October 1, 2020
By Dwight Akerman, OD, MBA, FAAO, FBCLA
Lifestyle counseling should be provided to all children, especially those at risk of developing myopia, and it should encompass outdoor exposure, time limits on close work and working distance. Several national and international organizations recommend that all children follow the 20-20-20 Rule (take a 20 second break every 20 minutes of close work and gaze at objects at least 20 feet away.) This rule was created initially by Jeffrey Anshel, OD, in the 1990s to help alleviate the symptoms of digital eye strain.
While Dr. Anshel’s Rule is helpful, I believe that the 20-20-2 Rule, proposed by Prof. Caroline Klaver, MD, PhD, and her co-researchers at the Erasmus University Myopia Research Group in Rotterdam, Netherlands, is more effective in reducing the incidence of myopia and possibly slowing progression. (Klaver et al, 2020) What is the 20-20-2 Rule? After 20 minutes of close work, children should gaze at objects in the distance for at least 20 seconds, and they should be outside intermittently for at least 2 hours per day.
Outdoor light exposure during childhood is the most critical known modifiable risk factor for myopia. Outdoor light exposure prevents or delays the onset of myopia and may slow progression. (Ho et al., 2019) The protective effect of being outside is currently explained by high light intensity triggering the release of retinal dopamine, an ocular growth inhibitor that inhibits myopic development. (Ramamurthy et al, 2015) Another potential explanation is that pupils are more constricted outdoors, causing a greater depth of field and less image blur, resulting in less myopic stimulus. (Flitcroft 2012)
Most well-controlled studies show a significant effect of outdoor light exposure when children have a minimum of 2 hours of intermittent outdoor light exposure per day, including recess time, physical education time and additional outdoor time after school. (Wu et al., 2020, Ho et al., 2019, Lan et al, 2014) Research also shows that children must avoid working distances of less than 12 inches (30 cm). (Huang et al, 2019)
I strongly suggest that eye care professionals recommend the 20-20-2 Rule to all children, especially those at risk of developing myopia and those already myopic.
Best professional regards,
Dwight H. Akerman, OD, MBA, FAAO, FBCLA
Chief Medical Editor