I've got the same issue, but on a late-2009, 27-inch iMac. I've seen other users say that they used a baby wipe or lens cloth wrapped around a credit card to clean the lens. Any reason I shouldn't give that a try before I spring for an external reader?
I wouldn't try those methods on my machine, I would use a commercial kit available from your local office supply store. However it's your machine.....
Only clean with a special drive-cleaing disk. Stuffing odd-shaped items in the slot may damage the drive beyond repair.
The disks are available at computer stores, home electronics stores, and many office supply outlets taht sell comptuer gear. Usually about US$5-15.
An example:
DVD is not recognized
