New research from the United States is suggesting that prolonged close-up focus in low-light environments is one factor driving the rise in myopia.
The eye disease is thought to be the result of too much screen time, especially among children and young adults.
But scientists at the SUNY College of Optometry in New York have discovered that indoor lifestyles are a key driver.
In a new study published in Cell Reports, they concluded that a common underlying factor might be how much light reaches the retina during sustained near-work, particularly indoors.
“In bright outdoor light, the pupil constricts to protect the eye while still allowing ample light to reach the retina,” said Urusha Maharjan, a SUNY Optometry doctoral student who conducted the study.
“When people focus on close objects indoors, such as phones, tablets, or books, the pupil can also constrict, not because of brightness, but to sharpen the image.
“In dim lighting, this combination may significantly reduce retinal illumination.”
In the study, 34 human subjects (13 emmetropes and 21 myopes) wore Tobii pro glasses 3 to measure their eye position and pupil size.
Researchers used a small square stimulus of to generate robust accommodative responses of eye vergence and pupil constriction while minimising fixation variability.
Pupil constriction becomes stronger when accommodation is increased by shortening viewing distance or wearing excessively-strong negative lenses.
Moreover, pupil constriction becomes even stronger when lens accommodation is sustained for prolonged periods of time, and even stronger when the eye becomes myopic.
The study also demonstrates additional myopia disruptions of eye turning with accommodation and eye-blink efficacy at constricting the pupil.
The researchers said more study was needed to confirm the findings.
But if proven correct, it could lead to a shift in the understanding of myopia progression and control through exposing the eye to safe bright light levels under limited accommodative pupil constriction.
“This is not a final answer,” said Professor Jose-Manuel Alonso, senior author of the study.
“But the study offers a testable hypothesis that reframes how visual habits, lighting, and eye focusing interact. It’s a hypothesis grounded in measurable physiology that brings together many pieces of existing evidence.
“More research is needed, but it gives us a new way to think about prevention and treatment.”
