High Quality Content by WIKIPEDIA articles! Retinal, also called retinaldehyde or vitamin A aldehyde, is one of the many forms of vitamin A (the number of which varies from species to species). Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision. Bound to proteins called type 1 rhodopsins, retinal allows certain microorganisms to convert light into metabolic energy.