Juan Ding, OD, PhD

We all know that the sunlight is the best light to prevent and control myopia in children. I have previously published multiple media items to talk about this and you can view them here. Indeed playing outside is the best way to prevent myopia. However, given the modern lifestyle, it is inevitable that we are still spending majority of the awake time inside a house, be it home, school, work or even entertainment. What can we do to reduce myopia while inside the house?

The key is to ensure that children have sufficient ambient light when staying indoors [1,2], including doing all activities, such as studying, eating, having fun, that is, except for sleeping at night.

If you can afford a glass house such as the one below, then you are all set. The sun will be your light source. It’s like you are living outside all the time. No one will develop myopia in such a house, ever.

Image source: https://www.santambrogiomilano.com/

However, as dreamy as this house may be, you and I most likely will never get to live in one, so we have to resort to having good lamps.

Living in New England, most of the houses here are old, without the floor to ceiling windows you see in modern homes, and winter here is basically 6 months long with extended dark nights. Mind you, it gets dark at 4 PM, so when you get home from work or school, you will not have any natural light to do myopia-preventing outdoor activities. This will be a good time to crack up your home light intensity. The brightest light indoors is still several orders of magnitude weaker than outdoor sunlight. So never worry that your light may be too bright. On the contrary, always worry that your light is too dim.  

Most homes will use some or all of the lighting sources: desk lamp, floor lamp or ceiling lamp. I will provide some guidelines for how to choose a good one for myopia control for each of these.

Desk lamp

1. Sufficient brightness

Desk lamps should provide sufficient brightness to ensure that reading materials such as books, documents, and screens are clearly visible and reduce eyestrain. Usually, the suitable reading brightness is about 300 to 600 lumens.

2. Good color accuracy

Choose desk lamps with a high color rendering index (high Ra) as they can render colors more accurately and reduce visual fatigue. By definition, Ra under natural light is set as 100. When you choose a desk lamp, try to choose Ra95 or above, so that the color accuracy is closer to that under natural light.

3. Good uniformity of illumination

Make sure the light from the desk lamp is evenly distributed and does not create noticeable shadows or glare. The smaller the variation in lighting, the less likely it is that the pupils will dilate or constrict, which can lead to visual fatigue.

4. Comfortable color temperature [3, 4]

The color temperature of a light is an indicator that describes its color appearance, usually expressed in units of Kelvin (K). Different color temperatures will produce different visual effects. Here are some differences between different color temperatures:

1. Lower color temperatures (2700K – 3000K): Lower color temperatures typically appear as warmer tones, similar to yellow or orange light. This color temperature is warm and comfortable, suitable for casual environments.
2. Medium color temperature (3500K – 4500K): Medium color temperature usually appears as natural white or natural daylight color. This color temperature is fresh and neutral, which is more suitable for studying. It helps improve alertness and concentration.
3. Higher color temperature (above 5000K): Higher color temperature appears as cool colors, similar to a bluish white light. This color temperature is typically used in environments that require a high degree of lighting and visual precision, such as operating rooms, laboratories and workshops. Higher color temperatures can increase alertness and concentration, but may feel cold when used in a home environment.

In addition, the color temperature of the lights can also be adjusted between different activities and time periods to suit different needs.

For example, you can use a medium color temperature when studying during the day; and at night, if you plan to read a book before going to bed, you can adjust the color temperature to a lower color temperature to help you relax and get ready for asleep.

Some desk lamps can have settings to adjust between different color temperatures as well as brightness of the light, which are helpful.

5. Ability to adjust brightness

Even though it is beneficial to prevent myopia by using as bright a light as possible, in some cases, you may find it difficult to tolerate bright light, such as when you have dry eye syndrome, conjunctivitis, or migraine headaches. Turn down the brightness if you suffer from these conditions.

6. Blue light

There is a lot of debate about blue light for eye health. Blue light is part of the natural visible light spectrum. A normal dose of blue light exposure is good for the eyes, circadian rhythm, and a happy mood, but excessive exposure is bad [5].

The visible light spectrum of sunlight is a continuous spectrum, including blue light and all the way to red light. Compared with natural light, the spectrum of many LED lights contains a disproportionately high amount of blue light. When you choose desk lamps, try to choose light bulbs with a continuous spectrum and no excessive blue light.

7. Avoid flickering

Desk lamps should not produce significant flicker, as flickering light sources may cause eye discomfort.

8. Proper positioning, height and angle

Place the desk lamp in a suitable position to ensure that the reading material is illuminated without the light shining directly into the eyes. Avoid light shining on the screen or reflect onto your eyes. Some desk lamps have adjustable arms, lampshades, diffusers or beam angles that allow you to adjust the direction and range of light as needed.

9. Additional functionality

Some modern desk lamps come with remote controls, touch controls, or smartphone app controls for easier operation and adjustment. These have nothing to do with myopia control and can be selected according to personal preferences.

10. Energy efficiency

Choosing energy-efficient desk lamps can reduce energy consumption, help save money on electricity bills, and be greener on the environment. LED desk lamps generally have high energy efficiency. Although our focus is on preventing myopia, it would be better if it could also save energy.

Although desk lamps are the direct source of light for children to study, the lighting of the environment in which children live and play is also important. When we are outdoors, the entire environment is bright, not just the 40 centimeters in front of our eyes.

So while using a desk lamp, you can also consider turning on a floor lamp or ceiling lamp. The considerations for selecting these lamps are similar to those introduced before for desk lamps, but there are a few additional considerations.

∎For ceiling lights, good design and shading should also be considered: try to prevent the light from directly entering the eyes.

∎For floor lamps, in addition to good design and shading, you can also consider the appropriate height and whether the light direction can be adjusted: Some floor lamps have adjustable arms or lampshades, allowing you to control the direction and range of light.

Good indoor lighting is necessary not only in the study room, but the entire environment should be as bright as possible. For example, install a good ceiling light above the dining table so that family can enjoy food in a nice a bright environment. If you are like me, you would spend a good amount of time eating dinner every day. Many families have a sunroom for children to play in, which is a fantastic idea. If children are playing or watching TV in the living room, it will be beneficial to add ceiling lights or additional floor lamps to increase the brightness of the environment.

In summary, the best indoor lighting for myopia control is bright illumination as well as a few other perks, possibly utilizing multiple light sources throughout the house. Ideally this is in addition to the out door activities, not instead of them.

References:

[1] Jiang X, Kurihara T, Torii H, Tsubota K. Progress and Control of Myopia by Light Environments. Eye Contact Lens. 2018 Sep;44(5):273-278. doi: 10.1097/ICL.0000000000000548. PMID: 30048342

[2] Landis EG, Yang V, Brown DM, Pardue MT, Read SA. Dim Light Exposure and Myopia in Children. Invest Ophthalmol Vis Sci. 2018 Oct 1;59(12):4804-4811. doi: 10.1167/iovs.18-24415. PMID: 30347074

[3]Weitbrecht WU, Bärwolff H, Lischke A, Jünger S. Wirkung der Farbtemperatur des Lichts auf Konzentration und Kreativität [Effect of Light Color Temperature on Human Concentration and Creativity]. Fortschr Neurol Psychiatr. 2015 Jun;83(6):344-8. German. doi: 10.1055/s-0035-1553051. Epub 2015 Jun 22. PMID: 26098084.

[4]Chao Wang, Fan Zhang, Julian Wang, James K. Doyle, Peter A. Hancock, Cheuk Ming Mak, Shichao Liu, How indoor environmental quality affects occupants’ cognitive functions: A systematic review, Building and Environment, Volume 193,2021,107647,ISSN 0360-1323,https://doi.org/10.1016/j.buildenv.2021.107647.

[5]Wahl S, Engelhardt M, Schaupp P, Lappe C, Ivanov IV. The inner clock-Blue light sets the human rhythm. J Biophotonics. 2019 Dec;12(12):e201900102. doi: 10.1002/jbio.201900102. Epub 2019 Sep 2. PMID: 31433569; PMCID: PMC7065627.