Optometrists are experts in light and eyesight. We are trained with a deep understanding of the optics of light rays and ocular anatomy, and we prescribe lenses to optimize eyesight and provide clear vision at all distances and different lighting conditions.
But natural daylight does more than provide illumination for eyesight. It is a powerful regulator of our body’s internal clock, influencing our cognitive function, stress levels, mood, sleep patterns, metabolism, and energy levels. In a world dominated by screens and artificial lighting, many of us are depriving ourselves of crucial light during the day and getting too much artificial light exposure at night.
The eye contains cells called ipRGCs (Intrinsically Photosensitive Retinal Ganglion Cells). These are separate from rods and cones. When exposed to light, ipRGCs send signals to control the timing of various biological processes in the body, such as sleep-wake cycles, hormone secretion, body temperature, and metabolism.
Natural daylight gives much higher overall lux levels and a higher proportion of blue wavelengths than artificial lighting. This intensity is crucial for the ipRGCs to send strong regulating signals to the body.
To support wellness, aim for regular exposure to natural daylight during the day, especially in the morning. Many experts are recommending a minimum of 10min of early morning daylight viewing (without sunglasses or blue-light lenses) to set the internal clock. At night, minimize exposure to artificial light, particularly blue light from screens, to promote healthy sleep and maintain the body's natural circadian rhythm.
We are learning more about the importance of maintaining a balanced relationship with light to support not only vision but also mental and physical health. Stay tuned for more developments, particularly around light therapies for health and vision conditions.
Dr. Lisa Scharf, BSc, OD