Full-spectrum light exposure: Participants will be exposed to a full-spectrum white light designed to replicate the spectral quality of natural daylight while maintaining safe, indoor intensity levels. The light source delivers an illuminance of approximately 1000 lux and is free of ultraviolet and infrared wavelengths. Each participant will undergo two periods of light exposure, intermittently, during the laboratory visit at the Eye N' Brain Research Platform (NUS).
Standard indoor light exposure (Control): Participants will be exposed to a standard indoor light with an illuminance of approximately 300 lux. Each participant will undergo two periods of light exposure, intermittently, during the laboratory visit at the Eye N' Brain Research Platform (NUS).
Study summary
The goal of this study is to understand how light sensitivity in the eye affects sleep, mood, alertness, and cognition in adults with glaucoma compared to healthy individuals aged 45-75 years.
The main questions it aims to answer are:
1. Do patients with glaucoma experience poorer sleep, mood, alertness, and cognitive function than age-matched healthy adults?
2. Are these changes related to reduced light sensitivity in special retinal cells called intrinsically photosensitive retinal ganglion cells (ipRGCs), lost in glaucoma?
3. Can exposure to safe, full-spectrum indoor light help improve these functions?
Researchers will compare patients with glaucoma and age-matched healthy controls to see if differences in light sensitivity can explain changes in non-visual light responses (i.e., sleep, mood, alertness, and cognition) and whether full-spectrum light exposure can enhance alertness and wellbeing.
Participants will:
1. Complete eye exams and baseline questionnaires about their sleep, daytime sleepiness, mood, and wellbeing.
2. Wear a wrist-worn device for 8-16 days to record their sleep patterns and light exposure.
3. Visit the laboratory for cognitive and attention tests following exposure to two lighting conditions (randomized, cross-over):
This study will help researchers understand how glaucoma affects the brain beyond vision and explore whether light-based interventions can improve quality of life for people living with glaucoma.
Eligibility
Sex
ALL
Min age
45 Years
Max age
75 Years
Healthy volunteers
Accepted
Inclusion Criteria:
* Patients with glaucoma must meet all of the inclusion criteria to participate in this study.
* Patients diagnosed with primary open-angle glaucoma (POAG), as indicated by Humphrey Visual Field (HVF) mean deviation (VFMD) scores better than -12 dB in at least one eye during their most recent clinic visit.
* Patients having spared central vision.
* Patients aged 45 to 75 years old.
* Patients with a best-corrected visual acuity better than 6/12
* English-speaking patients
Healthy controls must meet all of the inclusion criteria to participate in this study:
* Participants aged 50 to 70 years old.
* Participants with a best-corrected visual acuity better than 6/12
* Normal ophthalmic examination
* English-speaking participants
Exclusion Criteria:
* All subjects (patients and controls) meeting any of the exclusion criteria at baseline will be excluded from participation:
* Participants with myopia exhibiting a refractive error exceeding -8.00 diopters (D)
* Participants with a history of complicated previous intraocular surgery
* Participants taking alpha-adrenergic agonist eye drops or other systemic medications or drugs that could affect the pupillary response
* Participants with any past or current ocular condition (i.e., age-related retinal diseases (e.g., age-related macular degeneration), retinal pigment epithelium diseases (e.g., Best's disease), diabetic retinopathy, or other optic or generalized neuropathies, significant ocular trauma, or any eye condition affecting fixation (eg. Nystagmus)).
* Participants diagnosed with cataracts at NS3+ (Nuclear Sclerosis) and above, as well as those with Posterior Subcapsular (PSC) cataracts
* Participants with clinically diagnosed psychiatric or neurologic disorders, including cognitive impairment or dementia
* Participants with diagnosed mood disorders
* Participants engaged in night shift work within the past three months, are currently using sleeping pills, or have recently travelled across timezones within a month prior to the study
* Participants with obstructive sleep apnea
* Participants with abnormal auditory function
* Participants with impaired color vision
* Pre-menopausal women (last menstrual period \< 1 year) (If applicable)
* Patients having unilateral glaucoma, congenital glaucoma, non-glaucomatous optic neuropathy, abnormal central vision
* Diabetics on treatment
Primary outcome measure(s)
Subjective Sleep Quality — Baseline (Visit 1) Sleep quality is assessed using the Pittsburgh Sleep Quality Index (PSQI), a validated self-report questionnaire measuring subjective sleep quality, sleep latency, duration, efficiency, disturbances, use of sleep medication, and daytime dysfunction over the past month. Higher scores indicate poorer sleep quality.
Subjective Daytime Sleepiness — Baseline (Visit 1) Daytime sleepiness is assessed using the Epworth Sleepiness Scale (ESS), a validated questionnaire evaluating the likelihood of dozing in common daytime situations. Higher scores indicate greater daytime sleepiness.
Depressive Symptoms — Baseline (Visit 1) Depressive symptoms will be assessed using the Patient Health Questionnaire-9 (PHQ-9), a validated self-report questionnaire measuring the frequency and severity of depressive symptoms over the past two weeks. Higher scores indicate greater depressive symptom severity.
Global Cognitive Function — Baseline (Visit 1) Global cognitive function will be assessed using the Montreal Cognitive Assessment (MoCA), a standardized screening tool evaluating executive function, attention, memory, language, and visuospatial abilities.
Global Cognitive Function during light exposure — Immediately after the procedure Global cognitive function will be assessed using the Montreal Cognitive Assessment (MoCA), a standardized screening tool evaluating executive function, attention, memory, language, and visuospatial abilities. Alternate validated versions will be used across visits to minimize learning effects.
Median Reaction Time — Immediately after the procedure Median reaction time will be assessed using a laboratory-based auditory Psychomotor Vigilance Task (aPVT). Participants will respond to auditory stimuli presented via headphones by pressing a key on a keyboard while viewing a fixation display on a monitor. Reaction time is defined as the interval between stimulus onset and the participant's button press. The primary outcome measure is the median reaction time calculated across all valid trials within the task.
Vigilance Lapses — Immediately after the procedure Vigilance lapses will be assessed using a laboratory-based auditory Psychomotor Vigilance Task (aPVT). Participants will respond to auditory stimuli presented via headphones by pressing a key on a keyboard while viewing a fixation display on a monitor. Omission lapses are defined as trials in which no response is registered within the predefined response window following stimulus onset. The outcome measure is the total number of omission lapses across all valid trials.
Long Reation Time Lapses — Immediately after the procedure Long reaction time lapses will be assessed using a laboratory-based auditory Psychomotor Vigilance Task (aPVT). Participants respond to auditory stimuli by pressing a key on a keyboard. A long reaction time lapse is defined as any trial in which the reaction time exceeds two times the participant's median reaction time for the task. The outcome measure is the total number of long reaction time lapses across all valid trials.
Anticipatory Responses — Immediately after the procedure Anticipatory responses will be assessed using a laboratory-based auditory Psychomotor Vigilance Task (aPVT). Participants respond to auditory stimuli by pressing a key on a keyboard. An anticipatory response is defined as a button press occurring before stimulus onset, reflecting premature responding. The outcome measure is the total number of anticipatory responses across all valid trials.
Sustained Attention Variability — Immediately after the procedure Additional reaction time metrics will be derived from the auditory Psychomotor Vigilance Task (aPVT) to characterize response speed distribution and variability. These metrics include reaction time slope across trials, fastest reaction times (e.g., fastest 10%), slowest reaction times (e.g., slowest 10%), and measures of intra-individual reaction time variability. These outcomes provide complementary information on vigilance stability and performance dynamics beyond central tendency measures.
Associative Learning — Immediately after the procedure Associative Learning is assessed using a computerized variant of the Digital Symbol Substitution Task (DSST). Associative learning is quantifies by the proportion of correct responses across all trials (accuracy).
Processing Speed — Immediately after the procedure Processing speed is assessed using a computerized variant of the Digital Symbol Substitution Task (DSST). Processing speed is quantifies by the median reaction time taken across trials to judge if the presented combination is correct or incorrect (button press).
Visual Attention Allocation — Immediately after the procedure Visual attention allocation during the Digit Symbol Substitution Task (DSST) is assessed using eye tracking. Predefined areas of interest (AOIs), including the reference symbol-number set and the presented test pair, will be used to quantify visual strategy. Outcome measures include the number and sequence of visits to each AOI and the proportion of viewing time spent within each AOI across valid trials.
Eye-Movement Behavior — Immediately after the procedure Eye-movement behavior during the Digital Symbol Substitution Task (DSST) will be assessed using video-based eye tracking. Metrics will characterize visual exploration and oculomotor behavior and include fixation count and duration, saccade frequency and amplitude, and related summary measures averaged across valid trials.
Selective Attention — Immediately after the procedure Cognitive processing of infrequent auditory stimuli will be assessed using a laboratory-based auditory oddball task. Auditory tones will be presented via headphones while participants view a fixation display on a monitor and respond using a keyboard. Accuracy is defined as the proportion of correctly detected target tones and correctly ignored non-target tones across all trials.
Auditory Discrimination Performance — Immediately after the procedure Auditory discrimination performance will be assessed using an auditory oddball task. Sensitivity (d') will be calculated based on hit rates (correct detection of target tones) and false alarm rates (responses to non-target tones). Higher d' values indicate greater ability to discriminate infrequent target tones from frequent non-target tones.
Task-Evoked Pupillary Responses — Immediately after the procedure Task-evoked pupillary responses will be recorded during performance of the auditory Psychomotor Vigilance Task (aPVT) as well as the oddball task using eye-tracking pupillometry. Changes in pupil size measured during task performance, following stimulus presentation and participant response, will be quantified as indicators of cognitive effort and alertness. Outcome measures include pupil dilation amplitude and response dynamics averaged across valid trials.
Pupillary Responses to Shapes — Immediately after the procedure Changes in pupil size during image presentation will be quantified as physiological correlates of the perceived features of a shape, independent of physical luminance.
Objective sleepiness — Immediately after the procedure Objective sleepiness will be assessed using a computerized time estimation task. Participants will be instructed to press a button when they believe that a specified time interval has elapsed (10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds). Time estimation accuracy will be quantified as the difference between the estimated and actual interval duration across trials.
Risk Taking Behavior — Immediately after the procedure Risk-taking behavior is assessed using the Balloon Analogue Risk Task (BART), a computerized decision-making task. Adjusted average pumps is calculated as the mean number of pumps on balloons that do not burst (i.e., excluding balloons that explode), providing an index of risk-taking propensity.
Subjective Sleepiness, Mood, and Wellbeing — Immediately after the procedure Change in subjective sleepiness, mood, and wellbeing assessed using the Stanford Sleepiness Scale (SSS) and Likert scales before each light exposure (baseline), immediately after exposure (acute effect), and following cognitive assessments (sustained effect).
Sleep Quantity — 8-16 days in between the visits Night time sleep quantity (minutes) will be collected through actigraphy watches given to participants.
Sleep Efficiency — 8-16 days between the visits Night time sleep efficiency (%) calculated as the amount of time spent asleep (in minutes) by the total amount of time in bed (in minutes) will be measured using actigraphy watches given to participants.
Phasic Pupil Constriction to Blue Light — Baseline (Visit 1) Phasic pupil constriction to blue light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Phasic pupil constriction to blue light refers to the rapid, transient decrease in pupil diameter that occurs immediately after the onset of a blue light stimulus. It is calculated as a percentage change from baseline.
Phasic Pupil Constriction to Red Light — Baseline (Visit 1) Phasic pupil constriction to red light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Phasic pupil constriction to red light refers to the rapid, transient decrease in pupil diameter that occurs immediately after the onset of a red light stimulus. It is calculated as a percentage change from baseline.
Maximum Pupil Constriction to Blue Light — Baseline (Visit 1) Maximum pupil constriction to blue light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Maximum pupil constriction to blue light refers to the greatest reduction in pupil diameter observed following the onset of a blue light stimulus. It is calculated as a percentage change from baseline.
Maximum Pupil Constriction to Red Light — Baseline (Visit 1) Maximum pupil constriction to red light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Maximum pupil constriction to red light refers to the greatest reduction in pupil diameter observed following the onset of a red light stimulus. It is calculated as a percentage change from baseline.
Pupil Constriction Latency to Blue Light — Baseline (Visit 1) Maximum pupil constriction to blue light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Constriction latency is defined as the time from blue light onset to the first detectable decrease in pupil diameter relative to baseline. It is measured in seconds.
Pupil Constriction Latency to Red Light — Baseline (Visit 1) Maximum pupil constriction to red light will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. Constriction latency is defined as the time from red light onset to the first detectable decrease in pupil diameter relative to baseline. It is measured in seconds.
Post-illumination Pupillary Responses — Baseline (Visit 1) Post-illumination pupillary responses (PIPR) will be quantified using chromatic pupillometry with a handheld chromatic pupillometer. PIPR refers to the sustained pupil constriction that persists after the termination of a light stimulus.
Trial sites (2)
Facility
City
Region
Status
National University Hospital
Singapore
Singapore
Not Yet Recruiting
Singapore National Eye Center
Singapore
Singapore
Recruiting
More National University of Singapore trials in Singapore
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
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