Reacción a "Increased daily screen time associated with risk of developing myopia"

What do you think of the study overall? How does it fit in with existing evidence?

‘The analysis is scientifically correct in terms of meta-analysis and systematic review, but it is not conclusive in terms of causality. The relationship between screens and myopia seems real, but without including outdoor activity and other key factors (genetic factors, distance to screens, schedule...), the results must be interpreted with caution.

The study reinforces previous evidence suggesting a link between prolonged use of digital screens and the risk of myopia, a link that has been explored in several investigations. However, its approach is limited, as it focuses only on screen exposure and does not consider other key factors, such as outdoor activity and exposure to sunlight. What's new is:

• It confirms that there is a dose-response relationship, which suggests that more hours spent in front of a screen can translate into a greater risk of myopia.
• It analyses different types of screens and their differentiated effects, something that has not always been done in previous studies.
• It identifies a possible safety threshold (<1h/day of screens), although without evaluating how natural light could compensate for these effects'.

Wasn't the hypothesis that the cause of myopia was not so much the effort of accommodation as the lack of sunlight becoming more and more widespread?

‘Yes, in recent years the hypothesis that myopia is not exclusively due to the effort of accommodation (focusing up close), but to a lack of exposure to natural light, has gained strength. Recent studies have shown that:

• Sunlight stimulates dopamine in the retina, which slows down the elongation of the eye and, therefore, the progression of myopia.
• It has been observed that children who spend more time outdoors have a lower risk of developing myopia, regardless of their time spent reading or using screens.

The study we are analysing does not contradict this hypothesis, but it omits a crucial factor: it does not measure whether exposure to natural light can mitigate the negative effects of screens. It is possible that screen use is a bigger problem in children who also spend little time outdoors, but this study does not allow us to prove it.’

What implications could this have?

• ‘For research: studies are needed that analyse screens + natural light, as focusing only on screens can lead to incomplete conclusions.
• For public health: if the screen-myopia relationship is confirmed, time limits for screen use could be recommended, but combined with strategies for exposure to natural light in children.
• For education and technology: it could justify the design of educational programmes that balance the use of screens with outdoor activities. It could also encourage the industry to develop screens with more natural light spectra’.

Are there any important limitations to be taken into account?

• ‘Lack of control over other risk factors: there is no analysis of whether the participants had a genetic predisposition to myopia, nor are variables such as outdoor activity, ambient lighting or reading habits controlled.
• Observational design: most of the studies included are cross-sectional or observational, which prevents the establishment of a direct causal relationship between screen use and myopia. There may be confounding factors not considered.
• Possible bias in the measurement of screen time: many studies depend on self-reporting by participants, which can introduce errors in the actual quantification of exposure time'.

Does this study demonstrate the cause of the increased risk?

‘Partially, there is still a lack of analysis of other risk factors such as genetics and the decrease in outdoor activities that can lead to this increase in screen time. For our study group, the decrease in these is still much more important than the increase in screens (although this is also important). This study and this other one of ours support this hypothesis.’