Sleep, Photosensitivity and Retinoblastoma
Saturday May 26, 2018 (updated 16 Sep 2021)
Dr. Iona Alexander explores how the body’s sensitive biological clock regulates sleep, and how some effects of retinoblastoma treatment may disrupt this highly tuned system.
The Symphony of the Circadian Rhythm
You are the conductor of a symphony, you are applauded as you walk on stage and every member of the orchestra is patiently waiting for you to signal the start of the symphony. From that point, you are responsible for maintaining the synchronicity of the crescendos, the diminuendos, the opening and closing of each movement and ensuring each instrumentalist is keeping to the same beat.
The same can be thought of our biological clock.
Our biological clock is like the conductor of an orchestra, autocratically dictating the synchrony of many bodily processes across a 24-hour cycle, in line with the rotation of the earth’s axis. These 24-hour biological processes include our concentration, blood pressure, body temperature, hormone release, urine volume and mood. They are known as circadian rhythms, from the Latin ‘circa-diem’ meaning ‘about a day’.
What Is Sleep and What Does It Do?
Sleep is just one of these finally tuned orchestral processes, dictated by the biological clock across a 24-hour cycle. Sleep is an essential component of our lives – we spend approximately a third of our lifetime in a state of sleep. But it is hard to think why any behavior such as sleep would have survived the vicious claws of evolution as it makes us so vulnerable to the outside world.
Needless to say there is still considerable debate amongst sleep scientists about the fundamental reasons why we sleep, but we do know sleep is integral to replenishing and restoring cells in the body. This process of sleep permits maximal performance during our waking hours.
The Challenge of Disrupted Sleep
The intricacy of the sleep-wake system makes it vulnerable to disruption. Particularly as behavioral disruptions can occur as a normal part of everyday life. The use of alarm clocks to meet daytime obligations, drinking caffeine to compensate for a period of too-brief sleep, then in turn using sleep-promoting medication in the evening to correct for the stimulants taken during the day. This can easily become a habitual cycle.
To repeat this vicious cycle daily often means we need to compensate by having a morning ‘lie in’ on the weekends or free days. This constant misalignment (referred to as ‘social jet lag’) is just one of many ways we can compromise the sleep-wake regulatory systems and experience sleep and circadian rhythm disruption (SCRD).
These constant disruptions can have a large impact on our emotional responses (irritability, depressed mood, frustration and increased impulsivity), cognitive responses (attention, memory, decision making) and somatic responses (increased risk of cancer, diabetes, heart disease and reduced immunity to disease).
What Has All This Got To Do With Retinoblastoma?
Specialised cells in the back of the eye (photosensitive retinal ganglion cells) are crucial to the timing of these circadian rhythms. Unlike other cells in the eye that use light for vision, these cells have a unique role. They send information about the quality and quantity of light from the environment to the Suprachasimatic nucleus (SCN) in the brain. The SCN – the master clock of our circadian biology and conductor of its symphony – uses this information to communicate the time of day to the rest of the clocks in our body.
In the absence of these specialised cells in the eye, the SCN has no idea what time it is and is unable to conduct effectively. The SCN still keeps time, but it is typically slightly longer than 24 hours, and when it isn’t set to 24 hours by sunlight, the results can lead to SCRD.
Therefore, individuals who are blind are more likely to experiences a SCRD. This is a bit like having permanent jet lag and affects our health and well-being, particularly our sleep and mood.
It isn’t just blind people who are affected. Individuals with photosensitivity often prefer to avoid natural light, which can make things difficult for the master clock. Imagine a conductor who started to dislike the sound of music…? Decreased exposure to light makes it more difficult for the SCN master clock to interpret the time of day and in turn the phase of the cycle. Research tells us that avoiding light impacts both wellbeing and quality of life.
The loss of cells in the back of the eye that communicate the light-dark cycle to the brain, and reduced light exposure both impact our circadian biology. Due to sight loss and photosensitivity resulting from treatment, individuals with retinoblastoma may also be at risk of SCRD, but we don’t know. Research needs to focus on furthering our understanding of this relationship.
I Have / Had Retinoblastoma, What Can I Do?
This is an area of research still needing considerable attention as we have no idea whether people with retinoblastoma do experience poor sleep or have mood disturbances – both of which can be indicative of SCRD.
When this article was first published, we invited you to complete an online anonymous questionnaire about sleep and mood so we could have a better idea of how things are for the retinoblastoma survivor community. This survey is now closed.
However, if you live in the UK and would like to participate in our research, please follow the link below to our ongoing study to understand more about vision status, health, and sleep.
Top 10 Tips for Improving Your Sleep
In other areas of research, it is thought that addressing unhelpful beliefs surrounding sleep, tackling sleep efficiency and regulating both light exposure and sleep timing can all be helpful. Indeed, these techniques form the crux of the psychotherapeutic intervention known as Cognitive Behavioural Therapy for Insomnia, a very prevalent sleep disorder.
As the research continues, Dr Bryony Sheeves and Professor Colin Espie from the Sleep and Circadian Neuroscience Institute at the University of Oxford have compiled a guide to the best techniques to help you improve your sleep quality and quantity.
More information and sleep tips specifically for blind and visually impaired people is provided by the Circadian Therapeutics Sleep Study team.
About the Author
Dr. Iona Alexander is a post-doctoral researcher in Professor Russell Foster’s lab at the University of Oxford, investigating sleep and circadian biology. She is particularly interested in the impact of eye disease, blindness and mental health on circadian biology.
After her A Levels, Iona worked for three years as a research technician in Fran Ebling’s lab, investigating the neural mechanisms underlying biological timing.
She studied zoology at the University of Sheffield, then joined Professor Passsingham in Oxford as a research assistant, investigating neural mechanisms in the perception of actions.
Her D.Phil thesis focused on the neural underpinnings of time perception. At the same time, she worked with Professor Alan Cowey on brain mechanisms involved in visual perception and visual awareness in blind individuals and those with a condition known as blindsight. This ignited her interest in the connection between the eye and circadian biology.
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