Researchers studied how vitamin A deficiency affects the eyes’ ability to see in the dark. They tested five people—three with normal vision and two with eye conditions—using special eye tests that measure how the eye responds to light. They found that vitamin A deficiency doesn’t simply reduce how much light the eye can catch. Instead, it creates a kind of “background noise” in the eye that makes it harder to see dim lights at night. This explains why people without enough vitamin A struggle in low light, while their daytime vision stays relatively normal. The findings could help doctors better understand and treat night vision problems.

The Quick Take

  • What they studied: How vitamin A deficiency damages night vision and whether it works by simply reducing light sensitivity or by creating interference in the eye’s light-sensing system
  • Who participated: Five people total: three healthy adults aged 21-47, one 70-year-old with severe vitamin A deficiency, and one 43-year-old with a genetic color blindness condition
  • Key finding: Vitamin A deficiency appears to work like adding a dim light in the background of your vision, making it harder to see faint lights at night—rather than simply making your eyes less sensitive to light
  • What it means for you: If you have vitamin A deficiency, treating it with vitamin A supplements may restore your night vision. This research suggests the problem isn’t permanent damage but rather a reversible interference in how your eye processes light

The Research Details

Researchers recruited five volunteers and performed specialized eye tests called electroretinograms (ERGs). These tests measure how the eye’s light-sensing cells respond to flashes of light. The team used tiny electrodes to record electrical signals from the eye while delivering carefully controlled light flashes in dark rooms. They tested people in complete darkness and also while showing them dim blue backgrounds. One participant had severe vitamin A deficiency, and researchers retested them after treatment to see if responses improved.

The researchers also tested two different ways light sensitivity could decrease: by making the light flashes dimmer (like reducing the actual light reaching the eye) and by adding a dim background light (like having interference in the eye’s system). They compared how these two methods affected the eye’s electrical responses to see which one matched what happens in vitamin A deficiency.

This approach allowed them to distinguish between two possible mechanisms: simple loss of light sensitivity versus a more complex interference effect happening inside the eye’s light-sensing system.

Understanding exactly how vitamin A deficiency damages night vision is important because it tells us whether the damage is reversible and how to best treat it. If it’s just reduced sensitivity, treatment might work differently than if it’s an interference effect. This research also helps explain why vitamin A deficiency specifically hurts night vision but leaves daytime vision relatively intact—a pattern that wouldn’t make sense if it were simple light sensitivity loss.

This is a small study with only five participants, which limits how much we can generalize the findings. However, the researchers used precise, objective measurements (electrical recordings from the eye) rather than relying on what people report they can see. The fact that one participant was retested after treatment and showed improvement strengthens the findings. The study included control participants without vitamin A deficiency, which helps confirm the findings are specific to the deficiency. The research was published in a respected peer-reviewed journal focused on eye science.

What the Results Show

The patient with severe vitamin A deficiency showed significantly reduced electrical responses from the eye’s night-vision cells (rods) in darkness, but normal responses in light. After vitamin A treatment, these responses returned to normal. This selective effect on dark vision is the key finding.

When researchers compared the two ways of reducing light sensitivity, they found important differences. When they made the light flashes dimmer, the eye’s response became both weaker and slower—the response took longer to happen and reached its peak later. However, when they added a dim background light, the response became weaker but stayed at normal speed—it didn’t slow down.

In the patient with moderate vitamin A deficiency, the eye’s response to dim flashes was reduced but not slowed, matching the pattern seen with dim backgrounds. This suggests vitamin A deficiency creates an effect similar to having a dim light constantly on in the background of the eye.

Importantly, this pattern held true even in the participant with genetic color blindness, showing that this is a property of the rod cells (night-vision cells) specifically, not something unique to vitamin A deficiency.

The research revealed that light-adapted responses (how the eye responds in bright light) were not affected by vitamin A deficiency, which explains why daytime vision remains relatively normal. The researchers also found that the ’equivalent background’ effect likely comes from free opsin—a protein in the eye that can be activated even without light. This activation creates noise in the system, similar to having a dim light constantly present. The fact that this doesn’t happen in cone cells (daytime vision cells) explains why vitamin A deficiency selectively damages night vision.

Previous research suggested vitamin A deficiency might simply reduce how much light the eye can detect. This study provides more detailed insight, showing the mechanism is more complex. The ’equivalent background’ explanation fits with what scientists know about how light-sensing proteins work in the eye. This research builds on decades of understanding about vitamin A’s role in vision, adding a more precise explanation of the mechanism.

The study included only five people, which is very small. Results from such a small group may not apply to everyone with vitamin A deficiency. The participants varied widely in age and eye conditions, making it harder to draw general conclusions. The study was conducted in a laboratory with specialized equipment, so it’s unclear if the same patterns would appear in real-world conditions. Additionally, the study focused on electrical measurements rather than testing actual vision ability in daily life. More research with larger groups is needed to confirm these findings.

The Bottom Line

If you have vitamin A deficiency, vitamin A supplementation appears likely to restore night vision based on this research (moderate confidence). The evidence suggests the problem is reversible with treatment rather than permanent damage. However, treatment should be guided by a healthcare provider, as too much vitamin A can also be harmful. For people with normal vitamin A levels, maintaining adequate vitamin A intake through diet (foods like carrots, sweet potatoes, spinach, and liver) supports healthy night vision.

This research is most relevant to people experiencing night blindness or difficulty seeing in dim light, especially those at risk for vitamin A deficiency (including people in developing countries, those with malabsorption disorders, or strict dietary restrictions). Healthcare providers treating vision problems should be aware of this mechanism. People with normal vitamin A levels don’t need to worry about this specific issue. However, anyone experiencing persistent night vision problems should see an eye doctor for proper diagnosis.

Based on the case study showing improvement after treatment, vitamin A supplementation may begin improving night vision within weeks to months, though the exact timeline varies by person and severity of deficiency. Complete restoration of normal night vision may take longer. Results depend on the degree of deficiency and how quickly vitamin A levels are restored to normal.

Want to Apply This Research?

  • Track night vision quality on a simple scale (1-10) weekly, noting specific situations like driving at night or navigating dimly lit spaces. Also track vitamin A intake through food and supplements to correlate with vision improvements.
  • Users can set daily reminders to consume vitamin A-rich foods (carrots, sweet potatoes, spinach, kale, liver, eggs, dairy) and log these meals in the app. For those taking supplements, set reminders for consistent timing and dosage as recommended by their healthcare provider.
  • Create a simple log tracking: (1) subjective night vision quality, (2) specific vision challenges encountered, (3) vitamin A food/supplement intake, and (4) any medical appointments or lab results related to vitamin A levels. Review monthly trends to see if vision improves as vitamin A intake increases.

This research describes how vitamin A deficiency affects night vision at a cellular level. It is not medical advice. If you experience night vision problems, difficulty seeing in dim light, or suspect vitamin A deficiency, consult with an eye doctor or healthcare provider for proper diagnosis and treatment. Do not start vitamin A supplements without medical guidance, as excessive vitamin A can be toxic. This study involved only five participants, so individual results may vary. Always work with qualified healthcare professionals for vision concerns and nutritional supplementation.