Effect of Different Color Lights on the Internal Clock and Alertness in Humans (CONE)

University of Basel

Status: Not yet enrolling

Conditions: Light Flashing

Treatments: Other: Constant light stimuli; Other: Flickering light stimuli; Other: Dim light

Study type: Interventional

Funder types: Other

Identifiers

NCT05423002

ID 2022-00401

Details and patient eligibility

About

The main aim of this study is to investigate the effects of cone-modulated light emitted from a visual display on human circadian physiology and cognitive performance in the evening.

Full description

The investigators will generate single/multiple cone-isolating contrasts with equivalent stimuli for other cones and melanopsin photoreceptors. The investigators will assess melatonin suppression under three different light scenarios generated using the method of silent substitution by tuning the spectral composition of the light primaries (e.g. LEDs) such that a single target photoreceptor class is maximally stimulated compared to an equal stimulation of the remaining photoreceptors. Additionally, The investigators will examine pupil response, subjective sleepiness, psychomotor vigilance, visual comfort, and skin temperature under three different light scenarios. This allows for new insights into the lights' cone-contribution mechanism to neuroendocrine physiology in the human retina.

Enrollment: 68 estimated patients

Sex: All

Ages: 18 to 35 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Age: 18 - 35 years
• Sex: male or female normal color vision, male dichromat (i.e. tested by CCT, HRR, Farnsworth Munsell 100 Hue Test)
• BMI: 18.5 - 29.9 self-reported weight and height (i.e. normal and overweight according to WHO)
• Signed consent form of participants
• Chronotype: Morningness-Eveningness Questionnaire (31 - 69)
• Sleep Quality: Pittsburgh Sleep Quality Index, PSQI (≤5)

Exclusion criteria

• High myopia (> -6 diopters)
• High hyperopia (< +6 diopters)
• Transmeridian travel (>2 time zones) <1 month prior to the first session of the study
• Shift work <3 months prior to the beginning of the study
• Ophthalmological or optometric conditions (cataract, glaucoma, retinal detachment, macular conditions, chronic inflammations, eye injuries, or operations)
• General health concerns or disorders, including heart and cardiovascular, neurological, nephrological, endocrinological, and psychiatric conditions
• Medication impacting on visual, neuroendocrine, sleep, and circadian physiology
• For females only: pregnancy, use of hormonal contraceptives, lactation or breastfeeding
• Drug (urinary drug screening) and alcohol use
• Non-compliance with sleep-wake times: >1 deviation from ±30 minute window sleep and wake-up time
• Extreme chronotype (Munich Chronotype Questionnaire <2 or >7)
• Current participation in other clinical trials

Exclusion criteria due to study requirements:

• Inability to understand and/or follow study materials or procedures
• Insufficient knowledge of project language

Trial design

Primary purpose: Basic Science

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: Single Blind

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68 participants in 3 patient groups, including a placebo group

Control

Placebo Comparator group

Description:

Dim light condition as a baseline

Treatment:

Other: Dim light

Modulation

Active Comparator group

Description:

Flickering light will be added sinusoidally onto the background light.

Treatment:

Other: Flickering light stimuli

Background

Sham Comparator group

Description:

Constant light with maximum half irradiance (50%) of all primaries.

Treatment:

Other: Constant light stimuli