Resources / Interactive
Why screens dry your eyes
Relaxed, people blink about 22 times a minute. Working at a screen, that drops to about 7 — roughly a third — according to a classic study in the New England Journal of Medicine (Tsubota & Nakamori, 1993). Every blink spreads a fresh layer of tear film over the surface of your eye; skip two out of three blinks and that film gets old, thin, and patchy. That's the gritty late-afternoon feeling.
Numbers are abstract, though. Try it instead — drag the slider and watch what your blink rate does to the eye below.
Measured blink rates: Tsubota & Nakamori, N Engl J Med 1993. Dashed line = your slider value. Tear-film meter is a simplified visualization, not a medical measurement.
View the data as a table
| Condition | Blinks per minute |
|---|---|
| Relaxed | 22 |
| Reading a book | 10 |
| Working at a screen | 7 |
What the simulator is showing
Blinking is your eye's maintenance cycle. Each blink wipes the surface and lays down a fresh tear film — a micro-thin layer of moisture that keeps vision crisp and the surface comfortable. Between blinks, that film evaporates and thins. Blink every ~3 seconds (a relaxed rate) and the film never gets old; blink every 8–9 seconds (a typical screen rate) and it spends most of its life stretched thin.
The villain isn't the screen itself — it's concentration. Focused visual work suppresses blinking whether it happens on a display or on paper; the same 1993 study measured reading at about 10 blinks per minute. Screens simply hold our focus for longer stretches, with fewer natural pauses, than anything else in modern life.
The American Optometric Association groups the resulting symptoms — dryness, strain, headaches, blurred vision — under digital eye strain (computer vision syndrome), and its everyday advice is exactly what the simulator suggests: blink more often, and take regular distance breaks like the 20-20-20 rule.
Find your own number
The slider is hypothetical; your actual blink rate is measurable. Our 30-second webcam blink test counts your real blinks right in the browser — nothing uploaded, nothing stored. Most people are surprised which side of the chart they land on while reading.
A cat can watch your blinks for you
Slow Blink detects when you stop blinking — 100% on-device — and sends a gentle cat to remind you. Free for macOS.
Download Slow Blink Take the blink testSources
Tsubota K, Nakamori K. Dry eyes and video display terminals. N Engl J Med. 1993;328(8):584.
American Optometric Association —
Computer vision syndrome (digital eye strain)
The simulator is an educational visualization based on published averages — individual blink rates vary widely, and the tear-film meter is illustrative, not diagnostic. Slow Blink is not a medical device and this article is not medical advice. If you have persistent eye discomfort, please consult an eye-care professional.