Well-sampled optical light curves of 50 gamma-ray bursts (GRBs) with plateau features are compiled from the literature. By empirical fitting, we obtained the parameters of the optical plateaus, such as the decay slopes ($alpha_{rm 1}$ and $alpha_{rm 2}$), the break times ($T_{rm b}$), and the corresponding optical fluxes ($F_{rm b}$) at the break times. The break time of optical plateaus ranges from tens of seconds to $10^6$ seconds, with a typical value about $10^4$ seconds. We have calculated the break luminosity, and it mainly ranges from $10^{44}$ erg $s^{-1}$ to $10^{47}$ erg $s^{-1}$, which is generally two or three orders of magnitude less than the corresponding break luminosity of the X-ray afterglow plateaus. We reanalyzed the optical plateaus and also found that a significantly tighter correlation exists when we added the isotropic equivalent energy of GRBs $E_{rm gamma,iso}$ into the $L_{rm b,z}-T_{rm b,z}$ relation. The best fit correlation is obtained to be $L_{rm b,z}propto T_{rm b,z}^{-0.9}E_{rm gamma,iso}^{0.4}$. We next explored the possible correlations among $L_{rm b,z}$, $T_{rm b,z}$ and $E_{rm p,i}$, and found there is also a tight correlation between them, which takes the form of $L_{rm b,z}propto T_{rm b,z}^{-0.9}E_{rm p,i}^{0.5}$. We argue that these two tight $L_{rm b,z}-T_{rm b,z}-E_{rm gamma,iso}$ and $L_{rm b,z}-T_{rm b,z}-E_{rm p,i}$ correlations are more physical, and it may be directly related to radiation physics of GRBs. The tight correlations are possible to be used as standard candles.
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