Purpose: To describe the use of the slow motion video function on a digital point and shoot camera for qualitative and quantitative blink assessment.
Method: The camera is held at eye level 50 cm away from the participant. The participant is asked to relax and look in the distance over the photographerís shoulder. The super slow motion setting is available on several cameras including the Canon G16 and iPhone 6. A 30-second video is taken. The following parameters can be measured:
1) Blink rate: number of blinks divided by recording time.
2) Blink type: e.g. complete (greater than two-thirds corneal cover), twitch (upper lid twitch), incomplete (less than two-thirds corneal cover).
Results: Video 1 shows normal blinking with a blink rate of 38 per minute, all of which are complete (90-100% corneal coverage). Video 2 shows a participant with partial left facial nerve palsy who has a rate of 14 blinks/30 seconds and 2/14 (14%) complete blinks, 3/14 (21%) twitch blinks and 9/14 (64%) incomplete blinks. The corneal coverage during incomplete blinks ranges from 20-50%.
Discussion: Healthy blinking is fundamental for corneal protection and wetting. Blink assessment is an important part of corneal and lid examination and can be done accurately and routinely in the eye clinic with the super-slow-motion function of modern point and shoot cameras.