  The temporal behaviour of the early optical emission from Gamma-Ray Burst
afterglows can be divided in four classes: fast-rising with an early peak,
slow-rising with a late peak, flat plateaus, and rapid decays since first
measurement. The fast-rising optical afterglows display correlations among peak
flux, peak epoch, and post-peak power-law decay index that can be explained
with a structured outflow seen off-axis, but the shock origin (reverse or
forward) of the optical emission cannot be determined. The afterglows with
plateaus and slow-rises may be accommodated by the same model, if observer
location offsets are larger than for the fast-rising afterglows, or could be
due to a long-lived injection of energy and/or ejecta in the blast-wave. If
better calibrated with more afterglows, the peak flux-peak epoch relation
exhibited by the fast and slow-rising optical light-curves could provide a way
to use this type of afterglows as standard candles.
