While rising rates of myopia are often attributed to increased screen time (as well as genetics), researchers at State University of New York (SUNY) College of Optometry propose that a common underlying risk factor may be prolonged close-up focus in low-light environments, which limits how much light reaches the retina.

The research offers a new hypothesis that could help explain a long-standing puzzle in vision science: why so many seemingly different factors, from near work and dim indoor lighting to treatments like atropine drops, multifocal lenses, and time spent outdoors, all appear to influence myopia progression.

“In bright outdoor light, the pupil constricts to protect the eye while still allowing ample light to reach the retina,” explained Urusha Maharjan, SUNY Optometry doctoral student, who conducted the study.1 “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.”

According to this mechanism, myopia develops when poor retinal illumination fails to generate robust retinal activity because the light sources are too dim and pupil constriction is too excessive at short viewing distances. Conversely, myopia does not develop when the eye is exposed to bright light and the pupil constriction is regulated by image brightness instead of viewing distance.

The new study demonstrates that negative lenses reduce retinal illumination by constricting the pupil through accommodation. Such 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 prologued periods of time (e.g., tens of minutes), 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.

If proven correct, the mechanism proposed could lead to a paradigm shift in our understanding of myopia progression and control. According to this mechanism, myopia can be controlled by exposing the eye to safe bright light levels under limited accommodative pupil constriction. Accommodative pupil constriction can be limited by reducing accommodation strength with lenses (multifocal or contrast-reduction), blocking directly the muscles driving pupil constriction (atropine drops), or by simply spending time outdoors without engaging accommodation (looking at far distances).

Perhaps most importantly, the new mechanism predicts that any approach to myopia control will fail if the eye is exposed to excessive accommodation indoors under low light for prolonged periods of time.

“This is not a final answer,” Ms Maharjan said. “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.”

Reference available at mivision.com.au.