<font color="purple">There is no universal optimal strategy, since it is a game of imperfect information, although I would guess that there are good game theoretical approximations to an optimal strategy based on ratios of chip counts to blinds.</font color>
Actually there is an optimal game-theoretic strategy for heads-up holdem, but it would take existing computers way too long to do the calculation. A group at the University of Alberta recently used some clever techniques to develop an approximation of the optimal game-theoretic strategy, which they call pseudo-optimal. Here are some links:
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University of Alberta Computer Poker Research Group</font color>
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Article in Poker Theory forum</font color>
It appears that the game of "headsup preflop holdem" (i.e. where all but the first betting round is eliminated, a.k.a. "roll-out holdem") has been solved by Alex Selby:
Optimal Headsup Preflop Poker
It's important to understand what is meant by an "optimal game-theoretic strategy". It is a strategy that cannot be beaten by any counter-strategy. However, against any given opponent the optimal strategy might not win as much as another strategy tailored to exploit the opponent's particular weaknesses.