WASHINGTON (dpa-AFX) - Short-sightedness, also known as myopia, is rising quickly across the world, and a new study found that spending more time indoors may be one of the main reasons.
'Myopia has reached near-epidemic levels worldwide, yet we still don't fully understand why,' said senior author Jose-Manuel Alonso. 'Our findings suggest that a common underlying factor may be how much light reaches the retina during sustained near work - particularly indoors.'
Researchers at SUNY College of Optometry tested 34 people. Out of the total participants, 21 had myopia and 13 had normal vision. Participants were asked to focus on square targets with different levels of brightness and contrast, using one eye at a time.
The results, published in Cell Reports, showed that people with myopia may be affected by too much 'near work' activities like reading, using phones, or working on screens. When we focus on things up close, the pupil becomes smaller to control how much light enters the eye, and this may play a role in worsening short-sightedness.
'In bright outdoor light, the pupil constricts to protect the eye while still allowing ample light to reach the retina,' explained optometry doctoral student Urusha Maharjan.
'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 study also found that negative lenses, which is used to correct myopia, reduce the amount of light reaching the retina by causing the pupil to shrink when focusing on nearby objects. This effect becomes stronger when the viewing distance is very close, the lenses are too strong, or when the eyes focus on near objects for long periods. Notably, it becomes even more intense in people who already have myopia.
Researchers also noticed other issues in myopic eyes, such as problems with eye movement during focusing and reduced effectiveness of blinking in helping pupil adjustment. The researchers warned that treatments to control myopia may not work well if people continue spending long hours focusing on nearby objects indoors, especially in low-light conditions.
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