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. 2022 Aug 20;62(6):849–854. doi: 10.2169/internalmedicine.0132-22

Prophylactic Treatment for Patients with Migraine Using Blue Cut for Night Glass

Muneto Tatsumoto 1,2, Eiji Suzuki 3, Mayumi Nagata 4, Keisuke Suzuki 5, Koichi Hirata 1,6
PMCID: PMC10076141  PMID: 35989269

Abstract

Objectives

Migraine is a disease that leads to social loss due to a decrease in productivity since it is a primary headache with a high prevalence and readily occurs in working-age persons. As described in the diagnostic criteria of the International Classification of Headache Disorders, 3rd edition (beta version), migraine causes hypersensitivity, especially photosensitivity, during attacks, suggesting that light is an inducer of headaches. We developed Blue Cut for Night (BCN) glass, which reduces light stimulation to intrinsically photosensitive continental ganglion cells (ipRGCs), photoreceptors that can lead to exacerbation of migraine attacks.

Methods

Ten patients with migraine participated in the study. Each participant was made to wear BCN glasses only at night for four weeks. The number of headache days and Headache Impact Test-6 values before and after using the BCN glasses were compared.

Results

When the 10 patients with migraine wore the BCN glass at night only for 4 weeks, the number of headache days within that time tended to decrease (7.0±4.37 days) compared to before wearing the glasses (8.7±5.03 days). No participants had any side effects.

Conclusion

BCN glass, which reduces light stimulation to ipRGCs, was suggested to be a tool for reducing migraine attacks.

Keywords: migraine, Blue Cut for Night glass, intrinsically photosensitive continental ganglion cells (ipRGCs), prophylactic treatment

Introduction

Approximately three billion people worldwide are estimated to have headache disorders. The prevalence of migraine and its hindrance to life are both very high, and its treatment has become one of the most important global issues in health policy (1). In Japan, migraine has a prevalence of 8.4% (8.4 million people). Considering age, it is high among working-age women in their 20s and 40s, and in addition to the cost of medical expenses, there are significant economic losses, such as reduced productivity. Nevertheless, it is estimated that patients with migraine consult medical institutions at a rate of approximately 30%, and patients' awareness of headache treatment is insufficient compared to the prevalence (2).

Treatment of migraine is centered on drug therapy. However, drugs present the risk of side effects and substance abuse. In addition to pharmacotherapy, various other treatments, such as cognitive behavioral therapy, have been proposed (3), but there is a burden on medical institutions to secure professional staff and on patients to cover treatment costs and pay for hospital visits. If there an easy-to-use, side-effect-free, and inexpensive treatment for migraine were to be developed, it would broaden the scope of headache treatment and be beneficial in reducing economic losses.

The pathophysiology of migraine is not fully understood. However, its triggers have been identified, and approximately 38% of cases are reported to be due to ‘light’ (4). The third edition of the diagnostic criteria for the International Classification of Headache Disorders, 3rd edition (beta version) also included the status of photosensitivity as an associated symptom of migraine. In addition, there have been reports that differences in exposure by season affect the frequency of migraine onset (5). In 2010, it was revealed that light stimulation also exacerbated migraine attacks even in patients with visual impairment.

As a mechanism, the involvement of intrinsically photosensitive continental ganglion cells (ipRGCs), a photoreceptor not involved in image formation, was pointed out (6). The non-visual effects of ipRGC-mediated light on human organisms include adjusting pupil diameter, adjusting circadian rhythms, and influencing changes in body temperature and heart rate. The action efficiency of light by wavelength on this non-visual effect has been shown to be high for short-wave blue light (480 to 500 nm) (7). The Deutsche Industrie Normen (DIN) Lighting Engineering Division normalized the action spectrum (melanopic function) peaking at 490 nm to quantify the amount of light-induced action on circadian rhythms via IpRGCs (8).

Tatsumoto et al. have been conducting studies focusing on the visual effects of ipRGCs. Blue light of 480 nm, which is approximately the peak sensitivity wavelength of ipRGCs, is likely to cause unpleasant glare in patients with migraine, unlike other wavelengths of light (550 nm, 610 nm), even at a low brightness of about 110 cd/m2 (9). Noseda et al. pointed out that light receptivity, i.e. visual information, by pyramidal cells is also involved in the exacerbation of migraine (10). Nevertheless, the wavelength range of light received by ipRGCs and the wavelength range of light received by cone and rod cells have broad overlap. It is thus extremely difficult to evaluate each effect separately, except in special cases. It is important to examine the relationship between light and migraine while keeping in mind the visual and non-visual effects of light.

The present study examined whether or not the frequency and degree of migraine could be reduced by controlling the light environment surrounding patients with migraine. However, it is difficult to control all lighting that patients with migraine are exposed to daily, such as that from the screen of a personal computer or mobile device in addition to sunlight and typical indoor lighting. Therefore, we decided to focus on whether or not the symptoms of migraine patients could be reduced by creating an eyeglass lens that blocks certain wavelengths of light, enabling patients to wear the glasses for an extended period of time. The eyeglasses effectively block blue light with short wavelengths of 480 to 500 nm, taking into account the visual and non-visual effects of ipRGC-induced headaches. Since light stimulation of ipRGCs suppresses melatonin secretion, the glasses are assumed to be suitable for wearing, especially at night, and were thus named Blue Cut for Night (BCN) glasses.

Materials and Methods

Participants

The study period was from March 2017 to September 2017. The participants were 10 patients diagnosed with migraine (average age 35.2 years old, range 24-47 years old, 10 women), including 3 with aura and 7 without aura and all 10 with photophobia. Lights from oncoming vehicles, such as headlights, brake lamps, and streetlights while driving at night, also trigger headaches, so we targeted individuals who had a habit of driving at night. In addition, the BCN glasses have no refractive power and are intended for patients who have no refractive error or who have refractive correction other than glasses.

This study was conducted in accordance with the Declaration of Helsinki and was approved by the ethics committees of the Dokkyo Medical University hospitals with which the authors are affiliated. Written informed consent was obtained from all subjects prior to their inclusion.

BCN glasses specifications

The lens spectral transmittance of BCN glass is shown in Figure 1, 2. Considering that the luminous transmittance τV is used for nighttime operation, it was set to exceed 75%, which is the standard for night operation as defined in JIS T7333. The light stimulation cut-off rate for each photoreceptor was calculated using [Formula 1], in which the calculation formula for luminous transmittance is used.

Figure 1.

Figure 1.

Spectral transmittance. Melanopic action spectrum (broken line) specified in DIN SPEC 5031-100 and the blue light cut lens for night use.

Figure 2.

Figure 2.

Study glasses using Blue Cut for Night (BCN) glass.

[Formula 1]

graphic file with name 1349-7235-62-0849-i001.jpg

B: Light stimulation blocking rate (%) to each photoreceptor

L(λ): BCN glass lens spectral transmission (%)

D65(λ): Relative spectral radiant intensity of standard D65 light sources

P(λ): Efficiency function for each photoreceptor

In P(λ), cone cells, the luminous efficiency of rod cells, or the melanopic function, is inserted from DIN SPEC 5031-100, and the calculated value is summarized in Table (11). While the lens of BCN glass has an attenuation rate of approximately 17% of the luminosity, the glasses have an attenuation rate of light stimulation to ipRGCs of 41%. Each participant selected an eyeglass frame that matched their face.

Table.

Luminous Transmittance and Cut Rate of Light Stimulation to Each Photorecepters under Standard Illuminants D65.

Luminous transmittance τV 83 %
S-cone 31 %
M-cone 16 %
L-cone 22 %
Rod 35 %
ipRGCs 41 %

Study design

For each participant, a pre-use period of 28 days and a BCN glasses-wearing period of 28 days were set. During the glasses-wearing period, participants were instructed to continue wearing the glasses for at least three hours per day after dark. During each period, headache conditions and medication were recorded using a headache diary (headache onset times were divided into morning, afternoon, and night, and severity levels of headache were rated one to three; names of drugs were also included for medications administered). Hours of night driving and the actual duration of glasses use during the BCN-glasses-wearing period were also recorded in the headache diary. During both periods, there were no restrictions on the administration of medications for acute attacks.

Prior to the wearing period, each participant was surveyed on a 10-point scale to assess “brightness of light while outdoors,” "brightness of light in the night due to headlights of cars," and "brightness of light while indoors watching television or on a portable computer when wearing glasses." In addition, the survey also evaluated the level of brightness in the same scenes with the glasses on. The Headache Impact Test-6 (HIT-6), which evaluates daily life distress due to headaches; Beck Depression Inventory (BDI), which evaluates depression; and the Japanese version of the Pittsburgh Sleep Quality Index, which evaluates sleep conditions, were administered before and after the glasses-wearing period.

Results

All 10 participants ended the test period without dropping out. During the BCN glasses-wearing period, the number of days wearing the glasses was 22.8±7.30, and the average wear time was 179.1±61.0 mins. The number of night-driving days in the pre-BCN glasses-wearing period and during the BCN glasses-wearing period were 17.8±6.01 and 17.7±7.56, respectively, and the total driving time was 48.0±32.9 minutes and 53.0±33.5 minutes, respectively, showing no marked difference between the periods.

Changes in frequency and intensity of headaches

On comparing the number of headache days between the pre-BCN glasses-wearing period and the BCN glasses-wearing period, the number of headache days was significantly reduced during the BCN glasses-wearing period. However, there was no marked change in the number of medication administration days (Fig. 3). There was also no significant change in the number of days taking medicine between the pre-BCN glasses-wearing period (5.8±5.16 days) and the BCN glasses-wearing period (4.5±4.62 days).

Figure 3.

Figure 3.

Comparing the number of headache days and days taking medicine between the pre-BCN glasses-wearing period and the BCN glasses-wearing period. Average of 10 subjects, error bar is 1 standard deviation. The number of headache days during the BCN glasses-wearing period (7.0±4.37 days) was significantly lower than the number in the pre-BCN glasses-wearing period (8.7±5.03 days) (p<0.05).

The number of days of medication use each month was 8.48±8.07 days in the pre-BCN glasses-wearing period and 7.1±8.21 days in the BCN glasses-wearing period, showing no significant difference, although there was a declining trend during the BCN glasses-wearing period. The intensity of headaches was examined in the morning, afternoon, and night. When the frequency of headaches at each time zone was compared by the intensity of headache (three stages), nighttime headaches were greatly reduced by wearing the BCN glasses, but there was marked variation. When all time zones were averaged, the intensity of headache was significantly reduced during the BCN glasses-wearing period compared with the non-glasses-wearing period (Fig. 4).

Figure 4.

Figure 4.

The intensity of headaches was examined in the morning, afternoon, and night. The frequency of headaches during each time zone was compared by the intensity of headache (three stages). Before wearing BCN glasses: 4.3±5.12 in the morning, 4.9±2.77 in the afternoon, 5.7±6.04 at night, 5.0±2.56 on average. While wearing BCN glasses: 4.1±3.60 in the morning, 4.3±6.43 in the afternoon, 3.2±3.71 at night, 3.9±3.05 on average. Wearing BCN glasses showed a reduction in nighttime headaches, with a significant reduction in headache intensity over time on average (p<0.05).

Regarding changes in the intensity of photophobia, daytime, nighttime, and indoors photophobia intensities were significantly reduced by the wearing of BCN glasses (Fig. 5). In addition, although the intensity of photophobia in the indoor area was relatively low, a positive correlation was observed with the number of headache days in each participant (Fig. 6).

Figure 5.

Figure 5.

Regarding changes in the intensity of photophobia, daytime, nighttime, and indoors photophobia intensities were significantly reduced by wearing BCN glasses. A questionnaire was conducted on a 10-point scale from 0 to 10 with and without spectacles on the individual subject’s photophobia intensities during the daytime, nighttime, and indoors (watching a personal computer or TV, indoor lighting). Significant reductions in daytime photophobia from 6.0±2.45 to 3.3±2.00, nighttime photophobia from 6.7±2.11 to 2.8±1.69, and indoor photophobia from 4.5±2.32 to 1.9±1.79 were noted (p<0.01).

Figure 6.

Figure 6.

In the pre-BCN glasses-wearing period, there was a significant positive correlation between the number of headache days and the subjective evaluation of photophobic intensity in the indoor environment (R=0.728, p<0.01).

Regarding other evaluations, HIT-6 showed no marked difference before and during the BCN glasses-wearing period: 58.3±5.14 and 55.6±7.34, respectively. The BDI (12.43±6.92 and 11.0±7.93) and PSQI (5.1±2.69 and 4.8±2.39) also showed no marked difference before and during the BCN glasses-wearing periods, respectively.

Discussion

The use of BCN glasses reduced both the number of headache days and headache frequency×intensity of migraine. The number of dosing days and dosing frequency did not differ markedly between the two periods, and it was confirmed that the decrease in the number of headache days was not due to other factors, such as medications.

Based on the average HIT-6 score (50 points or higher), these results could be interpreted that the target is patients with migraine with moderate degree of disability. However, BCN glasses did not reduce the occurrence of headaches, as the HIT-6 score was unchanged after their use. The BDI score also did not change to any meaningful degree, and there was no psychological effect due to the use of the BCN glasses. There was no marked difference in the PSQI score, either, but this may have been because fewer participants had advanced sleep disorders than before the use of the BCN glasses.

The intensity of photophobia was significantly reduced during the daytime, at nighttime, and while indoors, although the attenuation rate of luminosity of the BCN glasses was very small. The results supported the findings of the preceding study by Tatsumoto et al. In addition, a significant correlation was noted between indoor luminous transmittance, which is generally less obtrusive, and the number of headache days, which may indicate that patients with migraine are also sensitive to relatively weak light.

Given the physiological effects of light on the living body, we believed that light stimulation of ipRGCs should be suppressed at night; we therefore instructed the participants to wear the BCN glasses after dark. In Fig. 4, nighttime headaches were suppressed, and it was possible that the hatred of headaches caused by lights from oncoming vehicles (headlights, brake lamps) while driving at night reduced. Notably, a check of events the following morning revealed that the frequency of headache attacks was 10.1% the following morning after the BCN glasses were worn. This is compared to a frequency of headache attacks of 34.6% the following morning when BCN glasses were not worn, suggesting that the effect of wearing the glasses may have persisted through to the following day. There have been reports of the utility of eyeglasses using filters that block light around 480 nm for patients with migraine (12), so it will be necessary to compare BCN glasses with such glasses in the future.

The average age of the participants in the study was 35.2 years, and the melanopic function of DIN SPEC5031-100 was close to that produced based on data from participants with an average age of 32 years old. The results obtained in this study may be a reference for future studies on the relationship between the amount of light stimulation of ipRGCs and headaches based on the melanopic function as a pre-standard.

This study was limited by its inclusion of only a small number of cases and setting at a single institution.

Our BCN glasses, which were designed for use at night, do not require extensive work, such as changing the ambient light environment, and individual patients can be treated with them alone, providing a simple and effective response to migraine photosensitivity.

The authors state that they have no Conflict of Interest (COI).

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