I do not think there is any best optimized adsense theme but it need our hard work and it changes all the time
Buy a decent theme, there are plenty of them out there. Or if you can read a bit of PHP and CSS, take a good free theme and modify it. I do it all the time. I like Cutline by Chris Pearson - http://www.pearsonified.com/ and Fusion by Digital Nature - http://digitalnature.ro/projects/fusion/
I've found the uglier the theme the better the CTR. It's not about a pretty website it's about getting the visitor to feel the need for more info and to click. Any adsense optimized wordpress theme should give you a good ctr if your ad placement is prominent and you don't give the visitor all the info they're looking for in your content.
Personally, I wouldn't think in terms of themes; I would think in terns of layouts. Believe it or not, EZA probably has one top layouts for Adsense income. Go to their website, click on a article and notice the layout. BE ADVISED: they do violate the GA TOS with the number of Ad blocks, however, they are allowed the exception because of the income they generate. Notice the block of ADs under the title and the two block of ADs to the right running parallel to the article. Top those of with some Chitka ADs at the bottom and you're good to go! I've recently starting implementing the exact same layout and have seen CTR increase from and average 8% up to 11.5%
i like using the Swift theme, since i am not a pro at web building, something like Swift works perfect for me. it is neat and does everything you need it to do as long as you got the plugins for it you will do fine
you know, many a times the theme depends on the niche you are working with... for eg. hxxp://leviscopperjeans.com has given me the best CTR so far
I suggest getting a custom adsense done by a professional if you have the buck. It might cost a bit much but it's worth it!
I also like bluesense in Wordpress. There are many nice customize and kick ass template you can mess around with too..