compound eye

An ommatidium is the individual optical unit of a compound eye, containing a corneal lens, crystalline cone, and photoreceptor cells (retinula cells with rhabdomeres). Each ommatidium detects light from a slightly different angle, and the brain integrates thousands of these inputs into a mosaic image.

Compound eyes are found predominantly in arthropods, including insects (flies, dragonflies, bees), crustaceans (crabs, shrimp), and some chelicerates. Dragonflies have among the largest compound eyes, with up to 30,000 ommatidia providing nearly 360-degree vision.

Compound eyes generally have lower spatial resolution than vertebrate camera-type eyes but excel at detecting rapid motion, which is critical for flying insects. Their large field of view and flicker fusion rate make them highly effective for motion detection despite lower image sharpness.