“The abuse of sunglasses prevents us from synthesizing vitamin D”

Walking without glasses, avoiding glare, in daylight is good for eye health.Getty.

There are many benefits of sunlight. With timely protection, the sun helps us synthesize vitamin Dto grow when we are children and, as adults, avoid osteoporosis. But, in addition, the latest research indicates that the eyes also benefit of sunlight baths. Sunbathing in your eyes It has important consequences for ocular health, as revealed in this interview by Dr. Ainhoa ​​de Federico, specialist in Natural Vision, research professor at the University of Toulouse and director of the first Visual Coach Diploma. She is also the creator of Volver a Ver Claro, a method made up of natural, non-invasive and scientifically validated techniques, which teaches how to take care of the eyes and learn healthy habits.

Why is sunlight important for vision?

Our eyes need light to function properly, and the amount of light influences how we perceive the world. When it is dark, the pupil dilates to capture more light, stimulating a larger part of the retina, which is larger than the fovea.

What is the fovea?

The fovea is a small area of ​​the retina, 2 millimeters by 2 millimeters, that has the highest concentration of cones. Cones are photosensitive cells that capture color and the precision of shapes. With cones, we see more clearly. The rest of the retina contains mainly rods with fewer and fewer cones as we move away from the fovea and macula. Rods capture general structure, movement and light contrasts, but they do not see as clearly as cones.

Therefore, in bright conditions, the pupil constricts and we use more foveal vision, allowing us to see more accurately. Sunlight is more intense than any artificial light, so it especially favors our foveal vision and allows us to see more clearly.

What benefits does the sun provide, in its proper measure, to correct vision?

Sunlight has many beneficial properties for the eyes and stimulates retinal regeneration. In particular, reddish sunlight, such as that at dusk or dawn, has a wavelength of 670 and, especially if received at dawn or in the morning, stimulates the mitochondria of photosensitive cells, allowing for a retina healthier by protecting from shorter and potentially harmful frequencies, such as blue, violet and even ultraviolet light.

The contrasts between light and shadow outdoors allow the regeneration of intraocular pressure through the movement of the iris. They also keep it in shape with the ability to regulate pupil size to better adapt to night vision, prevent photophobia from developing, and take advantage of the sharpness that foveal vision offers in good light. On the other hand, moments of darkness allow the generation of opsins, specific proteins that the cones and rods use to perceive contrasts and colors clearly.

Sun, vision and vitamin D: is there a relationship?

By penetrating through the eyes, which are the most transparent part of the body, sunlight optimizes the synthesis of vitamin D. Recent scientific discoveries since 2016 suggest that we synthesize much more vitamin D through the light that enters through the eyes, which for the skin. Therefore, sunlight is very beneficial for health and is essential for the proper functioning of the eyes.

What harm does a lack of sun exposure cause?

Vitamin D deficiencies are a well-known harm of lack of sun exposure, in addition to the general worsening of mood. Along with this, a very direct damage would be the continuous dilation of the retina, with the consequent loss of tolerance to light, also known as photophobia.

This generates a vicious circle, since it is usually compensated with the use of sunglasses that keep the retina and eyes in that state and deprive them of the benefits of sunlight. On the other hand, exposure to blue sunlight has been shown to prevent myopia, indicating that lack of exposure favors this refractive error.

Is there a relationship between sunlight and circadian rhythms?

The nervous system and endocrine system are informed relatively to the circadian cycle by the specific frequencies of sunlight perceived by non-optic photosensitive cells that the eyes also have. Depriving ourselves of exposure to sunlight not only has unfavorable consequences for our eyesight but also for our health in general: lack of sleep, lower concentration, learning, memory, alterations in metabolism… In fact, recent scientific studies suggest that a lack of Sunlight can be one of the factors that favor the appearance of cancer.

Is there any relationship between myopia and lack of sunlight?

Blue sunlight is beneficial and has been shown to prevent myopia as it regulates optical dopamine, which is involved in eye growth. This has led schools in Australia and Singapore to allow children to play outdoors at midday to benefit from this light.

¿Do we abuse sunglasses? How long is it good for your eyes to be exposed to outside light?

Early humans spent most of the day in the sun. The ideal would be to have exposure to sunlight for two hours a day, even if it is cloudy and the light reaches us ‘filtered’. However, in our current way of life, this is often not possible. We recommend daily exposure, depending on the time that is possible and convenient for each individual, and listening carefully to the body’s warning signals so as not to fall into possible excesses.

What consequences does the abuse of sunglasses have?

Constantly wearing sunglasses is not beneficial for visual health and can be a barrier to stimulation and nutrition of the eyes. The constant use of sunglasses generates a lazy iris, which leads to constant excessive dilation of the pupil, which in turn generates photophobia.

On the other hand, with an excessively dilated pupil we will see less clearly, due to the characteristics of foveal vision already explained. Sunglasses deprive the eyes of the possibility of synthesizing vitamin D. And, in general, any glasses tend to inhibit blinking, so important to stimulate tears, clean the eyes and maintain an optimal curvature of the eyes. surface tension of the tear. They also reduce peripheral vision awareness, alter the perception of colors and depth of field, which misinforms our brain about the environment and our position in space.

Therefore, your recommendation is to ‘sunbathe’ your eyes, with due precautions.

Yes. As I said, it is important that the eyes can be exposed to sunlight at various times of the day to regulate the body with the circadian cycle, which is also essential for the nervous and endocrine system. Except for specific situations, such as skiing in the snow, being in the desert or on the beach (with very intense reflections in the water), driving with the sun in front of you or being an airplane pilot, moderate use of sunglasses is preferable. sun.