Filtered Eyewear to Prevent Light-induced Melatonin Suppression - Aim 1

Filtered Eyewear to Prevent Light-induced Melatonin Suppression While Maintaining Visual Performance and Alertness in Night-shift Working Nurses - Aim 1

The aim of this study is to determine the relative effectiveness of monocular and binocular light exposures, with and without selective blue-blocking filtering, on nocturnal melatonin suppression, subjective sleepiness, and visual performance of night shift workers.

Over the course of six, 5-hour study nights, 30 participants will be randomized to 6 study conditions, 1) binocular dim-light control unfiltered, (2) monocular dim-light control (one eye occluded), (3) unfiltered binocular, (4) unfiltered monocular (non-dominant eye occluded), (5) filtered binocular (both eyes filtered), (6) filtered monocular (non-dominant eye filtered, the other non-filtered). Saliva samples will be collected every 30 minutes for melatonin levels. Participants will also be asked to provide subjective sleepiness and visual performance will be assessed. Study nights will be separated by one week and each participant will be randomized to one of the six study conditions each night. All participants will see all conditions.

Inclusion Criteria:

• Healthy

Exclusion Criteria:

• Bipolar disorder
• Seasonal depression
• Diabetes
• High blood pressure
• History of cancer
• Obstructing cataracts
• Macular degeneration
• Diabetic retinopathy
• Glaucoma
• Use of melatonin supplements
• Use of beta blockers
• Use of sleep medications
• Use of antidepressant medication