Researchers discovered that not having enough vitamin B12 in your body can change the tiny blood vessels in the back of your eyes, specifically in areas important for seeing details. Using special eye imaging technology, scientists compared 34 people with low B12 levels to 36 healthy people. They found that B12 deficiency caused unusual changes in eye blood vessels—some areas had more blood vessels than normal, while other areas had fewer. These changes could potentially affect vision over time. The good news is that doctors can now use advanced imaging to catch these problems early and help prevent vision problems before they start.

The Quick Take

  • What they studied: Whether vitamin B12 deficiency causes changes in the tiny blood vessels at the back of the eye, particularly in the part responsible for detailed vision
  • Who participated: 70 adults total: 34 people with confirmed vitamin B12 deficiency and 36 healthy people without B12 deficiency, used as a comparison group
  • Key finding: People with B12 deficiency showed unusual blood vessel changes in their eyes—some areas had abnormally high blood vessel density while the overall blood vessel layer became thinner. These changes were confirmed using advanced imaging technology that can see tiny structures in the eye.
  • What it means for you: If you have vitamin B12 deficiency, your eye health may be at risk. Getting your B12 levels checked and corrected through diet or supplements may help protect your vision. However, more research is needed to confirm whether these blood vessel changes actually cause vision problems or if treating B12 deficiency reverses these changes.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot in time by comparing two groups of people at the same moment rather than following them over years. One group had vitamin B12 deficiency, and the other group was healthy. The researchers used two types of advanced eye imaging: OCTA (a special camera that photographs blood vessels in the eye) and EDI-OCT (another imaging tool that takes detailed pictures of the deeper layers of the eye). These tools allowed them to measure blood vessel density, thickness, and structure in specific areas of the eye without any pain or surgery.

The study measured several specific features: the density of blood vessels in two different layers of the retina (the light-sensitive tissue at the back of the eye), the size of the area in the center of the eye that naturally has no blood vessels, and various measurements of the choroid (a layer of blood vessels that feeds the retina). This detailed approach allowed researchers to see exactly how B12 deficiency affects different parts of the eye’s blood vessel system.

The researchers used statistical analysis to determine whether the differences between the B12-deficient group and the healthy group were real or just due to chance. They set a standard threshold where differences had to be very unlikely to occur by random chance (p-value less than 0.05) to be considered meaningful.

This research approach matters because it uses cutting-edge imaging technology that can detect microscopic changes in blood vessels before they cause noticeable vision problems. By identifying these early changes, doctors might be able to intervene sooner with B12 treatment. The cross-sectional design is efficient for identifying associations between B12 deficiency and eye changes, though it cannot prove that B12 deficiency directly causes these changes.

Strengths of this study include the use of objective, advanced imaging technology that leaves no room for observer bias, and a reasonable comparison between B12-deficient and healthy groups. Limitations include the relatively small sample size (70 people total), which means results might not apply to everyone. The study is cross-sectional, so it cannot prove cause-and-effect—only that these conditions occur together. The study doesn’t tell us whether these blood vessel changes actually harm vision or whether treating B12 deficiency reverses the changes. Additionally, the study doesn’t account for other factors that might affect eye blood vessels, such as diabetes, high blood pressure, or other nutritional deficiencies.

What the Results Show

The most striking finding was that people with B12 deficiency showed paradoxical (contradictory) changes in their eye blood vessels. In certain areas of the macula (the part of the retina responsible for detailed vision), blood vessel density was actually higher than in healthy people. Specifically, the superficial layer of blood vessels in the upper-middle area of the macula showed significantly increased density, as did the deeper blood vessel layer in the upper areas.

However, when researchers looked at the overall blood vessel layer beneath the retina (called the choroid), they found the opposite pattern: this layer was significantly thinner in people with B12 deficiency. The total area of blood vessels in this layer decreased, and the proportion of actual blood vessel tissue compared to supporting tissue increased (meaning the blood vessels were more densely packed but in a thinner overall layer).

These contradictory findings suggest that B12 deficiency causes complex, region-specific changes in eye blood vessel structure. The increased density in some areas might represent the eye’s attempt to compensate for reduced blood flow in other areas, or it might indicate abnormal blood vessel growth patterns.

Most other measurements of blood vessel structure in the macula did not show significant differences between the two groups, suggesting that the B12 deficiency’s effects are localized to specific regions rather than affecting the entire eye.

The study also measured the foveal avascular zone (FAZ), which is the small area in the center of the macula that naturally contains no blood vessels. This measurement did not show significant differences between B12-deficient and healthy groups, suggesting that B12 deficiency doesn’t affect this particular structure. The researchers also found that the specific pattern of blood vessel changes was not uniform across all areas of the macula, indicating that B12 deficiency affects different regions of the eye differently.

This research adds important new information to our understanding of how vitamin B12 deficiency affects the eye. Previous research has shown that B12 deficiency can cause neurological problems and affect the optic nerve, but this study is among the first to carefully document how it affects the tiny blood vessels in the retina and choroid using advanced imaging. The finding of paradoxical blood vessel changes (increased density in some areas while overall thickness decreases) is particularly novel and suggests that B12 deficiency causes more complex vascular changes than previously understood.

Several important limitations should be considered: First, the sample size is relatively small (only 34 people with B12 deficiency), which means the findings might not apply to all people with this condition. Second, this is a cross-sectional study, meaning it captures only one moment in time—researchers cannot determine whether these blood vessel changes develop before, during, or after B12 deficiency develops, or whether they persist after B12 is treated. Third, the study doesn’t measure whether these blood vessel changes actually cause vision problems or affect how well people can see. Fourth, the study doesn’t account for other factors that could affect eye blood vessels, such as diabetes, high blood pressure, smoking, or other nutritional deficiencies. Finally, the study doesn’t provide information about how severe the B12 deficiency was in each participant or how long they had been deficient, which could affect the results.

The Bottom Line

If you have been diagnosed with vitamin B12 deficiency, ensure you receive appropriate treatment through dietary changes, supplements, or injections as recommended by your doctor (high confidence). Consider having your eye health monitored by an eye care professional, especially if you have other risk factors for eye disease (moderate confidence). Maintain adequate B12 intake through diet or supplementation to support overall health, including eye health (high confidence). However, do not assume that these blood vessel changes will definitely harm your vision—more research is needed to understand the clinical significance of these findings (important caveat).

This research is most relevant to people who have been diagnosed with vitamin B12 deficiency or who are at risk for deficiency (including vegetarians, vegans, older adults, and people with certain digestive conditions). Eye care professionals should be aware of these findings when examining patients with B12 deficiency. People with other eye conditions or risk factors for eye disease should discuss B12 status with their healthcare providers. This research is less immediately relevant to people with normal B12 levels, though maintaining adequate B12 is important for overall health.

The timeline for seeing benefits from treating B12 deficiency is unclear from this research. B12 deficiency typically takes months to develop, so it may take weeks to months of treatment to restore normal B12 levels. Whether the blood vessel changes reverse after B12 treatment, and how long that reversal takes, is not addressed in this study. Vision changes, if they occur, would likely develop gradually over time rather than suddenly.

Want to Apply This Research?

  • Track your B12 supplementation or dietary B12 intake daily, noting the type and amount. Also track any changes in vision quality, such as difficulty focusing, blurriness, or floaters. Record eye exam dates and results from your eye care provider.
  • If you have B12 deficiency, set a daily reminder to take your B12 supplement or eat B12-rich foods. Schedule regular eye exams (at least annually) and log the results in the app. If you’re vegetarian or vegan, use the app to track B12-containing foods or supplements to ensure adequate intake.
  • Create a long-term tracking system that monitors B12 levels (through periodic blood tests with your doctor), vision quality (through self-assessment and professional eye exams), and treatment adherence (daily supplement tracking). Set quarterly reminders to review trends and discuss results with your healthcare provider.

This research describes associations between vitamin B12 deficiency and changes in eye blood vessel structure, but does not prove that B12 deficiency causes vision problems or that treating B12 deficiency will prevent vision loss. This information is for educational purposes only and should not replace professional medical advice. If you have concerns about your vision or B12 levels, consult with your eye care provider or primary care physician. Do not start, stop, or change any B12 treatment without consulting your healthcare provider. People with specific eye conditions or other health concerns should discuss this research with their healthcare team to determine its relevance to their individual situation.