HARI SREENIVASAN:

About 40 million Americans wear contact lenses to correct their vision, and how much the lenses cost is now the subject of a courtroom battle.

A recent federal appeals court ruling temporarily allows discounters like 1-800-CONTACTS to charge less than the largest lens manufacturers would prefer. The lens makers don't want eye doctors who sell contacts to be undercut by discounters who go below a suggested minimum price.

At stake is $4 billion Americans spend on contact lenses.

Yesterday, I spoke with Associated Press reporter Lindsay Whitehurst, who is covering the case.

Four billion dollars is a big amount. Forty million Americans using contact lenses is something that we all sort of take for granted. What happened in this specific case?