Light does far more than simply help us see. It is one of the main environmental signals used by the body's internal clock to help regulate when we feel alert and when we begin to feel ready for sleep.

That means your sleep environment matters. Street lighting, early morning daylight, televisions, lamps and unfamiliar hotel rooms can all introduce light at times when you would rather be sleeping.

A blackout sleep mask offers a very simple solution: reduce the light reaching your eyes without having to change the entire room around you.

The body follows an approximately 24-hour internal rhythm often referred to as the circadian rhythm. Among other things, this helps regulate when you naturally become more alert and when you begin to feel sleepy.

Light is one of the most important external cues for this system. During the day, exposure to light helps reinforce wakefulness. As evening approaches and light levels fall, the body begins shifting towards the conditions associated with sleep.

That is why a dark bedroom is generally considered one of the foundations of a good sleep environment.

Melatonin is naturally produced by the body and plays an important role in the timing of sleep. Its production is closely linked to light exposure, with darkness encouraging night-time melatonin production and bright light tending to suppress it.

This does not mean you need absolute darkness every second before bed. But it does help explain why reducing unnecessary light can make sense when creating a more sleep-friendly environment.

For many people, that means dimmer lighting in the evening, less screen exposure immediately before bed and a bedroom that is as dark as practical once it is time to sleep.

A number of controlled studies have investigated whether reducing environmental light with an eye mask can improve aspects of sleep quality.

In one UK randomised controlled pilot trial involving hospital patients, the group given eye masks and earplugs reported higher sleep-quality scores than those receiving standard care.

Other randomised studies in cardiac and coronary-care patients have also reported improvements in measures of sleep quality among participants using eye masks.

These studies took place in clinical environments rather than ordinary bedrooms, but they support a straightforward principle: reducing unwanted environmental light can make the conditions for sleep more favourable.

For a sleep mask to become part of your routine, it needs to feel comfortable enough to wear for several hours at a time.

That is where the design becomes important. Generous coverage can help block light without relying on a narrow strip over the eyes, while soft padding helps create a cushioned feel around the face.

An adjustable fit also matters because head and face shapes vary. Being able to fine-tune the fit helps the mask feel secure without unnecessary tightness.

A regular wind-down routine can help create a clearer separation between the active part of your day and the time you intend to rest.

That does not have to mean an elaborate sequence. Lower the lights, finish your skincare, put away bright screens where practical, make the room comfortable and then use the mask when you are ready to sleep.

Repeated consistently, small cues like these can help make bedtime feel more deliberate and less like simply stopping whatever you were doing because the clock says it is late.

Aircraft cabins, hotel corridors, unfamiliar curtains and changing time zones can all make your sleep environment feel less predictable.

A sleep mask does not solve jet lag on its own, but it does give you one familiar and controllable element: darkness when you want to rest.

That can be useful on overnight flights, for an afternoon rest after travelling, or simply in a hotel room where the curtains allow more light in than you expected.

The Pure Tone Aesthetics Sleep Mask combines 22 momme mulberry silk, soft cloud-like padding, generous blackout coverage and an adjustable fit.

The silk provides a smooth surface around the delicate eye area, while the padded construction makes the mask feel comfortable enough for regular overnight wear.

It fits naturally alongside the rest of a considered evening routine: finish your skincare, reduce unwanted light and give yourself a calmer environment in which to switch off.