Your eyes are amazing. From catching a glimpse of golden sunlight dappling through the trees, to witnessing a loved one smile, a lot can be credited to this wonderful organ. But did you know that your eyes have some very special brain cells that have nothing to do with vision whatsoever? In fact, these marvellous cells even work in people who are blind, as long as they still have eyes. They have nothing to do with seeing, and have everything to do with sleep.
The eyes are the only part of the human brain that sit outside of the skull. Yes, you read that right - you have brain cells in your eyes which connect directly to the rest of your brain! Still, what does this have to do with sleep? As it turns out, your eyes are not only relevant to sleep, but are a key player in the most powerful way to improve sleep, according to Neuroscience.
The reason these specialised brain cells in your eyes are so instrumental to good sleep is because they are responsible for setting your brain’s internal master clock. You may have heard this referenced before if you’ve ever read or heard about the circadian rhythm. This master clock actually controls not only your sleep but a whole host of other processes such as your alertness, hunger and even your mood! If you’ve ever changed time zone then you will have felt the effects of this master clock being…a bit out of whack. No one likes jet lag and, unfortunately, these clocks are to blame for that. But what most people don’t realise is that you can be slightly jet lagged even if you haven’t gone anywhere. Your master clock, though it ticks away by itself, needs a lending hand from these special brain cells in your eyes to help set it correctly. When these cells are activated first thing in the morning, they send a signal to your brain’s internal clock telling it it’s time to wake up and start the day. This sets the clock ticking away so that you end up feeling sleepy around 16 hours later. Also, it sets off a little spike of cortisol which makes you feel alert and ready to take on the day. Cortisol has developed a bad name due to it being the stress hormone, but this little spike in the morning is actually really beneficial. Additionally, everyone gets a spike of cortisol in every 24 hour period regardless, but it’s vitally important for this to happen earlier in the day, as opposed to later (as late spikes in cortisol have been associated with anxiety and even depression).
So, how exactly do you activate the specialised brain cells in your eyes? With light. Very, very bright light. In fact, the only thing powerful enough to activate them in the morning is the sun. Annoyingly, you see, these cells are very insensitive in the morning (when you want them to be activated) and very sensitive in the evening (when you definitely don’t). The thing is, the activation from the morning sun is not going to work through a window. Even if you might be sitting with the sun shining through your window straight at you, looking all bright and lovely, it doesn’t work. The reason for this is, all the little particles of light actually get scattered when they hit a window, so it’s nowhere near as bright on the other side as it seems! Luckily, the solution to this is very simple. You just need to open that window. Now, for the more motivated of you, a 7am run outside is obviously one way of getting this bright morning daylight in your eyes, but for most people, it can simply be wrapping up warm in a dressing gown and standing by an open window, looking out. About 10 minutes on a sunny day and up to 30 minutes on a highly overcast day is enough to do it, ideally as soon after waking as possible. It’s also important to do this within around 2 hours of sunrise, when the sun is still low in the sky. This is because not only do you need the right brightness of light to activate your specialised cells, you also need the right colour. When the sun is still low but rising in the morning, the colour that reaches you is this perfect cocktail of blue and yellow that your cells need.
Though these cells in your eyes are brain cells - and as you may know, human brains are pretty stubborn and they take a little while to change - these particular brain cells are extremely special because they only take around three days to fully align the relevant internal mechanisms of your clock. Put simply, this means just three days of getting that morning daylight will set your clock, helping you fall asleep faster and wake up at the same time each day, even without an alarm. The only downside is that as fast as they are to catch on, they’re also pretty quick to drop off again. For this reason, it’s important to keep up this habit ideally every day to fully reap the benefits of this practice. When your clock is strongly set to the outside world like this, not only does your sleep improve, but so does your energy, alertness and mood, just to name a few! The benefits speak for themselves, but from a habit forming perspective, it can really help to make it a bit of a ritual, something you can look forward to. Be that sitting in your garden watching the birds or looking out of your open window with your favourite podcast and a hot drink, whatever works for you.
You may be wondering “but what if I need to wake up before sunrise?”. This is an incredibly common question, especially in winter when the sun may be rising later. This is where powerful light boxes such as SAD lamps have a role. Whilst most artificial lights are not bright enough to activate your specialised cells, SAD lamps, those of 10,000 lux, are the exception. They still take a little longer than the sun would, but they will do the trick. If one of these lamps is not accessible to you, however, then it is still important to get outside as soon as the sun is up.
Lastly, it’s important to touch on the night time. Remember that these cells in your eyes are actually more sensitive in the evening. Sadly, this means that bright artificial lights and yes, the light from your screens, is enough to activate them and start telling your brain “it’s time to wake up”. To avoid this, winding down without screens for around an hour before bed in dim lighting is ideal to not offset all that hard work you’re doing by setting your clock in the morning. If you really want to get nerdy about it, you can also physically place your evening dim light source lower in the room that you’re in. This is because these specialised cells actually sit at the bottom of the back of your eyes, meaning that they receive the most input from light high above (aka the sun in the sky). This means that light that is below your eye level doesn’t reach them as easily! Practically, this looks like using desk lamps or candles on the side next to you instead of overhead lights. Some people even go as far as placing their lamps on the floor in the evenings! But of course, be mindful of trip hazards and, if you’re using a candle, always prioritise safety.
Leveraging your hardwired biology in this way is the most powerful way to improve your sleep. Just one more reason why your eyes are so amazing. So next time you admire the sunshine dappling through the leaves, why not make it around sunrise? Your clock will thank you for it.