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but it's moot.  i was responding to the ongoing conversation about needing some sort of transparency and special geometry to achieve an iris with a realistically soft edge, when that's only needed when you've separated the iris from the scelera.  i guess it could even be different materials, as long as it was one contiguous UV map.

If you're referring to SaintFox asking about how to get transparency between the sclera and the iris a page or two back and where the two met, that's because they were separated.
Separate UV islands, but not separate objects.