It May Not Be the Screen Causing Nearsightedness - It May Be the Darkness Around It

The conventional explanation for the global rise in nearsightedness points to screens. Children stare at phones and tablets for hours. Their eyes strain at close range. The eyeball elongates. Vision blurs at distance. The story is intuitive, and it has shaped pediatric advice about screen time for years.

A study from the State University of New York College of Optometry, published February 17, 2026 in Cell Reports, challenges that explanation - not by dismissing the role of near work, but by identifying a more specific mechanism that may explain why near work causes myopia and why being outdoors appears to prevent it. The key variable, according to the hypothesis the researchers propose, is not screens or close distances themselves. It is how much light actually reaches the retina.

The Accommodative Pupil Constriction Hypothesis

When the eye focuses on something close, the lens must change shape to sharpen the image - a process called accommodation. Accommodation is accompanied by two other changes: the eyes converge, and the pupils constrict. That pupil constriction during near focus is separate from the constriction that occurs when moving from dim to bright environments. It happens regardless of the ambient light level.

The SUNY team, led by senior author Jose-Manuel Alonso, MD, PhD, SUNY Distinguished Professor, and doctoral student Urusha Maharjan, propose that this accommodative pupil constriction becomes problematic in low-light indoor environments. Outside on a bright day, the pupil is already somewhat constricted due to ambient brightness, and the eye receives abundant light even while accommodating for near distances. Inside in typical home or classroom lighting, the pupil constricts further during near focus - but the ambient light is insufficient to compensate. The result is a substantial reduction in the amount of light reaching the retina.

According to the hypothesis, this retinal underillumination weakens the activity of ON-pathway retinal ganglion cells - neurons that respond to light increments and whose signals appear to regulate the elongation of the eyeball during development. When ON-pathway activity is chronically reduced, the eye grows longer than it should - the defining anatomical change in myopia.

A Unifying Framework for Existing Treatments

One test of any proposed mechanism is whether it can explain things that are already known. The SUNY hypothesis passes that test in a specific way: it offers a single explanation for why multiple apparently different myopia interventions all reduce progression.

Atropine eye drops, which are among the most effective pharmacological treatments for slowing myopia progression, work partly by blocking the muscular contraction that drives accommodative pupil constriction. Multifocal contact lenses reduce the degree of accommodation needed for near tasks. Time spent outdoors exposes the eye to light levels 10 to 100 times brighter than typical indoor environments. Contrast-reduction lenses reduce the stimulus for accommodation itself. All four approaches, despite their different mechanisms, converge on the same outcome: more light reaching the retina during or around near work.

What the Experimental Data Show

The researchers measured accommodative pupil constriction responses in people with different levels of myopia, demonstrating that myopes show excessive accommodative pupil constriction compared to emmetropes (people with normal vision). They also showed that pupil constriction becomes stronger when accommodation is sustained for prolonged periods - tens of minutes of sustained near work produce stronger constriction than brief periods - and that the constriction is amplified by wearing negative lenses.

The study also demonstrates that myopes have disrupted patterns of eye vergence and reduced effectiveness of the blink reflex at momentarily dilating the pupil. These are consistent with the hypothesis that myopia involves broader deficits in accommodative visuomotor function, not just optical changes in eye length.

A Hypothesis, Not a Proof

Alonso was explicit about the status of the work: "This is not a final answer. 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."

What the study does not establish is causation. Whether reducing accommodative pupil constriction in children during near work would actually slow myopia progression requires prospective trials. Myopia affects nearly 50 percent of young adults in the United States and Europe, and close to 90 percent in parts of East Asia. The scale of the problem justifies serious investment in understanding its mechanisms. The SUNY hypothesis provides a specific, testable, and physiologically grounded target for that investigation.