Nokia was awarded a patent this week for a wearable device to track eye movements. Nokia’s wearable device attaches to a user’s eyelid and can be used to provide data about sleep cycles. Electrooculography (EOG) testing, which measures movement of the eye, is often used in sleep studies to determine sleep stages.

This is Nokia’s first patent for an eye movement sensor. Eye movement sensors comprise a small percentage of the overall movement sensor sub-sector of the Consumer Sleep Technology Sector. Competitors also making eye movement sensors include Interaxon, which includes an EOG sensor along with its EEG sensor, and Johnson & Johnson, which is making contact lenses that can track eye movement.