(Reuters) - The third director in a week has resigned from the Eastman Kodak Co. as the former film giant struggles to survive the dominance of digital photography.

Laura Tyson, a professor and White House adviser, told Kodak on Thursday she was resigning from its board, the company said on Friday in a Securities and Exchange Commission filing.

Kodak, once synonymous with photography, is looking to sell patents to shore up its shrinking cash position and stay in business after failing to turn an annual profit since 1997.

Last month, the Rochester, N.Y.-based company warned that unless it could raise $500 million in new debt or sell some patents in its portfolio, it might not survive 2012.

Tyson, who did not immediately respond to a request for comment, is a professor at the Walter A. Haas School of Business at the University of California at Berkeley.

She also has served as a member of President Barack Obama's Economic Recovery Advisory Board, and advised the Clinton administration on the economy in the 1990s.

Earlier this week, Kodak said directors Adam Clammer and Herald Chen had resigned.

Clammer and Chen were representatives of private-equity firm KKR & Co. and had joined Kodak's board in 2009, after KKR bought $300 million of Kodak's senior secured notes and warrants to buy 40 million of the company's shares.

Kodak's shares edged lower in extended trade to 63 cents after closing marginally down at 65 cents.