There is no way to deny the potential impact of blue light, given the digital era we are in. To put this into perspective, there are approximately 340 million Americans, yet 383.4 million cellular mobile connections.¹ The average American spends over seven hours a day looking at a screen, with Gen Z averaging nine hours per day.² Can this incredible shift in blue light radiation have an impact on our ocular or more generalized health?

Not Proven, Yet

One area that can’t be proven is the negative impact of blue light on the retina. While it is certainly possible, studies would require decades to prove. I believe this controversy pushed people away from the entire subject of blue light regardless of the volume of exposure. As optometrists, we must know the impact of light on the eye and general health. There is a wealth of proven studies to guide us and significant options to help patients ranging from screen protectors (Eyesafe) to high energy visible light-blocking lenses.

Negative Impacts

We know that blue light exposure influences sleep patterns, which can lead to issues ranging from dry eye disease to obesity. A systematic review examined 24 high-quality studies and found that blue light exposure from electronic devices significantly disrupted sleep by increasing sleep latency and decreasing sleep quality. The suppression of melatonin production, a hormone essential for sleep regulation, was consistently lowered. The review highlighted the need for practical measures to mitigate blue light exposure, especially in the evening.³

Looking more specifically at late-day exposure, another study explored the effects of short-wavelength light from devices on melatonin suppression and sleep disturbances. It concluded that pre-bedtime exposure to blue light from electronic devices delayed melatonin secretion, disrupted circadian physiology and reduced sleep quality.⁴

A similar study found that reading on a smartphone without a blue light filter before bedtime reduced sleep quality and increased morning cortisol levels, affecting overall sleep physiology and alertness.^5,6 Yet another article, from the Sleep Foundation, explains that blue light suppresses melatonin production and delays sleep onset, leading to reduced sleep quality.⁷

The question is: Does this lack of quality sleep have repercussions, or does blue light exposure alone lead to other diagnoses, including diseases and disorders such as depression, obesity and even cancer? A study involving over 85,000 participants found that high nighttime light exposure increased the risk of depression by 30%, while bright light during the day reduced depression risk by 20%. Similar patterns were observed for other mental health issues including anxiety and post-traumautic stress disorder.⁸ Furthermore, another study indicated that blue light exposure is associated with increased risks of depression and other mood disorders, including bipolar disorder. It even suggests that reducing blue light exposure could be beneficial for one’s mental health.⁹

Another study explored the connection between light pollution and obesity and found that nocturnal light exposure is linked to an increased risk of obesity and related diseases. It also discusses how nighttime light exposure might contribute to cancer risk.⁹ One more study worth mentioning found that higher levels of light exposure at night were associated with a 21% higher risk of obesity and related metabolic disorders, suggesting a strong link between blue light exposure and type 2 diabetes.^9,10

When I was young, in my residency and fellowship it was considered a badge of honor to be the first one to arrive at the clinic in the morning and the last one to leave. I recall times when I covered call and slept on a cot at the clinic for multiple days. I only wish I knew then what I know today—that quality and duration of sleep not only would have helped me retain more information and be more productive, but also decrease long-term risks ranging from metabolic health issues to cardiovascular disease and cancer.¹¹ The difference today is we have the sleep-deprivation knowledge and are aware that blue light exposure late in the day can affect circadian rhythms; this demands that we educate our patients.

The National Institutes of Health National Heart, Lung and Blood Institute outlines how sleep deficiency affects overall health. It can impair learning, decision-making and emotional regulation and is linked to increased risks of obesity, diabetes, heart disease, high blood pressure and stroke. Proper sleep is essential for physical health, including maintaining a healthy hormone balance and immune function.¹² 

Further research showed a statistically higher risk of cancers such as those of the breast, colon, ovaries and prostate. The interplay between sleep and cancer is also significant during treatment, as sleep problems can persist long-term and impact survivors’ quality of life.¹³

So, while we may never know the effects of blue light exposure on the retina, we can be assured our recommendations to block or limit exposure late in the day will have a significant effect on our patients’ cognitive ability and risk of diseases such as cancer, mental illness, cardiovascular disease and diabetes.

Dr. Karpecki is medical director for Keplr Vision and the Dry Eye Institutes of Kentucky and Indiana. He is the Chief Clinical Editor for Review of Optometry and chair of the New Technologies & Treatments conferences. A fixture in optometric clinical education, he consults for a wide array of ophthalmic clients, including ones discussed in this article. Dr. Karpecki's full list of disclosures can be found here.