Standard UV index tells you about your skin. Your eyes receive something quite different.
Skin exposure peaks when the sun is overhead. Eyes do not — the brow shades them at high sun angles, while low morning and afternoon sun enters the eye almost directly. Ground reflection adds another path that the standard index ignores entirely. The result is that ocular UV often peaks hours away from solar noon.
UVI·eye estimates UV at eye level from four inputs:
Solar elevation, computed from your location and the date
Direct incidence, weighted by the geometry of the human orbit
Ground reflection, scaled by surface albedo
Gaze direction relative to the sun
The model is documented, not hidden. Assumptions and limitations are stated in the app, and the physics is written out so you can judge it yourself rather than trust a number.
Weather data from Apple Weather.
UVI·eye does not diagnose or prevent any condition. It is a physical estimate, not a medical device.
