Is it possible to damage your eyesight if you read in the dark?

To understand the issue, the therapist and publicist Andrey Sazonov studied a lot of high-quality medical sources. His book Debunking the Myths of Medicine. The whole truth about our body” was published by the publishing house “AST”. Lifehacker publishes chapter 14.

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Each of us in childhood heard the phrase more than once at home and at school: “Do not read in the dark - you will ruin your eyes!” ABOUT, how many fascinating nightly readings under the covers under the dim light of a flashlight were mercilessly interrupted parents! And every time the “guilty” children were read a notation that began and ended with a rhetorical question: “What, do you want to go blind?” None of the children wanted to go blind, but everyone liked to read at night under blanket. This innocent occupation had a distinct flavor of adventure.

But is it actually harmful to read “in the dark”, that is, not completely in the dark, but in low light?

You, of course, have already guessed that it is not harmful, otherwise this topic would not have been touched upon in this book.

And, most likely, you are perplexed: “How can this be?” And the strictest ones are indignant: “Well, this is already too much! After all, any fool knows... "Many of you can remember the favorite saying of sellers of lamps and light bulbs:" Light does not happen much, only little. Sellers can be understood, it is important for them to sell as much as possible. In fact, there can be a lot of light, too much, so much that it hurts the eyes.

Let's figure it out. To begin with, let's briefly get acquainted with the structure of our organ of vision.

The eyeball consists of an inner core surrounded by three shells: outer, middle and inner. The outer shell, called the sclera, is a dense connective tissue capsule that protects the eyeball from damage. In the front part, which is called the cornea, the sclera is transparent. This is necessary in order for light waves to penetrate through the cornea into the eye. The oculomotor muscles (each eye has six of them) are attached to the sclera, which turn the eyeball, changing the direction of gaze.

Under the sclera is the vascular membrane of the eye, rich in blood vessels, which provides nutrition and excretion of metabolic products. The choroid contains a certain amount of pigment - this is a kind of "darkening" of the eye, preventing the penetration of light through the sclera. The part of the choroid located directly under the sclera is called the iris. The color of the iris (that is, the color of the choroid) in everyday life is called "eye color".

In the center of the iris there is a round hole - the pupil, through which light rays penetrate into the eyeball. Thanks to the special muscles that are located in the iris, the size of the pupil changes depending on the intensity of the light.

In the light, the pupils constrict, protecting the eyes from excessive irritation by abundant light rays, and in the dark they dilate to let in as many rays as possible.

Behind the pupil on the round ligament, the lens is suspended - a transparent body that plays the role of a lens in the eye. He looks like a biconvex
lens. A special muscle called the ciliary, or ciliary, regulates the curvature (bulge) of the lens, providing accommodation of vision, that is, focusing, adjusting the eye to a certain distance from the considered object. Thanks to this, we can look both far and close, while clearly distinguishing the details of objects. When the ciliary muscle contracts, the curvature of the lens increases and its refractive power increases. The eye gets the opportunity to see objects that are close. When the ciliary muscle relaxes, the curvature of the lens and its refractive power decrease, the eye receives a clear image of distant objects.

The inner shell of the eyeball is called the retina, or retina. The retina contains light-sensitive receptors - rods and cones, which convert light energy into impulses that are transmitted along the optic nerve to the brain. The cones are located in the center of the back of the retina, directly opposite the pupil. They provide daytime vision. Cones are able to perceive colors, shapes and details of objects. But the rods, which are irritated by twilight light, are not sensitive to color, and therefore at twilight we do not distinguish colors - at night all cats are gray. The rods are located both between the cones and on the periphery, surrounding the cones with a ring. Light rays enter the area of ​​​​this ring only with a significant expansion of the pupil at twilight, so sticks that are sensitive to twilight light are needed there.

Under the membranes of the eye is the vitreous body - a transparent jelly-like substance that fills the space between the lens and the retina. The vitreous humor gives the eye its shape.

What happens when you want to look at something? The oculomotor muscles turn the eyes in the right direction. The pupil expands as much as necessary. The ciliary muscle compresses the lens in such a way that light rays from an object are focused on the retina. Cones and rods perceive light rays that are irritants for them and convert this irritation into electrical nerve impulses. Through the optic nerve, impulses enter the cerebral cortex, in the occipital region, where a special area responsible for vision is located - the visual zone. Here, nerve impulses are converted into a picture - into what we see.

Did you know that the rays of light from the object under consideration, refracted in the lens, falling on the retina, form an inverted image of the object on it? Why don't we see everything upside down then? What's the matter?

It's about adaptation (adaptation) carried out by our brain. Newborn babies see the world upside down, but
thanks to the constant checking of visual sensations, they very soon develop a conditioned reflex, which allows them to perceive objects in a normal, uninverted form.

The introductory part is over, let's move on to the reasoning.

We are able to see as long as the light-sensitive cells of the retina are able to perceive the irritation caused by light rays. When this irritation becomes very weak, we stop seeing.

If the light is sufficient to see the letters, then we can read. If the lighting is insufficient for reading, we simply cannot read - that's all.

In low light, light-sensitive cells are slightly irritated. The eye adjusts to the lack of light by dilating the pupil. The fact that the muscles that regulate the width of the pupil are in a relaxed state (and this is exactly what happens when there is a lack of lighting), there is nothing dangerous for our vision. In a relaxed state, all muscles are at rest.

For any sensitive cells in our body, weak irritation does not pose any danger, unlike too strong, which can lead to disruption of their work. Reacting to a strong stimulus, the cells at once spend all their internal reserves on transmitting too strong a signal to the brain, and they need some time to recover. The simplest example - after a bright flash in front of our eyes, we see dark spots. This phenomenon is due to the fact that some of the photosensitive cells "turned off" for a while, ceased to function.

In low light, our eyes rest. What do you do if you feel like your eyes are tired? Do you turn on bright lights or dim the lights? Most likely, mute it. Any relaxing environment involves weak, not strong lighting.

Operation in low light conditions creates absolutely no problems for the eyes. Any light intensity at which it is possible to distinguish letters is suitable for reading. Another thing is that it is uncomfortable to read in low light. But it's not bad for your eyes. Reducing the comfort of any process does not mean its harm.

To date, there is no scientific evidence or theoretical explanation that reading (or writing) in low light is in any way harmful to vision. Lighting may be sufficient or insufficient. With enough, we are able to read and write, and with insufficient, we are unable. In other words, any lighting that allows reading and writing is considered appropriate. The only difference is that in low light, the process slows down a bit. But it does not harm the eyes and does not impair vision! Not at all!

Saying that reading in low light is bad for your eyes is like saying that listening to soft music is bad for your hearing. Is not it?

The essence is the same - the effect of a weak stimulus on the sense organ.

Let me draw your attention to the fact that now we are talking about irritants, and not about some substance that our body needs for normal life. It is impossible to draw a parallel between weak lighting and, for example, low oxygen content in the atmospheric air. The weakness of the stimulus or its complete absence of the vital activity of the organism as a whole and any of its organs in particular does not violate. Not at all.

What then is harmful to the eyes? What can really make your eyesight worse?

It is harmful to hold the book too close before the eyes! The optimal distance from the book to the eyes is 40-45 centimeters. The minimum allowable is 30 centimeters. You can't get any closer! You already know that when viewing close objects, the ciliary muscle contracts and compresses the lens from the sides so that it becomes more convex.

Frequent and prolonged tension adversely affects the work of the ciliary muscle. In addition, when viewing objects close to the eyes, a compensatory change in the shape of the eyeball occurs, namely, elongation. Our body is designed to try to compensate for everything unfavorable. With elongation of the eyeball, the retina moves away from the lens so that the ciliary muscle does not have to strain too much. If you read regularly, holding the book too close to your eyes, then the transient compensatory change in the shape of the eyeball will become permanent.

Please note that when the eyeball is lengthened in the case of the normal position of the lens, the image from objects is focused not on the retina, but in front of it. There is myopia. The myopic eye clearly sees only nearby objects, which is ensured by the contraction of the ciliary muscle and an increase in the bulge of the lens.

If you hold a book too close in front of your eyes, you will develop myopia. If after that you continue to behave in this way, then myopia will progress.

The intensity of illumination does not affect either the curvature of the lens or the shape of the eyeball. Only the pupil dilates or constricts.

What else is bad for the eyes?

Reading in a moving vehicle, in which, due to shaking, a book or tablet moves closer to the eyes, then moves away from them and, in addition, shifts left-right and up-down. The oculomotor muscles have to constantly rotate the eyeball, and the ciliary muscle has to constantly change the curvature of the lens. From such unbearable labor in the literal sense of the word, the muscles are excessively tired.

If you constantly read in transport, you can get visual impairment.

In the subway, it is better to listen to music or think about something, but not to read or watch movies on your tablet or phone.

The same goes for reading while lying on your back. It doesn't matter if you hold the book with one hand or both. Still, it keeps moving back and forth. Slightly shifted, you may not notice it due to the huge adaptive work that your eyes do. But what is imperceptible to you is given to the eyes with great difficulty. Sooner or later, the ciliary muscle will not control the lens so well, and the oculomotor muscles will not turn the eyeball so accurately. And do not flatter yourself, please, thinking that such a “training” is good for your eyesight. By no means! Only to the detriment.

Why were these two examples needed - with a book located too close in front of the eyes, and with reading in transport? To demonstrate what is harmful to the eye. Anything that causes excessive tension of the ciliary muscle and oculomotor muscles is harmful. Too strong irritation of photosensitive cells with very bright light is also harmful. But reading in low light does not strain the muscles of the eye and does not greatly irritate the cone rods. We can say that while the eyes are in a calm, relaxed state. So what harm can we talk about?

To the question "What kind of lighting is optimal for reading?" There is only one correct answer: "The one that makes you comfortable reading." Each of us has his own, purely individual indicator.

“Why, then, do the sanitary rules set standards for average illumination for various rooms? some readers may ask. “For schools, for production workshops, and so on…”

Because there are the most favorable, comfortable levels of illumination, which are accepted as a general norm. For example, for school classes, this figure is 500 lux (this is a unit of measurement of illumination) on the blackboard and 400 lux on tables. But illumination refers to such indicators, the reduction of which does not harm health, but only complicates the educational or work process.

Should You Take Vitamin C? Do you have dysbacteriosis? How dangerous is cholesterol? Does garlic improve immunity? Are you sure you need gluten-free products? Evidence-based medicine has clear answers to these and other questions. And they are collected in this light and ironic book. So it can change your idea of ​​a healthy lifestyle, teach you how to take better care of yourself, make informed decisions.

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