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

By: Alyssa Chen

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 to reach the retina directly, causing what is commonly known as the blue light hazard - 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 and (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 (Sparrow, 2018). 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 (Maple Grove Eye Doctors, 2018).

References

Blume, C., Garbazza, C. & Spitschan, M. Effects of light on human circadian rhythms, sleep and mood. Somnologie 23, 147–156 (2019). https://doi.org/10.1007/s11818-019-00215-x

Bolaños-Jiménez, R., Navas, A., López-Lizárraga, E. P., Ribot, F. M., Peña, A., Graue-Hernández, E. O., & Garfias, Y. (2015). Ocular surface as barrier of innate immunity. The Open Ophthalmology Journal, 9(1), 49–55. https://doi.org/10.2174/1874364101509010049 

Choi, W., Lee, J. B., Cui, L., Li, Y., Li, Z., Choi, J. S., Lee, H. S., & Yoon, K. C. (2016). Therapeutic efficacy of topically applied antioxidant medicinal plant extracts in a mouse model of Experimental Dry Eye. Oxidative Medicine and Cellular Longevity, 2016, 1–10. https://doi.org/10.1155/2016/4727415 

Ishii M, Rohrer B. Bystander effects elicited by single-cell photo- oxidative blue-light stimulation in retinal pigment epithelium cell networks. Cell Death Discov 2017;3:16071.

Jaadane, I., Boulenguez, P., Chahory, S., Carré, S., Savoldelli, M., Jonet, L., Behar-Cohen, F., Martinsons, C., & Torriglia, A. (2015). Retinal damage induced by commercial light emitting diodes (LEDs). Free radical biology & medicine, 84, 373–384. https://doi.org/10.1016/j.freeradbiomed.2015.03.034

Jiao, Y., Jin, Y., Meng, H., & Wen, M. (2018). An analysis on treatment effect of blue light phototherapy combined with bifico in treating neonatal hemolytic jaundice. Experimental and Therapeutic Medicine, 16(2), 1360-1364. doi:10.3892/???.2018.6340

LaVail, M. M., Yasumura, D., Matthes, M. T., Lau-Villacorta, C., Unoki, K., Sung, C. H., & Steinberg, R. H. (1998). Protection of mouse photoreceptors by survival factors in retinal degenerations. Investigative ophthalmology & visual science, 39(3), 592–602.

Lee HS, Cui L, Li Y, Choi JS, Choi J-H, Li Z, et al. (2016) Influence of Light Emitting Diode-Derived Blue Light Overexposure on Mouse Ocular Surface. PLoS ONE 11(8): e0161041. https://doi.org/10.1371/journal.pone.0161041

Li, R., Ying, B., Qian, Y., Chen, D., Li, X., Zhu, H., & Liu, H. (2021). Prevalence of Self-Reported Symptoms of Computer Vision Syndrome and Associated Risk Factors among School Students in China during the COVID-19 Pandemic. Ophthalmic epidemiology, 1–11. Advance online publication. https://doi.org/10.1080/09286586.2021.1963786

Marek, V., Mélik-Parsadaniantz, S., Villette, T., Montoya, F., Baudouin, C., Brignole-Baudouin, F., & Denoyer, A. (2018). Blue light phototoxicity toward human corneal and conjunctival epithelial cells in basal and hyperosmolar conditions. Free Radical Biology and Medicine, 126, 27–40. https://doi.org/10.1016/j.freeradbiomed.2018.07.012 

Niwano Y, Iwasawa A, Tsubota K, et al. Protective effects of blue light-blocking shades on phototoxicity in human ocular surface cells. BMJ Open Ophthalmology2019;4:e000217. doi:10.1136/ bmjophth-2018-000217

O'hagan, J. B., Khazova, M., & Price, L. L. A. (2016). Low-energy light bulbs, computers, tablets and the blue light hazard. Eye, 30(2), 230-233. https://www.researchgate.net/publication/290598307_Low-energy_light_bulbs_computers_tablets_and_the_blue_light_hazard

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.

Tosini, G., Ferguson, I., & Tsubota, K. (2016, January 24). Effects of blue light on the circadian system and Eye Physiology. Molecular vision. Retrieved September 25, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/. 

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

Yang, P. -., Tsujimura, S. -., Matsumoto, A., Yamashita, W., & Yeh, S. -. (2018). Subjective time expansion with increased stimulation of intrinsically photosensitive retinal ganglion cells. Scientific Reports, 8(1) doi:10.1038/s41598-018-29613-1

Zheng QX, Ren YP, Reinach PS, Xiao B, Lu HH, Zhu YR, Qu J, Chen W. Reactive oxygen species activated NLRP3 inflammasomes initiate inflammation in hyperosmolarity stressed human corneal epithelial cells and environment-induced dry eye patients. Exp Eye Res 2015;134: 133-140.

Zhao, Z. C., Zhou, Y., Tan, G., & Li, J. (2018). Research progress about the effect and prevention of blue light on eyes. International journal of ophthalmology, 11(12), 1999–2003. https://doi.org/10.18240/ijo.2018.12.20

Images

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.