Photopia

Part of speech: noun

Definitions

1. Vision in well-lit conditions, when the cone cells of the eye do the work of seeing colour and fine detail
2. The kind of sight the eye uses in bright daylight, relying on cones rather than the rod cells used in dim light
3. Eyesight under strong illumination, in which colour perception and sharp detail are provided mainly by the cones

Etymology: Photopia is vision adapted to daylight or bright light, the eye's ordinary working mode when there is plenty of light. It is built from "phot-", from Greek "phōs" meaning light, and "-opia", from Greek "ōps" meaning eye or sight, the same combining element that appears in words for other visual conditions. The pairing is a modern scientific coinage, so the Greeks themselves never used it; they simply supplied the building blocks, as they did for many technical terms in optics and physiology. The noun names one of the two main states of human vision, in contrast with scotopia, the dim-light state in which the rod cells do most of the work. Because the word is assembled from two classical parts, its meaning is transparent: light plus sight, the vision that operates when light is abundant.