We Can’t Look Away: The Effect of Screens on Ocular Physiology

Screens are everywhere in today’s world. As the world operates more and more efficiently through technological advancement, the implications of digitization on our eyes have, until recently, been overlooked. Luckily, screens are more harmless than harmful to our eyes. However, its risks are important and should not be overlooked. Although still requiring further research, it is essential in this day and age for people of all demographics to understand screens’ dangerous and potentially irreversible effects on our ocular physiology. 

What is it about screens that pose a danger to our eyes? The answer lies in the blue light they radiate. We are exposed to blue light when we use mobile phones, computers, TVs, LED lights, and other displaying technologies. Blue light, with a wavelength of 415-455 nm, is only slightly less powerful than ultraviolet rays (Zhao, 2018). While high exposure levels pose negative risks, healthy amounts of blue light help regulate the circadian cycle (Blume, 2019), serve as a means of therapy to lower serum bilirubin levels (Jiao, 2018), and stimulate photosensitive retinal ganglion cells, improving alertness (Yang, 2018). 

Overall, blue light poses no concern for public health. (O’hagan, 2016). The International Commission on Non-Ionizing Radiation Protection (ICNIRP) exposure limit for long-term viewing is 100 W m-2 sr-1. Under extremely prolonged viewing conditions, blue light weighted radiance of computers, smartphones, and other blue-light-emitting-sources is less than 1% the ICNIRP blue light exposure limit (O’hagan, 2016). In fact, even during normal use conditions, no evidence suggests blue light exposure increases risks for photochemical injury (O’hagan, 2016). Undoubtedly, it is safe to use manufactured blue-light-emitting sources, including screens, if utilized properly. 

While there is little reason to be concerned about blue light under normal use conditions, it is crucial to acknowledge that blue light presents potentially harmful risks to our ocular physiology. In particular, many studies show how excessive light exposure affects the retina, which, through interplay between photoreceptor cells and retinal pigment epithelium (RPE) cells, plays an important role in visual formation. Studies have shown the ability for high energy blue-light to penetrate through both the lens and cornea, reaching the retina directly, causing what is commonly known as the blue light hazard, which is the potential for photochemical damage to the retina due to blue light phototoxicity (O’hagan, 2016). Resulting retinal degeneration takes a variety of forms, starting from heightened oxidative stress in RPE cells that increase production of reactive oxidative species (ROS) (Ishii, 2015). Production of ROS-induced signals leads to activation of apoptosis and necrosis pathways, prompting photoreceptor cell death (Jaadane, 2015) and RPE cell death (Sparrow, 2000).

Blue light phototoxicity also negatively impacts the ocular surface. This system primarily comprises tear film, corneal epithelial tissues, and conjunctival tissues (Marek, 2018). As the first barrier to physical, chemical, and infectious environmental factors, this system plays a critical role in ocular immune defense and damage prevention (Bolaños-Jiménez, 2015). Similar to retinal responses, blue light increases production of reactive oxygen species (ROS), contributing to oxidative stress that triggers inflammation of corneal epithelial cells (Zheng, 2015). Such inflammatory responses reduce tear and mucin secretion, functions critically important for healthy ocular physiology; furthermore, such responses have been suggested to contribute to the development of dry eye disease (Zhao, 2018; Marek, 2018). Moreover, as a result of blue light phototoxicity, microvilli in the corneal epithelial tissues lose dependability and stability of the tear film; this instability also contributes to dry eye formation (Zhao, 2018). The risks outlined thus far present some potential implications of blue light overexposure; a look into a multitude of research studies must be done to better understand the big picture.

Figure 1. Cell death after blue light exposure. Nuclear labeling with membrane-imper-meant dye marks nonviable cells, which are visible with varying levels of blue light exposure duration, A2E concentration, and length of time after blue light exposure.

While all age demographics face exposure to blue light phototoxicity, elderly and children are most at risk. Research suggests thinning transparency of the crystalline lens reduces with age, placing the older population at greater risk for increased blue light absorption (Lee, 2016). While previous literature postulated a direct connection between blue light and age-related macular degeneration (AMD), Jaadane indicates that blue light is only a risk factor in AMD (Jaadane, 2019). In addition to the elderly, children also face blue-light phototoxicity risks due to the COVID-19 pandemic, as many experienced increased screen time through quarantine, school closures, and a transition to virtual learning (Wong, 2021). Research by Wong and colleagues linked increased screen time and limited outdoor activities with myopia onset and progress. Other members in the high-risk population for blue light phototoxicity include contact-lense users and patients suffering from dry-eye and malnourishment (Niwano, 2018).

There is still only limited knowledge regarding long term effects of blue light on eyes (Tosini, 2016). However, there are many efforts working to minimize the effects of blue-light phototoxicity. Attempts to reduce blue light exposure through physical protection include blue-light blocking products; these include blue light glasses, eyewear shields, and blue light emission control software. In addition, researchers have suggested new proposals of new methods such as gene therapy, retinal transplantations, and antioxidant base scavengers. To suppress oxidative stress, studies have shown the benefits of topical antioxidants such as lutein and zeaxanthin, which both have blue-light absorbing properties (Choi, 2016). Furthermore, researchers have brought to light discussions surrounding gene therapy, particularly the injection of ciliary neurotrophic factor (CNTF) to significantly delay light’s degeneration and necrosis of retinal photoreceptor cells (Lavail, 1998). Some researchers also suggest increasing parent education about effects of reduced outdoor time on ocular health and myopia risks so that parents can aid their children in developing healthy relationships with screens (Wong, 2021).

Overall, through continued efforts regarding blue light research, it is important that we stay educated about blue lights’ effects and exude our own efforts to protect our eyes from blue light. Luckily, there exists several methods that we can all implement into our daily routines, such as the 20-20-20 rule which involves looking 20 feet away for 20 seconds every 20 minutes of screen viewing (Li, 2021). Only through these efforts will we be able to continue technologically advancing without sacrificing the health of our eyes.

Figure 2. A visual representation of the 20-20-20 rule, a helpful technique used to reduce eye strain and blue light exposure.

Edited by Edward Xue

References

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Wong, C. W., Tsai, A., Jonas, J. B., Ohno-Matsui, K., Chen, J., Ang, M., & Ting, D. (2021). Digital Screen Time During the COVID-19 Pandemic: Risk for a Further Myopia Boom?. American journal of ophthalmology, 223, 333–337. https://doi.org/10.1016/j.ajo.2020.07.034

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Image References

20-20-20 Rule. (2018). Maple Grove Eye Doctors. Retrieved October 29, 2021, from https://maplegroveeye.vision. 

Sparrow, J. R., Nakanishi, K., & Parish, C. A. (2000). The lipofuscin fluorophore A2E mediates blue light-induced damage to retinal pigmented epithelial cells. Investigative ophthalmology & visual science, 41(7), 1981–1989.

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