Heliotherapy, the treatment of lethargy with the help of sunlight, has been recommended by the classics of medicine for centuries, and the Czech proverb "where the sun doesn't go, the doctor goes" is true. Optical radiation has many uses in medicine: e.g. the whole spectrum of laser applications, the treatment of neonatal jaundice (photodegradation of bilirubin), photodynamic therapy (local activation of a drug by light) or the treatment of tuberculosis of the skin with radiation of λ ≈ 400 nm (Finsen's discovery). However, treatment with light hitting the eye has long been classified as alternative medicine, with a few exceptions. Since the first attempts in the 1970s and 1980s [1] to [4], light therapy has become one of the accepted methods of chronobiological treatment, thanks to the discoveries of chronobiologists, neurologists, and psychiatrists, and has been reimbursed by health insurance companies since this year [5, exercise 35115]. In addition to phototherapy, chronobiological treatments include sleep deprivation and controlled shifts in sleep/wake rhythms, which can also be supported by light. The prefix chrono- conveys the importance of the correct timing of therapy within the daily rhythm.

Chronobiological phototherapy (ChBFT) This method brings a rapid improvement (within a few days) in the condition of patients (in 50 to 66% of cases) suffering from non-seasonal depressive disorder, in the depressive phase of bipolar disorder, in sleep cycle disorders or in attention disorders [6]. Phototherapy helps to bridge this period. Comparable efficacy of light and antidepressant medication has also been demonstrated for seasonal affective disorder (SAD) [7], and a significant proportion of patients are thus satisfied with regular and well-timed home phototherapy.

As an adjunctive treatment, ChBFT is also used for schizophrenia, schizoaffective disorder and dementias, including Alzehimer's. A study [8] shows the potential of bright light to improve quality of life and achieve operational savings in nursing homes.

 

ChBFT methods

- Bright Light Therapy (BLT) - the patient's face is illuminated for typically 30 minutes in the morning with light of approximately 10 klx intensity. Use: treatment of depression, treatment of SAD.

- All-day phototherapy: light dose of 10 klx per 30 min (i.e. 5 klx-h) can be spread over a longer period of time, e.g. 5 klx for 1 h or 2 klx for 2 to 3 h. Use: treatment of depression, treatment of SAD, improvement of sleep rhythm.

- Bright light therapy in the evening: 10 klx on the face for 30 min. End of application is typically 2 h before desired bedtime. Use: against premature evening sleep, after which the patient wakes up and cannot sleep. Improvement of sleep rhythm.

- Dawn (and Dusk) Simulation Therapy (DDS) - the patient is gently awakened at a certain hour by a light that smoothly simulates sunrise in the bedroom. Before falling asleep, on the other hand, the lighting decreases. In [9], an exponential dimming from approximately 200 to 10 lx in 30 min is reported. If the chromaticity temperature of the light (biodynamic illumination) decreases with intensity, the lowest intensity on the Kruithof diagram corresponds to approximately 1 900 K and the highest to 2 700 to 3 700 K. Use: adjustment of sleep rhythm.

- Combination of sleep deprivation (patient stays awake for more than 40 h) with bright light (WT+BLT). Typical illumination is 10 klx on the face for 60 min around 2 am. In addition, illumination of approximately 1 klx can be used, which can be variable (e.g., cloud simulation) to help the patient stay awake. Typical use: treatment of depression.

 

Extra-visual effects of light

Suppression of melatonin production at night - (Melatonin Suppression) - short-acting: the effect starts within a few minutes and disappears within 2 h (Fig. 1). Uses: treatment of depression, facilitating awakening, postponing sleep.

Entrainment - long-acting: the effect is not apparent until the following day and lasts for several days. Bright light in the morning shifts the start of the day to an earlier hour (anticipation). In the evening, on the other hand, it delays sleep and the start of the next day to a later hour (delay) (Fig. 1 and Fig. 2). Use: adjustment of the sleep rhythm.

Change in melatonin amplitude - inadequate light during the day can cause an increase in minimum daytime melatonin levels, and disturbing light at night can reduce peak levels. Uses: improving sleep/wake rhythms by correcting light conditions.

Pupillary photoreaction - the light-sensitive ganglion cells of the retina form the slow component of the photoreflex (reaction time is approximately 1 min). The fast component (less than a few seconds) consists of rods and cones. Use: improvement of depth of field. Activation of attention - bright light on the retina increases attention and has a beneficial effect on cognitive processes. In addition to the visual pathway, contribution from light-sensitive ganglion cells is assumed. Uses: improving work and study performance.

What affects the extra-visual effects of light:

- illuminance - measured at the patient's eye level - see Figure 1,

- spectral composition - for light with a large blue component the threshold E is lower - see Figure 6,

- exposure time - (in interaction with spectrum and intensity) - subthreshold, linear (~minutes) and saturated region (~ tens of minutes),

- the phase of the circadian rhythm (day or night time) when the light is applied - see Figure 2,

- pupil diameter - regulation of the amount of light hitting the retina,

- condition of the visual system - with increasing age, the lens absorbs more effective radiation.

 

Light sources for ChBFT

Již v prvních pokusech [1] byly použity zářivky o Tc = 6 000 K a Ra = 87. Tato volba dává smysl jak z intuitivního hlediska podobnosti dennímu světlu, tak z hlediska velkého podílu účinné modré složky (Ac = 83). Energetická úspora může mít podobu menšího příkonu nebo kratší expozice. Podíl účinné modré složky je zásadní v oblasti prudkého nárůstu účinku (E < 1 klx, obr. 1), ale v oblasti nasycení (E > 1 klx) má jen malý význam. Nejnižší příjemná teplota chromatičnosti při E = 10 klx je podle Kruithofova diagramu 4 000 K. V praxi se u BLT nejčastěji používá Tc = 5 000 až 6 500 K. Běžné chladné umělé světlo (865) je však všeobecně považováno za málo příjemné. V dotazníkovém výzkumu NASLI respondenti hodnotí jako příjemné světlo o Tc = 6 500 K v kombinaci s výborným podáním barev Ra = 93 a s pěkným podáním syté červené R9 > 80 K terapii simulací úsvitu a soumraku lze využít i žárovky, ale přímo určené pro toto použití jsou světelné diody. Pěkných výsledků (Ra > 90 pro Tc = 1 800 až 6 500 K) lze dosáhnout s moduly RGBW (teplá bílá) a čtyřkanálovou regulací. U dvoukanálového prolínání teplé (2 700 K) a chladné bílé (6 500 K) LED leží většina kombinací pod linií černých těles či denních světel, a nejde tedy v pravém smyslu o bílé světlo. Velké úspory energie skýtá využití modrých světelných diod (λp = 450 až 490 nm); limitujícím faktorem zde může být fotobiologická bezpečnost. Při terapeutickém použití světelných diod je třeba zamezit míhání, tj. periodickým změnám světelného toku. Frekvence míhání v rozsahu 3 až 30 Hz (někdy až 60 Hz) mohou u epileptiků vyvolávat záchvaty. Proto je třeba dát přednost měničům, jejichž výstup se blíží stejnosměrnému průběhu. V [11] jsou jako minimální frekvence pro PWM uváděny 3 kHz.

 

Luminaires for ChBFT

In addition to the basic requirements for luminaires (LVD and EMC directives), phototherapy luminaires must provide the required level of illuminance, which is typically five to ten times the illuminance of work areas. The light must also have the necessary proportion of activating blue component. During phototherapy, the patient may be dazzled, but other persons should preferably not be dazzled.

Portable phototherapy luminaires

Phototherapy luminaires sold under the names Light-box, anti-SAD box or solar simulator have been on the market for more than 30 years. The version with two single-wire 36W fluorescent lamps and a frosted diffuser is widespread. As a basic parameter, an illuminance of 10 klx at a certain distance from the luminaire is specified. The Morningness- Eveningness Questionnaire [12] is used to determine at what time in the morning the therapy should start in order to be most effective. A prerequisite for successful bright light therapy is its regularity.

Stationary phototherapy luminaires

For BLT, powerful NASLI fluorescent luminaires with four to six T5 fluorescent lamps can be used, based on a range originally developed to illuminate demanding visual tasks in dentistry. A pair of MedicoSun 4×80 W luminaires suspended at a height of 2.5 m above the head of the bed provide 4 klx illuminance. In 2013, in a pilot project for the Psychiatric Clinic 1. In the pilot project of the Clinical Faculty of Medicine and University Hospital in Prague, a room with four beds and a lounge were equipped in this way (3 klx on table tops). The luminaires in each room can be controlled by a dimmer on the DALI bus from 1 to 100% of the luminous flux.

Mobile phototherapy luminaire

The need to move patients to stationary phototherapy lighting led to the requirement for a relocatable luminaire that could be brought to the patient's bedside. A prototype of the NASLI ADS2max luminaire was developed during 2014 and after certification, the first units were delivered to the pilot project at the VFN. The solid iron base provides the necessary stability for the luminaire and the swivel castors allow the luminaire to be driven under the bed even in confined spaces. The body of the luminaire rests on an arm that can be partially retracted into a stand anchored in the base for transport. The light sources of the luminaire are ten NASLI T5 24 W (965) fluorescent lamps, powered by three DALI ballasts, and two RGBW LED power strip modules. The optical system consists of a curved micropyramidal prism. The processor control unit incorporates a precision real-time clock and provides timing commands to the ballasts over the DALI bus and to a four-channel digitally controlled linear current source for the LEDs. Programs for individual therapy methods can be easily selected on the display using the remote control, or a special program prepared by the doctor can be loaded from a removable SD memory card. The control unit provides smooth transitions between intensities and chromaticity temperatures for individual program points. The built-in PIR sensor and reflected light sensor allow the orientation light to be automatically switched on when motion is detected during nighttime hours. The firmware can be customised to the operator's exact needs. The design is protected by utility model No. 28109.

 

Standards

DIN SPEC 67600:2013 Biologically Effective Lighting offers biodynamic lighting scenarios for different spaces and supplements EN 12464-1 with the degree of relevance of biological effects for individual spaces and visual tasks. The prescription DIN V 5031-100:2009 has been replaced by DIN SPEC 5031-100:2015 Melanopic effects of transocular light on humans - quantities, markers and effective spectra, which changes the terminology from "biological" to "melanopic" and introduces the melanopic daylight equivalent quantity D65 as an analogy to photometric quantities. The conversion factor mV, mel, D65 corresponds to Ac/100 [13]. A surprising novelty (and the subject of a DIN-FNL query) is the shift of the maximum of the effective spectral composition from the original 450 to 490 nm.

 

Conclusion

Light treatment for depression and other mental health conditions has a long history in various forms and has been coming to the fore again in the last few years - this time taken seriously by legislators and health insurers. The developed phototherapy luminaires form the necessary technical background, and the ChBFT courses for doctors and nurses are underway to provide the necessary knowledge for health professionals. Several ongoing phototherapy pilot projects in hospitals and hospitals or centres for dementia patients are providing practical experience and enabling further development of the method. A brochure [14] contributes to its popularisation and more detailed information is available at www.chbft.cz.

The light synchronizes the inner clock of man and gives his life a temporal order and rhythm. Lack of light during the day, on the other hand, disrupts this order. Most psychiatric illnesses are themselves accompanied by a disturbance of the sleep rhythm, the improvement of which is a clear indicator of the effectiveness of the treatment used, which has led to an improvement in the patient's condition [15] - the first law of chronobiology. So let light penetrate into the dark corners of hospital rooms!

I would like to thank Pavel Doubek, M.D., Ph.D., from the Psychiatric Clinic of the 1st Faculty of Medicine in Prague, for his comments on the article.

 

Glossary of terms

- Light-sensitive retinal ganglion cells (ipRGCs)

- Photosensitive neurons used to detect light intensity but not to see.

- Melanopsin - photosensitive dye ipRGCs - sensitive especially to blue light.

- Retinohypothalamic tract (RHT) - part of the optic nerve transmitting the signal from ipRGCs

to the brain.

- Suprachiasmatic nuclei (SCN) - the central clock of the mammalian organism connected to the RHT, in humans they are located almost in the middle of the head.

- Chronobiology - a branch of biology studying the life manifestations of organisms in terms of their temporal (rhythmic) dependencies.

- Biorhythm - an internal cycle of changes in a particular state, quantity, property or behaviour of an organism.

- Circadian rhythm - a biorhythm with a period of approximately 24 h, synchronized mainly by light for 24 h. In this rhythm, sleep and wakefulness alternate.

- Melatonin - the hormone of sleep and regeneration, peaking after midnight, is the main indicator of the phase of the circadian rhythm. Light stops its production.

- Depression - a mental state characterized by excessive sadness.

 

Literature:

[1] Wurtman, R. J.: The effects of light on the human body. Scientific American, 1975, 233, 1, pp. 69-77. ISSN: 0036-8733.

[2] LEWY, A. J. - WEHR, T. A.: Light Suppresses Melatonin Secretion in Humans. Science, 1980 Dec., 210, pp. 1267-1268. ISSN 0036-8075.

[3] Rosenthal et al.: Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy. Arch Gen Psychiatry, 1984 Jan, 41, 1, pp . 72-80. ISSN 0003-990X.

[4] PRAŠKO, J. - GOLDMANN, P. - ZINDR, R. - ZINDR, V. Acceleration of the onset of action of tricyclic antidepressants by the use of bright white light. Československá psychiatrie, 1987, vol. 83, no. 6, pp. 386-384. ISSN 0069-2336.

[5] CR. Regulation No. 326/2014 Coll.: Decree of the Ministry of Health issuing a list of medical procedures with point values. In. Prague, Printing House of the Ministry of the Interior, 2014. ISSN 1211-1244.

[6] Doubek, P.: Chronobiological treatment of psychological disorders. Health E15, Annex: Medical letters, 08/2012 [online]. [cited 2015-11-01]. Also available from: http://goo.gl/F494sA.

[7] LAM, R. W.: The Can-SAD Study: A Randomized Controlled Trial of the Effectiveness of Light Therapy and Fluoxetine in Patients With Winter Seasonal Affective Disorder. Am. J Psychiatry, 2006, 63, pp. 805-812.

[8] SUST, C. A. - DEHOFF, D. - LANG, D. - LORENZ, D. Improved quality of life for resident dementia patients: the St. Katharina research project in Vienna [on-line]. Zumtobel Research, 2012 [cited 2015-11-01]. ISBN 978-3-902940-11-7. Also available from: http://goo.gl/eJ9P99.

[9] Gasioa, P. F. et. al. al.: Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly. Experimental Gerontology, 38, 2003, pp. 207-216. ISSN: 0531-5565.

[10] Duffy, J. F. - Czeisler, C. A.: Effect of Light on Human Circadian Physiology. Sleep Med Clin, 2009 Jun, 4, 2, pp. 165-177. doi:10.1016/j.jsmc.2009.01.004.

[11] U.S. Department of Energy: A Much-Noted Recommended Practice for LED Flicker. [on-line]. SSL Postings, June 11, 2015 [cited 2015-11-01]. Available from: http://goo.gl/GDe2fc.

[12] Center For Environmental Therapeutics: AutoMEQ survey [online]. [cited 2015-11-01]. Available from: http://www.cethosting.com/limesurvey/.

[13] FUKSA, A.: Light and the biological clock [on-line]. Light, 2010, no. 6, pp. 56-58 [cited 2015-11-01]. ISSN 1212-0812. Available from: http://goo.gl/tXjMtp.

[14] FUKSA, A. et al.: Chronobiological phototherapy in practice [on-line]. Prague, Blue step, 2015. 10 s. [cited 2015-11-01]. ISBN 978-80-905767-1-1. Available from: http://www.chbft.cz/ke-stazeni/.

[15] Wirz-Justice, A.: Chronobiology and psychiatry. Sleep Medicine Reviews, 2007, 11, pp. 423-427. ISSN 1087-0792.

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Fig. 1. Suppression of melatonin production and phase shift of circadian rhythm as a function of light intensity and their dispersions; redrawn from [10]

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Fig. 2. Phase shift of circadian rhythm as a function of the phase at which light is applied; redrawn from [10]

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Fig. 3. NASLI SunSun 2×55 W solar simulator in use demonstration

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Fig. 4. Patients' room with NASLI MedicoSun® EP 4×80 W DALI phototherapy luminaires during the test run, later the room was painted brown-pink

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5. Programmable phototherapy luminaire NASLI ADS2max, working height 235 cm, transport height 185 cm, base 70 × 90 cm

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Fig. 6. Biologically/melanopically effective spectrum according to DIN 5031-100 from 2009 and 2015

Author. Antonín Fuksa, NASLI & Blue step spol. s r. o.
Published in Světlo 6/2015