We've had a number of Great Horned owls on our property over the years, some (mostly juveniles) died. Dennis found a carcass last year, and he made a hardware cloth "cage" that allowed insects access, but nothing else. He wedged it securely in an area where we wouldn't smell it and other animals could not carry it away. He unearthed it this morning (6/14/2015) and [the photos below show] the result. The skull has been exposed and one of the scleral ring bones (the structure that looks like a collar of sorts extending out of the right eye socket) was preserved. This structure is what causes ocular immobility in the owl, hence the need for the great range they have in turning their heads. The bone stabilizes the eye, which is not a "ball" per se, but is more tube shaped.
Big thanks to Dennis and Lyn for this eye-witness report.