I did do a butter X lesser pairing and produced 3 BEL's out of 6 eggs, 2 females and a male.
One female and the male turned out blind, no bug eyes, just blind as a bat.
We bred the male this season but he lost interest in breeding after a few locks with his cinny pewter girlfriend so I replaced him with our black back enchi male.
Personal opinion is this is a bad breeding, too many chances of bug eyes or like ours, blindness.
The blindness is not hereditary so it won't pass on, but no way will I make more BEL's with a lesser/butter pairing.
And contrary to my nooby responses back a couple of years, they are the same mutation, possibly different lines, but the same gene none the less.