Ms Tsering lamu shongmu, Master’s in Optometry

Assistant Professor, Assam Downtown University, Guwahati, India.


Reading on a computer screen can differ from reading on a printed page in terms of viewing distance, gaze angles, blinking rate, text appearance, and demand of accommodation, broadening of a palpebral fissure while reading. The characters on a computer monitor are created by an electrical beam striking the phosphor coating near the screen’s surface, resulting in tiny dots known as a pixel.(1) These pixels are bright at their centre and decrease towards the outer edge,(1,2) cause difficulties for the eye to focus on a computer screen and produces a slight difference in contrast, because of which even at high resolutions, the edge of the letter looks fuzzy. (3,4 ) This makes it difficult for human eyes to maintain focus on pixel characters, thus adding strain on the eyes.(4) When the eye fails to maintain focus on the computer’s plane, it relaxes and focuses behind the screen, which is known as the resting point of accommodation (RPA) or dark focus.(5) As a result, the eyes are continuously relaxing to their resting point of accommodation or dim focus, and they are constantly attempting to focus on the pixel’s character. This frequent focusing and re-focusing of the eye by the ciliary body leads to eye fatigue and causes accommodative symptoms(6) Thus, this lag of accommodation results in ocular symptoms associated with computer vision syndrome. Therefore, visual work in a computer is demanding and includes frequent rapid eye moments, continuous focusing, and alignment demands, all of which involve continuous relaxation and contraction of the eye muscles.(7) During a pandemic, the number of students using e-devices continues to grow, educational programs and initiatives are needed to help address the issue of eye health. Unfortunately, it is difficult to reduce the amount of screen time that students spend during this pandemic due to their online classes. To compensate for the time students, spend on online classes, they should limit their other screen-related activities. Teaching institutions should limit the total duration of online classes (8) thus giving adequate breaks between classes. The 20–20-20 rule, i.e., for every 20 minutes of screen time, looking at an object 20 feet or 6 m away for 20 seconds, is advised (2,9) and may interrupt the onset of visual fatigue. If one exceeds continuous use of 2 hours, a 15-minute break is recommended. (10)  Students are advised to blink frequently. Adding small sessions for yoga, meditation, tasks, or physical activities in between online classes, will be beneficial for them. Computer screens are kept at ideal distances of more than 36 inches and smartphone screens should be kept at distances beyond 40 cm.(11,12) Screens should be kept at 20 degrees lower than the eye level.(13). Improvement of study environments like adjusting the ambient light in the surroundings to prevent glare and reflections is an essential ergonomic issue when using a computer. (14) Further, the use of computer glasses like blue-light filtering glasses with anti-reflective coating lenses improves the dryness of the eye and enhances contrast. (14) Use of night-mode during the evening hours be advised. Students should be advised to increase the height of letters while working on the screen, as this will give more comfort.(1)  Finally, students should be counselled about the negative effects of extended use of mobile and computer technologies.



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  2. Chang PC, Chou SY, Shieh KK (2013) Reading performance and visual fatigue when using electronic paper displays in long duration reading tasks under various lighting conditions. Displays 34(3): 208-214.
  3. Sheppard AL, Wolffsohn JS. Digital eye strain: Prevalence, measurement, and amelioration Open Ophthalmol. 2018;3(1), e000146. https://doi. org/10.1136/bmjophth-2018-000146
  4. Wimalasundera, S., 2009. Computer vision syndrome. Galle Medical Journal, 11(1), pp.25–29. DOI:
  5. Ripple PH (1952) Variation of accommodation in vertical directions of gaze. Am J Ophthalmol 35(11): 1630-1634.
  6. Anshel J (2005) Visual ergonomics handbook: CRC Press, USA. Publisher. CRC Press. Year. 2005. ISBN. 9781420032055
  7. Association AO (1997) The effects of computer use on eye health and vision. St. Louis, MO 63141 (314) 991-4100 FAX (314) 991-4101
  8. Lee JW, Cho HG, Moon BY, Kim SY, Yu DS. Effects of prolonged continuous computer gaming on physical and ocular symptoms and binocular vision functions in young healthy individuals. PeerJ. 2019;7: e7050. doi:10.7717/peerj.7050.
  9. American Optometric Association. Computer vision syndrome. (accessed 28 April 2020).
  10. Turgut B. Ocular ergonomics for the computer vision syndrome. J Eye Vis 2018;1(1:2). http://www. (accessed 22 May 2020).
  11. Von Stroh R. Computer vision syndrome. Occup Health Saf. 1993; 62:62–66.
  12. Bababekova Y, Rosenfield M, Hue JE, Huang RR. Font size and viewing distance of handheld smart phones. Optom Vis Sci. 2011; 88:795–797. doi:10.1097/OPX.0 b013e3182198792.
  13. Jaschinski W, Heuer H, Kylian H. Preferred position of visual displays relative to the eyes: a field study of visual strain and individual differences. Ergonomics. 1998;41: 1034–1049. doi:10.1080/001401398186586.
  14. Leung TW, Li RW, Kee CS. Blue-light filtering spectacle lenses: optical and clinical performances. PLoS One. 2017;12: e0169114. Doi: 10.1371/journal.pone.0169114.

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