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Coloured filters, worn in spectacle frames or used as overlays, have been used in the

treatment ofdyslexia, migraine and photosensitive epilepsy (Fowleret al, 1992; Wilkins

et al. 1999; Wilkins et al, 2002). Recently, 'blue-blocking' coloured filters have also been

shown to modulate the circadian pattern of melatonin output and sleep-cycle variables

(Sasseville et al, 2006; Sasseville et al, 2010).

Oxford Blue Filters (OBF) (Fig. 1) have been used in the treatment of Dyslexia in Oxford for

twenty years, although understanding of their mechanism of action has remained illusive.

Joe A Taylor and John F Stein. Department of Physiology, Anatomy and Genetics, The University of Oxford

Current applications of coloured filters OBF impact sleep quality and altertness Discussion and conclusions

Implications and further research

To determine the effects of daytime OBF use over sleep quality and continuity, we asked

eleven healthy adult volunteers to wear OBF filters for one-hour immediately after waking

each morning over a period of thirty days. In a randomised order, they also wore 'yellow'

filters, with an opposite transmission profile, for thirty days.

Each morning, participants completed visual analogue scales (VAS) to indicate their

perceived alertness on waking and the quality of their previous nights' sleep. They also

recorded the number of times they had woken during the night. Repeated measures

comparisons were made of responses between the period during which OBF were worn

and that during 'yellow' filter use against a thirty-day baseline period without filter use.

During the period of OBF use, participants reported improved sleep quality (p = 0.05) and

felt more alert when they woke (p = 0.05) (Fig. 3). No change was observed during 'yellow'

filter use.

Seasonal affective disorder (SAD)Fowler et al. Lancet. 1992;340:724. Sasseville et al. J Pineal Res. 2006;4(9):73.

Sasseville et al. Prog Neuropsychopharmacol Biol Psychiatry. 2010;34(7):1236. Wilkins

et al. Seizure. 1999;8(8):444. Wilkins. Cephalalgia. 2002;22:711-19.

This work is supported by the Dyslexia Research Trust and Medical Research Council.

Further research employing objective measures of sleep quality and consolidation,

including electroencephalography and actigraphy, are warranted on the basis of these

initial findings.

There are a large number of neurological conditions subject to circadian variation in

expression of their symptoms and associated with sleep disturbance. These includeAlzheimer's Disease (AD), Diffuse Lewy Body Disease (DLBD), Parkinson's Disease (PD)

and depression. In addition, there are many well-characterised disorders of sleep

regulation. We expect that OBF will improve sleep quality in a range of disorders and may

prove a means of influencing the pattern of primary symptom expression in some

neurological conditions.

Further research should initially focus on the effects of filter use in conditions known to

involve dysfunction of the SCN:

Cluster headache

Sleep disorders

Jetlag

One hour wearing blue filters in the morning improves sleep quality

Fig. 1: OBF are worn in spectacle frames

OBF influence retinohypothalamic driveOBF block the transmission of longer-wavelengths of light. In addition, we previously

demonstrated that OBF use results in pupil dilation sufficient to increase the energy of short

wavelength (WL) light reaching the retina (Fig. 2). On the basis of these changes, we have

calculated that OBF use increases retinohypothalamic (RHT) drive by more than 35%.

The RHT is dominated by short-wavelength sensitive ipRGCs and projects to the

suprachiasmatic nucleus (SCN), which is the central circadian pacemaker. The SCN

projects to the medial preoptic area (MPA) and the ventrolateral preoptic area (VLPo), both

important in the regulation of sleep. It is via the RHT that light exposure influences the

sleep-wake cycle and circadian patterns of alertness.

Although not statistically significant, participants tended to wake less frequently in the night

(p = 0.08) during the period of OBF use, whilst no such trend was evident with the use of

'yellow' filters (Fig 4).

Fig. 2: OBF increase short WL light incident at retina

Fig. 3: VAS scores at baseline against OBF use period

Fig. 4: Sleep continuity at baseline against OBF use period

The findings reported in Figures 3 and 4 support our hypothesis that OBF increase photic

influence over the SCN, and thereby improve sleep quality via the connections of the SCN

(Fig. 5).

The failure to reach significance for influence of OBF over the frequency of nighttime

waking may reflect either the low incidence of nocturnal waking in our healthy participant

group or the failure of participants to accurately recall each occurrence of waking.

The improvement in subjective sleep quality and alertness on wearing OBF for a short

period, raises the prospect that they may of use in the general population.

0

Baseline

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OBF

'Very alert'

'Very sleepy' 0

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'Very goodquality'

'Very poorquality'

Fig. 5: Pathways subject to modulation by OBF

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Meannumberofnocturnalawakenings

duringperiod

Excitator y inp ut Inhibitory input Endocrine output

VLPo

RETINA

SCN PN

PPC

SC

DMN LC

PVN

IML SCG PIN aMT

aMT Melatonin

DMH Dorsomedial nucleus

IML

LC

PIN

PN

PPC

PVN

SC

SCG

SCN

VLPo

Intermediolateral column of the spinal cord

Locus coeruleus

Pineal gland

Pulvinar nucleus

Posterior parietal cortex

Paraventricular nucleus

Superior colliculus

Superior cervical ganglia

Suprachiasmatic nucleus

Ventrolateral preoptic nucleus