The unconscious perception of online lighting Australia light is crucial for health, argue professor Domien Beersma and colleagues. It would be good if doctors took this into account in ophthalmic treatments. For example, the standard placement of a yellow lens during a cataract operation is unwise.

It is known that the conscious perception of light in the retina – seeing – is of great value to our well-being Eye, Blue, People, Look, Pupil, Iris, View, Blindnessand health. Less known is that also the unconscious, non-imaging perception of light in the brain evokes responses that play a major role in our healthy functioning. The direct effects of unconscious light perception are changes in our alertness, for example: in a dark room the chance that someone falls asleep during a presentation is much greater than in a room with lots of light. In the longer term, unconscious perception of light has an effect on one’s biological clock and chronotype, among other things.

Chronotype is defined as the middle of sleep on days off: if someone goes to bed on their own at 11:00 am and gets up at 7 am, their chronotype is 3 hours. Extra light exposure in the evening will shift the chronotype to a later time, extra light in the morning to an earlier time.

When people work at night, they deviate from their chronotype and problems arise when they stay awake and alert, causing errors and accidents to lurk. It is also more difficult to fall asleep quickly and continue to sleep. This explains, for example, the sleep and alertness problems with jet lag. Many people experience a form of jet lag every week because their sleep times on a day off differ from their sleep times on a working day.

Ganglion Cells
The non-imaging effects of light have only recently entered the research agenda, and the underlying physiological system is now being unraveled rapidly. Intrinsically light-sensitive retinal ganglion cells in the retina play an important role in this, referred to in the English-language literature as ip-RGC (intrinsic photosensitive retinal ganglion cells).

Blindness and Cataracts
Blindness and cataracts are common to elderly. The vastness of the network of projections shows that non-visual effects of light play a role in many places in the brain. The investigation into this has only just begun and the knowledge is therefore patchy. Yet in general we can already conclude that not only seeing can determine whether an eye is still functioning and that doctors must take this into account in ophthalmic interference. People can be blind while the non-imaging system is functioning and the sleep-wake rhythm normally synchronizes with the light-dark cycle. If the eyes of blind people are removed, their possibly still functioning non-visual system disappears, which means that the sleep-wake rhythm can no longer be synchronized normally by light. That can cause sleeping problems.

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