidiol Did Not Affect Eyesight: Understanding CBD vs THC and Marijuana

The contrasting effects of THC and CBD offer useful context. THC binds strongly to receptors in areas of the brain involved in visual processing. Studies have shown that THC can temporarily affect motion detection, contrast sensitivity, and depth perception.

CBD, on the other hand, acts more subtly. It interacts with the endocannabinoid system in ways that do not produce intoxication or perceptual distortion. Its influence is more regulatory than disruptive. This difference appears to be reflected in the neutral findings of the study - the body seems to manage CBD in a way that maintains stable visual function.

This does not mean CBD never affects the body; rather, it highlights that its impact is not comparable to THC in the context of vision. It also shows why research that isolates CBD - rather than studying mixed cannabis products - is so valuable.

A Closer Look at CBD and Night Vision

Night-time conditions often reveal weaknesses in visual function. That’s why the study specifically measured glare and halo perception - those bright rings or scattered light patterns that make night driving difficult.

Even here, CBD did not increase objective visual disturbances. Although a few participants felt they noticed slightly more glare, the equipment used to measure actual light scatter and retinal image quality found no measurable changes.

In the publication, parameters such as straylight, objective scatter index, and Strehl ratio remain consistent across all CBD conditions, reinforcing the conclusion that optical quality stays stable. 

This is particularly relevant for people who use CBD and still need to perform visually demanding activities, whether that’s driving, working on screens, or navigating environments with mixed lighting.

Eye Health and CBD Use: What Current Research Means for People Using Cannabidiol

This study contributes important information to the conversation about CBD and safety. It suggests that, at typical short-term doses, CBD did not impair visual performance.

For many people who turn to CBD for balance, relaxation, or wellbeing, this research provides reassurance that their visual clarity is unlikely to be affected, at least in the short window examined.

It also highlights that CBD may offer potential for people seeking plant-based support without compromising functional abilities. This aligns with a growing body of evidence suggesting CBD is well tolerated, though more research is always needed - especially across different age groups and long-term use patterns.

What This Research Didn’t Address

Responsible interpretation matters. While this research fills a major gap, it also has limitations:

• It looked only at short-term effects of CBD.

• It involved healthy young adults, not older individuals or those with eye conditions like glaucoma.

• The doses reflected typical user amounts, not higher therapeutic doses.

• It examined vaporised CBD, not CBD oil, CBD capsules, CBD gummies, or topicals like eye drops.

Future research may help answer these remaining questions. For now, the study offers valuable insight into what CBD doesn’t do: it doesn’t appear to hinder the visual abilities we rely on every day.

Final Thoughts on CBD, Eyesight, and Eye Health: What Current Research Suggests 

The world of CBD research is evolving quickly, and this study marks an important milestone. It is the first randomised controlled trial to thoroughly assess how the use of CBD affects vision, using both subjective reports and precise optical measurements. And the conclusion is clear: CBD did not impair visual function or reduce optical quality in the short term.

For everyday CBD users, this is encouraging. It means that incorporating the cannabinoid into a wellbeing routine is unlikely to compromise visual clarity during ordinary activities.

As with all aspects of health, ongoing research will continue to deepen our understanding. But this study provides a strong foundation for evidence-based reassurance - showing that CBD, unlike THC, does not appear to interfere with how we see the world around us.

If you’re exploring CBD for balance, stress support, or general wellbeing, it’s worth knowing that current research suggests your vision remains unaffected. 

Curious to learn more? Reach out with any questions - our team is here to help!

Sources

[1] Martino F, Ortiz-Peregrina S, Casares-López M, Granados-Delgado P, Castro-Torres JJ, Anera RG. Influence of Cannabidiol Use on Visual Function and Optical Quality: A Randomized Controlled Trial. Transl Vis Sci Technol. 2025 Oct 1;14(10):10.