Dim Indoor Lighting, Not Just Screen Exposure, Is Causing The Global Nearsightedness Epidemic: Study

Nearsightedness, also known as myopia, is a condition in which close objects appear clear, however, far objects look blurry. Most individuals develop the condition during childhood and adolescence and it tends to run in families. Myopia can be corrected with eyeglasses, contact lenses or refractive surgery. There has been a rise in cases of myopia. The International Myopia Institute says that "30% of the world is currently myopic and by 2050, almost 50% will be myopic." It is thought that the rise in myopia is due to growing screen use, particularly among children and young adults. However, a new study proposes "that myopia may be driven less by screens themselves and more by a common indoor visual habit: prolonged close-up focus in low-light environments, which limits how much light reaches the retina."

The research was conducted by scientists at the SUNY College of Optometry and published in the journal Cell Reports. "Myopia has reached near-epidemic levels worldwide, yet we still don't fully understand why," said Jose-Manuel Alonso, MD, PhD, SUNY Distinguished Professor and senior author of the study. "Our findings suggest that a common underlying factor may be how much light reaches the retina during sustained near work - particularly indoors."

It is known that spending more time outdoors can help protect against myopia. Also, prolonged indoor near work under low light may increase the risk. Treatment for myopia includes atropine eye drops, multifocal lenses, and contrast-reducing optics. However, scientists haven't been able to understand why these diverse approaches work. To resolve this, scientists proposed a unifying explanation centered on the pupil, which is the eye's natural "aperture," similar to a camera diaphragm.

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

The New Theory And Study Findings

According to the hypothesis, reduced retinal stimulation over long periods may weaken specific neural pathways involved in visual processing, contributing to myopia development and progression.

Myopia can happen when too little light hits the retina during extended near work in dim environments. If light is inadequate and the pupil constricts too much at close distances, retinal signaling might lack the intensity needed for proper visual development. On the other hand, bright light exposure lets the pupil shrink due to light rather than focal distance, thereby helping maintain healthier retinal stimulation.

The study also found that negative lenses reduce retinal light by prompting pupil narrowing via accommodation (that is, the eye's lens powering up to focus on nearby objects). This effect worsens with shorter viewing distances or stronger minus lenses. It grows more severe during prolonged periods of time (such as for tens of minutes) and escalates in already myopic eyes. The team also found irregularities in eye alignment during focusing and reduced blink-induced pupil response in myopia.

If this mechanism holds true, it could change perspectives on myopia advancement among researchers and eye care professionals. The theory says that ensuring ample bright light exposure while curbing accommodative pupil narrowing might help prevent myopia. Such narrowing reduction is possible through reduced accommodative stress from specialised lenses, pharmacological blockade of constrictor muscles, or outdoor time focused on distant views without near effort. The researchers warn that treatments may be less effective if people continue with extended indoor near tasks in low light.

Alonso added, "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. More research is needed, but it gives us a new way to think about prevention and treatment."

What Does This Mean For Indians?

In India, where myopia is increasing due to rising screen time among urban kids and young adults, this study can be beneficial. It shifts blame from devices to dim indoor lighting during prolonged near work which constricts the pupil, starving the retina of light and stunting visual development. Households that are highly dependent on screens with limited natural light, this can prompt simple fixes. Brighter rooms, increased time outdoors daily for sunlight, and pairing treatments like atropine drops or multifocals with better-light habits.

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