There wasn't even a hint of losing any definition at the edge of any of the Radian's field. I have had the pleasure of owning these eyepieces for a few months now, and have come to the conclusion that they are the best overall eyepieces I have ever owned. The eyeguards are a bit looser on the more recent ones I have bought, but are still functional. I preferred the stiffer earlier models. Contrast and planetary performance has been superb, so has light throughput.
Objects are sharp right to the very, very edge of field.
All objects look their best through these eyepieces. Particularly impressive is the performance of the 3mm Radian which deserves special mention. The eye relief is so huge for a 3mm eyepiece, that there was no awareness of it being different than any other kind of eyepiece in terms of comfort of use. In fact, using it in two scopes with focal lengths near 1000mm, it worked out very well on Mars, which was shrinking in size, and needed the boost to over 300 power. The only negatives reported to me have been an occasional ghost reflection, and also lack of color purity towards the edge of field.