Is reading in the dark bad for your eyes?

‘Turn the light on, or you’ll ruin your eyes.’ Generations of children have heard that while reading under the covers with a torch, and today the same sentence accompanies the phone switched on in bed. But does reading in the dark really ruin your eyesight?

Mostly false. In low light the eyes tire more, and this is documented^1,2; but in the studies we examined the fatigue is a passing complaint, not lasting damage. For children the picture is more nuanced: light matters for myopia, but above all daylight, and what counts is the total time spent looking at things up close^3,4,5.

In this article

1. Why the eyes tire in low light
2. And with a screen in the dark?
3. Is reading in the dark bad for your eyes? The myopia chapter
4. Frequently asked questions
5. Sources

Why the eyes tire in low light

In low light characters have less contrast, and it comes naturally to bring the page closer and to keep your gaze fixed for a long time. How much the lighting matters was measured by a small experiment in 2023: 22 healthy postgraduate students read for two hours under eight LED lighting conditions, combining four intensities (from 300 to 1,000 lux) and four colour tones, from the warmest to the coolest¹.

In all conditions visual fatigue increased after reading, but to different degrees. It was lower with intermediate, neutral light (500 lux, 4000 K), higher with the dimmest, warmest light (300 lux, 2700 K) for the reported symptoms, and with the most intense, coolest light (1,000 lux, 6500 K) for the optical quality of the eye¹. Two lessons: more light is not always better, and the study measured fatigue after two hours, not effects over time.

And with a screen in the dark?

A 2024 experiment studied reading on a screen with light text on a dark background, the so-called ‘dark mode’, in dimly lit environments, using an eye-tracking instrument to record changes in the pupil and the blink rate. Increasing the ambient light reduced visual fatigue; the colour of the text also mattered, with red the most tiring and yellow the least².

Here too we are talking about fatigue, not damage. The fear that screen light could harm the retina we address in Does the blue light from screens damage your eyes?; breaks and workstation are in the article on computer eye strain.

Is reading in the dark bad for your eyes? The myopia chapter

Myopia is the defect in which distance vision is poor, because the eye is a little too long: we discuss it in the article on myopia. A 2023 meta-analysis brought together 78 studies with 254,037 people aged 6 to 39: those exposed to near work had a 26% higher probability of being myopic than those who were not, 31% in children and 21% in adults³. This is a relative measure: it does not mean 26 more myopic people per 100.

The flip side is daylight. A 2023 systematic review concludes that more time outdoors and less near work reduce the onset of new myopia in school-age children⁴. In a randomised trial in Taiwan with 693 first-year primary-school children in 16 schools, encouraged to spend up to 11 hours a week outdoors, after one year myopia had grown less than in the comparison schools (0.35 versus 0.47 dioptres) and the risk of rapid worsening was roughly halved. According to the authors even less intense light was enough, such as that under trees⁵.

Classroom light also seems to matter. In a study in four schools in north-eastern China, with 317 children aged 6 to 14, the lighting of the classrooms was redone in two schools: after one year new cases of myopia were 4%, against 10% in the schools that stayed as they were⁶. It is a single study, with few schools, and the authors themselves ask for the result to be confirmed⁶.

And what about reading in low light itself? In a study of 1,400 students in a district of northern India, myopia was more frequent in those who read more hours, used the phone or video games more, and in those who said they read in low light⁷. It is a cross-sectional study: it captures an association at a given moment, does not say what comes first, and cannot separate the effect of light from that of the hours spent on books.

The message from the studies is therefore different from that of the proverb: more than the torch under the covers, what counts is the total hours spent up close and those spent outdoors^3,4.

Frequently asked questions

Does reading in low light cause myopia?

There is no evidence that it does so in itself. One observational study found more myopia in those who said they read in low light, but it cannot distinguish light from hours of reading⁷. The link with near work in general³ and with little time outdoors^4,5 is more solid.

What light do you need for reading?

There is no rule that suits everyone. In a small experiment visual fatigue was lower with intermediate, neutral light (500 lux, 4000 K) and higher both with dim, warm light and with very intense, cool light¹.

Is looking at your phone in the dark bad for your eyes?

With little light around, reading on the screen is more tiring². What we know about screen light and the retina we describe in the article on blue light.

A torch under the covers can leave tired eyes, not ruined eyes. If one lesson remains, it comes from the studies on myopia: for children’s eyes, what matters is daylight, the kind you find by going out of the house^4,5.