Using two-photon excitation of Fluorescent indicator dyes, we measured calc
ium concentration transients in retinal ganglion and amacrine cells without
destroying the light sensitivity of the retina by maximally activating or
bleaching the photoreceptors. This allowed an immediate assessment of the c
ellular morphology and study of the calcium signals evoked by visual stimul
i. Calcium dynamics in individual dendritic processes could be examined for
extensive periods without deterioration and with little apparent phototoxi
city at excitation wavelengths of from 930 to 990 nm. Light-evoked increase
s in calcium were resolved in ganglion- and amacrine-cell neurites, making
it possible to use optical recording to study the relationship between calc
ium signaling and retinal function.